Sorghum Tillage i n t h e T e x a s H i g h P l a i n s

Ordie R. Jones, Paul W. Unger, R. Louis Baumhardt and Brent Bean*

Tillage Management ToolsProducers can manage sorghum crops by differ-

ent types of tilling — no-tillage, stubblemulch till-age, reduced and clean tillage.

No-TillageNo-tillage management uses chemicals applied

with a multi-row sprayer to control weeds, with theonly soil disturbance occurring during planting. Forestablishing a crop, residue cutting coulters or trashwhippers (fingers) are often mounted ahead of thedouble- or single-disc seed openers to cut or moveresidues away from the seeding area, whichimproves seed-soil contact. Herbicides for in-seasonweed control are often banded behind the opener.Starter fertilizer or insecticides can then be appliedin or near the seed row. The planting operation isnormally accomplished in one pass over the field.

Stubblemulch TillageStubblemulch tillage has the goal of killing

weeds, loosening the soil and maintaining a major-ity of crop residues on the surface to combat winderosion and reduce evaporation. Several imple-ments can be used to do this — field cultivators,sweeps or blades and chisels. In the TexasPanhandle, the most common stubblemulch imple-ment is the V-blade plow originated by Noble.These blades, 3-5 feet wide, are operated at a 3- to5-inch depth, undercutting weed roots and leavingapproximately 75 percent of crop residues on thesoil surface.

Seeding operations can be performed with mosttypes of planters or drills. A mulch treader withground-driven, rotating fingers (similar to a sand-

MATER IS ALL we sellin agriculture.”Whether the enter-prise is corn, cattle,cauliflower, cotton, orgrain sorghum wateris essential for its pro-duction and the R

North Texas (Rolling Plains, South Plains and

Panhandle regions) is produced on dryland or with

limited irrigation. Consequently, water manage-

ment, both precipitation and supplemental irriga-

tion water, is the most important factor in sorghum

production.

Tillage practices can greatly affect soil water con-tent both at planting and during the growing season.For maximum sorghum production and profit,planned crop rotations and tillage practices are crit-ical to enhancing soil water contents and ensuringsuccessful sorghum production. Successful tillagepractices are those that:

• Control weeds

• Control erosion

• Reduce evaporation

• Reduce runoff

• Are economical and practical.

*Panhandle AgriPartners Coordinator, Texas CooperativeExtension—Amarillo; Soil Scientist, USDA-ARS, Bushland(retired); Soil Scientist, USDA-ARS, Bushland; ExtensionAgronomist, Texas Cooperative Extension—Amarillo, TheTexas A&M University System.

OST SORGHUM grown inMR

L-54395-03

fighter) can be attached to stubblemulch plows todislodge weed roots. A disadvantage of stub-blemulch tillage is that weeds will often reset if arain occurs within a day or two after tilling.

Reduced TillageReduced or minimum tillage uses a combination

of stubblemulch tillage and chemicals for weedcontrol and residue management. This method isused by most producers. It takes advantage of theexcellent in-season and fallow water-conservingweed control made possible with selected chemi-cals, and the stubblemulch tilling reduces the costof weed control and seedbed preparation.

Clean TillageClean tillage uses disks or moldboard plows to

bury crop residues, kill weeds and prepareseedbeds. This traditional tilling system leaves thesoil vulnerable to wind and water erosion andresults in soil drying from water evaporation andloss to the depth of tillage. It should be avoided ifpossible. Listing (corrugating to form beds and fur-rows) is sometimes used in the spring to expose ero-sion-resistant clods on soils prone to erosion. Thepractice is prevalent following low residue produc-ing crops, such as cotton, to prevent or reduce winderosion.

Weed ControlWhether weed control is mechanical, chemical

or a combination, weeds must be controlled whilethey are small so that soil water is conserved foruse by the sorghum. Timely and effective weedcontrol during crop and non-crop (fallow) periods isessential for successful dryland or limited-irrigatedcrop production.

Erosion ControlNatural soil formation processes take 30 years or

more to form an inch of topsoil. Clean tillage onsloping ground without conservation practices canallow the loss of several inches of topsoil from onehigh-intensity rainstorm. Using soil conservationpractices — terracing, contour rows and furrows,land leveling and waterways — in conjunction withimproved tillage and residue management practicescan prevent or reduce both wind and water erosion.Improved tillage and residue management practicesinclude no-tillage, reduced- or minimum-tillage andstubblemulch tillage. The primary advantage of

leaving some or all of crop residues on the soil sur-face is to reduce the effect of raindrop impact onthe soil surface, which promotes water erosion. Tocontrol wind erosion, residues, particularly stand-ing residues, reduce wind energy reaching the soilsurface and lessen soil loss.

In practice, tillage (chiseling or listing) is oftenused to produce a roughened soil surface to controlwind erosion following crops such as cotton or sun-flower, which produce low amounts of residue.Including sorghum in the crop rotation, in conjunc-tion with improved residue management practices,is an effective method to control both wind andwater erosion. The residues improve water infiltra-tion, reduce surface evaporation and reduce bothwind and water erosion.

Reduce Evaporation and Runoffto Improve Water Conservationand Storage

Residues decrease wind speeds and shade thesoil surface, which reduce evaporative energy andlessen the ability of water vapor to be removed rap-idly from the soil surface. Likewise, residues protectthe soil surface from raindrop impact and soil crust-ing, which keeps the soil surface open and receptiveto water infiltration.

Since precipitation and irrigation water mustinfiltrate the soil surface to become available forplant root uptake, it is advantageous to sorghumproduction to maintain residues on the soil surface.By doing so, infiltration rates remain high, and themaximum amount of water enters the soil and ismoved deeply into the soil profile. Water stored inthe root zone below the one-foot depth will normal-ly be available for extraction by roots, even afterseveral months. Water stored near the surface issubject to evaporation.

Tillage with cultivators, sweeps, disks or chiselsis a primary method of loosening the soil to destroysoil crusts and enhance infiltration. However, tillageis also largely responsible for much of the evapora-tion that occurs from the soil. Tilling often causesthe soil surface to dry to the depth of tillage, result-ing in the loss of 1/2 to 1 inch of soil water. This drysoil must be re-wet before additional rain or irriga-tion water can be stored in the soil profile.

Water conservation can also be enhanced andrunoff reduced or eliminated by using furrow dik-ing. With furrow dikes, small dikes or dams are con-structed at intervals along furrows or in the inter-

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row area between crop rows. This results in smalldepressions that retain potential storm runoff so itcan infiltrate. Furrow dikes are applicable to dry-land or irrigated crop production. The use of fur-row dikes is normally recommended for use onfields that are irrigated with LEPA (low energy pre-cision applicator) because water is applied at a highrate to a small area. When pivots are aligned up anddown slope, considerable runoff can occur. Furrowdiking is applicable for reduced tillage or cleantillage management but is difficult to employ withno-tillage.

Reducing or eliminating tilling reduces evapora-tion and increases soil water storage. The results ofa 6-year dryland study of the effects of tillage onsoil water contents at planting of sorghum andwheat (after 11-months of fallow) are shown inFigure 1 and Table 1. Deep chiseling with a para-plow was performed on half the field-sized water-sheds, and subsequent management was witheither no-tillage or stubblemulch (large V blades)dryland tillage management. Paratillage had littleeffect on soil water content or on grain yield witheither no-tillage or stubblemulch management witheither sorghum or wheat. However, compared tostubblemulch management, no-tillage managementresulted in greater amounts of water in the soil con-tents. The soil in this study was Pullman clay loam,precipitation averaged 18 inches per year and thecropping rotation was a 3- year wheat-sorghum-fal-low sequence. Paratillage was performed everythird year after sorghum harvest when the soil pro-file was relatively dry.

No-tillage management of wheat residues priorto planting sorghum resulted in nearly an inchmore stored water in the soil profile, whichincreased sorghum yields in comparison to stub-blemulch management. Long-term research hasshown that on dryland, each inch of additionalstored soil water will result in a 300-400

pound/acre increase in sorghum yield. Wheat,however, does not respond in a similar fashion toincreased soil water content at planting, becausewheat yield is closely related to the timing andamount of spring rains. Thus little difference inyield results from no-tillage management ofsorghum residues prior to planting wheat. Jonesand Popham (1997) suggest a reduced tillage system— no-tillage of wheat residues and stubblemulchmanagement of sorghum residues. No-tillage man-agement of wheat residues during fallow periodsincreases soil water storage, increases sorghumyields and reduces erosion. Stubblemulch manage-ment of sorghum residues alleviates soil crustingand water runoff problems associated with no-tillage management of sorghum residues on clay

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Table 1. Tillage and residue management effects on 6-year (1990-1995) average soil water contents at plant-ing and grain yields in a dryland wheat-sorghum fallow rotation — Bushland, TX

Sorghum—Available Sorghum—Grain yield Wheat—Available Wheat—Grain yieldTreatment soil water (inches) (bu./ac.) soil water (inches) (bu./ac.)

NT-No PT 7.2 56.5 7.4 28.5

NT-PT 7.6 51.3 7.6 30.2

SM-No PT 6.1 44.9 6.8 30.8

SM-PT 6.5 49.2 6.8 29.5

NT = no-tillage; PT = para-tillage; SM = stubblemulch

Figure 1. Six-year (1990-1995) mean average plant availablesoil water contents at sorghum and wheat planting for field-sized plots cropped in a 3-year wheat-sorghum-fallow dry-land rotation at Bushland, TX. A deep-chiseling paraplowtreatment (PT) was applied to one-half the plots, and sub-sequent management was no-tillage (NT) or stubblemulch(SM). The NOPT treatment was not paraplowed but receivedonly the NT or SM management. Fields were soil sampled(soil cores) by 1 foot increments to a 6-foot depth at plant-ing and harvest. Every treatment was present every year.

soils. Alternating tillage methods will also aid inweed control, particularly with herbicide resistantweeds such as atrazine-resistant kochia.

In a 10-year dryland cropping and tillage study atBushland, Texas, annual cropped (continuous)sorghum yields were 4 bushels/acre greater withstubblemulch tillage than with no-tillage manage-ment. Annual returns were $24/acre greater withstubblemulch, primarily due to the increased pro-duction costs of no-tillage management (Jones andJohnson, 1996).

RecommendationsWhen production costs and returns are com-

pared for a total no-tillage management system fordryland sorghum production, whether in rotationor continuous cropping, it is difficult to justify thehigher herbicide costs associated with no-tillagemanagement. Yields are not increased sufficientlyto offset higher herbicide costs (Jones and Johnson,1996).

We recommend a reduced tillage approach tosorghum production, using no-tillage for managingwheat residues prior to planting sorghum in a wheat-sorghum-fallow rotation and stubblemulch to man-age sorghum residues. Weed control can be a accom-plished with a combination of herbicide applicationsand/or tillage. To reduce in-season herbicide costs,crop rows can be banded with herbicides to controlweeds. Control of inter-row weeds can be accom-plished with a cultivator or with under-canopy hood-ed sprayer herbicide applications of glyphosate,paraquat or other chemicals.

Conclusion• Weed control during cropped and non-

cropped (fallow) periods is critical to suc-cessful dryland or irrigated crop produc-tion. Weeds can use soil water at a rateexceeding 1/3 inch per day. An inch of stored

soil water will increase sorghum yield bymore than 300 pounds per acre. Weed control,either chemical or mechanical, is best accom-plished when weeds are small.

• Tillage breaks up soil crusts, kills weeds, alle-viates compaction and prepares seedbeds.However, it also increases evaporation ofsoil water. Soil will normally dry to thedepth of tillage, so that 1/2 to 1 inch of wateris re-quired to re-wet the tilled soil zonebefore additional infiltration to evaporation-resistant soil depths (2-4 feet) occurs. Stubble-mulch tillage is preferable to clean tillagebecause crop residues left on the soil surfacereduce erosion and evaporation.

• Tillage and crop management strategiesshould provide a profile full of stored soilwater at sorghum planting. An additional6-8 inches of soil water can practically guar-antee a good crop of sorghum on dryland andgreatly reduce irrigation pumping for irrigat-ed sorghum production.

• An inch of stored soil water is much morevaluable than an inch of rain or irrigationwater because much of the water stored inthe top foot will eventually evaporate.

• Crop residues should be considered asanother resource and should be managedas carefully as soil and water resources.Crop residues should remain standing as longas possible to reduce wind erosion and evap-oration. Not all residues are equally efficient.A ton/acre of wheat residues is much moreeffective in reducing evaporation and erosionthan is a ton/acre of high density (largerstalks) residues such as sorghum or corn.

For more information, see the sorghum websiteat http://sorghum.tamu.edu (perform an advancedsearch for “tillage”). To contact individual authors,see or-jones@tamu.edu, lbaumhardt@cprl.ars.usda.gov,pwunger@tcac.net or b-bean@tamu.edu.

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