A Publication to Help FarmersUnderstand the Effects of

No-Till Systems on the Soil.

BETTER SOILS WITHTHE NO-TILL SYSTEM

by Sjoerd W. Duiker & Joel C. Myersby Sjoerd W. Duiker & Joel C. Myers

A Publication to Help FarmersUnderstand the Effects of

No-Till Systems on the Soil.

ACKNOWLEDGEMENTS:

“Better Soils with the No-Till System”

is written to encourage farmers

to obtain the benefits of reduced

time spent tilling, increased moisture

content in the soil, and healthy

soil for growing crops from the

micro- and macro-invertebrates

that live within.

Many thanks to those farmers

who have put these practices to

work on their land and shared

their successes. They are truly

stewards of the land.

This publication is a product of the Pennsylvania Conservation Partnership. It wasproduced with funding, editing and production assistance from Pennsylvania StateUniversity, USDA Natural Resources Conservation Service, Pennsylvania Association ofConservation Districts, and the Pennsylvania Department of Environmental Protection.

PA6/05

USDA Natural Resources Conservation Service is an equal opportunity employer and provider.

BETTER SOILS WITHTHE NO-TILL SYSTEM

Sjoerd Duiker, Ph.D. is an assistant professor of soil management at the Pennsylvania State University.Sjoerd has both research and extension responsibilities in his position in the Department of Crops and Soilsat Penn State University. Much of his time is devoted to the impact of no-till on soil quality management.His specialization focuses on the effects of soil management practices on soil properties and processes. Hehas extensive experience working in the Netherlands, Spain, Africa and the United States. Sjoerd has activelysupported no-till throughout Pennsylvania and the northeast and successfully started no-till programs andfield days with the Amish in Lancaster County, Pennsylvania. He has actively supported the regional no-tillgroups in Pennsylvania and made presentations relating to no-till systems at many producer meetings.

Joel Myers is the State Agronomist for the USDA Natural Resources Conservation Service in Pennsylvania.He has promoted no-till through his support of field days, no-till programs and other programs inPennsylvania. He integrates the principles of no-till into numerous training sessions he conducts. Hispersonal farm experience with complete no-till systems has enabled him to discuss the practical aspectsof no-till with producers, agency personnel and others. Joel has spoken several times at the National No-TillConference. He has been a member of the Mid Atlantic No-Till Conference for over 20 years and hassupported and helped start three regional no-till groups in Pennsylvania. He has also been working withresearchers and equipment representatives to address the issues of managing manure in no-till systems.

CREDITS:

Page 2. Figure 8. John Bradley, Milan Experimental Station, Tennessee

Page 9. Figure 12. University of Minnesota Extension

Page 9. Figure 13. Don Reicosky, Agriculture Research

Page 12. Figure 16. Better Soil Better Yields, Conservation Techology Information Center (2002)

Page 12. Figure 17. Agricultural Research Service

Page 14. Figure 19. Eileen Kladivko, Purdue University

Page 15. Figure 20. USDA - Natural Resources Conservation Service

This publication is based on an original document titled “Better Soils, Better Yields”

developed by the Conservation Technology Information Center,

1220 Potter Drive, Suite 170, West Lafayette, IN 47906,

and printed in 2002.

We thank those authors for permission to use some of the graphs

and sources from the original publication.

For more information on No-Till in your county contact your local conservation district, NRCSoffice, Extension agent or the Pennsylvania No-Till Alliance.

The Pennsylvania No-Till Alliance seeks to bring together farmers and others interested in improving soilquality and crop production through the promotion of no-till agricultural systems within the Commonwealth.The main goal of the Alliance is to serve as a network for farmers interested in no-till practices as well as toprovide the most recent resources available regarding no-till research, technology and funding. The Alliancewill promote the development of strong relationships between producers, private sector, agencies andresearch institutions in Pennsylvania.

Participation in the Alliance is open to no-till farmers and those supporting no-till agriculture in the privatesector. In addition, legislative and governmental agencies provide support and technical guidance as needed.

The successful formation of the PA No-Till Alliance has been the result of a great collaborative effort, andwill continue to be mainly a producer-driven organization. Partnering groups/agencies that have been providingsupport for the effort include:

• USDA/Natural Resources Conservation Service• Pennsylvania Department of Agriculture• State Conservation Commission• Pennsylvania Department of Environmental Protection• Penn State College of Agricultural Sciences• Penn State Cooperative Extension• PA Association of RC&D Councils• Chesapeake Bay Foundation• Pennsylvania Farm Bureau• PennAg Industries Association

For additional information or to join the PA No-Till Alliance, contact Susan Parry at the Capital ResourceConservation and Development Area Council office at (717) 948-6633, or email susan.parry@pa.usda.gov

AUTHORS

Sjoerd Duiker and Joel Myers are known throughout the Northeastern United States as staunch supporters of no-till farming.

20

It should be noted that when surface appliedmanure receives 0.5 inches rainfall or more,ammonia volatilization losses are the same asif manure had been incorporated. Early in thespring of the year when temperatures aregenerally cooler, the chances of rainfall occurringto reduce nitrogen losses is greater. Also, withcooler soil temperatures, nitrogen lost on a dailybasis is reduced so rainfall several days afterapplication will save more nitrogen than ifmanure is applied when temperatures are higher.

USE OF COVER CROPSThe use of cover crops becomes a very

important consideration in the application ofmanure in terms of the uptake of nutrients,reduced runoff and increased infiltration and,in general, a reduction in soil erosion. Covercrops are essential to conserve nitrogen fromfall-applied manure. The cover crop should beestablished using no till equipment, by airplaneor helicopter, or by lightly incorporating duringthe process of manure handling as describedearlier in this section.

EQUIPMENT BEING STUDIEDResearch is currently underway to

evaluate the use of minimal disturbanceequipment such as rotary harrows, spiked rollers,and manure injectors to improve infiltration ofliquid manure and to mix solid, semi solid orslurry manure with the upper several inchesof the soil or place the manure under the soilsurface. In all these instances, the key is to causeminimal impacts to the integrity of the soil ina no till system, which includes using noadditional tillage equipment and retaining ahigh percentage of the surface residue whichexists prior to the application of manure.

CONCLUSION

In a no-till systems

approach, a producer aims

to keep soil covered with

crop residue, reduce soil

disturbance to zero, and

maximize the number of

days with living roots in the

soil. This system can lead

to dramatically reduced

erosion, increased soil quality,

and improved water quality

when compared with

conventional tillage. It can

help agricultural producers

improve the efficiency

and profitability of their

operation and to improve

their environmental

stewardship. Society will

benefit from the improved

water and air quality that

result from increased use

of no-till systems.

BETTER SOILS WITH THE NO-TILL SYSTEM

CONTENTS

INTRODUCTION .............................................................................2

Soil is Important ..........................................................................2

Soil is at Risk ................................................................................3

Tillage, Major Cause of Erosion .................................................3

THE USE OF CONSERVATION TILLAGE IN THE U.S. ..............4

SOIL EROSION ................................................................................6

When to be Ready........................................................................6

Types of Erosion ...........................................................................7

Does It Really Work? ...................................................................8

SOIL QUALITY ................................................................................9

Tillage Effects ...............................................................................9

Where You Live Matters ............................................................10

Cover Crops Are Important ......................................................10

Soil Structure Improvement .....................................................11

Checking Your Soil Conditions.................................................12

WATER IN THE SOIL ...................................................................13

The Role of Earthworms............................................................13

Contradictory Results ................................................................14

Pesticide Effects on Water Quality...........................................17

SOIL COMPACTION .....................................................................17

Compaction is Different in No-Till ..........................................18

Minimizing and Alleviating Compaction in No-Till .............19

MANURE IN NO-TILL ..................................................................19

Pros and Cons of Manure in No-Till ........................................19

Use of Cover Crops .....................................................................20

Equipment Being Studied .........................................................20

CONCLUSION ................................................................................20

19

reduce porosity and infiltration in no-till soils.In a controlled traffic study in long-term no-till,infiltration was significantly reduced in wheeltracks compared to non-wheel tracks. In thenon-trafficked area, the first inch of water took2 min 15 sec to infiltrate and the second inchtook 31 minutes. In a wheel track, the first inchtook 7 minutes, whereas the second inch tookmore than 3 hours. This illustrates that soilcompaction can significantly compromise soilquality in long-term no-till.

MINIMIZING AND ALLEVIATINGCOMPACTION IN NO-TILL

Farmers have some options to manage soilcompaction in no-till. The very first principle isthat soil compaction does not pose a significantthreat if a farmer limits his traffic to dry soilconditions. It is only because field operationscannot always be tailored to soil moistureconditions that soil compaction becomes athreat. To limit soil compaction a farmer shouldlimit his axle load to 10 tons (preferably6 tons), and use flotation tires or tracksinstead of road tires.

Another, even better solution is to use trafficlanes. By keeping all wheel traffic limited topermanent tracks, the areas between tracks willnever be affected. If wide wheel spacing can be

used, a limited area of the field will be impactedby traffic. The disadvantage of such anapproach is that all heavy equipment has tobe re-engineered to be on the same wheelspacing.

Research into using cover crops to alleviatesoil compaction has not resulted in widelyaccepted solutions, although there areindications that cover crops with vigorous rootsystems or tap roots help loosen compacted soil.

A compromise of the no-till system may beto use vertical, in-row tillage techniques. Thereare different equipment options to alleviate soilcompaction without disturbing surface residuecover. These ‘vertical tillage tools’ are consistentwith the no-till system because they maintainsurface residue cover. This method combinesthe benefits of mulch cover between rowswith the compaction alleviation of tillageequipment in the row.

MANURE IN NO-TILLPROS AND CONS OF MANUREIN NO-TILL

Many successful long-term no-tillers use surface-applied poultry and animal manure.Surface-applied manure serves:

1. as food for soil microbes, earthwormsand night crawlers.

2. to enhance supplement surface residue,especially when solid manure and/orbedded pack manure is used.

3. as a source for soil organic matter.4. to reduce the transition period for those

just beginning no-till systems.It should also be noted that surface

application of manure reduces equipment costsfor manure incorporation and saves time.

A disadvantage of the surface applicationof manure is the nitrogen loss due to ammoniavolatilization that is likely to be higher com-pared to immediate incorporation into the soil. FIGURE 22. Manure injection limits ammonia losses and odor

from liquid manure in no-till.

2

SOIL IS IMPORTANT

Soil is Important forCrops and Life

Most people do notrecognize the important rolesoil plays in our lives. Soil is avery thin mantle or layerbetween rock or unconsolidatedmaterial in the atmosphere.Because it is such a thin layer,soil is also very fragile and canbe easily damaged or evendestroyed.

Soil thrives with life … if allis well. It provides many criticalecosystem functions that are necessary for lifeon Planet Earth. A productive agriculture

depends on healthy soil. Thesoil guarantees that nutrientsare made available in sufficientamounts during a plant’s lifecycle. Soil holds water andmakes it available to plantsso they don’t wilt during dryweather. Water is filtered as itpercolates or moves throughsoil. The soil releases waterslowly to the surface andsubsurface water systems andthus acts as an importantflow regulator.

Soil is nature’s recyclingsystem, where waste products

and dead bodies of organisms are decomposedand their components made available for re-use. Soil is the habitat of a myriad of living

FIGURE 1. The top 1-2" of the soildetermines many soil quality

properties that impact production and the environment.

FIGURE 2. Soil erosion, the number one cause of soil degradation.

INTRODUCTION

18

COMPACTION IS DIFFERENTIN NO-TILL

Compaction is caused by the movement ortraffic of vehicles, livestock or humans over thesurface of the soil. There are a few factors thatchange the effects of traffic in no-till fieldscompared to tilled fields. Over time, organicmatter content in the surface soil increases withno-till. Soils with high organic matter contentcannot be compressed as easily as those withlow organic matter content. This means thatcompaction in the top 2 inches is not of greatconcern in long-term no-till. In addition, a firmno-till soil matrix with macropores for air andwater movement can better support trafficwithout being compressed than a soft, tilled soil.

The higher biological activity in no-till soilsalso helps alleviate the effects of compaction.However, the soil under crop residue often stays

wet longer than in clean tilled conditions. Thismakes it more likely the farmer will be in thefield when soil conditions are really too wet fortraffic in no-till.

In addition, no quick alleviation of com-paction with tillage equipment takes place inno-till. Overall, research is suggesting that soilcompaction can be a significant threat inno-till systems. In one study, extreme soilcompaction of the complete soil surface to adepth of 12 inches reduced crop yields 98%compared to non-compacted long-term no-tillfields. It was interesting that the following year,the yield in the compacted fields increased to85% of that in the non-compacted plots. Therecovery from soil compaction (without tillage)was attributed to high biological activity.

In another study, soil compaction due toheavy axle loads caused a 15-30% reductionin yield in a long-term no-till field. Soilcompaction can increase soil density, and

FIGURE 21. Care has to be taken not to compact the soil in no-till. This can be achieved by avoiding traffic at suboptimalsoil moisture conditions, using low tire pressure or tracks, and reducing axle load at least below 10 tons. Improving soilorganic matter contents and stimulating soil biological activity make soil more resilient to compaction.

3

organisms. Because soil is so important, we, ashuman beings, need to insure that we are goodstewards of this valuable resource.

SOIL IS AT RISK

While soil is a resource that can re-createitself, it is a very slow process. Unfortunately,our nation’s soils have been and continue to bedegraded at an alarming rate. Soil erosion isstill the number one cause of soil degradation.Other causes of soil degradation include: soilcompaction, soil acidification, soil pollution,and salinization. Dramatic increases in the useof no-till systems by American farmers have ledto many benefits, including reductions inerosion, and savings of time, labor, fuel, andmachinery. Between 1990 and 2000, no-tillfarming acreage rose from 16 million acres to52 million acres, an increase of 300 percent.Now that some fields have been under no-tillproduction systems for many years, farmers andresearchers have begun to notice additional

benefits including changes in soil physical,chemical, and biological properties. The mostnotable of these benefits include increases inorganic matter and improved water infiltration.Improved water infiltration can lead to moreefficient use of rainfall, increasing yields whenrainfall is in short supply.

Although conservation practices havebrought about improvement, the average soilerosion rate on U.S. cropland is still 3.1 tons/acre

(Table 1). The erosion rate is often greater thanthe soil formation rate. As an example, theaverage soil erosion rate in Pennsylvania was5.1 tons/acre in 1997, whereas the tolerablesoil loss level is 3-4 tons /acre per year for mostof the soils of this state. With the average loss of5.1 tons/acre, you can see that the tolerable soilloss level was far exceeded on many fields. Thatmeans that our current rate of erosion is a threatto the future productivity of the soil.

Soil erosion removes the best portion of thesoil—the part that contains most of the plantnutrients and soil organic matter. In manycases, the topsoil has more favorable soil texturefor crop growth than the subsoil. When thetopsoil is gone, the farmer is left with lessproductive subsoil. In addition, eroded soilbecomes an environmental threat; pollutingstreams, lakes, and estuaries. In Pennsylvania,sediment is still the number one pollutant ofstreams and other bodies of water.

TILLAGE, MAJOR CAUSEOF EROSION

The process of planting, growing andharvesting brings about a certain amount ofexpected erosion that is considered acceptable tobring a crop to the table. The tolerable soil losslevel is called “T” by soil conservationists. Themajor soil management practice that causes soilerosion is tillage, the process of preparing a fieldfor seeding. Erosion due to tillage can be keptin check through methods such as contourfarming, contour stripcropping, conservationbuffers, grassed waterways, terraces anddiversions to meet soil loss tolerance levels.

You will find that soil can still move withina field––for example, in a strip cropping systemwhere sediment from unprotected soil is trappedby a down-slope strip with high residue orpermanent cover. In fact, average soil loss onthis entire field or system may be at, or below T,where it exceeds T on the tilled strips. But,if soil can be kept covered, erosion can be

1982 4.4 0.7 - 1.1

1987 4.0 0.7 2.0 1.0

1992 3.5 0.6 0.6 1.0

1997 3.1 0.7 0.4 0.9

Cultivatedcropland

Uncultivatedcropland

CRPland

Pastureland

SOIL LOSS (TONS PER ACRE)

USDA National Resources Inventory, 1997

TABLE 1. Soil loss by erosion in the U.S.

17

decomposition, leave large vertical channelsthat help improve infiltration.

The benefits of starting no-till in a sod wereillustrated in one study. Corn was establishedinto sod with and without tillage. Water runoffoccurred on the tilled plots when less than1.5 inches of water was applied while no runoffoccurred on the no-till plots even when5.3 inches of water was applied. In anotherstudy in Kentucky, runoff was reduced 83%when planting no-till into a bluegrass sod ascompared to conventional tillage, despite thefact that 5.2 inches of rain fell after tillagewhen infiltration is highest.

PESTICIDE EFFECTS ONWATER QUALITY

Reduced runoff with long-term, continuousno-till has many environmental advantages.However, some may comment that no-till islikely to pollute the natural environment dueto a heavy reliance on chemical pesticides anda fear that those pesticides will end up in oursurface and groundwater.

A decade ago, a review of the impact ofconservation tillage (no-till, ridge till or mulchtill) on pesticide runoff into surface waterappeared in the Journal of Soil and WaterConservation. In the article, it was firstconcluded that total pesticide use inconservation tillage has not appreciablyincreased when compared with conventionaltillage. Many people forget that even withconventional tillage, most farmers useherbicides for weed control and someinsecticides and fungicides for insect and diseasecontrol. With the use of crop rotation, pesticideuse in conventional tillage as well as no-till canbe significantly reduced. Crop rotation is anessential component of sustainable no-tillsystems.

In no-till systems, a farmer will have to usea burndown herbicide application to eradicateany weeds or cover crops that are present atplanting. After that, there is no need fordifferent amounts of herbicide applied in

no-tillage versus conventional tillage, althoughthe types of herbicides may be different.Common burndown herbicides such asparaquat and glyphosate bind very tightlyto soil particles and are mainly lost fromfields associated with sediment.

Because erosion is dramatically reducedin no-till, and these herbicides are very quickly broken down by soil organisms into harmlesscompounds, the threat of surface watercontamination is very small. What is moreimportant, however, is that runoff is significantlyreduced in no-till compared to conventionaltillage. Because of this, the likelihood of thepesticides ending up in surface water is small(even those that do not bind to soil particlesand are easily dissolved in runoff).

In a review of a large number of naturalrainfall studies, the average herbicide loss inrunoff from no-till and chisel plowed fields was30% of that in moldboard plowed fields. Thegreatest threat of surface-applied herbicidesleaving the field in runoff was if heavy rainfalloccurred very soon after herbicide application.It should be noted that sometimes theconcentration of herbicide in runoff was higherin no-till than conventional tillage, but becausethe total volume of runoff was small, total losseswere significantly less with no-till. In summary,it is justified to expect lower pesticide lossesfrom no-till fields than from conventionallytilled fields because of smaller runoff andreduced erosion rates.

SOIL COMPACTIONSome say soil compaction in no-till is less;

some say it is more than with tillage. What tobelieve? It is first of all important to note thatmost soil compaction research has been donewith conventional tillage, not with no-till.We know far less about soil compaction in no-tillthan in tillage systems. With increased adoptionof no-till, however, more research is beinginitiated.

stopped before itstarts and T can bemet on the entirefield every year.

The way todramatically reducesoil erosion is theno-till systemsapproach. Thismethod keeps thesoil covered withcrop residue,reduces soildisturbance toalmost zero, andattempts to maxi-mize the number ofdays in the yearwhen living rootsgrow in the soil.

Farmers andresearchers have demonstrated that there aremany other benefits to the no-till system besidessoil savings. For example, a farmer can savesignificant amounts of time not working the fieldsprior to planting. That can result in more timelyplanting as well as increased acreage that can bemanaged with the same equipment and laborforce. The efficiency of field operations will alsoincrease because the farmer can often meet soilconservation requirements in a no-till systemwithout adding as many conservation practices.Finally, the costs of producing a crop aredecreased by excluding tillage machineryexpenses.

Soil will improve over time in a no-tillsystem through increased organic matter. Soilstructure and water infiltration will improvein a no-till system through the slow, butcontinuous decomposition of crop residue androots and the high activity of living organismscreating a permanent macro-pore system in thesoil. Due to this high biological activity inno-till, soil compaction can be minimized.Finally, there are other environmental benefitsof a no-till system that extend beyond the

farm––cleaner air and streams and increasedgroundwater recharge.

THE USE OF CONSERVATIONTILLAGE IN THE U.S.

In the 1970s, many researchers believed thatby the year 2000, most cropland in the UnitedStates would be farmed without tillage. That prediction has not come true, although there

• Erosion control• Higher infiltration• Lower evaporation• Organic matter conservation• Improved soil structure• Higher biological activity• More earthworms• Reduced total phosphorus losses• Lower labor needs per acre• Higher efficiency of farm operations

FIGURE 4. Ten Benefits of a No-Till Systems Approach

FIGURE 3. Soil tillage is the major cause of soil erosion.

4

16

B 56% Corn, soybean,cotton, rye, tobacco

5 IA, KY, MO, MD, NC, AL

67% Corn, soybean,sorghum, cotton, tobacco, rye

6 OH, MS, NC

101% Corn, soybean, 4 MO, MS, MD

C

D

HYDROLOGICSOIL GROUP

AVERAGE WATER RUNOFFIN NO-TILL AS % OFCONVENTIONAL TILL

CROPS STATESAVERAGE #YEARS IN NO-TILL

TABLE 4. Summary of natural rainfall studies comparing water runoff with continuous no-till to conventional tillage (usually moldboard plow).

their activity. Soil hydrologic categorization isone way of grouping soils with respect totheir potential to result in reduced runoffwith no-till. Hydrologic groups are mostlydetermined by soil texture and restrictive layersin the soil that slow water movement in thesoil (Table 3).

Table 4 is a summary of runoff measured invarious studies with natural rainfall. The studieshave been grouped according to hydrologic soilgroup and the average number of years inno-till as indicated. The salient result of thesestudies is that runoff was dramatically reducedin continuous no-till fields on Group B and Cbut not on Group D soils. It must be concludedthat the runoff-reducing benefits of no-tillwill be greatest on coarse to medium texturedsoils that do not have an impeding layer orwater table near the surface.

Even on soils that have a moderate to finetexture or an impeding layer, no-till can stilloffer substantial runoff reduction as long asthey are not too heavy and the impeding layeris not too close to the soil surface. Soils that arefine-textured have heavy swell/shrink clay or arestricted layer near the surface are not likely toshow reduced runoff with no-till. It is interestingto note that the coarse to moderately texturedsoils also respond favorably to no-till cropproduction.

Clay soils are the most challenging forno-till. No-till crop yields are customarily higher

or equal to those achieved with conventionaltillage on Group A, B and C soils, but are oftenreduced on Group D soils. It may be necessaryto make modifications to no-till equipment toimprove crop yields and infiltration on Group Dsoils. Examples are in-row tillage techniquessuch as strip or zone-tillage that leave fullresidue cover between rows. Artificial drainagewill also help to make these soils more suitablefor no-till crop production. Crop rotationalso becomes more important on these morechallenging no-till soils.

When a farmer changes from plowing tono-tillage, the soil (and the farmer!) needs toadapt to the new management system. Organicmatter content slowly increases and biologicalactivity creates a new soil macro-pore system.This period may be associated with reducedyields in no-till until a new ecological equilibriumis achieved in the soil. There are some ways toget around this transition period.

If no-till annual crop production can bestarted immediately following a perennial grassor legume crop, the transition period can bereduced or eliminated. The perennial crop givessoil organisms the chance to develop amacro-pore system and improve soil tilthwithout tillage and with residue cover. Theextensive root systems and high root turnoverof grasses will stimulate porosity andaggregate stability. Taproots of some perenniallegumes such as alfalfa will, upon death and

5

has been a steady increasein the acreage of no-till (Figure 5). TheConservation TechnologyInformation Centersummarizes data collectedby USDA-NRCS,Conservation Districts andCooperative Extension.

Two broad categoriesof tillage systems arerecognized: conservationtillage, which includes alltillage systems that leavemore than 30% cropresidue cover after planting;and conventional tillage,which leaves less than 30%crop residue cover afterplanting. A 30% residuecover limit has been setbecause significant soilerosion reduction isachieved only whenmore than this amountis present (Figure 6).

Conservation tillageincludes no-till, mulch-till,and ridge-till. No-till isdefined for the survey as

Intensive till

Reduced tillNo tillMulch till

Ridge till

1990 1992 1994 1996 1998 2000 2002 2004 2006

Tillage Systems in the U. S.160-

140-

120-

100-

80-

60-

40-

20-

0-

10 20 30 40 50 60 70 80 90 100

100-

90-

80-

70-

60-

50-

40-

30-

20-

10-

0-

So

il l

oss

(%

)

Soil cover (%)

FIGURE 7. No-till leaves crop residue at the soil surface and reduces soil erosion dramatically.

FIGURE 6. Residue cover – relative soil loss relationship.With 30% residue cover, soil loss is reduced 70%.

FIGURE 5. No-till is used on a growing amount of acreage in the U.S.

high. Little time is available for surfaceroughness to disappear as happens ina field situation. In the field, runoff usually increases with

time in tilled fields and decreases withtime in no-till fields. Anotherpeculiarity of these simulationstudies is that the fields may notbe in no-till for a long period oftime. There has not been timefor the macro-pore system todevelop, or for surface soil tilthto improve. It is more realistic,therefore, to determine the effectsof continuous no-till on infiltra-tion in long-term field studiessubject to natural rainfall whererunoff is measured continuously.

Even if the infiltration ofnatural rainfall is measuredover the full growing season incontinuous no-till, there may beno measured improvement ofinfiltration. Two factors may helpto explain the disparity: soil typeand time in no-till. If soils haverestrictive subsurface layers or arepoorly drained, increased cropresidue and organic matter at the

FIGURE 20.This table top

rainfall simulator shows the dramatic

differences in quantityand quality of runoffassociated with high

residue farming versus clean tillage. All trays

received the sameamount of simulated

rainfall.

A Soils having high infiltration rates, even when thoroughlywetted and consisting chiefly of deep, well to excessively-drained sands or gravels. These soils have a high rate ofwater transmission.

B Soils having moderate infiltration rates when thoroughlywetted and consisting chiefly of moderately deep to deep,moderately fine to moderately coarse textures. These soilshave a moderate rate of water transmission.

C Soils having slow infiltration rates when thoroughly wettedand consisting chiefly of soils with a layer that impedesdownward movement of water, or soils with moderatelyfine to fine texture. These soils have a slow rate ofwater transmission.

D Soils having very slow infiltration rates when thoroughlywetted and consisting chiefly of clay soils with a highswelling potential, soils with a permanent high water table,soils with a claypan or clay layer at or near the surface,and shallow soils over nearly impervious material.These soils have a very slow rate of water transmission.

SOIL GROUP

SOIL GROUP CHARACTERISTICS

TABLE 3. Hydrologic soil group characteristics.

surface cannot overcome a profile that isalready full of water or has a restricted ability totransmit water to lower layers. These soils arenot a good habitat for nightcrawlers and otherearthworms, and will not benefit as much from

15

conservation tillage acreage where no tillage isdone from harvest to planting. It may includevery limited in-season tillage for weed control.No-till includes in-row tillage systems such aszone- and strip-till that disturb less than 30% ofthe soil surface. In 2002, almost 20% of plantedacres in the U.S. were no-tilled. Mulch-tillincludes all other tillage systems which leavemore than 30% crop residue cover on the soilsurface at planting. It was practiced on 16% ofplanted acres in 2002. Ridge-till was practicedon 1%. This brings the total percentage of con-servation tillage to 36%. Reduced tillage leaves15-30% residue after planting and was practicedon 23% of planted acres, while intensive tillage(

7

enough to have erosionprotection 95% of the timebecause the rainstorm thatcauses massive erosion mightjust occur in that 5% timewindow that the soil isnot protected.

TYPES OF EROSIONThere are four different

kinds of erosion: sheet, rill,gully and streambankerosion. Only the first three occur on farmland.Sheet erosion is the washing of a uniform sheetof soil from the soil surface. Rill erosion occurswhen small parallel rivulets start to form in thefield. When these rivulets begin to concentrate,they form gullies. Most soil is lost due to sheetand rill erosion, although these are the leastvisible forms of soil erosion.

Sheet erosion represents the beginning ofthe erosion process. Ifsheet erosion can bestopped, the soil erosionproblem is ‘nipped inthe bud.’ Sheet erosionis primarily caused bythe effect of raindropshitting the soil surface.If soil is protectedagainst raindropimpact by crop residue,little sheet erosion takesplace. Therefore, thekey to erosion controlis to keep the soilcovered.

It is important toremember that not all rain-storms are equally erosive.Gentle, drizzling rains causevery little erosion in contrastto heavy rainstorms.Raindrops from gentle stormsare smaller and fall moreslowly than raindrops fromheavy storms. The energy ofthe raindrops is a function oftheir velocity and their mass,in other words, their speed

and size. The kinetic energy of large raindrops ismuch greater that that of small drops. Whenthose large drops hit the soil surface, they actas small bombs that dislodge soil particles fromthe soil matrix. Convective rainstorms (heavythunderstorms) are frequent in spring orsummer in the U.S. These storms are themost erosive so soil cover is especiallyimportant during these periods of the year.

FIGURE 9. The impact of large raindropsis the major cause of sheet erosion.

Figure 10. The purpose of

conservation tillage is to keep crop residue

at the soil surface.

14

nightcrawlers. These earthworms need surfaceresidue that they pull to the mouth of theirburrow. If a soil is devoid of crop residue,nightcrawlers will be scarce or absent.

There are other earthworms that live in thesurface of the soil. These earthworms are not assensitive to tillage. They fill their burrows withcasts as they go. These earthworms also have apositive influence on soil structure, which helpsinfiltration. In a study in Indiana, the numberof earthworms (nightcrawlers and other speciescombined) was twice as high in continuous

no-till fields as in moldboard plowed fields. InMissouri, up to 8 times more earthworms werecounted in continuous no-till corn than inmoldboard plowed corn.

CONTRADICTORY RESULTSIn some cases, tillage temporarily increases

infiltration compared to no-till. Severalexplanations can be offered.• Shortly after tillage, infiltration can be high

because of increased surface roughness andhigh porosity. This increase is usually shortlived. After heavy rainstorms hit the soil,surface clods start to break down, roughnessdecreases, and because of sealing andcrusting, infiltration decreases. Despite thefact that total porosity may be lower incontinuous no-till, infiltration may still behigher because of pore continuity, soilprotection against the action of raindrops,better surface tilth, and surface residue thatobstructs runoff. However, if a farmer causescompaction in no-till, infiltration can benegatively affected. Judicious use of “verticaltillage” may be justified in these conditions.Vertical tillage disturbs below the soil surfacewithout a reduction of surface residue cover.The use of vertical tillage is recommended tomaintain the benefits of maximum residuecover.

• Another reason infiltration is not alwayshigher in no-till versus full tillage may bedue to the methodology used in someresearch studies. In one review of 45 differentstudies, runoff with no-till was on averagereduced only 14% compared with conven-tional tillage. In some studies, runoff wasgreatly reduced due to no-till, but in otherstudies, there was no reduction or evenincreased runoff with no-till. Many of thesestudies were rainfall simulation studies. Inthese studies, it is typical to prepare a site(preferably without a growing crop) andsimulate a very heavy rainfall event for halfan hour to an hour. The methodology oftendictates that the rainfall is applied shortlyafter tillage when infiltration may still be

FIGURE 19. Nightcrawlers live in vertical burrows thatcan extend 4-6 feet deep. Water can quickly infiltratethrough these burrows. Nightcrawler excrementsare called casts. Deposited at the soil surface, castscontain high contents of organic matter andnutrients. They form stable aggregates when dry.

the effect of tillage sys-tems on organic mattercontents.

The bulk density ofno-till soil is sometimesgreater than that ofconventionally tilledsoil. In those cases,differences in organicmatter contentbetween the two sys-tems are greater on aper-acre basis than ona weight basis. Muchdepends on the time of the sampling and theamount of time a soil has been in no-till.Shortly after tillage, a tilled soil is usually fluffyand has a lower bulk density than its no-tillcounterpart. However, at the end of the season,the difference in bulk density may be negligiblebecause the tilled soil has settled. Increasedorganic matter contents in no-till may furtherreduce bulk density.

WATER IN THE SOILMany long-term no-till farmers have

noted improvements in water infiltration orabsorption in their fields. There are times during

the same storm when no runoff occurs in no-tillfields while adjacent tilled fields produce largeamounts of water and sediment runoff. Similarobservations have been made by researchers.At the North Appalachian ExperimentalWatershed, runoff from the no-till watershedwas only a fraction of that of the moldboardplowed watershed (Table 2). Here we see thepower of residue cover illustrated again. Bybreaking the impact of falling raindrops, soilsealing and crusting is reduced dramatically.Improved surface tilth also stimulatesinfiltration. The channels created by soilorganisms such as worms, soil insects and thedecomposed plant roots that are found in the

continuous no-till system increase waterinfiltration. The residues on the soil surfaceact as small barriers, slowing runoff and giv-ing water a greater opportunity to infiltrate.

THE ROLE OF EARTHWORMS Burrows of earthworms and soil insects

have been discovered to be important inimproving water infiltration. One earth-worm species are nightcrawlers (Lumbricusterrestris L). They are surface feeders andconstruct vertical burrows. In one study, upto 10.3% of simulated rainfall infiltratedthrough these burrows although they onlyoccupied 0.3% of the horizontal area ofthe no-till field. Tillage not only destroysthe tops of the burrows, but moreimportantly destroys the habitat of the

1979 44 0.14 5.52 8 4361980 46 0.19 12.47 15 84551981 42 0.00 5.60 1 76451982 35 0.00 4.46 0 2461

Average 0.09 7.01 6 4748

NO-TILL MOLDBOARD NO-TILL MOLDBOARD

TABLE 2. A 4-year comparison of runoff and erosion on a no-till and moldboardplowed watershed at the North Appalachian Experimental Watershed.

13

FIGURE 18. Soil organic matter is conserved by using no-till,which results in better soil structure.

8

Once soil is dislodged from its matrix, it canbe easily carried away. With shallow runoff,raindrops act as stirring rods that keep theeroded soil in suspension. This makes it possiblefor a shallow flow to transport soil that wouldnormally settle out. More runoff occurs on baresoils than covered soils because small, dislodgedsoil particles settle out and form a seal thatsubsequently dries to become a crust. Infiltrationor absorption decreases rapidly once a sealor crust is formed.

If the velocity and size of the raindrops canbe reduced, sheet erosion will be minimal. Thiswas most vividly illustrated in an experimentwith two types of plots—both were cultivatedand bare, but one had mosquito gauze placedabove it to break up the rain drops and reducetheir velocity. When a heavy rain storm hit thetwo plots, the erosion on the plot with the gauzewas 1/100 of the other plot. Again, keepingsoil covered is the secret of soil conservation.

The purpose of a no-till system is to keepsoil covered.

DOES IT REALLY WORK?How do these principles work in practice?

At the North Appalachian ExperimentalWatershed, one watershed (9% slope) was inlong-term no-till corn, where another watershed(6% slope) was moldboard plowed every yearprior to corn planting. Because only the grainwas harvested and all crop residue was left inthe field, virtually 100% of the soil of the no-tillwatershed was covered all the time.

The most critical period for soil protectionin the Northeastern United States is from April-July when most rain falls in high-intensity thun-derstorms. When crops are planted using tillage,residue levels are low and therefore susceptibleto erosion, as compared to no-till planted cropswhere residues are present to protect the soil.

FIGURE 11. Chisel plowing is between moldboard plowing and no-till. It does less soil inversion and leaves more residue cover than the moldboard.

YEAR RUNOFF (inches)

RAINFALL (inches)

EROSIONLbs / A

12

crops. Finally, the increased organic matter inno-till helps improve soil structure. Stableaggregates in no-till soil resist the sealing ofsoil surfaces which can cause crusting andwater runoff.

Increased aggregation in no-till helps toincrease water infiltration and the resistanceof the soil to erosion. (Infiltration is themovement of water into and through the soil,feeding plant roots and working its way intogroundwater systems.) Additionally, theaggregates enhance conditions for adesirable mix of air and water for goodplant growth. They hold more water inplace for crops to use.

CHECKING YOUR SOILCONDITIONS

If you are interested in changes in totalorganic matter contents, it is important tosample to the same depth over a period oftime. Follow state recommendations for

the appropriate depthfor soil fertilitysampling. If soil fertilityrecommendations inyour state are basedon a sampling depth of6 inches, it is importantto use that samplingdepth. With theincreased popularity ofcontinuous no-till,future recommendationsmay be based onshallower samplingdepths. It is importantto use the same methodof determination totrack changes in organ-ic matter over a periodof time. Methods varyso check which methodis used by your lab andstick with that methodto track change.

Soil organic matter content as determined bya lab is on a weight basis (For example, per centor grams of organic matter per kilogram of soil).It may be more appropriate to compare soilorganic matter content on a per acre basis. Tocalculate soil organic matter content per acre,you need to know the bulk density of the soilor the weight of soil per unit volume. Bulk den-sity is usually expressed as metric tons per cubicmeter. This becomes important when determining

FIGURE 17. Residue is food for fungi and bacteria. The fungalhyphae and fine roots surround and stabilize soil aggregates.These aggregates don’t easily fall apart with the action of rainor wind.

FIGURE 16. Soil organic matter will be concentrated near the surface of no-till soilwhere it is distributed throughout the plowed layer in moldboard plowed soil.

9

During a 4-year period, the annualerosion rate from the no-till watershed wasonly 6 lbs/A, while it was 4750 lbs/A from theconventionally-tilled watershed. The erosionfrom the conventionally tilled watershed wasalmost 700 times greater than that from theno-till watershed! This shows the power ofmaximum-residue no-till.

In a follow-up study, chisel-plowing wascompared with no-till in a corn-soybeanrotation. Annual soil loss in the chisel plowedwatersheds was a small–1100 lbs/A; but it wastwice as much as that in the no-till watershed(500 lbs/A). Chisel plowing is an intermediatepractice for soil erosion control betweenmoldboard plowing and no-till, primarilybecause soil cover is considerably reducedwith chisel plowing.

SOIL QUALITYTILLAGE EFFECTS

The most important factor in determiningsoil quality is soil organic matter. The organicmatter consists of living organisms, freshorganic residue, decomposing organic matter,and stabilized organic matter (Figure 12).Carbon makes up about 60% oftotal soil organic matter content.When the soil is opened up bytillage, large amounts of carbondioxide are released in a matterof days (Figure 13). This resultsin reduced organic mattercontents and explains why it isvery difficult to build up organicmatter contents with tillage.

Inversion tillage with themoldboard plow results in thegreatest carbon dioxide losses.The deeper the depth of inversiontillage and the greater the volumeof soil disturbed, the greater thelosses of carbon dioxide. Long-term cropping studies haveshown a steady decline in soilorganic matter with conventional

FIGURE 12. Different fractions of organic matterare: living organisms, fresh organic residue, andactive and stabilized organic matter. Tillage causesyoung organic matter to oxidize more quicklyleading to a decrease in organic matter content.

Stabilized organic matter

33-50%

LivingOrganism

10

In a Minnesota study, five times morecarbon was lost shortly after moldboardplowing than without tillage. The carbon lostin 19 days after plowing was more than whatwas present in the roots and straw of thepreceding wheat crop. In a review of 20long-term studies with moldboard plowing,the average loss of organic matter was 256lbs/acre/yr. These studies were conducted withcontinuous corn or wheat and rotations of cornwith soybeans and oats in Illinois, Oregon, andMissouri.

However, in 10 long-term no-till studiesconducted in Ohio, Alabama, Georgia, Kentucky,Illinois, Minnesota and Nebraska, organic matterincreased an average 953 lbs/acre/yr. Thesestudies were with continuous corn or soybeans,and corn-soybean rotations. A summary ofresults with continuous corn or corn-soybeanrotations from 4 Midwestern states (Figure 14)shows that approximately 400 lbs/acre/yr werelost with moldboard plowing, 200 lbs/acre/yrwere gained with chisel plowing, and more than1000 lbs/acre/yr were gained with continuousno-till.

WHERE YOU LIVE MATTERS The potential for increases

in soil organic matter is greaterin the northern states than inthe southern states. This is dueto higher temperatures in thesouth, leading to the higherdecomposition of organicmatter which increases losses.In dry climates, the potentialfor organic matter build-up isalso smaller because the cropsgrown produce little residue.

The amount of residuevaries per crop. Corn andwheat, for example, returnmore residue to the soil thansoybeans. This means thepotential for increases in organ-ic matter is greater with cornand wheat than with soybeans.

In a long-term study, the soil organic matter content was greatest with corn-wheat rotations,smaller with corn-wheat-soybeans-wheat, andsmallest with soybeans-wheat.

COVER CROPS ARE IMPORTANTGrowing cover crops can increase organic

matter beyond what is possible by simplyleaving crop residue in the field. The potentialand need for cover crops to build organic matterin the soil is greatest in the southern parts of theUnited States. Because of higher temperatures,organic matter oxidation is greater in the South.However, cover crop options as well as covercrop biomass production are also greater.

Pioneer research from the southeasternUnited States is showing the benefits of havingactively growing crops in the field 365 days ayear. The increased losses of organic matterfrom heat can be compensated for by combin-ing cover crops and intensive cropping to pro-duce increased residue. In colder regions,options are reduced due to freezing tempera-tures during part of the year, but there is worktaking place to increase opportunities to maxi-mize the time that crops or cover crops grow inthe field.

FIGURE 14. Tillage system effects on soil organic matter changerecorded throughout long-term studies in 4 Midwestern States.

1200-

1000-

800-

600-

400-

200-

0-

-200-

-400-

-600-Rate

of

Org

an

ic M

att

er

Ch

an

ge (

lbs/

ac/

yr)

Chisel

Moldboard Plow

No-till

Tillage Effects on Continuous Corn and Corn /Soybean Rotations in 4 Midwestern States

11

Nitrogen fertilization to provide optimalplant growth can also increase the rate oforganic matter formation. The primary reasonfor this is the increased root and above-groundbiomass production.

Besides increasing total soil organic mattercontent, no-till results in a different distributionof organic matter (Figure 16). Most organicmatter is concentrated at the surface of the soilin no-till where it is mixed in the plow layerwith tillage. The residue protects the soil fromerosion, surface sealing and crusting. Theincreased surface organic matter content helpsimprove soil tilth and aggregate stability. Ina conventional tillage situation, the reversehappens and a lack of residue cover exposesthe soil to the elements. The result is sealing,crusting, and erosion. No-till has also been

found to affect the stability of organic matterpools. The residence time of organic matter inno-till can increase by 10-15 years overconventional tillage.

SOIL STRUCTURE IMPROVEMENTOver time, soil structure, also referred to

as “soil tilth,” will improve with no-till. Onereason for this is the increased presence offungal communities in no-till soils whencompared with tilled soils (Figure 17). Tilledsoils have more bacteria instead of fungi. Fungiform hair-like structures called “hyphae” whichact like a net holding small aggregates togetherin larger units. Another reason for increasedaggregation in no-till is the presence of old,partly decomposed roots from the previous

FIGURE 15. A cover crop can serve a multitude of functions, such as erosion protection, nitrogen fixation,additions of crop residue to build soil organic matter contents, and weed control.

10

In a Minnesota study, five times morecarbon was lost shortly after moldboardplowing than without tillage. The carbon lostin 19 days after plowing was more than whatwas present in the roots and straw of thepreceding wheat crop. In a review of 20long-term studies with moldboard plowing,the average loss of organic matter was 256lbs/acre/yr. These studies were conducted withcontinuous corn or wheat and rotations of cornwith soybeans and oats in Illinois, Oregon, andMissouri.

However, in 10 long-term no-till studiesconducted in Ohio, Alabama, Georgia, Kentucky,Illinois, Minnesota and Nebraska, organic matterincreased an average 953 lbs/acre/yr. Thesestudies were with continuous corn or soybeans,and corn-soybean rotations. A summary ofresults with continuous corn or corn-soybeanrotations from 4 Midwestern states (Figure 14)shows that approximately 400 lbs/acre/yr werelost with moldboard plowing, 200 lbs/acre/yrwere gained with chisel plowing, and more than1000 lbs/acre/yr were gained with continuousno-till.

WHERE YOU LIVE MATTERS The potential for increases

in soil organic matter is greaterin the northern states than inthe southern states. This is dueto higher temperatures in thesouth, leading to the higherdecomposition of organicmatter which increases losses.In dry climates, the potentialfor organic matter build-up isalso smaller because the cropsgrown produce little residue.

The amount of residuevaries per crop. Corn andwheat, for example, returnmore residue to the soil thansoybeans. This means thepotential for increases in organ-ic matter is greater with cornand wheat than with soybeans.

In a long-term study, the soil organic matter content was greatest with corn-wheat rotations,smaller with corn-wheat-soybeans-wheat, andsmallest with soybeans-wheat.

COVER CROPS ARE IMPORTANTGrowing cover crops can increase organic

matter beyond what is possible by simplyleaving crop residue in the field. The potentialand need for cover crops to build organic matterin the soil is greatest in the southern parts of theUnited States. Because of higher temperatures,organic matter oxidation is greater in the South.However, cover crop options as well as covercrop biomass production are also greater.

Pioneer research from the southeasternUnited States is showing the benefits of havingactively growing crops in the field 365 days ayear. The increased losses of organic matterfrom heat can be compensated for by combin-ing cover crops and intensive cropping to pro-duce increased residue. In colder regions,options are reduced due to freezing tempera-tures during part of the year, but there is worktaking place to increase opportunities to maxi-mize the time that crops or cover crops grow inthe field.

FIGURE 14. Tillage system effects on soil organic matter changerecorded throughout long-term studies in 4 Midwestern States.

1200-

1000-

800-

600-

400-

200-

0-

-200-

-400-

-600-Rate

of

Org

an

ic M

att

er

Ch

an

ge (

lbs/

ac/

yr)

Chisel

Moldboard Plow

No-till

Tillage Effects on Continuous Corn and Corn /Soybean Rotations in 4 Midwestern States

11

Nitrogen fertilization to provide optimalplant growth can also increase the rate oforganic matter formation. The primary reasonfor this is the increased root and above-groundbiomass production.

Besides increasing total soil organic mattercontent, no-till results in a different distributionof organic matter (Figure 16). Most organicmatter is concentrated at the surface of the soilin no-till where it is mixed in the plow layerwith tillage. The residue protects the soil fromerosion, surface sealing and crusting. Theincreased surface organic matter content helpsimprove soil tilth and aggregate stability. Ina conventional tillage situation, the reversehappens and a lack of residue cover exposesthe soil to the elements. The result is sealing,crusting, and erosion. No-till has also been

found to affect the stability of organic matterpools. The residence time of organic matter inno-till can increase by 10-15 years overconventional tillage.

SOIL STRUCTURE IMPROVEMENTOver time, soil structure, also referred to

as “soil tilth,” will improve with no-till. Onereason for this is the increased presence offungal communities in no-till soils whencompared with tilled soils (Figure 17). Tilledsoils have more bacteria instead of fungi. Fungiform hair-like structures called “hyphae” whichact like a net holding small aggregates togetherin larger units. Another reason for increasedaggregation in no-till is the presence of old,partly decomposed roots from the previous

FIGURE 15. A cover crop can serve a multitude of functions, such as erosion protection, nitrogen fixation,additions of crop residue to build soil organic matter contents, and weed control.

12

crops. Finally, the increased organic matter inno-till helps improve soil structure. Stableaggregates in no-till soil resist the sealing ofsoil surfaces which can cause crusting andwater runoff.

Increased aggregation in no-till helps toincrease water infiltration and the resistanceof the soil to erosion. (Infiltration is themovement of water into and through the soil,feeding plant roots and working its way intogroundwater systems.) Additionally, theaggregates enhance conditions for adesirable mix of air and water for goodplant growth. They hold more water inplace for crops to use.

CHECKING YOUR SOILCONDITIONS

If you are interested in changes in totalorganic matter contents, it is important tosample to the same depth over a period oftime. Follow state recommendations for

the appropriate depthfor soil fertilitysampling. If soil fertilityrecommendations inyour state are basedon a sampling depth of6 inches, it is importantto use that samplingdepth. With theincreased popularity ofcontinuous no-till,future recommendationsmay be based onshallower samplingdepths. It is importantto use the same methodof determination totrack changes in organ-ic matter over a periodof time. Methods varyso check which methodis used by your lab andstick with that methodto track change.

Soil organic matter content as determined bya lab is on a weight basis (For example, per centor grams of organic matter per kilogram of soil).It may be more appropriate to compare soilorganic matter content on a per acre basis. Tocalculate soil organic matter content per acre,you need to know the bulk density of the soilor the weight of soil per unit volume. Bulk den-sity is usually expressed as metric tons per cubicmeter. This becomes important when determining

FIGURE 17. Residue is food for fungi and bacteria. The fungalhyphae and fine roots surround and stabilize soil aggregates.These aggregates don’t easily fall apart with the action of rainor wind.

FIGURE 16. Soil organic matter will be concentrated near the surface of no-till soilwhere it is distributed throughout the plowed layer in moldboard plowed soil.

9

During a 4-year period, the annualerosion rate from the no-till watershed wasonly 6 lbs/A, while it was 4750 lbs/A from theconventionally-tilled watershed. The erosionfrom the conventionally tilled watershed wasalmost 700 times greater than that from theno-till watershed! This shows the power ofmaximum-residue no-till.

In a follow-up study, chisel-plowing wascompared with no-till in a corn-soybeanrotation. Annual soil loss in the chisel plowedwatersheds was a small–1100 lbs/A; but it wastwice as much as that in the no-till watershed(500 lbs/A). Chisel plowing is an intermediatepractice for soil erosion control betweenmoldboard plowing and no-till, primarilybecause soil cover is considerably reducedwith chisel plowing.

SOIL QUALITYTILLAGE EFFECTS

The most important factor in determiningsoil quality is soil organic matter. The organicmatter consists of living organisms, freshorganic residue, decomposing organic matter,and stabilized organic matter (Figure 12).Carbon makes up about 60% oftotal soil organic matter content.When the soil is opened up bytillage, large amounts of carbondioxide are released in a matterof days (Figure 13). This resultsin reduced organic mattercontents and explains why it isvery difficult to build up organicmatter contents with tillage.

Inversion tillage with themoldboard plow results in thegreatest carbon dioxide losses.The deeper the depth of inversiontillage and the greater the volumeof soil disturbed, the greater thelosses of carbon dioxide. Long-term cropping studies haveshown a steady decline in soilorganic matter with conventional

FIGURE 12. Different fractions of organic matterare: living organisms, fresh organic residue, andactive and stabilized organic matter. Tillage causesyoung organic matter to oxidize more quicklyleading to a decrease in organic matter content.

Stabilized organic matter

33-50%

LivingOrganism

the effect of tillage sys-tems on organic mattercontents.

The bulk density ofno-till soil is sometimesgreater than that ofconventionally tilledsoil. In those cases,differences in organicmatter contentbetween the two sys-tems are greater on aper-acre basis than ona weight basis. Muchdepends on the time of the sampling and theamount of time a soil has been in no-till.Shortly after tillage, a tilled soil is usually fluffyand has a lower bulk density than its no-tillcounterpart. However, at the end of the season,the difference in bulk density may be negligiblebecause the tilled soil has settled. Increasedorganic matter contents in no-till may furtherreduce bulk density.

WATER IN THE SOILMany long-term no-till farmers have

noted improvements in water infiltration orabsorption in their fields. There are times during

the same storm when no runoff occurs in no-tillfields while adjacent tilled fields produce largeamounts of water and sediment runoff. Similarobservations have been made by researchers.At the North Appalachian ExperimentalWatershed, runoff from the no-till watershedwas only a fraction of that of the moldboardplowed watershed (Table 2). Here we see thepower of residue cover illustrated again. Bybreaking the impact of falling raindrops, soilsealing and crusting is reduced dramatically.Improved surface tilth also stimulatesinfiltration. The channels created by soilorganisms such as worms, soil insects and thedecomposed plant roots that are found in the

continuous no-till system increase waterinfiltration. The residues on the soil surfaceact as small barriers, slowing runoff and giv-ing water a greater opportunity to infiltrate.

THE ROLE OF EARTHWORMS Burrows of earthworms and soil insects

have been discovered to be important inimproving water infiltration. One earth-worm species are nightcrawlers (Lumbricusterrestris L). They are surface feeders andconstruct vertical burrows. In one study, upto 10.3% of simulated rainfall infiltratedthrough these burrows although they onlyoccupied 0.3% of the horizontal area ofthe no-till field. Tillage not only destroysthe tops of the burrows, but moreimportantly destroys the habitat of the

1979 44 0.14 5.52 8 4361980 46 0.19 12.47 15 84551981 42 0.00 5.60 1 76451982 35 0.00 4.46 0 2461

Average 0.09 7.01 6 4748

NO-TILL MOLDBOARD NO-TILL MOLDBOARD

TABLE 2. A 4-year comparison of runoff and erosion on a no-till and moldboardplowed watershed at the North Appalachian Experimental Watershed.

13

FIGURE 18. Soil organic matter is conserved by using no-till,which results in better soil structure.

8

Once soil is dislodged from its matrix, it canbe easily carried away. With shallow runoff,raindrops act as stirring rods that keep theeroded soil in suspension. This makes it possiblefor a shallow flow to transport soil that wouldnormally settle out. More runoff occurs on baresoils than covered soils because small, dislodgedsoil particles settle out and form a seal thatsubsequently dries to become a crust. Infiltrationor absorption decreases rapidly once a sealor crust is formed.

If the velocity and size of the raindrops canbe reduced, sheet erosion will be minimal. Thiswas most vividly illustrated in an experimentwith two types of plots—both were cultivatedand bare, but one had mosquito gauze placedabove it to break up the rain drops and reducetheir velocity. When a heavy rain storm hit thetwo plots, the erosion on the plot with the gauzewas 1/100 of the other plot. Again, keepingsoil covered is the secret of soil conservation.

The purpose of a no-till system is to keepsoil covered.

DOES IT REALLY WORK?How do these principles work in practice?

At the North Appalachian ExperimentalWatershed, one watershed (9% slope) was inlong-term no-till corn, where another watershed(6% slope) was moldboard plowed every yearprior to corn planting. Because only the grainwas harvested and all crop residue was left inthe field, virtually 100% of the soil of the no-tillwatershed was covered all the time.

The most critical period for soil protectionin the Northeastern United States is from April-July when most rain falls in high-intensity thun-derstorms. When crops are planted using tillage,residue levels are low and therefore susceptibleto erosion, as compared to no-till planted cropswhere residues are present to protect the soil.

FIGURE 11. Chisel plowing is between moldboard plowing and no-till. It does less soil inversion and leaves more residue cover than the moldboard.

YEAR RUNOFF (inches)

RAINFALL (inches)

EROSIONLbs / A

7

enough to have erosionprotection 95% of the timebecause the rainstorm thatcauses massive erosion mightjust occur in that 5% timewindow that the soil isnot protected.

TYPES OF EROSIONThere are four different

kinds of erosion: sheet, rill,gully and streambankerosion. Only the first three occur on farmland.Sheet erosion is the washing of a uniform sheetof soil from the soil surface. Rill erosion occurswhen small parallel rivulets start to form in thefield. When these rivulets begin to concentrate,they form gullies. Most soil is lost due to sheetand rill erosion, although these are the leastvisible forms of soil erosion.

Sheet erosion represents the beginning ofthe erosion process. Ifsheet erosion can bestopped, the soil erosionproblem is ‘nipped inthe bud.’ Sheet erosionis primarily caused bythe effect of raindropshitting the soil surface.If soil is protectedagainst raindropimpact by crop residue,little sheet erosion takesplace. Therefore, thekey to erosion controlis to keep the soilcovered.

It is important toremember that not all rain-storms are equally erosive.Gentle, drizzling rains causevery little erosion in contrastto heavy rainstorms.Raindrops from gentle stormsare smaller and fall moreslowly than raindrops fromheavy storms. The energy ofthe raindrops is a function oftheir velocity and their mass,in other words, their speed

and size. The kinetic energy of large raindrops ismuch greater that that of small drops. Whenthose large drops hit the soil surface, they actas small bombs that dislodge soil particles fromthe soil matrix. Convective rainstorms (heavythunderstorms) are frequent in spring orsummer in the U.S. These storms are themost erosive so soil cover is especiallyimportant during these periods of the year.

FIGURE 9. The impact of large raindropsis the major cause of sheet erosion.

Figure 10. The purpose of

conservation tillage is to keep crop residue

at the soil surface.

14

nightcrawlers. These earthworms need surfaceresidue that they pull to the mouth of theirburrow. If a soil is devoid of crop residue,nightcrawlers will be scarce or absent.

There are other earthworms that live in thesurface of the soil. These earthworms are not assensitive to tillage. They fill their burrows withcasts as they go. These earthworms also have apositive influence on soil structure, which helpsinfiltration. In a study in Indiana, the numberof earthworms (nightcrawlers and other speciescombined) was twice as high in continuous

no-till fields as in moldboard plowed fields. InMissouri, up to 8 times more earthworms werecounted in continuous no-till corn than inmoldboard plowed corn.

CONTRADICTORY RESULTSIn some cases, tillage temporarily increases

infiltration compared to no-till. Severalexplanations can be offered.• Shortly after tillage, infiltration can be high

because of increased surface roughness andhigh porosity. This increase is usually shortlived. After heavy rainstorms hit the soil,surface clods start to break down, roughnessdecreases, and because of sealing andcrusting, infiltration decreases. Despite thefact that total porosity may be lower incontinuous no-till, infiltration may still behigher because of pore continuity, soilprotection against the action of raindrops,better surface tilth, and surface residue thatobstructs runoff. However, if a farmer causescompaction in no-till, infiltration can benegatively affected. Judicious use of “verticaltillage” may be justified in these conditions.Vertical tillage disturbs below the soil surfacewithout a reduction of surface residue cover.The use of vertical tillage is recommended tomaintain the benefits of maximum residuecover.

• Another reason infiltration is not alwayshigher in no-till versus full tillage may bedue to the methodology used in someresearch studies. In one review of 45 differentstudies, runoff with no-till was on averagereduced only 14% compared with conven-tional tillage. In some studies, runoff wasgreatly reduced due to no-till, but in otherstudies, there was no reduction or evenincreased runoff with no-till. Many of thesestudies were rainfall simulation studies. Inthese studies, it is typical to prepare a site(preferably without a growing crop) andsimulate a very heavy rainfall event for halfan hour to an hour. The methodology oftendictates that the rainfall is applied shortlyafter tillage when infiltration may still be

FIGURE 19. Nightcrawlers live in vertical burrows thatcan extend 4-6 feet deep. Water can quickly infiltratethrough these burrows. Nightcrawler excrementsare called casts. Deposited at the soil surface, castscontain high contents of organic matter andnutrients. They form stable aggregates when dry.

high. Little time is available for surfaceroughness to disappear as happens ina field situation. In the field, runoff usually increases with

time in tilled fields and decreases withtime in no-till fields. Anotherpeculiarity of these simulationstudies is that the fields may notbe in no-till for a long period oftime. There has not been timefor the macro-pore system todevelop, or for surface soil tilthto improve. It is more realistic,therefore, to determine the effectsof continuous no-till on infiltra-tion in long-term field studiessubject to natural rainfall whererunoff is measured continuously.

Even if the infiltration ofnatural rainfall is measuredover the full growing season incontinuous no-till, there may beno measured improvement ofinfiltration. Two factors may helpto explain the disparity: soil typeand time in no-till. If soils haverestrictive subsurface layers or arepoorly drained, increased cropresidue and organic matter at the

FIGURE 20.This table top

rainfall simulator shows the dramatic

differences in quantityand quality of runoffassociated with high

residue farming versus clean tillage. All trays

received the sameamount of simulated

rainfall.

A Soils having high infiltration rates, even when thoroughlywetted and consisting chiefly of deep, well to excessively-drained sands or gravels. These soils have a high rate ofwater transmission.

B Soils having moderate infiltration rates when thoroughlywetted and consisting chiefly of moderately deep to deep,moderately fine to moderately coarse textures. These soilshave a moderate rate of water transmission.

C Soils having slow infiltration rates when thoroughly wettedand consisting chiefly of soils with a layer that impedesdownward movement of water, or soils with moderatelyfine to fine texture. These soils have a slow rate ofwater transmission.

D Soils having very slow infiltration rates when thoroughlywetted and consisting chiefly of clay soils with a highswelling potential, soils with a permanent high water table,soils with a claypan or clay layer at or near the surface,and shallow soils over nearly impervious material.These soils have a very slow rate of water transmission.

SOIL GROUP

SOIL GROUP CHARACTERISTICS

TABLE 3. Hydrologic soil group characteristics.

surface cannot overcome a profile that isalready full of water or has a restricted ability totransmit water to lower layers. These soils arenot a good habitat for nightcrawlers and otherearthworms, and will not benefit as much from

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conservation tillage acreage where no tillage isdone from harvest to planting. It may includevery limited in-season tillage for weed control.No-till includes in-row tillage systems such aszone- and strip-till that disturb less than 30% ofthe soil surface. In 2002, almost 20% of plantedacres in the U.S. were no-tilled. Mulch-tillincludes all other tillage systems which leavemore than 30% crop residue cover on the soilsurface at planting. It was practiced on 16% ofplanted acres in 2002. Ridge-till was practicedon 1%. This brings the total percentage of con-servation tillage to 36%. Reduced tillage leaves15-30% residue after planting and was practicedon 23% of planted acres, while intensive tillage(

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B 56% Corn, soybean,cotton, rye, tobacco

5 IA, KY, MO, MD, NC, AL

67% Corn, soybean,sorghum, cotton, tobacco, rye

6 OH, MS, NC

101% Corn, soybean, 4 MO, MS, MD

C

D

HYDROLOGICSOIL GROUP

AVERAGE WATER RUNOFFIN NO-TILL AS % OFCONVENTIONAL TILL

CROPS STATESAVERAGE #YEARS IN NO-TILL

TABLE 4. Summary of natural rainfall studies comparing water runoff with continuous no-till to conventional tillage (usually moldboard plow).

their activity. Soil hydrologic categorization isone way of grouping soils with respect totheir potential to result in reduced runoffwith no-till. Hydrologic groups are mostlydetermined by soil texture and restrictive layersin the soil that slow water movement in thesoil (Table 3).

Table 4 is a summary of runoff measured invarious studies with natural rainfall. The studieshave been grouped according to hydrologic soilgroup and the average number of years inno-till as indicated. The salient result of thesestudies is that runoff was dramatically reducedin continuous no-till fields on Group B and Cbut not on Group D soils. It must be concludedthat the runoff-reducing benefits of no-tillwill be greatest on coarse to medium texturedsoils that do not have an impeding layer orwater table near the surface.

Even on soils that have a moderate to finetexture or an impeding layer, no-till can stilloffer substantial runoff reduction as long asthey are not too heavy and the impeding layeris not too close to the soil surface. Soils that arefine-textured have heavy swell/shrink clay or arestricted layer near the surface are not likely toshow reduced runoff with no-till. It is interestingto note that the coarse to moderately texturedsoils also respond favorably to no-till cropproduction.

Clay soils are the most challenging forno-till. No-till crop yields are customarily higher

or equal to those achieved with conventionaltillage on Group A, B and C soils, but are oftenreduced on Group D soils. It may be necessaryto make modifications to no-till equipment toimprove crop yields and infiltration on Group Dsoils. Examples are in-row tillage techniquessuch as strip or zone-tillage that leave fullresidue cover between rows. Artificial drainagewill also help to make these soils more suitablefor no-till crop production. Crop rotationalso becomes more important on these morechallenging no-till soils.

When a farmer changes from plowing tono-tillage, the soil (and the farmer!) needs toadapt to the new management system. Organicmatter content slowly increases and biologicalactivity creates a new soil macro-pore system.This period may be associated with reducedyields in no-till until a new ecological equilibriumis achieved in the soil. There are some ways toget around this transition period.

If no-till annual crop production can bestarted immediately following a perennial grassor legume crop, the transition period can bereduced or eliminated. The perennial crop givessoil organisms the chance to develop amacro-pore system and improve soil tilthwithout tillage and with residue cover. Theextensive root systems and high root turnoverof grasses will stimulate porosity andaggregate stability. Taproots of some perenniallegumes such as alfalfa will, upon death and

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has been a steady increasein the acreage of no-till (Figure 5). TheConservation TechnologyInformation Centersummarizes data collectedby USDA-NRCS,Conservation Districts andCooperative Extension.

Two broad categoriesof tillage systems arerecognized: conservationtillage, which includes alltillage systems that leavemore than 30% cropresidue cover after planting;and conventional tillage,which leaves less than 30%crop residue cover afterplanting. A 30% residuecover limit has been setbecause significant soilerosion reduction isachieved only whenmore than this amountis present (Figure 6).

Conservation tillageincludes no-till, mulch-till,and ridge-till. No-till isdefined for the survey as

Intensive till

Reduced tillNo tillMulch till

Ridge till

1990 1992 1994 1996 1998 2000 2002 2004 2006

Tillage Systems in the U. S.160-

140-

120-

100-

80-

60-

40-

20-

0-

10 20 30 40 50 60 70 80 90 100

100-

90-

80-

70-

60-

50-

40-

30-

20-

10-

0-

So

il l

oss

(%

)

Soil cover (%)

FIGURE 7. No-till leaves crop residue at the soil surface and reduces soil erosion dramatically.

FIGURE 6. Residue cover – relative soil loss relationship.With 30% residue cover, soil loss is reduced 70%.

FIGURE 5. No-till is used on a growing amount of acreage in the U.S.

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decomposition, leave large vertical channelsthat help improve infiltration.

The benefits of starting no-till in a sod wereillustrated in one study. Corn was establishedinto sod with and without tillage. Water runoffoccurred on the tilled plots when less than1.5 inches of water was applied while no runoffoccurred on the no-till plots even when5.3 inches of water was applied. In anotherstudy in Kentucky, runoff was reduced 83%when planting no-till into a bluegrass sod ascompared to conventional tillage, despite thefact that 5.2 inches of rain fell after tillagewhen infiltration is highest.

PESTICIDE EFFECTS ONWATER QUALITY

Reduced runoff with long-term, continuousno-till has many environmental advantages.However, some may comment that no-till islikely to pollute the natural environment dueto a heavy reliance on chemical pesticides anda fear that those pesticides will end up in oursurface and groundwater.

A decade ago, a review of the impact ofconservation tillage (no-till, ridge till or mulchtill) on pesticide runoff into surface waterappeared in the Journal of Soil and WaterConservation. In the article, it was firstconcluded that total pesticide use inconservation tillage has not appreciablyincreased when compared with conventionaltillage. Many people forget that even withconventional tillage, most farmers useherbicides for weed control and someinsecticides and fungicides for insect and diseasecontrol. With the use of crop rotation, pesticideuse in conventional tillage as well as no-till canbe significantly reduced. Crop rotation is anessential component of sustainable no-tillsystems.

In no-till systems, a farmer will have to usea burndown herbicide application to eradicateany weeds or cover crops that are present atplanting. After that, there is no need fordifferent amounts of herbicide applied in

no-tillage versus conventional tillage, althoughthe types of herbicides may be different.Common burndown herbicides such asparaquat and glyphosate bind very tightlyto soil particles and are mainly lost fromfields associated with sediment.

Because erosion is dramatically reducedin no-till, and these herbicides are very quickly broken down by soil organisms into harmlesscompounds, the threat of surface watercontamination is very small. What is moreimportant, however, is that runoff is significantlyreduced in no-till compared to conventionaltillage. Because of this, the likelihood of thepesticides ending up in surface water is small(even those that do not bind to soil particlesand are easily dissolved in runoff).

In a review of a large number of naturalrainfall studies, the average herbicide loss inrunoff from no-till and chisel plowed fields was30% of that in moldboard plowed fields. Thegreatest threat of surface-applied herbicidesleaving the field in runoff was if heavy rainfalloccurred very soon after herbicide application.It should be noted that sometimes theconcentration of herbicide in runoff was higherin no-till than conventional tillage, but becausethe total volume of runoff was small, total losseswere significantly less with no-till. In summary,it is justified to expect lower pesticide lossesfrom no-till fields than from conventionallytilled fields because of smaller runoff andreduced erosion rates.

SOIL COMPACTIONSome say soil compaction in no-till is less;

some say it is more than with tillage. What tobelieve? It is first of all important to note thatmost soil compaction research has been donewith conventional tillage, not with no-till.We know far less about soil compaction in no-tillthan in tillage systems. With increased adoptionof no-till, however, more research is beinginitiated.

stopped before itstarts and T can bemet on the entirefield every year.

The way todramatically reducesoil erosion is theno-till systemsapproach. Thismethod keeps thesoil covered withcrop residue,reduces soildisturbance toalmost zero, andattempts to maxi-mize the number ofdays in the yearwhen living rootsgrow in the soil.

Farmers andresearchers have demonstrated that there aremany other benefits to the no-till system besidessoil savings. For example, a farmer can savesignificant amounts of time not working the fieldsprior to planting. That can result in more timelyplanting as well as increased acreage that can bemanaged with the same equipment and laborforce. The efficiency of field operations will alsoincrease because the farmer can often meet soilconservation requirements in a no-till systemwithout adding as many conservation practices.Finally, the costs of producing a crop aredecreased by excluding tillage machineryexpenses.

Soil will improve over time in a no-tillsystem through increased organic matter. Soilstructure and water infiltration will improvein a no-till system through the slow, butcontinuous decomposition of crop residue androots and the high activity of living organismscreating a permanent macro-pore system in thesoil. Due to this high biological activity inno-till, soil compaction can be minimized.Finally, there are other environmental benefitsof a no-till system that extend beyond the

farm––cleaner air and streams and increasedgroundwater recharge.

THE USE OF CONSERVATIONTILLAGE IN THE U.S.

In the 1970s, many researchers believed thatby the year 2000, most cropland in the UnitedStates would be farmed without tillage. That prediction has not come true, although there

• Erosion control• Higher infiltration• Lower evaporation• Organic matter conservation• Improved soil structure• Higher biological activity• More earthworms• Reduced total phosphorus losses• Lower labor needs per acre• Higher efficiency of farm operations

FIGURE 4. Ten Benefits of a No-Till Systems Approach

FIGURE 3. Soil tillage is the major cause of soil erosion.

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COMPACTION IS DIFFERENTIN NO-TILL

Compaction is caused by the movement ortraffic of vehicles, livestock or humans over thesurface of the soil. There are a few factors thatchange the effects of traffic in no-till fieldscompared to tilled fields. Over time, organicmatter content in the surface soil increases withno-till. Soils with high organic matter contentcannot be compressed as easily as those withlow organic matter content. This means thatcompaction in the top 2 inches is not of greatconcern in long-term no-till. In addition, a firmno-till soil matrix with macropores for air andwater movement can better support trafficwithout being compressed than a soft, tilled soil.

The higher biological activity in no-till soilsalso helps alleviate the effects of compaction.However, the soil under crop residue often stays

wet longer than in clean tilled conditions. Thismakes it more likely the farmer will be in thefield when soil conditions are really too wet fortraffic in no-till.

In addition, no quick alleviation of com-paction with tillage equipment takes place inno-till. Overall, research is suggesting that soilcompaction can be a significant threat inno-till systems. In one study, extreme soilcompaction of the complete soil surface to adepth of 12 inches reduced crop yields 98%compared to non-compacted long-term no-tillfields. It was interesting that the following year,the yield in the compacted fields increased to85% of that in the non-compacted plots. Therecovery from soil compaction (without tillage)was attributed to high biological activity.

In another study, soil compaction due toheavy axle loads caused a 15-30% reductionin yield in a long-term no-till field. Soilcompaction can increase soil density, and

FIGURE 21. Care has to be taken not to compact the soil in no-till. This can be achieved by avoiding traffic at suboptimalsoil moisture conditions, using low tire pressure or tracks, and reducing axle load at least below 10 tons. Improving soilorganic matter contents and stimulating soil biological activity make soil more resilient to compaction.

3

organisms. Because soil is so important, we, ashuman beings, need to insure that we are goodstewards of this valuable resource.

SOIL IS AT RISK

While soil is a resource that can re-createitself, it is a very slow process. Unfortunately,our nation’s soils have been and continue to bedegraded at an alarming rate. Soil erosion isstill the number one cause of soil degradation.Other causes of soil degradation include: soilcompaction, soil acidification, soil pollution,and salinization. Dramatic increases in the useof no-till systems by American farmers have ledto many benefits, including reductions inerosion, and savings of time, labor, fuel, andmachinery. Between 1990 and 2000, no-tillfarming acreage rose from 16 million acres to52 million acres, an increase of 300 percent.Now that some fields have been under no-tillproduction systems for many years, farmers andresearchers have begun to notice additional

benefits including changes in soil physical,chemical, and biological properties. The mostnotable of these benefits include increases inorganic matter and improved water infiltration.Improved water infiltration can lead to moreefficient use of rainfall, increasing yields whenrainfall is in short supply.

Although conservation practices havebrought about improvement, the average soilerosion rate on U.S. cropland is still 3.1 tons/acre

(Table 1). The erosion rate is often greater t