Irrigated and Dryland

Grain Sorghum ProductionSouth and Southwest Texas

Charles Stichler, Mark McFarland, and Cloyce Coffman*

*Associate Professor and Extension Agrono-mist; Assistant Professor and Soil FertilitySpecialist; Associate Professor and ExtensonAgronomist, The Texas A&M UniversitySystem.

Many people try to put thegrowth, development and

eventual yield of the grainsorghum plant into a simpleformula, when it is a complexseries of many processess andinteractions. Only after de-cades of research, the effectsand interactions of fertility,row and plant spacing, plant-ing date, environmental condi-tions (water, temperature, etc.),insects, diseases and hybridsare better understood. All areimportant factors in determin-ing crop yield. A brief sum-mary of the basic growthprocesses and importantinteractions follows to assist inmaking better productiondecisions as conditions in thefield change. Informationrelated to weed and insectcontrol is not addressed in thispublication, but can be foundin Suggestions for WeedControl in Sorghum (B-5045)and Managing Insect andMite Pests of Sorghum(B-1220).

Growth and

DevelopmentLike other crops, seed produc-tion in sorghum is a one-timeevent and all root, leaf andstem development is directed

toward completion of thereproductive cycle. Since boththe number and weight of seeddetermine yield, it is importantto understand the plant pro-cesses that influence seeddevelopment. Plant growth ineach stage of development isdependent on the previousstage. Stress in any stage ofdevelopment will reduce yieldpotential.

Many producers falsely believethat sorghum is “tough” andrequires little management.Although sorghum can surviveand produce seed under ad-verse conditions, yields can begreatly reduced by environ-mental stress and poor man-agement. Like any other crop,sorghum responds to optimumgrowing conditions and goodmanagement.

Seedling DevelopmentThe seedling developmentstage begins at germinationand ends 30 to 35 days afteremergence when plants havefive to six mature (fully ex-panded) leaves. Emergence andearly plant growth are highlydependent upon growingconditions. Plant growthrequires energy, but it takestime to produce carbohydrateswith a few small leaves whichare subject to destruction bywind, hail, frost, insects andpests. As plants slowly developtheir root systems and absorbwater and nutrients, leaf tissueexpands and produces carbo-

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

hydrate energy for futuregrowth. During this period ofdevelopment, water andnutrient uptake are low, andonly about 25 percent of thetotal crop nutrient demand willbe absorbed.

Rapid GrowthIn the rapid growth stage, 40 to65 days after emergence,growing point differentiationoccurs and the panicle or headbegins to develop. This stagecontinues through head exer-tion. During this period, plantsare especially sensitive to anytype of stress such as tempera-ture extremes, nutrient defi-ciencies, or water deficits orexcesses, any of which mayreduce potential seed numbers.Some herbicides (e.g., phenoxyor atrazine) applied at this timemay cause florets to abortresulting in a “blasted” head.The rate of water and nutrientuptake increases rapidlyduring this period with about70 percent of the nitrogen, 60percent of the phosphorus and80 percent of the potassiumbeing absorbed into the plant.Plants use a portion of thesenutrients for growth with theremainder stored in the leavesand stalks for later use. By thetime the “flag leaf” is visible inthe whorl, 80 percent of thetotal leaf area is capturingsunlight and converting it intoenergy. The rapid growth stageis the most critical stage ofplant development and theperiod during which growingconditions have significantimpacts upon yield.

ReproductionThe final growth stage beginswith booting or head exertionand ends with mature grain.Water stress during this periodreduces the manufacturing ofcarbohydrates and ultimately

reduces yield. Water usagepeaks shortly after flowering at0.30 to 0.35 inches of water perday. The remaining portion ofnutrients is absorbed duringthis high water use period. (R.L. Vanderlop describes in detailnine stages in How a SorghumPlant Develops, Bulletin No.S-3 Kansas State University.)

PlantingSorghum seed are small in com-parison to the seed of cotton,corn and soybean. Sorghumdoes not have the large reservesof energy and minerals to with-stand as much stress as othercrops with larger seeds. About75 percent of the seeds plantedmay be expected to survive andproduce emerged seedlings.Thus, planting rates should beadjusted according to plantingconditions. Relatively slowgrowth due to cool tempera-tures, poor soil moisture condi-tions and competition fromweeds may delay developmentand seriously reduce grainyields. The minimum soiltemperature at the desiredplanting depth for germinationand emergence of sorghum isabout 55° F.

The size of sorghum plantingseed may vary greatly amonghybrids; therefore, carefulattention should be given toproper equipment calibrationduring planting to obtain thedesired seeding rate. Seedingrate should not be based onpounds of seed per acre, butrather the correct number ofseed per acre.

Plant DensitySorghum plants are very waterefficient and have the ability tocompensate considerably ingrain yield with respect to

growing conditions and plant-ing rates. If soil moisture islimiting, grain yield will begreater if plant density islower. Furthermore, if soilmoisture is favorable due toirrigation or adequate rainfall,there is a level of plant densityabove which no additionalgrain yield will be achievedfrom an increase in plantdensity. If a modest plantdensity is used for an areatypically limited by adequatemoisture and above averagerainfall is received, sorghumplants can adjust their grainnumbers and weight consider-ably to compensate for theimproved growing conditions.

Depending upon soil moistureconditions, recommendedseeding rates vary between30,000 and 100,000 plants peracre for South Texas. Underlimited moisture conditions, 2 to4 plants per foot for 38-inch rowspacings will normally use allavailable soil moisture (Table 1).Irrigated sorghum performsbetter with about 80,000 plantsper acre when planted in widesingle or double row configura-tions or when narrow rowpatterns are used (Table 2).Sorghum plants are moreefficient when each plant isgiven space to intercept sunlightand competition between plantsis minimized. In addition,closer spacing (i.e., double rowor narrow rows) will promoteshading of the soil surface toreduce evaporation losses andweed competition.

Tests conducted at the NorthPlains Research Center at Etterdemonstrate a similar responseto irrigation levels and seedingrates (Figure 1).

FertilityThe concentration of nutrientsin different plant parts may

2

sorghum plants during variousstages of development in theprocess of producing 7,500pounds of 14 percent moisturegrain per acre. The amounts ofsecondary and micronutrientsused to produce 7,500 poundsof grain per acre are shown inTable 5. Nutrient distributionin dry matter between grainand stover is presented inTable 6. Note the amount ofnitrogen and phosphorus in thegrain. Conversely, a substantialamount of potassium is con-tained in sorghum stoverrelative to nitrogen and phos-phorus. If green stover isremoved repeatedly, soilphosphorus and potassiumlevels may be depleted.

NitrogenThe standard nitrogen (N)recommendation for grainsorghum in Texas is 2 poundsper acre of elemental N foreach 100 pounds per acre ofgrain production expected.

Table 1. Effects of plant density and row spacing on grain yields of dryland sorghum.

Row Plants/Acre Plants/Acre Plants/Acre Plants/Acre

Width 27,000 41,000 55,000 76,000

38 2,358 2,745 2,635 2,567

2 rows/bed38 in. rows 2,440 2,687 2,415 2,617

Source: Texas Agricultural Experiment Station, Uvalde, Texas (1976 -1980)

Table 2. Ef fects of plant density and row spacing on grain yields of irrigated sorghum.

Row Plants/Acre Plants/Acre Plants/Acre Plants/Acre

Width 27,000 41,000 55,000 82,000

26 3,564 4,075 4,787 4,815

38 2,906 3,026 3,203 3,726

2 rows/bed38 in. rows 2,725 3,547 3,976 4,100

Source: Texas Agricultural Experiment Station, Uvalde, Texas (1977 -1981)

3

Figure 1. Relationship of seeding rate, water use and yield.

(PP=preplant; E = Early, 6-8 leaf; H = heading, f lowering to soft dough; B =boot, f lag leaf; M = milk to sof t-dough)

Source: Texas Agricultural Experiment Station, Etter, Texas

vary considerably dependingupon the conditions underwhich the crop has been grown.Table 3 gives the approximatenutrient content of sorghumgrain and stover where grain

yield was 5,600 pounds peracre (100 bu/A).

Table 4 shows the amount ofnitrogen, phosphorus andpotassium absorbed by grain

Table 4. Approximate amounts of nutrients absorbed during various growth stages by

sorghum plants yielding 7,500 lb/A of grain.

Growth Days af ter Nitrogen (N) Phosphorus (P20

5) Potassium

(K

20)

Stage Planting lb/A % of Total lb/A % of Total lb/A % of Total

Seedling 0 - 20 9 5 2 3 18 7

Rapid Growth 21 - 40 61 33 18 23 103 40

Early Bloom 41 - 60 60 32 28 33 85 33

Grain Fill 61 - 85 27 15 21 26 39 15

Maturity 86 - 95 28 15 11 14 13 5

Totals Harvest 185 80 285

Source: Kansas State University - Grain Sorghum Production Handbook

Table 5. Approximate total lb/A of secondary and micronutrients required for a 7,500 lb/A

grain sorghum yield.

Sulfur Magnesium Calcium Iron Zinc Manganese Boron Copper

21 17 20 2.5 .21 0.17 0.1 0.3

Source: Kansas State University - Grain Sorghum Production Handbook

Thus a 5,000-pound grain yieldwould need about 100 poundsof elemental nitrogen per acre.Nitrogen is by far the mostimportant nutrient for sorghumto maximize production. Nitro-gen is normally used by plantsfor chlorophyll and proteinproduction, which in turn isused in formation of new plantcells. The seed also stores N toenable early growth aftergermination. Fifty-eight per-cent of the N absorbed bysorghum plants may be foundin the grain at harvest (Table 6).For maximum yields relative tothe available water, N shouldnot be lacking or grain develop-ment will be reduced.

Side-dress N applicationsshould be made by 20 daysafter emergence. Later applica-tions may excessively prunefeeder roots but more impor-tantly, developmental potentialof the grain head is determined30 to 40 days after emergence.

Table 3. Approximate nutrient content of a 5,600 lb/A

sorghum crop.

Plant Nutrient Pounds in Grain Pounds in Stover

Nitrogen (N) 84 95

Phosphorus (P20

5) 42 20

Potassium (K20) 22 107

Sulfur (S) 8 13

Magnesium (Mg) 7 10

Calcium (Ca) 1.4 19

Copper (Cu) 0.01 0.02

Manganese (Mn) 0.06 0.11

Zinc (Zn) 0.07 0.14

Source: Kansas State University - Grain Sorghum Production Handbook

4

Nitrogen stress during thisperiod will greatly influenceyield. Under center pivotirrigation, N fertilizer may beapplied several times during

the early part of the growingseason. Because N is relativelymobile in the soil, fertilizerplacement is not as critical forN as it is for most other nutri-

ents. Nonetheless, N must beabsorbed into the plant beforeit is supportive of plant growthand grain production.

Nitrate-nitrogen (NO-3, the

form most available to plants)dissolves in soil water, but isnegatively charged and thusnot attracted to negatively-charged clay and organicmatter particles. Nitrate-nitrogen will move with waterand can be readily broughtinto contact with crop roots forquick absorption.

Ammonium-nitrogen (NH4,also available to plants) ispositively charged and is heldby negatively-charged clay andorganic matter particles in thesoil until converted by soilbacterial action into the nitrateform. The conversion of Nfrom ammonium form tonitrate form in the soil is refer-red to as “nitrification,” and ismost likely to occur whenfields are arable. When fieldsare water-logged, nitrate canbe converted to nitrogen gas(referred to as “denitrifica-tion”) and lost from the soil byvolatilization. Whether fertil-izer N is applied as liquid ordry, ammonia, urea, ammo-nium sulfate or N-32, it shouldbe incorporated into the soil assoon as possible to reducepotential loss of N to theatmosphere, especially wheresoil pH is above 7.

must establish and grow inmuch cooler soils than ifplanted later in the spring.

Since soil P is relatively immo-bile, or “fixed” in soils, place-ment in a concentrated form isparticularly important in lowto medium testing soils. Bybanding P near the seed, 2 to 4inches below and 2 to 4 inchesto the side, developing rootscontact the fertilizer shortlyafter emergence. Placing Pfertilizer in direct contact withsorghum seed at planting maycause emergence problems dueto the salt effects caused bynitrogen in the fertilizer mate-rial.

Research has shown thatplants obtain a higher propor-tion of the needed P from soilreserves. Only about 30 per-cent of applied P is used by thecrop following fertilization,even though it may have beenbanded. Once soils are warm,some of the “reserve” P be-comes available for plant use.The rate at which fertilizer P isconverted to soil or “reserve” Pdepends upon several factors,but most important is the ferti-lizer P-to-soil contact. Confin-ing P fertilizer to a band reducesfertilizer-to-soil contact andslows the rate of conversion,compared to mixing the sameamount throughout the soil aswith broadcast applications.

Phosphorus can also be ap-plied as a “pop-up” fertilizer,sprayed in the seed furrow atplanting. Corn and sorghum

PhosphorusPhosphorus (P) is the mostcontroversial nutrient. Differ-ent soil testing laboratories usedifferent chemical extractantsto estimate “available P.” As aresult, there may be largedifferences between soil testvalues for the same soil sampleobtained from different labora-tories. In addition, fertilizerrecommendations from differ-ent laboratories may also varyconsiderably. In most cases,soil P levels are sufficient tomeet early season needs ofgrain sorghum plants. How-ever, grain sorghum seed aresmall and contain only enoughP to nourish young seedlingsuntil emergence. If youngseedlings develop under favor-able conditions, P-deficiencysymptoms often do not occur.However, if growing conditionsare unfavorable (i.e., cool and/or wet), seedlings may showtemporary P-deficiency symp-toms.

In years where the plantingenvironment is unfavorable forrapid growth and develop-ment, banding P fertilizer atlow rates in the seed row maybe beneficial. One key point toremember is that P is lessavailable in cold soils. Mostgrowers plant as early aspossible to reduce sorghummidge damage and to minimizethe effects of hot, stressfulweather normally experiencedlater in the season. By doingso, sorghum seedlings often

5

Table 6. Distribution of nutrients removed in sorghum grain and stover.

Crop Dry Matter Nitrogen (N) Phosphorus (P20

5) Potassium (K

20)

Dry Matter distribution lb/A % of Total lb/A % of Total lb/A % of Total

Grain 7,500 lbs 56% 107 58 28 35 28 10

Stover 5,280 lbs 44% 78 42 52 65 230 80

Source: Kansas State University - Grain Sorghum Production Handbook

usually respond better thancotton to “pop-ups.” However,when using a product like10-34-0 or 11-37-0 as a “pop-up,” it is important not toexceed the equivalent of 5pounds of elemental N per acrein the seed furrow, or saltinjury from the N is likely tooccur. Under irrigated or highrainfall conditions, up to 10pounds of N/acre may beapplied without injury. A rainfollowing planting will dilutethe nitrogen and also lessen thechance of injury. High P to lowN ratio specialty fertilizers,such as 4-29-2 or similar prod-ucts, lend themselves to “pop-up” applications with minimalinjury risk.

PotassiumPotassium (K) is needed in allplant parts for maintenance ofwater balance, disease resis-tance and stalk strength. How-ever, as indicated in Table 6,very little K is removed fromthe field if only grain is har-vested. If the stover is har-vested as green forage, then amuch larger amount of potas-sium is removed. Most mediumto fine textured soils in Texasare inherently high in potas-sium. Soil test levels should bemonitored over years to lookfor any trends of reduced K.

Other NutrientsTwo other important nutrientsfor grain sorghum productionin Texas are zinc and iron.Where soil phosphorus levelsare “high” or “very high” andzinc levels are “low” to “me-dium,” application of additionalphosphorus may induce a zincdeficiency. If soil test resultsindicate a possible zinc defi-ciency, zinc fertilizer should bebroadcast and incorporatedpreplant or banded at planting.

Foliar applications of zincshould be used as a salvagemeasure since this will onlyprevent symptoms on newgrowth.

If iron chlorosis has beenobserved during previous yearsin a field, iron fertilizer materi-als should be applied to thefoliage through multiplesprayings early in the season.Table 7 gives suggested foliartreatments to correct iron and/or zinc deficiencies.

Organic FertilizersIn areas where organic fertil-izer materials such as feedlotmanure, gin trash, poultrylitter, or treated municipalsewage are available, produc-ers may choose to use these asa nutrient source for grainsorghum. Since the nutrientcontent of organic fertilizerscan vary greatly, samples ofthe materials should be testedprior to use to determineproper rates of application.One significant advantage oforganic fertilizers is that thenutrients become availableover a longer period of time asthe material decomposes,compared to the immediateavailability of nutrients frominorganic sources.

Some problems in the use oforganic fertilizer materials are:1) obtaining the ratio of nutri-ents called for in the fertilizerrecommendation for thesorghum crop; 2) determiningthe amount of animal manureto apply to meet crop needs;and 3) minimizing weed seedsor other impurities (frommaterials such as gin trash).

By understanding the nutrition-al requirements of sorghum,adequate nutrients can beapplied to reach the yield poten-tial of the crop without apply-ing excess nutrients which may

reduce profits and/or contrib-ute to excessive nutrient loadsin water and soils.

WaterGrain sorghum is a verydrought tolerant crop. Sor-ghum develops a diffuse rootsystem that may extend to adepth of 4 to 6 feet. Table 8shows the amount of waterused by a sorghum crop fromvarious soil depths during aseason. Moisture stress earlyin the season will limit headsize (number of seed per head)and delay maturity — moretime is required to completethe plant’s life cycle. If stressoccurs later in the season, theseed size is greatly reduced.The number of heads per acreis not affected by moisturestress unless it is so severe asto prevent head formation.

During the seedling stage, onlya small amount of moisture inthe soil surface is required toestablish the crop. Moremoisture is lost during thisstage through evaporation fromthe soil surface than throughthe crop canopy. Water con-serving practices such asresidue management, timelyplanting for quick establish-ment, narrow row spacing andweed control will minimizesoil moisture losses.

About 30 to 35 days afteremergence, five to six trueleaves are visible and the plantbegins rapid growth. Nearlyhalf of the total seasonal waterwill be used during this stageprior to heading. Near the endof this period, daily water usewill be near maximum (about0.35 inches/day/acre).

The most critical period forwater availability for a sor-ghum plant begins about oneweek before head emergence

6

Table 8. Total water absorbed from various depths in a soil

profile.

Soil Depth Inches of Water Percent of

(feet) Absorbed Total

0 - 1 8.9 35

1 - 2 6.6 26

2 - 3 4.0 16

3 - 4 2.8 11

5 - 6 1.3 5

Source: USDA/ARS Report No. 29

Table 7. Suggested sources, rates and timing of iron and zinc foliar sprays.

Product/100 gals

Deficiency Product* water Product/Acre Timing

Iron Iron sulfate 20 lbs 1 lb 10-14 days af ter emergence - 5 gals/A over(20% Fe) (2.5% solution) 2 - 3 lbs crop row. Follow with 2 apps. @ 10-14 day

interval @ 10-15 gals/A

Iron chelate 8 lbs(10% Fe) (1%) 0.4 - 0.5 lbs same as above

Zinc Zinc sulfate 2 lbs 0.2 - 0.4 lbs 10-20 gals/A in first 30 days(30% Zn) (1/2 %)

Zinc chelate 2 qts 10-20 gals/A in first 30 days(9% Zn) (0.1%)

Iron & zinc Iron sulfate + 15 lbs + 3/4 Iron + 10-14 days af ter emergence - 5 gals/A overZinc sulfate + 1 lb + 0.1-0.2 Zinc crop row. Follow with 2 apps. @ 10-14 dayurea fertilizer 2 lbs 1.5 lb Iron + interval @ 10-15 gals/A

0.2-0.4 Zinc

Iron sulfate + 15 lbs 3/4 Iron + 10-14 days af ter emergence - 5 gals/A overZinc chelate 3 pts 2.4 f l oz. crop row. Follow with 2 apps. @ 10-14 day

1.5 lb Iron + interval @ 10-15 gals/A5 f l oz.

Iron chelate + 6 lbs follow mfg. 10-14 days af ter emergence - 5 gals/AZinc chelate 3 pts directions over crop row. Follow with 2 apps. @ 10-14

day interval @ 10-15 gals/A

*Include a surfactant or other wetting agent. Product conposition may vary. Select similar products or adjustmixing ratios to achieve comparable rates of nutrient application.

Source: Updated information based on research results and recommendations through the Texas Agricultural Exten-sion Service Soil, Water and Forage Testing Laboratory.

7

moisture prior to the “boot”stage will assure the highestpotential seed set. The actualseed number and seed size willbe dependent upon the avail-ability of soil moisture follow-ing flowering. Moisture de-mand drops rapidly after thegrain has reached the “soft-dough” stage. The soft-doughstage has occurred when imma-ture seeds squeezed betweenthe thumb-nail and the indexfinger do not exude a “milk” orwhite juice. The combineddrop in moisture demand,natural drought tolerance insorghum, and the extensiveroot system generally makelate irrigations unprofitable.

or the “boot” stage, and contin-ues through two weeks pastflowering (Figure 2). Sorghum

plants require good soil mois-ture during this period for max-imum yields. Adequate soil

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

••

•

Since water is the firstlimiting factor to crop

production in South Texas,yield goals should be basedupon the amount of wateravailable during the season.Research at Texas Tech Univer-sity indicates that a minimumof 10 inches of available wateris required for sorghum plantsto produce a head (D. R. Krieg,personal communication).Each additional inch will yieldapproximately 385 to 400pounds of grain. Thus, asorghum crop that receives 20inches of usable water duringthe growing season will use 6to 8 inches to produce thehead, while the other 12 to 14inches will produce approxi-mately 5,000 pounds of grain.

Maturity selection of hybridsis also important in watermanagement. Table 9 suggeststhe amount of expected waterneeded by the crop of differentmaturity groups.

Besides the total amount ofavailable water, the timing ofirrigation (or rainfall) is alsoimportant. Research done inthe Texas High Plains indicatesthat as the amount of waterreceived by the crop increases,grain yield/inch of waterapplied decreases. Results of

two years of field studies at theEtter Experiment Station onthe High Plains to determinethe best combinations forirrigation timing are shown inTable 10. Sixteen irrigationtreatments were used. In thefirst year of the test, 10.5inches of rain fell in the grow-ing season with 6.1 inchesoccurring late during bloomand grain fill. During thesecond year of the test, 8.9inches fell early in the growingseason with 6 inches fallingprior to and during bloom.

Average yields for the twoyears showed increased pro-duction with additonal water.The results also show impor-tant year-to-year yield differ-ences within the same irriga-tion timings when rain fellearly or late. Irrigation timingis just as important as theamount of water applied.Figure 3 shows the best timingfor one, two, three, and fourin-season irrigations and theamount of additional grainproduced with each subse-quent irrigation.

More recently, first year ex-periments conducted at theUvalde Research and Exten-sion Center support the Etterfindings. At Uvalde in 1996, no

Figure 2. Daily water use in inches.

8

9

Table 9. Approximate maturity and water use of grain sorghum by seasonal types.

Days to Number Plant Days to Inches of

Maturity Range Bloom of leaves Height Maturity* Water

Early 55 - 60 6 - 9 30 - 36 90 - 105 10 -15

Medium 65 - 75 9 - 12 36 - 45 110 - 115 15 - 20

Medium late 75 - 85 12 - 16 40 - 50 115 - 120 20 - 25

Full season or late 75 - 85 14 - 18 50 - 60 120 - 125 25+

* Physiological maturity - the point af ter which there is no increase in seed weight.

Table 10. Two-year sorghum grain yield responses to irrigation at various stages of plant

development. Preplant irrigations totalled 4 inches and all post plant irriga-

tions were 4 inches each (’69 late rains, ’72 early rains).

Early Mid to Heading/ Milk to 1969 1972 2 Yr

Preplant (6-8 leaf) Late Boot Flowering Dough Yield Yield Average

X 1,441 2,786 2,113

X X 1,799 2,842 1,820

X X 4,019 4,249 4,134

X X 3,167 4,908 4,037

X X 1,141 3,268 2,204

X X X 3,659 3,907 3,783

X X X 4,181 5,710 4,945

X X X 1,260 4,201 2,730

X X X 5,237 5,582 5,409

X X X 3,677 5,097 4,387

X X X 3,954 4,727 4,340

X X X X 6,396 5,990 6,193

X X X X 3,716 5,573 4,644

X X X X 4,417 5,932 5,174

X X X X 5,956 5,960 5,958

X X X X X 6,800 6,782 6,791

Source: Texas Agricultural Experiment Station, Etter, Texas

Figure 3. Estimated daily water use for grain sorghum.

Source: Texas Agricultural Experiment Station - Etter, Texas

effective rain fell during thegrowing season. Results indi-cate only the effects of irriga-tion rate and timing. (unpub-lished data, C. Fernandez).

Not only is the amount ofwater applied important, but

also the timing (Table 11),relative to the developmentalstage of the crop. Based on theresults of the experiments atEtter and Uvalde, severalimportant conclusions can bedrawn.

◆ Preplant irrigations alonedo not produce optimumyield.

◆ One irrigation at any timeprior to dough stage wasequal in yield to twoirrigations at heading anddough. If an irrigation ismissed during head initia-tion (45 DAE), later irriga-tions will not increaseyields substantially.

◆ If two in-season irrigationsare possible, 45 DAE andheading will produce thegreatest yields.

◆ If three inseason irrigationsare possible, 30 DAE, 45DAE and heading producegreater yields than 45 DAE,heading and dough stage.

◆ Irrigations at the doughstage failed to substantiallyincrease yields.

◆ Four irrigations in additionto the preplant wateringproduced the highestyields.

Table 11. Effects of irrigation timing on grain sorghum yield.

Preplant 30 45 Heading Dough Grain Yield Heads/ Grains/ Weight/

DAE DAE per Acre Acre Head Grain

X 1,079 31,914 627 22.6

X X 2,811 48,076 1,277 20.2

X X 2,890 51,653 1,406 17.5

X X 3,016 48,283 1,043 26.5

X X X 3,387 50,277 1,548 19.1

X X X 4,905 53,923 1,560 25.9

X X X 2,704 47,663 883 28.9

X X X X 5,404 52,006 1,746 26.2

X X X X 5,116 52,478 1,698 25.4

X X X X X 5,773 53,028 1,804 27

DAE = days af ter emergence; 30 DAE = head initiation; 45 DAE = rapid growth; Heading = boot-f lowering; Dough =soft dough stage

10

If the response of sorghumplants to 1 inch of irrigationwater is an additional 385 to400 pounds/acre of grain,every effort should be made toreduce water runoff. Not onlydo water conservation prac-

tices such as furrow dikingreduce the chances of erosionand nutrient loss, they alsoincrease grain yields. Threeyears of research on the TexasRolling Plains demonstrate thepotential for furrow diking to

increase sorghum yields (Table12). The greatest impact fromfurrow diking was observed indry years (1980, 1981).

Six years of studies in Uvaldeon dryland grain sorghumproduction produced up to 72

Table 12. The effects of furrow diking and subsoiling on sorghum grain yields.

Tillage Treatment 1979 1980 1981 Average Yield Percent

Lbs/A % Lbs/A % Lbs/A % (Lbs/A) of Check

Undiked 4,353 100 547 100 1,038 100 1,979 100

Subsoiled 4,941 114 580 106 1,116 108 2,212 112

Diked 4,865 112 751 138 2,240 216 2,619 132

Subsoiled and diked 5,136 119 791 145 2,248 217 2,725 138

Source: Texas Agricultural Research Center, Vernon

Table 13. Ef fect of furrow diking on dryland sorghum production.

Percent of Bedded

Treatment Average Yield* & no dikes**

Bedded and no dikes 1,747 a

Flat (no beds formed) 1,821 a 104

Bedded and diked during the growing season 1,826 a 105

Bedded and diked during the fallow season 2,128 b 122

Bedded and diked continuously 2,321 b 133

* Average yields followed by the same letter do not differ statistically.**Normal land preparation for dryland sorghum in the Wintergarden area.

Source: Texas Agricultural Research Center, Uvalde

11

percent higher yields in dryyears when fields were diked.Table 13 shows the effects ofvarious tillage systems onaverage production between1984 and 1990, which includedboth wet and dry years.

SummaryEfficiency is doing the rightthing and effectiveness is doingthe right thing at the righttime. Not only are productioninputs important, but propertiming often determines if

these inputs are fully utilized.Crop management is effec-tively managing all aspects ofproduction to enable the cropto produce its best economicyield. Careful management ofall aspects of production, fromland preparation to harvest,will maximize yields andprofits.

ReferencesFernandez, Carlos. Texas A&M University,

Uvalde, Texas. Unpublished data.

Fertilizer Rates for Irrigated Grain Sorghum onthe High Plains. Agricultural ExperimentStation Bulletin 523. New Mexico StateUniversity, Las Cruces, New Mexico.

Grain Sorghum Production Handbook. Coop-erative Extension Service, Kansas StateUniversity, Manhattan, Kansas.

Grain Sorghum Production with DifferentNutrients, Populations, and IrrigationFrequencies. New Mexico ExperimentStation. Bulletin 613.

Grimes, D.W. and T.J. Musick. Effect of PlantSpacing, Fertility and Irrigation Manage-ment on Grain Sorghum Production.Agronomy Journal.

Krieg, D.R. Texas Tech University. Personalcommunication.

Musick, T.J. et al. Irrigation Water Manage-ment and Nitrogen Fertilization of GrainSorghum. Agronomy Journal.

Mulkey, J.R. et al. Dryland Sorghum Responseto Plant Population and Row Spacing in

Southwest Texas. Texas AgriculturalExperiment Station. PR-4294.

Phosphorus Fertilization for Grain SorghumProduction in the Texas Blacklands. TexasAgricultural Experiment Station. L-1550.

Profitable Grain Sorghum Production in theRolling Plains. Texas Agricultural Exten-sion Service. B-1577.

Sorghum for Grain: Production Strategies inthe Rolling Plains. Texas AgriculturalExperiment Station. B-1428.

Sorghum Takes Up Much Plant Food. Phos-phate and Potash Institute of NorthAmerica.

Tewolde, H. et al. Furrow Diking Effects onYield of Dryland Grain Sorghum andWinter Wheat. 1993. Agronomy Journal.

Vanderlip, R.L. How a Sorghum Plant Devel-ops. Cooperative Extension Service,Kansas State University, Manhattan,Kansas.

Water Response in the Production of IrrigatedGrain Sorghum, High Plains of Texas.Texas Agricultural Experiment StationReport. MP-1202, 1975.

12

Educational programs of the Texas Agricultural Extension Service are open to all people without regard to race, color, sex,disability, religion, age or national origin.

Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914,as amended, and June 30, 1914, in cooperation with the United States Department of Agriculture, Zerle L. Carpenter,Director,Texas Agricultural Extension Service, The Texas A&M University System.

5M—5-97, New AGR14