undestanding soil

8/10/2019 Undestanding Soil

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Contents

We acknowledge the contribution made by the

late Ralph Jurgens to this publication. He gave ofhis extensive knowledge in sustainable agriculturefreely.

Copyright May 2008, Organic Farming Systems

Although all care has been taken to provide accuratescientific information on sustainable agriculture, noguarantee or responsibility can be accepted for cropperformance based on the use of information from thispublication.


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1. Why sustainable farming? 3

2. Understanding Soil 4

2.1 What is a cation? 4

2.2 Why are cations important? 4

2.3 Cation Exchange Capacity 5

2.4 Where do you start? 6

3. What is Humus? 7

4. Improving Soil Humus 7

5. Soil minerals that affect pH - A Closer Look 9

5.1 Calcium 9

5.2 Magnesium 11

5.3 Potassium 12

5.4 Sodium 13

5.5 Hydrogen 13

6. Nitrogen in soil 14

7. Phosphorus 18

8. Sulphur 21

9. Importance of Trace Elements 22

10. Plants Obtain Nutrients in Three Ways 26

11. Do you have a problem field? 28

12. The Carbon Cycle 29

13. Plant & Soil Nutrient Inter-relationships 30

14. Diseases & Insects vs. Nutrient Deficiencies 33

www.organicfarming.com.au : [email protected] : Ph 08 9384 3789 : Fax 08 9384 3379

Contents


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1. Why sustainable farming?

There is no doubt organic/sustainable agriculture improves ourenvironment. Britains Institute of Science in Society (BSIS -2008) reports organic agriculture has the potential to mitigatenearly 30% of global greenhouse gas emissions and save one-sixth of global energy use.

Sustainable farming is not low input, but efficient input, and startswith examining the health of the soil. It is based upon currentanalytical data where the aim is to help build soil structure, ad-dress field limitations and meet nutritional needs for future crops.

Sustainable farming practices consistently show in research,field demonstration trials and in practice:

More organic carbon (eg 28% more on 20 organic farms inCalifornia - BSIS 2008 )

Higher organic matter in the soil (eg Compost Demonstra-tion Project 2005)

Increased soil organic matter Reduced soil erosion Improved soil physical structure resulting in better water

holding capacity Increased soil nutrients

The cornerstone of sustainable farming practices is understand-ing the soil which is the focus of this booklet. Nutritional balanceis critical which in turn helps build healthier plants which needless pesticides and are superior in nutritional mineral value, thusmeeting todays marketing trends.

Organic Farming Systems has been helping growers achievethese goals since 1995. Our recommendations providebiologically integrated & organic (BIOS) crop programs that allowfarmers to choose between traditional N-P-K inputs and modernbiological farming systems. Mainstream agriculture is intransition, and Organic Farming Systems can provide BIOSCrop Programs and input products for sustainable farming.

Our goal is to educate and equip growers with cost-effective fer-tility programs which meet the needs of the current crop andcontinually improve the quality and productivity of farmersgreatest asset - the soil.

Sustainability

Ecologically Sound

Environmentally Safe

EconomicallyAchievable

Balanced Soil Fertili ty=Better Crops

BIOS ProgramsBiologicallyIntegrated

&Organic Systems


5/[email protected] 4

2. Understanding Soil

2.1 What are cations?

Cations are the positive charged nutrients in the soil. The mostcommon cations are calcium, magnesium, potassium, sodiumand hydrogen. The ratios to each other are vital for a balancedpH and optimised biological activity in the soil.

Following are some basic truths to consider about cations:

1. Calcium is the most important nutrient in your soil and theproper balance of it to all other nutrients is very impor-

tant.2. All cation nutrients have a pulling or holding power that is

expressed in relationship to calcium. Ca is the base nutri-ent and the comparison ratios will be 1 to 1 for Mg, withNa the highest at 1.82 to 1. This means Na (sodium) has1.82 times more holding power than Ca.

3. A soil test is incomplete when the sodium (Na) level isnot included. If you have been using a traditional dry fer-tilizer program, sodium is the salt index to your soil.Watch it closely!!

NOTE: If other cation nutrients are not in proper balance tocalcium (Ca), then normally hydrogen (H) will be out of bal-ance. So watch hydrogen percent levels in the cation balanceinstead of soil pH . If all soil cation nutrients are in balance,both hydrogen and your soil pH will be correct.

2.2 Why are cations so important?

All clay and humus colloidal soil particles carry a negativecharge on their surface, which attracts desirable positively

charged nutrients.

If in proper balance, positive cations are loosely held in the soilsolution so a growing plant, whose roots are negativelycharged, attracts and takes positively charged cation nutrientsas needed.

EXAMPLE: As a plant needs calcium it removes it from thesoil and it is replaced by another cation which will flow or moveeasily when the soil is in proper balance. This is Base orCation Exchange at work! BEWARE cations can go out of bal-

ance with high levels of magnesium and/or sodium, causingheavy soil to tighten up, cutting off the soils oxygen supply,which can result in poor nutrient movement to the plants.

Calcium is themost importantnutrient in your

soil



CEC determinesthe ability of thesoil to hold onto

nutrients

Nutrients in leastsupply will

regulate plantgrowth and health,

not how muchN-P-K

you add.

As you addnutrients to the soil

it is veryimportant to add

the right nutrientsto maintain proper

balance.

2.3 Cation Exchange Capacity (CEC)

The Cation Exchange Capacity is the "ability of the soil" to holdpositively charged (cation) nutrients. It reflects the holding abilityof the clay and humus components of the soil and is measuredby analysis to provide a capacity (in meq/100g soil) and the basesaturation percentage level of each cation.

Diagram 1Cation Exchange Capacity

Proper CEC balance with healthy "soil life" (adequate humus andbiological activity) will help determine nutrient release in properratios and amounts to all growing crops!

NOTE: Nutrients in the least supply will regulate plant growthand health, not how much N, P, K is added.

REMEMBER: The soil clay particles and plant roots are bothnegatively charged. They have a natural attraction of cation nutri-ents. Therefore, as minerals (nutrients) are added to the soil, itis very important the right nutrients are added to maintain properbalance. As fertiliser is added, the soil is improved or harmeddepending on the quality and kind of fertiliser.Be careful what you add!

The most natural way to improve soil CEC is to increase soilminerals (nutrients) through compost (animal manure), crop resi-

dues, and natural soil amendment such as biological products,gypsum, limestone and other "naturally formed" products. Suchpractices build humus and "soil life". This is sustainable farming.



The Cation Exchange Capacity is based on soil texture and organicmatter which classifies your soil as being sand, loamy sand, loam orclay. 30 to 60% of the soil's CEC is attributed to the % Organic

Matter.

By increasing soil organic matter content (as active HUMUS) thesoil's nutrient exchange and holding capacity will greatly increase.

2.4 So where do you start?

The best place to start is with a BIOS Crop Program soil analysis/report. The most important part of this is the information on the per-centage base saturation of cations. Soil nutrient balance is very im-portant, even more than high nutrient levels! You can have high soilNPK levels, and plants can still starve because of unbalanced soil

cations. The table below shows the proper balance of cation's inyour soil.

Good soil reports should list all the important cations, their desiredlevels and the levels your soil achieved. Recommendations shouldthen be made to you on what you need to balance your soil. Thereis a sample Bios Crop Program Soil Report in on page 32 of thisbooklet to give you an idea of what a soil report should contain tohelp you balance your soil.

Table 1: Base saturation (%) of five major soil cations -Cation Exchange Capacity

Sand 1 to 4 Loam or Silt Loam 15 to 30

Loamy Sand 4 to 7 Clay 30 to 45

Sandy Loam 7 to 15 Organic Matter 70 to 200

Compost 20 to 80

Cation Exchange Capacity of Soils

NUTRIENT EXCHANGECAPACITY

NATURALBALANCE

%

RATIOTO Ca

TRADITIONALISTSSAY:

Ca 1 to 1 65-75% 1 >40%

Mg 1.67 to 1 10-15% 6 to 1 15 to 40%

K 1.03 to 1 3-7% 15 to 1 To exceed Mg

Na 1.74 to 1 0.5 to 2.0% 7.5 to 1 < 15%

H - 0 to 8% - Who cares, it'sFREE!

CEC is a goodindicator of soil

quality andproductivity.

The more CEC asoi l has, the morelikely the soil will

have a higherfertility level.

BIOS Soil Reportsgive you a good

indication of yoursoils CEC.

Bios Soil Reportsgive you specific

recommendationsfor balancing your

CECusing organic or

sustainableinputs.



3. What is Humus?

Humus is more of a generic term than a precise one - it isformed through the natural decomposition of organic matter inthe soil by micro-organisms. The quality of the humus is variablein its composition, reflecting the original material and theconditions of decomposition.

Humus is a dark colour and is the "living storehouse" of life andnutrients in the soil, containing significant amounts of nitrogenand sulphur, as well as other plant nutrients. Humus holds 3 to 4times more (per volume) nutrients and water than clay soil parti-cles. All of its nutrients and water is exchangeable to the plant. It

is an important buffer in the soil, slowing down changes inacidity and nutrient availability.

Humus has an electrical charge (negative) that allows it to holdonto positively charged soil nutrients (such as calcium, magne-sium, potassium) and in this respect has a similar role to clay inthe soil. It also has an ability to hold onto anions (see traceelements).

Humus can be divided into two basic types:1) Readily decomposed type which provides a short

term nutrient supply to plants; generally within the lifeof an annual crop or season (ie 3-4 months). Primarilyderived from sugar, starch and protein.

1) A more stable type that is resistant todecomposition for tens to hundreds of years.Provides little in the way of nutrients and generallyoriginates from woodier plant residues containingcellulose and lignin.

Humus is the soils bank account - Any product that burns upand depletes humus is destroying soil. NH3(anhydrous ammo-nia), DAP, and ammonium sulphate all can deplete humus.

4. Improving soil humus

Humus is what makes a living soil healthy and productive - inboth crop yields and quality.

Good "soil life" is reflected in aerobic bacteria, which are valu-able in producing nutrients, organic acids, humic acid, pricelessenzymes, etc. They require a well, aerated soil with a good pH

and balanced mineral nutrients. Calcium is the natural soil"flocculent" nutrient that enhances soil microbial life, but highlevels of magnesium, sodium, aluminium and iron resists soillife.

OFS Humus 26 wil limprove soil by

holding moisture andnutrients, promote soilbiological activity and

improve soil structure- 26% K-humate

Humus holds 3 to 4times more

nutrients and waterthan clay

Improving Soil

Soil organic mattermanagement is adynamic process.

All OFS natural farminputs promote the

biologicalprocesses in thesoil . Good farm

inputs feedbeneficial micro-

organisms as wellas supply them.

Ask for a BIOSProgram for your

crop.



Soil microbes decompose crop residue and manure into humus.These microbes form the sticky glue necessary to form soil crumbstructures in the presence of clay, and stop water and wind ero-

sion. Farming practices such as using compost, cover crops, greenmanure and additional biological mixes are favourable for good soillife. All these practices also favour fast efficient decomposition ofcrop residues.

Diagram 2: Humus Formation From Organic Residues(Cultivating a sense of humus)

A very "healthy" soil may contain up to 15 billion bacteria, 500 mil-lion actinomycetes and 30 million fungi per tablespoon of soil.

Soils that are tilled often or have extensively used soluble nitratefertilisers, can be near extinct of certain microbe species. Whensoil conditions are not favourable, micro-organisms including earth-worms go dormant or are killed. When favourable soil conditionseither return or are created, beneficial micro-organism activityincreases. These micro-organisms need a food source (carbon),water, heat and air, in which to increase their population.

Indicator: One excellent indicator of soil life is the common earth-worm! Anything that improves the environment for earthworms willalso improve the environment for other beneficial "soil life". If youcreate a condition that harms, or slows down worm activity, it willgenerally harm all other beneficial "soil life"!

Smell the soil:Does it have a rich, pleasant aroma which can beassociated with a forest humus smell? If so your beneficial soilbacteria are hard at work (mainly Actinomycetes). If your soil(especially subsoil) has a foul odour, anaerobic fermentation isoccurring, probably producing toxic phenols and alcohols.

Measuring SoilHumus

To measure humuslevel for a given soil

type you shouldconduct a BIOS SoilAnalysis, selecting

the soil humus

option. This humuslevel reflects the"soil life" energyrelease, or humusstorehouse level

rather than just thetotal amount of soilcarbon or organic

matter.

Humus should be atleast 1.5% with anideal level of 2%

(range 1-3%).



5. Soil minerals that affect pH - a closer look

One of the greatest assumptions made about soil tests is that soilpH is a good guide to the mineral requirements of the soil. Soil pHis simply a measurement of soil hydrogen level or acidity.Hydrogen is the element which causes soil to go acid if one ormore of the main four cation levels drops.

The pH alone tells us little of value. Your soil can have a perfect pHfor most common cropping systems (~pH 6.7), but the cations aretotally out of balance.

5.1 Calcium (Ca)

The leading soil nutrient! Proper amounts of Ca (65-75%), ideal70% base saturation, makes soil workable and well flocculated andimproves the air-water relationship. Air and water are two "free"elements, that are vital to plant growth and production. Anynutrient that aids a good air-water relationship is a priceless assetand Ca is the leading nutrient in maintaining this vital balance.

Diagram 3: Soil Composition

Calcium helps create a healthy soil environment for plants and itimproves uptake of other nutrients to the plant. As the calciumcontent in the plant decreases, so can the protein, energy level andminerals of the plant. Calcium stimulates growth of "soil life",including nitrogen-fixing bacteria.

Contains 32%Calcium which isimportant for soil

pH, soil health andcell wall

development inplants.



Any product that removes calcium from the soil can be expensiveand dangerous to soil health. The following products remove Ca(per kilogram of material applied):

Facts about Calcium

The lower the Ca level (pH) in the soil the greater the leachingloss of K and NH4.

The percentage of CEC saturated with Ca is more important thanthe total amount of Ca in the soil (high % Ca can stop toxic

aluminium, iron and Na conditions).

Independent soil scientists (worldwide), normally agree to a Ca-Mg ratio of about 6 or 7 to 1 for an ideal soil.

Many studies show soil Ca at the optimum levels will decreasedisease in most plants. With lower percent saturation of Cacombined with high levels of Mg and K more disease problemsoccur, such as seedling rots, soft rot in stored tubers, and variousroot and stalk rots.

Ideal Calcium-Potassium ratio should be (15 to 1). Example - Caat 75% and K at 5%. This proper ratio is one of the keys to higherproteins, nutrients and vitamin levels. High Ca with adequate Kproduces a high protein crop, while soil low in Ca produce a highcarbon crop. What does this mean? High carbon crops are low inenergy, minerals and vitamins. Yields increase by up to 25% byadding K.

Note: Ca combined with enzyme protein clusters and biologicallife (humus) forms a salt of saccharic acid, which is a natural gluein the soil. These oxides of calcium, along with massive rootsystems from green manures (cereal or grasses) offer control ofwater and wind erosion, and can restore soil back to its properbalance.

Products Calcium Removal

Anhydrous ammonia (NH3) removes 1.5kg of calcium forevery kg of NH3 applied

DAP (di-ammonium phosphate) removes 0.75kg of Ca for everykg applied

Ammonium sulphate removes 1kg of Ca for every kgapplied;

Muriate of potassium (KCl) removes 0.5kg Ca for every kg

applied.

Remember

Calcium is essentialfor proper cell wall

development inplants.

Calcium solubilitymust be maintained

for crop demand.

A soil wi th balancedcalcium is friable

and easily worked.

When calcium andother cations are

balanced, roothealth, nutrientavailability and

uptake is increased.

Calcium reduces thetoxicity effect of

magnesium and soilborn fungi such as

root rot andphytophthora.



5.2 Magnesium

The magnesium percent of base saturation is second place tocalcium, but requires a ratio of 6:1 to calcium (example Ca 75% toMg 12.5%). This provides optimum levels of Mg forphotosynthesis and protein formation. Over-saturation will hinderthese vital functions.

This optimum Ca to Mg ratio of 6 to 1, promotes soil life andadequate nutrient levels for growing crops. We recommend apercent base saturation of 10-15% (Ideal 12.5%) Mg, althoughsands are far more tolerant to excess Mg than clay - up to 20% ofbase saturation.

Mg deficient soil would normally have less than 6% basesaturation in sandy soils and less than 4% in loam-clay soils.

The Bad News about Magnesium

Excess Mg can become toxic to soil and plant life.

Excess Mg to Ca ratio forms a poisonous condition in thenucleus of plant cells, affecting its health and the continuing life ofthe plant, often striking the plant with diseases (fungi) to destroy

the plant and simultaneously calling for other plants to take itsplace - commonly called weeds and grasses!

Excess Mg (and/or Na) produces hard soils. Hard soils resistwater, have less air (oxygen), less soil life, more weeds, moreinsects (less plant sugar) and more plant diseases. Weeds andgrasses are soil indicators of danger. The soils are out of balance.There is a need for a new fertiliser program, not more herbicides,insecticides or fungicides.

Excess Mg means deficiency of N, P, K and Ca. Yes, the big

four go deficient! Only Mg with combination of Na, and Fe (if thepH is too low also include Al) can make concrete out of heaviersoil; it destroys the air-water ratio necessary for soil life. Soilefficiency is destroyed. These Mg-Na combinations are toxic toanimals too. Mg takes the place of Ca in plant cells, whichproduce a poor quality crop.

Excess Mg to Ca permits crop residues to decay into toxicalcohol, which kills or suppresses bacteria. It then forms aformaldehyde, which stops crop residue decay (this meansdisease carry over).

Excess Mg will not allow Ca and K to move into plant cells (plantabsorption is slowed down considerably).

BIOS SOILTESTING

Gives youorganic/

sustainablerecommendationson how to balance

Mg sothe big fourN P K Ca

are not deficient



Excess Mg to Ca causes soil micro-organisms to release soil nitrogen back to the atmosphere (as

gaseous nitrogen oxides). What a waste that we listen to people who would create such aproblem, and then let them sell us high rates of N every year.

Correct your soils Mg to Ca ratio.

5.3 Potassium

Potassium is essential for the translocation of sugars and for starch formation. It is required for theopening and closing of the stomata by guard cells. Potassium encourages root growth andincreases crop resistance to drought and disease. It is also needed for size and quality of the cropto be grown.

Potassium should be within the optimum range of 3-7% (ideal 5%).

Note: High to excessive levels of potassium can inhibit calcium, magnesium, zinc and manganeseuptake by the plant. It also can be a complicating factor in iron chlorosis.

Potassium combines with clay parti-cles in 3 ways. The available is onthe surface. The slowly availableis held between the clay plates. Abig share of the unavailable Kmoves out of reach. Most of broad-cast dry K fertiliser moves into theunavailable form.

When you apply potassium assulphate of potash, the solution is100% available! In heavier soils thepotassium in solution moves onlyfar enough to reach a clay particle

to attach to. Since potassiummoves very little in clay soils, theroot must come after it.

Potassium in composted manureand crop residues attaches quicklyto the closest clay and/or humusparticle and is then utilised by thecrop. Potassium releases from soilminerals far more slowly. In sandysoils with low clay and organicmatter content, much of thepotassium is leached quickly out ofthe root zone.



Understanding Potassium Fertil iser

A very small percentage of broadcast applied K will become ex-

changeable during the growing season, or even show up on asoil test. Why? Most commercial K is 100% soluble in the soil,making it highly leachable (up to 75%) on sandy soil. Most ofthe remaining K is fixed in soil due to unbalanced conditions.Most K fertilizer is broadcast applied in early spring and movingout of soil quickly with springs rains or early irrigation. A plant'sneed for K starts out in small amounts in young, growing plants.Less than 5%-10% of total K is needed in most plants duringthe first 21-28 days of growth cycle.

Most of the K that a plant will use is obtained by diffusion. Thatmeans the extraction of K by the root draws the K to itself as itis needed (K must be within 5mm of the root to be drawn downthe concentration gradient). This is why direct seed placement,applications through the irrigation system and foliar sprays canbe very profitable at very low rates. In the presence ofadequate moisture, plant roots in well flocculated, aerated soilhave a much higher up-take of K .

5.4 Sodium

Excessive Sodium (Na) is an enemy of soil life (plant and micro-bial), animals and man. As Na is released into the soil solutiona number of harmful things can happen. If sodium becomeshigher on the cation exchange than potassium, the plant willtake up sodium in the place of potassium, it cannot tell the dif-ference. In higher temperatures this causes cell wall collapse,affecting crop quality and yields. (it only takes 0.5kg of excessNa to affect 1kg of K uptake).

Na produces water stress on a growing crop and actually hasthe pulling power to hold water from roots. The soil can have

adequate moisture and the crop actually starves for water.

Na has the strongest exchange capacity of any cation (1.82times more pulling power than Ca). A small amount of Na willtake control in your soil.

Fight sodium with calcium, potassium and sulphur. Calciumsulphate (gypsum), cover crops, compost, a good biologicalprogram are all good methods to restore Na to a desired level.

5.5 Hydrogen

Hydrogen: The free exchange nutrient, it takes last place at thecation table.

Hydrogen only takes a place that is already empty at the cation

Scientific research hasshown that the fulvicacids in OFS Fol-Up

improves the response

time by plants to foliarfertiliser applications.

This is very important incorrecting any nutrientdeficiencies in plants

during growth.

Sodium is theenemy of soil li fe.A good biological

program helpsrestore Na to

desired levels.



table. Soil that has no H (or no acid) has nutrient limitations. Acidin soil solution is what allows most nutrients to become exchange-able to plant roots. Most soil microbes thrive on these slightly acidconditions. Check the BIOS Soil Analysis closely and monitor Hpercentage base saturation. Proper pH (measured in water) willnormally be 6.5 to 7.5.

Optimum natural levels of hydrogen are 0.5% to 8%. If the soilhas over 15% H it becomes acidic (low pH is normal). If hydrogenis at zero, this tells you the other cations are out of balance, orover saturation has occurred with one or more cations. Sohydrogen should be watched very closely. Soil life depends on it.

Notice: This is why keeping a "proper balance" of minerals in thesoil is much more important than using fertiliser by the tonne. Afew kilograms of an active, over saturated nutrient, like Na or Mgaffects the soil much more than hundreds of kilograms of calcium."Salt" fertilisers are destroying our soil balance. Crop diseases,weeds and insects come our way as a warning that our soil is indanger.

6. Nitrogen in soil

In sustainable & organic farming systems, the availability of

nutrients to the crop, particularly nitrogen, relies on the release(mineralisation) of the nutrient from the soil humus when needed.

Diagram 4: Nitrogen Cycle

Soil bacteria decompose organic residue (humus) and the N re-serve in soil converts to ammonium (NH4+), to nitrite (NO2

-)and

then nitrate (NO3-2

). This process is referred to as nitrification. Theamount of nitrogen released for plant uptake by this process isdirectly related to the organic matter and soil biological activity.

Summary of the MainCations

Ca, Mg, K & Na

On any soil audit, orsoil test the actual

amount (kg) of eachnutrient available isnot nearly as vital as

the properbalance between

each other.

Specifically watchtheir balance to Ca.

Remember thisimportant fact:

High levels of anutrient on a soil testmeans nothing to a

crop.

Fight against severeimbalances, whichcause nutrients to

become fixed in thesoil or even toxic to

the plant.

Watch the "balanceof soil nutrients" and

use safe, commonsense farm practices

that

promote balanceand soil life.



The breakdown of a urea fertiliser may also be termed as thenitrification process (see figures below).

The key factors that influence the rate of mineralisation oforganic matter are:

1. Soil oxygen2. Soil pH - mineral balance to enhance biological activity.3. Soil temperature4. Soil moisture.5. Soil organic matter (humus) content .

6. Soil biological activity

Soil OxygenOxygen is necessary for the production of nitrate and for the nitri-fying bacteria. If excess water is present, the oxygen supply islow and the rate of nitrification will be slow. Very compacted soilalso will lower oxygen supplies and thus slow-down nitrification.

Soil pHThe nitrifying bacteria are sensitive to acid or alkaline soil condi-tions. Speed of nitrification will be highest at a soil pH of 6.4 to7.0. The reaction will be slowed down (due to a reduction in theactivity of the bacteria as the pH becomes higher or lower).

Soil TemperatureThe rate of nitrification will be highest when soil temperatures arebetween 18

oand 27

oC. Nitrification is greatly reduced below a

soil temperature of 10oC.

Soil MoistureMicrobes require moisture to survive; excess soil water will slow

nitrification and extreme dry conditions will also retard thenitrification reaction.

Contains a sourceof carbon for soil

microbes andencourages

microbial activityin the root zone.



To sustain all growthprocesses plants

require relatively largeamounts of Nitrogen.

New Era High Nprovides a convenientsource of nitrogen for

broad-acre andhorticulturalsituations.

De-nitrification

In some conditions the "N process" in the soil can significantly addto the cost of farming. Water-logged soil, cation imbalanced soil,soil compacted from tillage, working soil wet, etc. all create a lackof oxygen in the soil.

Biological life must have oxygen. If microbes can't get oxygenfrom the air in the soil, then they turn to nitrogen (NO3) to supplytheir oxygen. The bacteria source will get their oxygen from NO3.This results in the soil NO3changing to nitrogen gases (N2), whichare lost to the atmosphere (see diagram below). This reversalprocess is called de-nitrification.

What causes de-nitrif ication losses?

Soil water logged for more than 36 hours creates high N losses.Anaerobic (no oxygen needed) bacteria multiply rapidly andchange NO3to N gases. This N is permanently lost for crop use.Crops are stunted and yellowed because of N deficiency.

Any soil condition that causes low oxygen levels will affect Nefficiency due to de-nitrification. High Mg and Na, which cancreate tight, compact soil conditions, will cause N losses. Excess

Mg in soil solution will require extra N for plant use.

Diagram 5: Nitrification/de-nitrification process



Immobilisation of NitrogenThis condition can exist when crop residues are high in carbon and

low in nitrogen, and then incorporated into the soil. Available N istied up for a short period of time. This immobilisation of nitrogen isalso called nitrogen draw-down and is caused by bacteria that aredecomposing the crop residues. These bacteria need nitrogen fortheir protein and are able to access the available nitrogen beforethe plant roots. Once most of the crop residues are broken down,the nitrogen is released from the bacteria and becomes availableto the growing crops. Under ideal weather conditions, it takesabout one month before nitrogen is released again. A good healthysoil has adequate N for all decomposition of crop residues, butspraying residue with a soil stimulant decomposer will speed up

the decomposition time.

VolatilizationVolatilization is the process of nitrogen loss as ammonia gas isformed from urea. Urea is broken down in soils by an enzyme toform ammonium carbonate. The carbonate creates an alkalinecondition for a short time. This alkaline (or high pH) condition con-verts NH4

+(ammonium) to NH3gas (ammonia). The NH3gas is

then lost to the air. In cooler conditions, the enzyme breaks downurea more slowly and the carbonate does not create as high a pH.Thus, little ammonia gas is lost when urea is applied to cool soils

(less than 70C). When manure, urea fertiliser or a nitrogen solutioncontaining urea are applied to the soil surface, nitrogen may be lostas ammonia (NH3) gas. Applying these fertilisers when soil and airtemperatures are cool or when rain occurs soon after applicationwill greatly reduce the potential for volatilization of urea.Incorporate these materials into the soil after applying and it willstop the losses by volatilization.

Applying urea whensoil and air

temperatures arecool or when rainoccurs soon after

applicationreduces the lossesof Nitrogen due to

volatilization.

Incorporating ureainto the soil

reduces N lossesvia

volatilization.



7.0 Phosphorus

Important facts about Phosphorus

The second most deficient soil nutrient (second only to calcium).

Most of agriculture has a real problem maintaining adequate phos-phate availability in our soil. Most of our soils naturally have poorlevels of phosphorus, however with years of super-phosphateapplication many soils have large reserves of phosphorus, most ofwhich are locked up chemically.

Man made phosphates such as DAP (di-ammonium phosphate;18-46-0) and MAP (mono-ammonium phosphate; 11-48-0) arewater-soluble and in an unhealthy, unbalanced soil the phosphoruscan be locked up in hours, unusable by the crop.

These products create a "three fold" problem in the soil. MAPrequires three times as much lime to neutralize as other nitrogenproducts (DAP requires 1 times). By producing very acidconditions, disease problems are common.

Phosphorus is the most important anion (negative charged).Phosphorus and its balance to N in the soil, is very important for

the health and vigour of any growing plant. Phosphorus is a vitalpart of the plants energy transfer system and is part of DNA/RNAmolecules.

Highest protein and mineral levels are achieved with high levels ofP, in balance with nitrogen. To keep a proper balance of N to P,the soil needs a high exchangeable P level or readily available P(Colwell) depending on your soils CEC. This is why in a younggrowing plant you never want to supply a large amount of avail-able N at one time. Ideally, available phosphorus levels (50-80ppm) in the soil should be approximately 2-3 times the soluble

nitrogen level (15-30ppm).

What can happen when N to P ratios are reversed ?

Low sugar levels are common with more stress from diseasesand insects.

Plant energy level is limited and will not with-stand climatestress (cold, wet, heat, etc.)

In soils low inbiological activity,only 2 to 10% of

phosphorus will beavailable to the

plant.

Normally, only 1 to4% of P wil l be

exchangeable atany one time forthe plants use.

No wonder wehave

phosphorus

deficiencies in ourcrops. This is why20 to 40L of a top

qualityliquid fertiliser

solution, is betterthan a ton of dryfertiliser (DAP).

Ideally, availablephosphorus levels(50-80ppm) in the

soil should beapproximately 2-3times the soluble

nitrogen level(15-30ppm).



Plant roots absorb P in the form of ions of ortho (P043-

), ordi-hydrogen phosphate (H2P04

-). Nearly all P needs come

through the bio-energy process of the soil (humus or "soil life").Direct foliar P is an excellent way to spoon feed plants that havea need for additional P.

Growing your own phosphorus

Many soils have reserves of P and a healthy soil with 3% organicmatter can have 150-200kg of P. Soluble P is built into themillions of microbes, and consequently they are a source ofexchangeable P. OFS MicroPlus is a source of microbes thatcan help release nutrients from the soil around the plant roots.

A green manure cover crop of cereal rye and hairy vetch canrelease up to 50kg/ha soluble P to the soil. Also applications ofcompost can supply up to 6kg/m

3of exchangeable phosphorus

(P).

Remember this fact!

Soil life and nutrient balance determines the amount ofexchangeable phosphorus in your soil, not necessarily the

amount of dry phosphorus fertiliser you apply.

Research has shown in some soils only 10 to 30% of the croprequirements come from added fertiliser applications. The restcomes from the soil's ability to feed the crop.

Build a humus rich soil teaming with biological life.

Take a look at the Bios Soil Analysis (page 32).

Readily available phosphorus is shown as Colwell P (ppm), but

this reading does not guarantee P to be available to the crop.Soil life and cation exchange balances decide the actual amountof exchangeable P to the plant. Very little P enters the plant rootswithout going through the microbe system.

A level of 50 to 80 ppm Pis adequate for most irrigated crops.

OFS LiquidPhosphorus viairrigation or foliar

spray is convenient,saves time andprovides readily

available phosphorus

for your current crop.



What happens to P in soil

Practically everyone thinks that phosphorus fertiliser is the answerto a phosphorus shortage in the soil.

But the area where we stand to gain the most, is by boosting theavailability of phosphorus already in the soil. Calcium at optimumsoil levels cuts down on the action of iron and aluminium materialswhich "fix" phosphorus in such a way that the plant can't access it.

Another place to gain phosphorus is where there's a choice be-tween shallow and deep-rooted plants. Deep-rooted legumes, suchas lupins, will help a phosphorus situation by pulling up phosphorus

from deeper soil layers.

In a typical soil, plant material and composted manure containmuch of the available phosphorus. This is broken down by bacteriaand then released onto clay particles. A very small amount goesinto the soil water, then directly to the root (see Diagram 6).

Also, phosphorus which is part of the soil mineral fraction, weathersand the amount released goes directly to the clay particles.

Roots feed more efficiently when soluble phosphorus solutions are

concentrated in layers or bands rather than mixing it in the soil.Diagram 7 shows increased root growth in the area of concentratedphosphorus which has dissolved out of the fertiliser band. Phos-phate is thus used more efficiently.

When soluble phosphates are mixed through the soil, they tend to"fix" or become available more rapidly.

Thieves of phosphorus are iron and aluminium oxides (Diagram 9).They combine with phosphorus in a chemical reaction and areextremely insoluble, therefore are locked out of the plant.

High Calcium can take phosphorus away from the plant bycombining and making insoluble calcium phosphate.

Diagram 6: AvailablePhosphorus

Diagram 7: Phosphorusin bands for improved uptake.

Diagram 8: Thieves ofPhosphorus


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9. Importance of Trace Elements

There are six trace elements (micro-nutrients) that are extremely important in the natural balanceprogram. They are zinc, boron, manganese molybdenum, copper and iron. In some cases, theanions (boron, molybdenum), and cations (copper, zinc, manganese, and iron) have complexchemical relationships which affects their availability in soils. The relative availabilities, however,are controlled by the balance that exist between the soil solution, the soil organic matter, thecation exchange sites, and insoluble compounds (see figure below).

Facts about Sulphur

The sulphur/nitrogen balance is very important to a plant's metabolism and energy level. In the Nprocess sugars are combined with natural phosphorus, nitrogen, and sulphur to complete theenergy/amino acid complex. Their balance to each other is vital.

Proper S levels build higher and better enzyme complex systems.

Proper S to N balance increases nitrogen efficiency by a plant.

Sulphur increases protein in grain & grasses, and controls nitrate build up (toxicities).

Sulphur can be used as a valuable tool to lower pH of alkaline soils (pH 7.8 & higher); thereforeincreasing the availability of other key nutrients such as phosphorus, manganese, boron, copper,zinc and nitrogen. It also, can be used to control sodium, magnesium, calcium and other saltbuild-up in problem soils.

Sulphur can be the "key nutrient" to improve the physical condition of your soil.

Building Sulphur Levels

If you have been on a traditional fertilizer/chemical program, apply some combination of the previ-ously mentioned natural practices to build sulphur levels. Also, supplementing S through naturalproducts may be wise for the first few years. Products to consider: New Era pelletised organicfertilisers, compost, gypsum (23% Ca,18%S), potassium sulphate (41% K, 18% S) elemental sul-phur (99% S), or a good grade of nitrogen sulphur solution (28% N 4% S or 30% N - 2% S). Ifyour sulphur levels are low to medium on your soil audit, nitrogen should always be supplied withsulphur. (Plants need an available ratio of 8 parts N to 1 part S). Normally, gypsum or soil sul-phur (99%) will supply adequate elemental S solution for 1-2 crop years.



ZincZinc is a necessary part of certain plant enzymes, calleddehydrogenases, which are vital in the metabolic functions of

cellular respiration. So a zinc-deficient plant will have limited cellfunctions so it will not be a normal healthy plant. Zinc isnecessary in an enzyme, called carbonic anhydrase, whichfunctions in maintaining equilibrium between carbon dioxide andcarbonic acid in tissues. This is essential for photosyntheticfixation of carbon dioxide - the carbon building block.

What might be the ultimate cause of the zinc deficiency in thesoil?

There may be plenty of zinc in the mineral material make up of

the soil, but it may not be available to the plant because of toomuch N, P, Ca, Cu and B. Exchangeable Zn is absorbedthrough roots as ZnO2or ZnSO4(this decreases sharply with theuse of ammonium N).

Zinc availability can be a problem as soil pH increases, in lightsandy soils and under cool, wet weather conditions.

High to excessive amounts of zinc can affect P, Ca, Mn, Fe andCu uptake and/or assimilation by the plant.

ManganeseManganese (Mn) is a weak cation held in the "humus store-house", usually in a complex with other nutrients. Manganese isnecessary for photosynthesis, nitrogen metabolism and other

Growth and yields ofplants are governedby nutrients in leastsupply - not by howmuch NPK we apply.

Although these nutrients do not all behave similarly, there areseveral common factors that affect their availability. The soil

humus acts as a "storehouse" for many of these elements,especially the anions such as boron, which are subject to losses.As the humus decomposes, the nutrients are released and thehumus tends to act as a continuous nutrient supply. Soils thatreceive regular additions of organic residues such as compostand pelletised manures often dont show micronutrientdeficiencies.

If any of these six, or any of the eight nutrients previouslydiscussed become deficient or are out of balance, then yields willsuffer. Remember, Liebigs law of the minimum! It was stated

and proved over 100 years ago that growth and yields of plantsare governed by the nutrients in least supply - not by how muchNPK we apply. Remember the law of the minimum. The nutrientin least supply determines the yield. Keeping this in mind, let ustake a good look at these six trace elements. All six are a vitalpart of all enzyme families.

The major di fferencebetween organic

and synthetic

fertilisers is theeffect on soil

biology and thesolubilit y of the

fertiliser.



OFS Soil Testingprovides simple

guidelines on howto balance yourmicro-nutrients- organic and/or

sustainablerecommendations

provided

amino acid compounds formed as part of plant metabolism. Mndeficiencies can occur in high pH organic soils and low organicmatter sandy soils.

Flooding and soil compaction will decrease Mn exchangeability.Working soil wet will cut availability of N, P, S, Mn and others.

Chelated (EDTA) manganese is usually unsatisfactory for plantuse (they only lock up P). Soil microbes produce their ownnatural chelates in rich humus (organic - acids).

Diagram 9: The Effect of pH Levels onMicro-Organisms and Nutrients

4 5 6 7 8 9

pH



MolybdenumMolybdenum (Mo) is an anion (-) nutrient, and exchangeability

increases with higher pH. Consequently molybdenumdeficiencies are often resolved with lime applications to increasesoil pH. Mo is involved in symbiotic nitrogen fixation in legumes,certain enzymes in nitrogen metabolism, protein synthesis andsulphur metabolism.

CopperCopper is a weaker cation (+) held in the "humus storehouse",and exchangeability to the plant is dependent upon certainbiological activity (like mycorrhizae fungi plants). Copper is anactivator, which allows enzymes to work at faster rates; helpingstimulate root metabolism and fruit elasticity.

Copper is essential in chlorophyll formation and it helps increasethe sugar content in fruits and vegetables especially when Ca andK are in ideal balance. Plants can use copper to buildantibiotics for better disease control.

High to excessive levels of Cu can become toxic to plants. High toexcess levels of N, S, Zn and Fe can affect copper uptake by theplant.

IronIron (Fe) also is a cation, which is needed in very small amountsin a plant, however it is generally abundant in the soil. Iron isessential for the formation of chlorophyll and activation of severalenzymes. It is also important in respiration, a vital part of theoxygen carrying system.

High to excessive levels of P, K, Ca, Zn, Mn, and Cu can affectiron uptake by the plant.

BoronBoron is an acid base anion (-) nutrient that does not likeexcessive levels of nitrogen and potassium. Over fertilisationwith potassium, can create a boron deficiency. Calcium cannotperform it's vital job of stabilising the metabolism process withoutboron.

Boron aids the plant's resistance against harmful fungi and otherdiseases. Boron allows sugars to translocate properly in the plantand aids in good sugar levels in lateral and terminal bud areas.

Organic Ferti liser.Contains a sourceof carbon for soil

microbes withquick and slowrelease forms of

nitrogen and

phosphorus.



10. Plants Obtain Nutr ients in Three Ways

You can broadcast fertiliser, incorporate fertiliser (via irrigation orcultivation), or foliar spray, but nutrients won't help the crop until

they are absorbed by the roots and move into the plant, or movedirectly into the plant through the leaves. Up to 100% efficiencycan be obtained through foliar feeding.

There are 3 ways plants can obtain nutrients through the roots:

1. Contact2. Mass flow3. Diffusion

Many miles of roots lie under each hectare of crop. The roots

however, occupy less than 1% of the total soil volume, and a verysmall amount of the total plant food is intercepted by them(ie direct contact) as they grow through the soil. Consequentlymost nutrients must move through the soil to the roots.

Mass flow is when plant roots take up water and the nutrients thatflow with the water, from the soil. Mass flow supplies much of thenitrate-N, calcium, sulphate and magnesium. In heavier soils, littleP & K moves to the roots by mass-flow.

For example, nitrate-N, or calcium need only be in the moist soil

that has actively absorbing roots, it makes little difference how theN is applied. Side-band placement moves N to the roots by mass-flow just as much as incorporated placement.

Boron can provide extra protection against frosts in early spring in

orchards or insect resistance later in the season.

Boron aids in regulating cell division, salt absorption, hormonemovement, nitrogen assimilation and in the flowering-fruitingprocedure.

For boron to be available to a plant, it must be converted into thenutrient anion level (borate), which is done by soil microbes.

Boron's availability to a plant can decrease in fine textured, heavyclay and high pH soils. Heavy applications of crushed limestone

can limit the amount of boron for plant growth.

Caution: High to excessive levels of boron can become toxic tothe plant, also affecting N, P, Ca, Zn and Mn assimilation by theplant.

Beneficialmicrobes to

promote plantvigour andstrength.


28/34



Soil biology and plant roots are adversely affected by acidic materials and those that contain chlo-

rine or are high in salts. Build a healthy soil life with green manure, cover cropping systems, com-posted animal manures, biological and root stimulants to provide a good healthy root system thatcan obtain all the P and K it needs.

Roots can also change the pH and salt content of the soil. This in turn will change the availability ofnutrients. The form of N used will affect the pH change that occurs. Plants that are fed only onAmmonium-N will make the soil near the root more acid. Biologically, the better synthetic N fertilis-ers contain ammonium-N (23%) and urea (52%) and nitrate-N (25%).

Table 2: Effects of nit rogen sources on pH of so ils.

N SOURCE CHEMICALFORMULA

N % CaCO3(kg)needed for

every kg of N

applied1

Ammonium sulphate (NH4)2SO4 21 5.2

Anhydrous ammonia NH3 82 1.8

Ammonium nitrate NH4NO3 34 1.8

Urea CO(NH2)2 46 1.8

Urea-ammoniumnitrate solution (UAN)

CO(NH2)2+NH4NO3 28-32 1.8

Mono-ammoniumphosphate (MAP)

NH4H2PO4 10

Di-ammoniumphosphate (DAP)

(NH4)2HPO4 18

Potassium nitrate KNO3 13 2.02

1. Amount of pure calcium carbonate (CaCO3) required to either offset the acid-formingreactions of 1kg of N.

2. The amount of CaCO3required to equal the acid-neutralizing effects of per kg of N.Most of the acid-forming effects are due to the activities of soil bacteria during nitrification.

11. Do you have a problem field?

Is performance down, or are crops experiencing stress from disease, weeds or grass problems?

Consider the following checklist:

Look for high to toxic levels of Mg, iron, aluminium, sodium, etc. A plant tissue test can helpdetermine toxic, unbalanced conditions.

Your soil test may show a soil with a good level of Ca (% base saturation), but may be lockedup by overpowering nutrients, such as Mg, iron, aluminium and sodium. Did you know thattraditional chemical products can kill and suppress the rhizosphere bacteria? Humus is

important to buffer the affects of synthetic fertilisers.



Diagram 11: The Soil

Problem fields usually show little or no earthworms and low biological activity.

Many problem areas of our fields are due to compaction. We overwork our soil. We work ittoo wet. We use the wrong tillage equipment. Think twice before you work your soil. Oncewe damage the physical conditions of our soil, soil life suffers. The soil goes anaerobic forthe lack of oxygen, therefore beneficial biological life suffers and plants have a poor,shallow root system. Both can mean poor performing crops.

12. The Carbon CycleCarbon is taken into the plants almost entirely from the atmosphere as carbon dioxide (CO2).The carbon cycle is when this carbon dioxide is transformed into living tissue, and later de-composed by soil organisms back into carbon dioxide.

Actively decaying organic matter can substantially increase the concentration of carbon diox-ide close to the ground, which can directly stimulate crop growth. Therefore a proper decaysystem of crop residues, using soil stimulants combined with a cover cropping system (greenmanure) and compost, adds a "priceless" fertilizer to your soil fertility program.

Remember - it takes a good biological, high energy organic system to supply carbon (CO2),not NPK fertilizer.

5cm 70%

12cm95%

12cm n



13. Plant & Soil Nutrient Inter-relationships

The elements and their relationships are the basis of the balance for healthy crops. Too much ofone item will affect the uptake of others. This chart explains some of the relationships betweenthe elements.

Common problems in the soil can also cause deficiency problems in the crop.

Tables 3 & 4: Plant and Soil - Nutr ient Inter-relationships

High to excessive levels of: Can cause low to deficient levels:

N P K Ca Mg Na S Zn Mn Fe Cu B

Nitrogen (N) X X X X X X X

Phosphorus (P) X X X X X X

Potassium (K) X X X X X X X

Calcium (Ca) X X X X X X X X

Magnesium (Mg) X X X X X X

Sodium (Na) X X

Sulphur (S) X X X X X X X

Zinc (Zn) X X X X X

Manganese (Mn) X X X X X

Iron (Fe) X X X X

Copper (Cu) X X X X

Boron (B) X X X X X

Problem: Can cause low to deficient levels:

N P K Ca Mg Na S Zn Mn Fe Cu B

High pH X X X X X X X

Low Organic Matter X X X X X X

Poor Drainage X X X X

Drought X X X

Poor Aerated Soil X X X X

Sandy Soil X X X X X X

Raw Manuring X X



Soil Analysis inserted on

this page


34/34

14. Diseases & Insects v Nutrients

Diseases and insect infestations are indicators of plant health problems signifying that the plant ispossibly nutritionally deficient and/or excessive: When nutrient levels are balanced within the plant there will be less disease and insect

problems Billions of dollars are spent every year on chemicals to fight diseases and insect infestations

which cure the symptoms, but not the problems that cause the symptoms. Paying close attention to plant health, nutrient balance and inter-relationship will greatly

enhance crop quality, and reduce insect and disease problems.

The following list of nutrients when deficient and/or excessive can induce disease or insect

infestations.

Table 5: Summary Diseases & Insects v Nutrient Defic iencies

Insect Attacks Nutrient Deficiencies Viral Diseases Nutrient Deficiencies

Aphids Ca, P, Fe, Cu, Si Mosiac Virus Ca, P, Fe, Cu

Mites Ca, P, Si Leaf Curl Virus Ca, P, Vitamin E

Slugs Ca, P, Fe, Cu Tobacco Streak Virus Ca, P, Fe, Mo

Lygus Ca, P, Vitamin C, Mn Tomato Ring Spot Virus Ca, P, Vit C, Fe, Vit A

Thrips Ca, P, Co, Si Potato Leaf Roll Virus P, Ca, Cu

Spider-mites Ca, P, Fe, Cu Si Ringspot Virus Ca, P, Carbohydrate, Co, Se

Beetles Ca, P, Fe Vit C, Vit E Leaf Pucker Ca, P, MoCutworms Ca, P, Cu, Co, Vit C, Si

Leaf Hopper Ca, P, Mn, Vit C, Si

Navel Orange Worm Ca, P, Cu, Mn, Co, Vit C, Si

Nematodes Ca, P (Lower Excess Salts (Na)

Fungal Diseases Nutrient Deficiencies Bacterial Diseases Nutrient Deficiencies

Damping Off Ca, Carbohydrates, Mn Fire Blight Ca, P, Vitamin C

Collar Rot Ca, K, Cu Bacterial Blight Ca, P, Vitamin C, Fe, Co

Septoria Leaf Spot Ca, P, K, Vitamin C Crown Gall Ca, P, Vitamin C, Co

Early Blight P, Vitamin C Cane Gall Ca, P, Mo

Late Blight P, Vitamin C Bacterial Wilt P, Ca, I, Vic C, Fe, Cu, K, Se, Co

Verticillium Wilt Ca, P, K, Cu, Mn, Co Bacterial Leaf Spot Ca, Vitamin C, N, P (K excess)

Fusarium Wilt Ca, P, K, Cu, Mo, Co Backleg Ca, B

Phytophthora Ca, Se, P Ring Spot Ca, P, K

Downy Mildew P, Ca, I, Vit C, Cu, Fe, Si Soft Spot Ca, K, B

Powdery Mildew Ca, P, K, Vit C, Si Bacterial Canker/Wilt P, C, Fe, Cn

Leaf Spot P, Ca, K, Vit C, Vit E, Si Bacterial Speck Ca, P, Mn, Fe, Ca (low level)Leaf Rust P, Ca, K, Vitamin A, Co, Si, Bacteria Spot Ca, P Mn, Fe, Ca (high levels)

Botrytis Ca, P, K, Vit A (early season), Si

Alternaria Ca, P, K, Co, Mn, Si

Cane Blight P, Vitamin C, Si, Se

Brown Rot Ca, P, K, Mn, Cu, SiCorn Smut Ca, PS f R C P K F C Si

Af ter reading the d isease and insect charts,notice how often calcium and phosphorusshow up as the number one or two defi-ciencies. Frequent vitamin deficiencies, es-

undestanding soil

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