EFFECT OF FALL AND SPRING TREATMENT OFSTUBBLE LAND ON YIELD OF WHEAT IN THE BLACKSOIL REGION OF MANITOBA AND SASKATCHEWAN

K.E. Bowren

Research Station

Research Branch, Canada Agriculture

Melfort, Saskatchewan

R.D. DrydenResearch Station

Research Branch, Canada AgricultureBrandon, Manitoba

INTRODUCTION

In the park belt region of the prairieprovinces the need for fall tillage ofstubble land which is to be seeded the

next spring has been questioned onnumerous occasions (9, 13). The removalof trash by burning combine straw, apractice condemned by conservationists(4, 9, 12) has been practiced consistentlyon many farms in the area. Severaldifferent types of machines are used withsuccess for fall tillage. Tillage with thesemachines reduces the combine trash on

the soil surface (1) facilitating trash clearance with seeding equipment (2, 10). Falltillage has also been recommended (13)for the control of annual and perennialweeds. By working the land, crop andweed seeds are encouraged to germinateand be killed by winter freezing or pre-seeding tillage in the spring. Trash coverreduces erosion and improves the physicaland chemical properties of the soil (4,12,13,14,15).

It has been shown (9) that at severallocations on the prairies, heavy combinetrash reduced the yield of the followinggrain crop. At all of these locationsexcept Regina there were, however, trashmanagement treatments that produced ayield that was not significantly differentfrom that obtained where all the trash

was removed by burning. At Brandon(12) it was found that straw applicationshad a beneficial effect on yields, while atLethbridge (3) up to 4480 kg/ha of strawmulch had no deleterious affect on cropyields.

The study reported here was conducted at Brandon, Manitoba andMelfort, Saskatchewan to compare theeffect of several methods of treatingstubble on the yield of second cropwheat.

METHODS

The experiments were established on

the stubble of a wheat crop grown following summerfallow on Melfort silty clay(10% organic matter) soil at Melfort andon Assiniboine clay loam (7% organicmatter) at Brandon. Five tillage machinesand the removal of straw in the fall and

spring by burning were compared with anuntreated plot as a control (Table 1). Inaddition, a combination of fall burningand cultivating was studied. The testswere conducted from 1961 to 1968 at

Melfort and from 1960 to 1968 (except1966) at Brandon. The treatments werearranged in a randomized split-plot designwith methods as main plots and fertilizerversus no fertilizer as the sub-plots. AtBrandon, chopped straw was comparedwith unchopped combine straw. Thetreatments were replicated four times inplots 3.7 x 30.5 m at Melfort and 3 x 6.1m at Brandon. The tillage machines wereset to cut 8—12 cm deep and wereoperated at 4.8 km/h.

TABLE I TILLAGE MACHINES COMPARED AT BRANDON AND MELFORT

Size of

ti.llage tool Approximate Speed of

Tillage Tool

cm depth of tillagecm

operation

Machine Brandon Melfort km/h

Moldboard Plow Share kO.6 35.6 8-10 4.8

1Discer Blade 40.6 40.6 8- 9 4.8

2Cultivator Shovel 30.5 40.6 8-10 4.8

3Cultivator Shovel —

5.0 10-12 4.8

Roto-tiller Blade 7.6 —8-10 4.8

Packer — — —4.8

1. Wide level disc harrow

2. Rigid frame cultivator (heavy duty) equipped with low lift sweep shovels

3. Rigid frame cultivator (heavy duty) equipped with narrow spike shovels

4. Crow foot

RECEIVED FOR PUBLICATION NOV. 15,1970

32 CANADIAN AGRICULTURAL ENGINEERING1, VOL. 13, NO. 1.JUNE 1971

In the spring, all plots were tilled witha discer, harrowed and seeded to wheatwith a press drill at the rate of 101 kg/ha.At Brandon, Selkirk wheat was sownfrom 1960-1965 and Manitou in 1967and 1968. At Melfort, Pembina wheatwas sown in 1961 and 1962, Canthatchfrom 1963 to 1965 and Manitou from

1966-1968. Prior to 1967, the fertilizerapplications recommended for stubbleland were used at both locations. In 1967

and 1968, soil tests were employed todetermine the levels of fertilizer required.On the average, 22.4 kg/ha of nitrogenwere used at each station. Some 22.4 and

15.7 kg/ha of phosphate were appliedeach year at Melfort and Brandon, respectively. Annual grass-type weeds such aswild oats (Avena fatua L.) and green foxtail (Setaria viridis L.) were usually not aproblem in these experiments. Broad-leaved weeds in the crop were sprayedwith MCPA or 2,4-D when required.

At Melfort, a swath 3 x 24 m was cutfrom the centre of each plot and threshedwith a self-propelled combine. The grainsamples were weighed on the combinewith a hydraulic cell weigher (5). Yield,weight per unit volume and percent protein were determined from each sample.At Brandon, an area 0.9 x 3 m in thecentre of each plot was harvested andthreshed to obtain the yield. At Melfort,the effect of the treatments on cropresidue was determined by collecting thesurface straw and stubble from an area0.9 m2 at five locations in each plot afterthe tillage or burning treatment had beenperformed. The weight of straw obtainedwas recorded and compared with similarmeasurements of the original trash interms of percentage reduction in dry matter. Prior to the treatments the wheatstraw and stubble varied from 1217 kg/haof dry matter in 1963 to 5232 in 1966and averaged 2691 kg/ha over the eight-year period. At Brandon, unchopped andchopped straw was applied to the plots tobuild up the residue to 3696 kg/ha beforethe treatments were applied. The weightof dry matter remaining on the soil surface after seeding was measured and recorded for each treatment.

At Melfort, soil stored moisture to adepth of 1.2 m was determined gravi-metrically on all plots before the falltreatments were applied and at seedingtime the following spring.

At Brandon, the effect of treatmentson soil aggregation was determined bymeans of the rotary sieve method (7, 8).

This procedure determined the percentage of surface soil aggregates less than0.84 mm in size. This fraction is considered to be the most susceptible toerosion.

RESULTS AND DISCUSSION

Yields of Wheat

At both stations the untreated plotsproduced good yields (Table II). Although the roto-tiller at Brandon and thediscer at Melfort gave slightly higheryields, these effects were not statisticallysignificant. Fall cultivating or plowingand fall or spring burning all gave loweryields than the non-treated plots. Dawleyet al (9) reported that spring burning wasthe highest yielding treatment at Melfortduring the term of their study. These conflicting results could be due to the factthat these tests were over a longer anddifferent period of time and that presentday equipment provides more uniformtillage for weed control and seed bed pre

paration in heavy trash. At Melfort, yieldswere significantly lower on the plowingand on the burning with cultivation treatment than on the non-treated plots. Fallplowing was also reported to have produced a lower yield (not statisticallysignificant) than non-treated plots atMelfort by Dawley et al (9).

Fertilizer increased average yieldssignificantly at Brandon in all yearsexcept 1960, but in only two (1963 and1966) of the eight years of the study atMelfort. The average yield of all treatments with and without fertilizer were

similar over the eight-year period atMelfort. Dawley et al (9), in trials with abroader range of fertilizer treatments,reported a significant increase in yieldfrom fertilizer at Melfort in their study.In the study reported here the summer-fallow wheat crop was fertilized with 11kg/ha of nitrogen and 45 kg/ha ofphosphorus to obtain a maximumquantity of straw for the study. These

TABLE II THE EFFECT OF FALL AND SPRING TREATMENTS OF STUBBLELAND ON YIELDS OF WHEAT AT BRANDON AND MELFORT

Treatment

YBrandon

1961-1965, 1967,

Leld, kg/ha

1968Melfort

1961-1968

Fall

Roto-till 2358

No treatment 2339 2330abPlow 2318 2168°Disc 2305 2357aCultivate 2278 2190bcCultivate, pack 2l97abcCultivate (spikes) 2249abcBurn and cultivate 2171°Burn 2250abcSpring

Burn 23l6abc

Straw, chopped 2339

Straw, not chopped 2298

Fertilized 2460 2252

Not fertilized 2184 2242

Means followed by the same letter are not significantly different atthe 5% level of probability.

CANADIAN AGRICULTURAL ENGINEERING, VOL. 13, NO. 1, JUNE 1971 33

rates were higher than those generallyused on summerfallow grown wheat atMelfort during the earlier study. Whilethe interaction of fertilizer x years wassignificant at both locations, that offertilizer x tillage treatment was not. Thisfinding agrees with that of Dawley et al(9). There was no significant difference in

TABLE HI THE EFFECT OF FALL TREATMENTS ON TRASH COVER AT

BRANDON AND MELFORT

Trash Cover, Soil Aggregation and SoilMoisture.

The loss in trash cover varied from88% on the fall plowed method to 26%on plots tilled with the discer as compared to undisturbed stubble at Melfort(Table III). These reductions are within

Crop Residue, kg/haBrandon Melfort

1961-1967

Treatment

No treatment

Disc

Cultivate

Cultivate, pack

Cultivate, (spikes)

Burn and cultivate

Burn

Roto-till

Plow

Straw, chopped

Straw, not chopped

Mean (before fall treatment)

1962-1964 ,^,-^w,After seeding After fall tillage

1131

8l8h

739*

549c

90d

437"

3696

2691

1991

1615

1668

1830

377

727

323

2691

1. Crop residue after fall tillage and seeding in the spring. Means

followed by the same letter are not significantly different at the

5% level of probability.

2. Crop residue after fall tillage.

the range reported by Anderson (1) forsimilar machines. The plow and burntreatments, depleted the surface trashwhile other methods retained sufficienttrash cover to provide reasonable protection against soil erosion.

Tillage with the plow at Brandon notonly depleted the trash cover, but alsoproduced a significant increase in the soilaggregate (<0.84 mm) that are mostsusceptible to wind erosion (Table IV).This combination of factors could have

contributed to very erosive conditions,particularly during the winter and springmonths before seeding. It has been shownthat dry soil aggregates are not stableduring the winter and spring period (6).Soil aggregation as a result of using theplow, varied more from year to year thanother treatments, probably because ofgreater freezing and thawing due to thelack of trash to hold a protective cover ofsnow on these plots. For example, in1963, an erodible fraction before seedingof 69.4% was recorded with the plowcompared to 48.3% on disced and 45.5%on untreated plots. On the average, thefall disc and no fall treatment had

significantly less fine material in thesurface soil than the cultivate and plowtreatments prior to seeding at Brandon.Fortunately, spring operations (discing,harrowing and seeding) reduced the percentage of erodible soil on all treatmentsand tended to even out the difference

between the treatments.

The effect of different treatments on

the storage of soil moisture from the fall

yield between chopped and unchoppedstraw at Brandon, however, choppedstraw facilitates spreading and tillage ofthe trash. These results also agree withthosereported by Dawley et al (9).

Weight per Unit Volume and PercentProtein

At Melfort, the untreated plots andthe discer treatment produced wheat withthe highest volume weight, (78.0 and77.9 kg/hi respectively); these were significantly greater than the weight per unitvolume resulting from the fall cultivation(sweep shovels) method (77.2 kg/hi).There was no significant differencebetween protein contents. The average ofall treatments was 15.8%. Fertilizer hadno significant effect on the weight perunit volume or the protein content of thewheat.

TABLE IV THE EFFECT OF FALL TILLAGE ON SOIL AGGREGATION ATBRANDON

34

Percent of surface soil less than 0.84 mm in size

Treatment

Plow

Cultivate

Roto-till

Disc

No treatment

Before seeding

1963-1965

47.0e

43.2;40.7

37.7

36.0d

ab

be

cd

After seeding

1963-1965

35.2°

36.0s

34.8£

33.6

30.hl

ab

1. Soil fraction most susceptible to erosion by wind.

2. Means followed by the same letter are not significantly different

at the 3% level of probability.

CANADIAN AGRICULTURAL ENGINEERING, VOL. 13, NO. 1,JUNE 1971

to spring seeding at Melfort was not significant. A five-year average of water storedto a depth of 1.2 m over the winterperiod was 5.1 cm.

Under certain conditions, fall tillagemay be necessary. It is a means of controlling weeds, and assists in preparing aseed bed (11, 13). This study supportsearlier work (11) and indicates that tillagewith a discer would be superior to theother methods tested. Depending uponthe method of seeding, discing may beneeded to reduce trash cover if largeamounts of crop residue (e.g. over 2240kg/ha) will interfere with good placementof the seed. This problem was encountered when a double disc drill was used for

planting (2).

An earlier report showed that thediscer was useful for the preparation ofstubble land in the spring, prior to seeding with a press drill (10). That reportalso indicated that the discer-seeder, as adirect seeding implement, produced oneof the highest yields.

CONCLUSIONS

At both stations, under medium torelatively high levels of crop residue, theuntreated plots were equal to the besttreatments in terms of yields and weightper unit volume of wheat and providedthe greatest amount of trash cover for thecontrol of soil erosion. There was no

significant increase in yield and hence noeconomic advantage from fall tillage ofthe soil or burning of the straw onstubble land.

The fall burning and cultivate treatment, a common practice on many farms,produced one of the lowest yields. Otherconsequences of burning straw, includingserious waste of organic matter, plantnutrients and probable loss of soil byerosion emphasize the importance of discontinuing this practice. In addition torelatively low yields, fall plowing alsoincreased the susceptibility of the soil toerosion. A serious decrease in trash cover

was accompanied by a significant increasein erodible soil, particularly in the overwinter and early spring period.

This study indicates that surface tillagein the fall to control weeds or reducelarge quantities of combine trash (e.g.over 2240 kg/ha) to facilitate seedingwillproduce better yields than untilled orburned stubble. It also shows that fall tillage with the discer is equal or superior to

fall tillage with the heavy duty cultivatorin terms of trash reduction, soil pulverization and yield of wheat on the black soilsof Manitoba and Saskatchewan.

SUMMARY

In an eight-year study at two sites(Brandon, Manitoba and Melfort, Saskatchewan) in the black soil region ofwestern Canada fall tillage or burning ofstubble did not significantly increase theyield, weight per unit volume or proteincontent of wheat. The study comparedfall tillage with several tillage machinesand burning on summerfallow grownwheat stubble under relatively high levelsof crop residue. The machines used forfall tillage reduced the trash on the surface facilitating the preparation of a seedbed the following spring. The moldboardplow depleted the surface trash and produced soil clods that broke down over

winter to create a soil surface that was

susceptible to erosion. Fall burning andcultivating, a common practice on manyfarms, was one of the lowest yieldingtreatments. Fall tillage with the discer, atreatment that provides a measure ofweed control, reduced the trash on thesurface by 26 percent at Melfort, wasamong the highest yielding treatments atboth stations, and provided satisfactorytrash and clod characteristics for seed bed

preparation and erosion control.

ACKNOWLEDGEMENTS

The assistance of Mr. A.L. Lagler andMr. Harold Moen, Computer Systems Programmers, Research Station, Lethbridge,Alberta and Swift Current, Saskatchewan,for analyzing the data for this report ishereby acknowledged.

REFERENCES

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3. Anderson, D.T. and R.G. Russell,1964, The effect of various quantities of straw on the growth and yield

CANADIAN AGRICULTURAL ENGINEERING, VOL. 13, NO. 1.JUNE 1971

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12. Ferguson, W.S., 1967, Effect ofrepeated applications of straw ongrain yields and on some soil properties. Can. J. Soil Sci.47:2:117-121.

13. Guide to Farm Practice in

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14. Manering, J.V. and L.D. Meyer,1963, The effect of various rates ofsurface mulch on infilatration anderosion. Soil Sci. Soc. of Amer. Proc.27:1:84-86.

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