South & Central Texas SORGHUM production handbook.pdf

8/11/2019 South & Central Texas SORGHUM production handbook.pdf

1/176

UNITED SORGHUM CHECKOFF PROGRAM

South & Central Texas

Production Handbook


2/176

Welcome to the United SorghumCheckoff Programs South Centralexas Production Handbook. We haveintegrated research rom various sources

to produce an easy-to-use guide that can

help armers manage their crop more

efficiently. Sorghum has tremendous

potential to return a profit to your arm

and the work o the Sorghum Checkoffwill only improve that potential over time.

As you manage your sorghum, keep these

tips in mind:

Make sure you are using the hybrid

that works in your area and plantingto get the right plants per acre in

your field.

Use an integrated weed management

strategy.

Most importantly, provide the cropwith adequate ertilizer.

By ollowing a ew guidelines, youll be

amazed at what this crop can do or you.

We strive to help you make sorghum

more profitable or your operation. But

remember, every situation is a bit different

so contact your local county extension

office, land-grant university or other area

sorghum armers to help you get the

most out o this water-sipping crop.

0

1

2

3

4

5

Chair, United Sorghum Checkoff Program BoardSorghum Farmer, Prairie View, Kansas


3/176

Produced and Edited by:

Dr. Jeff Dahlberg, USCP Research Director

Earl Roemer,USCP Research Committee ChairJeff Casten,USCP Research Committee

Gary Kilgore,USCP Research Committee

James Vorderstrasse,USCP Research Committee

Authored by:

Dr. Calvin rostle

exas AgriLie Extension Service Agronomist

Dr. Dan Fromme

exas AgriLie Extension Service Agronomist

Additional content contributed by:Roy Parker, exas AgriLie Extension Entomologist

Dennis Pietsch, exas AgriLie Research Crop esting Program

John Matocha, exas AgriLie Research Soil Fertility

Brent Bean, exas AgriLie Extension Agronomist/Weed Scientist

Juan Enciso, exas AgriLie Extension Agricultural Engineer

om Isakeit, exas AgriLie Extension Plant Pathologist

Nicholas Kenny, exas AgriLie Extension Program Specialist

Pat Porter, exas AgriLie Extension Entomologist

Kevin Bronson, ormer exas AgriLie Research Soil & Fertility

Funded by:

United Sorghum Checkoff Program

4201 N. Interstate 27, Lubbock, X 79403

806-687-8727

www.sorghumcheckoff.com


4/176

opic Page

Growth Stages 5

Hybrid Selection 8

Irrigation

Planting

19

43

Fertilization 68

Weed Control 87

Insect Management 109

Diseases 136

Harvesting 141

Budget & Custom Rates 152

Reerences 153

Calculations & Conversion 154

Appendices a. Te Sorghum Plant b. Photos

161164

Notes 167

Contents

Copyright 2010


5/176

Growth Stages |5

It is important to understand the various develop-mental stages o sorghum since this understandingwill assist in making irrigation and managementdecisions. Te stages are based on key stages osorghum growth that are used to describe sor-

ghum rom planting to maturity (Figure 1).

Another common scale that is used amongsorghum researchers is a more simplified growthscale. GS1 would equate to stages 0-5 in this

system. GS2 would represent rom stages 5-10, andfinally, GS3 would be rom stage 10 to 11.5.

Comprehensive grain sorghum growth anddevelopment guides are available, such as KansasStates How a Sorghum Plant Develops (http://

www.oznet.ksu.edu, currently being revisedwith your sorghum Checkoff dollars) and exasAgriLies How a Sorghum Plant Grows, (http://agriliebookstore.org). Both o these guidesprovide pictures o different growth stages, graphs

o cumulative nutrient uptake relative to growthstages (KSU), or approximate heat unit require-ments (base temperature 50F, maximum 100F)or attaining a particular growth stage (exasAgriLie). Cool or wet weather early in the seasonor an early planting date can significantly slow

growth early in the season adding a week or eventwo weeks to the time to hal bloom.

GROWTHSTAGES

Refer to Appendix A.


6/176

6 | Growth Stages


7/176

Growth Stages |7

Fig.1.Stagesosorghumgrowth:Stage0:0.0planting;0.1startoimbibition;0.5radicleemergenceromseed(caryopsis);

0.7coleoptileemergenceromseed(caryopsis);0.9leaatcoleoptiletip;Stage1:emergence;Sta

ge2:firstleavisible;Stage3:

thirdleasheathvisible;Stage4:fi

fhleasheathvisible;Stage5:Paniclediff

erentiationandstartotillering;5.1main

shoot

andonetiller;5.9mainshootand

severaltillers;Stage

6:stemelongation(latevegetativestage);

Stage7:flagleavisible,

whorl;Stage

8:booting(endove

getativestage);Stage

9:paniclejustshowing,inflorescenceem

ergence;Stage10:anthesis

(50%opanicleflowering);Stage

11:maturity;11.1grainsatmilkstage;11.2grainsatearlydoughstage;11.3grainsatlate

doughstage;11.4grainsatphysio

logicalmaturity(bla

cklayer,approximately30%seedmoisture);11.5maturegrain

(seed

moistureapproximately15%).(C

ourtesyK.Cardwell)

.Formoreinformatio

nseeAppen

dixA,page163.


8/176


9/176

Hybrid Selection | 9

Granger, Central exas Blacklands College Station, South Central exas

Leonard/Princeton, North exas Blacklands(between Dallas and the Red River)

In most cases, companies plant the hybrids theythink will perorm best at each site. Tese inde-pendent tests collect a variety o data including

days to hal bloom, lodging, test weight and yield.rial results are published at http://varietytesting.tamu.edu and producers may choose test sitesand then review several years o results, lookingor hybrids that have good consistent results overyears and locations.

Additional on-arm sorghum hybrid testingis also conducted in the Lower Rio Grande,Coastal Bend and Upper Gul Coast by CorpusChristi Research and Extension Center staff (Dan

Fromme) and cooperating county agents (resultsannually posted at http://coastalbend.tamu.edu,then locate Soil and Crop Sciences).

Producers are also encouraged to consult indi-vidual companies or their recommendations, as

well as plant their own on-arm observation withdifferent hybrids. Company data is not consid-ered independent in the manner that public testsare conducted. However, these tests can still bean excellent source o inormation particularlywhen comparing yields among hybrids rom thesame company.


10/176


11/176


rity while they await harvest in the event oextended rain, minimize germination in the

head, etc., are a plus. Sources o weatheringdurability include seed companies, the exasAgriLie Research Crop esting Program andproducer experience.

Lesser sorghum hybrid considerations include

the ollowing: Stay-greenAbility o grain sorghum

hybrids to maintain prolonged lea and stalkintegrity afer flowering. Tis trait can assistgrain fill as well, take better advantage o laterains and maintain stalk health later in theseason (which may reduce lodging).

Greenbug toleranceMany hybrids noteresistance to Biotype C and E greenbugs, butthese biotypes have been gone rom exasor many years. Biotype I is now predomi-

nant, but only a ew hybrids offer resistance.A small amount o Biotype K is also present.With the advent o numerous insecticidetreatments there is little emphasis placed ongreenbug resistance.

Head exsertionSome hybrids have headsthat do not emerge as much rom the whorl,hence they remain down in the leaves at harvestleading to more trashy harvest. Some hybridsmay have modest exertion, but then arepoorly exserted during droughty conditions.

Grain color and plant colorRed, bronze,crme, yellow and even white grain hybridsare marketed. Unless you are pursuing a


12/176

12 | Hybrid Selection

specialty market (ood sorghum, chickeneeding, etc.) where white grain seed coat is

desired, then there is little reason to choosea hybrid based on seed coat color, unless yousimply have a preerence. Yield consider-ations generally override any considerationso grain or plant color (purple, red, tan).

Panicle (head) typeLoose panicle hybrids(in contrast to tight, compact heads) that areast growing and dry down rapidly may bepreerred in areas with higher humidity andgreater panicle eeding pressure rom insects.

Plant disease resistanceTough some

hybrids may have tolerance o certain dis-eases, this consideration is largely ignored byproducers. I you have a particular diseasethat has affected your crop in many years,consult your exas AgriLie Extension plantpathology experts or your seed dealer orpossible suggested hybrids that may reducedisease injury potential.

Herbicide toleranceAlthough these tech-nologies are now in the testing phase withuniversities and will not be available until

about 2014, two major non-GMO herbicidetolerant lines will likely become importantselection criteria once the traits are bred intocompetitively yielding commercial hybrids.Tese include ALS-herbicide or sulonylureatolerance (metsuluron, nicosuluron, rim-suluron, e.g., Ally) and ACC-ase herbicidetolerance (quizaloop, e.g. Assure II).


13/176


14/176


ley north into the exas Blacklands. Tis is incontrast to harvest maturity which can be up to

several weeks later depending on weather condi-tions and drying.

Additional Seed Selection CriteriaSeed reatments: Many companies now treat all their seed

with Concep III which enables a producerto use s-metolachlor (e.g., Dual Magnum)herbicides, which is the preerred method ograss control in grain sorghum. Tis usuallycosts $10-15 per bag, and should not actorin your decision on which hybrid to choose.

Insecticides and ungicidesGaucho andPoncho or insects (the latter potentiallyoffers longer-season greenbug control) maycost about $30 per bag, but generics are inex-pensive and may enable some greenbug con-

trol or cents per acre. Advanced combina-tion o insecticide and ungicide treatmentslike CruiserMaxx, etc. may double the cost oa bag o seed. Early season control o yellowsugarcane aphids, southern corn rootworm,etc. make seed treatments a nearly essentialpart o grain sorghum production or manyproducers in South and Central exas.Modest seeding rates are usually more thanadequate or most production conditionsand this can reduce the cost o more expen-

sive grain sorghum seed treatments.


15/176


16/176


able1.Expectedandobserve

ddaystosorghumh

alfbloomaswellas

ex-

pecteddaystophysiologicalmaturityforSouthandCentralexasfrom

exas

AgriLifeResearchCropestingtrials.

Generalcompany

maturityrating

(#oleaves)

Production

system

Expected

mid-range

halbloom

E

xpected

p

hysiological

m

aturity

Comm

onob-

served

range,

halbloom

(2006-2009)

Days

Early(~15)

Rained

60

85-100

Medium-ea

rly

Rained

61-65

96-105

67-80

Medium(~

17)

Rained

66-70

100-110

67-82

Medium-long

Rained/

Irrigated

71-75

106-115

67-83

Long(~19)

Rained/

Irrigated

76

111-125

Expectedmaturityishighlydependenton

plantingdate,earlyseason

cooltemperatures,cloudy/rainy

weather,andheataccumulation.

PlantingdatesorTexasAgriLieResearchCropTestingtrialstypicallybeginningmid-FebruaryatWeslacoto

earlyAprilinthenorthTexasBlacklands.


17/176


maturing due to drought. Yield potential othe latter is a significant drop off rom even the

medium maturity hybrids.

South exasLower Rio Grande Valley and Coastal Bend:Due to less rainall than other areas we suggestproducers target medium and medium-early

hybrids. Seed companies routinely enter manymedium-long hybrids in exas AgriLie ResearchCrop esting trials in this area, but irrigatedproducers should be cautious about extendinghybrid maturities to medium-long unless theyare sure they will irrigate more heavily. Upper Gul Coast (Victoria to Houston)

up to I-10: medium-long and medium.exas AgriLie recommends, however, thati plantings are later in this region, ratherthan shorten maturities, producers consider

planting crops other than grain sorghum. San Antonio Region: some irrigated but

mostly dryland to west, rained to east:medium and medium-long hybrids (thelatter more appropriate i irrigated); orrained conditions in the area lower seedingrates and shorter maturities (medium andmedium-early) are recommended as onemoves west rom about Gonzales to Hondoand Uvalde.

Central to North exasFor the most part, medium-long and mediummaturity hybrids perorm best in this region.Medium-early maturity hybrid might be appro-


18/176


priate in a ew instances when later plantingconcerns raise the possibility o increased

sorghum midge potential, but yield potential willbe reduced.

Te Bottom Line o Hybrid Selection

When extension staff surveys the means by which

many producers choose their hybrids or plantinggrain sorghum, or both irrigated and rained pro-duction, we believe exas producers could moder-ately improve their yields by planting hybrids thathave a track record o better perormance.

Early maturity hybrids are requently criticizedor their lower yield potential. Tis is a act ohaving less time and less capacity to produce highyields. Tese hybrids may have their place whentime is short (oncoming midge potential, hotsummer conditions during flowering and grainfill), but or South and Central exas producersextension recommends never plant a shortermaturity hybrid than medium-early to retaingood yield potential. Some producers accept theincreased risk o planting a medium-maturity

hybrid in exchange or greater yield potentialknowing that oncoming sorghum midge poten-tial or summer heat in some years may limit thecrop and reduce yields.


19/176

Irrigation |19

IRRIGATION

South & Central exas Irrigation Methods

Most o the irrigated sorghum in the regionis lood irrigation via canals in the Lower RioGrande Valley. Producers may not have muchcontrol over the timing or the amount o theirrigation water, thus making its eiciency lower.Scattered irrigation in the Coastal Bend, Uvalderegion and river bottoms up, through Centralexas, may use pivot irrigation in a ew cases in

addition to urrow irrigation.

As with all grain crops, sorghum yield is mostdirectly related to available water during thecropping seasonapplied irrigation waterstored soil water, and in-season precipitation.Each o these sources o water can be managedto optimize the grain yield return per unit owater available. Studies have shown that prior tobloom, grain sorghum can use up to 10 inches owater, and that each subsequent inch o rainall

or irrigation will produce about 350 to 400lbs. o grain per acre though the eiciency ograin production is less rom lood and urrowirrigation (able 2). Where grain sorghum plantpopulations are restricted as part o a droughtmanagement and risk management strategy, theamount o water required to reach the point oinitial grain production can be reduced preserv-ing more moisture or grain ormation and yield.


20/176

20 | Irrigation

Grain Sorghum Water Use Pattern

Sorghums drought tolerance and water use charac-teristics make it an excellent crop or a wide rangeo irrigation scenarios in South exas. Sorghumcan yield reliably under rained conditions in manysemi-arid environments (15-20 inches annual pre-cipitation) and can be managed to reach significantyield capacity with ample rainall and/or timelyirrigation. Because o sorghums water use versatil-

ity, it fits well into many cropping and irrigationpatterns, a valuable trait considering current trendso declining available irrigation resources and pend-ing regulatory water use limitations.

able 2. ypical comparative expected eiciency or dierentagricultural irrigation systems under optimal ield conditions.

Irrigation Method Potential IrrigiationApplication Eiciency

Surace

Common lood 50%

Common lood w/land leveling 60%

Row (all urrow) 65%

Alternate urrow 70%

Furrow w/surge levels 80%

Center pivot

Low elevation spray app (LESA) 85%

Low elevation precision app (LEPA) 90%

LEPA with drag hoses 92%

Drip

Above ground 85-90%

Subsurace drip 90-95%

Surge has been ound to increase eiciencies 8 to 28% over non-surge urrow

systems in exas.


21/176

Irrigation |21

Moisture stress early in the season will limit head

size (number o seed per head) and delay matu-rity whereas i stress occurs later, in the seasongrain filling is reduced (either seed set or reduc-tion in seed size). Water needs or sorghum varyaccording to the different plant stagesdifferentamounts are used in the seedling development

phase, the rapid growth and development stage,and the bloom to harvest phase (Fig. 2).

Irrigation & Grain Sorghum Growth Stages

Seedling Development

During the seedling stage up to near 28 days ogrowth, only a small amount o moisture in thesoil surace is required to establish the crop. Moremoisture is lost during this stage through evapora-tion rom the soil surace than through the cropcanopy (to reduce soil moisture loss see Saving Rainand Irrigation below). Tis early-growth stage doesnot directly affect the number o seeds produced,but it does set the direction o development.

Fig. 2. Daily water needs or sorghum rise sharplyat the rapid growth stage, peak during boot stageand decline aferward.


22/176


23/176


24/176


25/176


26/176


27/176

Irrigation |27

it! Reap it! is a popular mantra or describingthe need to ensure that rainall is translated into

harvestable grain. Low impact, minimum tillageoperations are recommended where easible tominimize soil water evaporation and suracerun-off while maximizing soil water infiltrationand sub-surace organic matter to assist in waterholding capacity.

Capturing off-season precipitation through soilstorage is a recommended agronomic strategy,especially in lower rainall regions, that helpsearly season plant growth, can buffer drought

stresses throughout the season, and saves costsassociated with pumping and delivering irriga-tion water. Ideally, water rom soil storage shouldbe exhausted at the end o the season when grainreaches maturity.

In-Season Precipitation

Depending on location and weather patterns,in-season precipitation still may be the maincomponent o the water budget o irrigated sor-ghum, despite seasonal variations in quantity and

timing. Although difficult to manage, the returnon in-season precipitation can be optimized. Inareas where in-season precipitation is probable, aportion o soil water capacity should be main-tained to provide sufficient room to capture and

contain water rom small to moderate rainallevents. In addition to increased seasonal wateruse and reduced pumping costs rom holdingand utilizing in-season precipitation, run-off


28/176

28 | Irrigation

and erosion are reduced, leaching effectivenessis increased, and in many cases, nitrogen better

supplements the crop.

In regards to irrigation scheduling, in-seasonprecipitation should be evaluated on an effectiverainall basis. Research has shown that only aportion o the water received during a precipita-

tion event will actually become useul to thesorghum crop. o avoid overestimating waterreceived rom precipitation, a producer shouldonly credit precipitation events greater than 0.25inch (unless the soil is already wet), or the peakdaily sorghum evapotranspiration. Considerationshould be given to orgoing or delaying irrigationonly i a rainall event is larger than the sched-uled irrigation depth or exceeds available soilmoisture holding capacity. Te benefit o in-seasonprecipitation can ofen be redeemed at the end o

growing season by terminating irrigation earlierwith sufficient water stored in the soil profile.

Saving Rain and Irrigation Water by Mini-mizing Soil Evaporation

Producers can take steps to minimize moisturelosses rom the soil by adopting water-conservingpractices, such as: Spacing the plants equally in narrow rows.

Narrow-row crop production reduces theamount o bare soil, which loses moremoisture through evaporation than doshady and mulched soil suraces. However,i the row spacing is reduced it is likely


29/176

Irrigation |29

agronomically sound to NO increase theper acre seeding rate.

Leaving crop residues on the soil surace,which can reduce soil evaporation by 1 to3 inches during the season, as well as otherconservation tillage measures.

Uncontrolled weeds also contribute signifi-cantly to loss o soil moisture.

Proper planting date or rapid canopyestablishment.

Evapotranspiration & Grain Sorghum Irrigation

Identiying the amount o water to be applied to

a crop is one o the most important managementcontributions that a sorghum producer can make.Evapotranspiration (E) is the preerred methodor measuring and estimating the total cropwater use and the irrigation demand o a crop.

E is a comprehensive measure o crop wateruse in a production setting as it measures waterevaporated rom the soil and plant surace inaddition to water transpired through the plantsleaves during photosynthesis. Irrigation demandis the difference between the E value and the

water available rom precipitation and/or the soilstorage. E values or sorghum can be obtainedlocally or most exas agricultural regionsthrough weather station networks such as http://texaset.tamu.edu

Keep in mind, however, that ull irrigation osorghum is probably not the goal in most exassorghum production rather timely but limited


30/176

30 | Irrigation

(deficit) irrigation is most likely. Crops other thansorghum are more likely to receive ull irrigation,

thus understanding the timing o sorghum irriga-tion related to growth stage importantance.

In South exas the average peak daily grainsorghum E is about 0.35 inches. Tis value will

vary depending on seasonal climate or planting

date (early versus delayed, which aces higherevaporative conditions). In the Lower Rio GrandeValley or Coastal Bend sorghum water use com-mences at planting in February or March, and nor-mally peaks in late April and May and continuesthrough harvest. Under ully irrigated conditions,seasonal sorghum E can reach 28 inches.

Irrigation Scheduling Based on PotentialEvapotranspiration (PE)

Researchers have developed the means orsorghum growers to calculate the water require-ment or their crop. Tis method helps predictthe amount o water use and the replacementamount o water needed to sustain maximumcrop production. Tis method is predicated on

having sufficient irrigation resources to meet theull water requirement o the crop, which is notpractical in many, i not most cases as irrigationor sorghum and other crops is at a deficit versusthe potential water use in most o exas. In this

event, irrigators may target a set percent o ullE, ofen 75%, to ensure that water is being pro-vided at key growth stages even i less than whatthe crop can use.


31/176

Irrigation |31

For urther inormation on how to use PE orirrigating your crop as well as how to adjust or

differences in irrigation system efficiency, consultextensions Irrigating Sorghum in South andSouth Central exas, L-5434 (2003), which isavailable through county extension offices or canbe downloaded rom http://agrilifebookstore.org

Grain Sorghum Water/IrrigationRequirements in Relation to Heat UnitAccumulation

When a deficit irrigation strategy is implemented,either due to limited water or as part o a

producers overall agronomic approach, irrigationwater should be applied during the priorityperiods o rapid growth and reproduction.Smaller, timely applications are recommendedor sorghum under deficit irrigation to encourage

uniorm growth conditions. Te concept o heatunit accumulation is applied to many crops inexas, particularly cotton. Te same principle,using a base temperature is 50F (cotton is 60F),govern grain sorghum growth and development.Heat units can also be used to predict plant water

use at different stages o growth.Irrigation System Efficiency

Irrigation efficiency is defined as the percentageo water delivered to the field that is beneficially

utilized by the crop. Factors such as wind, leach-ing, evaporation and run-off all lead to decreasedirrigation efficiency. o determine the depth o


32/176

32 | Irrigation

able4.Examplesorghumevapotranspiration(E

)andapproximateirrigationlevels

(typicalrainfallpatternassum

ed)formedium-earlymaturitysorghumhybridgrowth

stagesbasedonheatunitaccumulation.

Sorghum

GrowthSt

age

Daysafer

Planting

A

pprox.

CumulativeHeat

UnitsaferPlanting

(Medium-earlyhybrid

)

ExampleWate

r

ETperStage(in

)

Suggested

Irrigationper

Stage(in)

Seeded

0

0

1.1

1

Emerged

8

200

2.2

0

Rapid

Growth

3Lea

20

500

0.6

1

4Lea

23

575

0.8

0

5Lea

27

660

1.6

2

GPD

35

925

3.2

2


33/176

Irrigation |33

Flag

49

1,290

2.7

2

Boot

59

1,550

2.5

2

Reproductive

Heading

67

1,710

0.9

1

Flower

70

1,850

3.5

2

SofDough

85

2,210

2.7

2

HardDough

98

2,510

1.8

None

BlackLayer

108

2,700

3.9

None

GrainH

ar-

vest

136

3,100

None

Totalwaterusethroughhard

doughbasedonET

23.6

Waterusewilldependgreatlyonclim

atehotterconditionswillleadtomorewaterevapora

tionromthesoilaswellas

highertranspirationalwaterusebytheplant.


34/176


35/176

Irrigation |35

racking Soil Moisture Levels

You may use soil moisture monitoring devicessuch as tensiometers, gypsum blocks or even thesimple soil probe to determine soil moisture lev-els and the date to restart irrigations afer rains.For more inormation on these methods, seeexas AgriLie Extensions Irrigation Monitoring

with Soil Water Sensors, B-6194, http://agrilife-bookstore.org

Irrigation CostsIn most sorghum regions, the most significant

portion o irrigation cost is related to the energyconsumed during pumping or delivery (i bycanal). Historically, natural gas and electricpumping plants offer the lowest cost per unit owater pumped, typically by a significant margin.Where natural gas pipelines or electrical service

are not available, diesel is the lowest cost pump-ing option. Although gasoline and propaneengines offer the same thermal efficiency as thenatural gas engines, they are traditionally moreexpensive to operate due to the higher cost o

uel on an energy basis, and should be avoidedexcept in very specific situations. Regardless oenergy source, the ollowing operational practicesuniversally promote lower irrigation water costs: Irrigate to crop needs, not irrigation system

capacity. Regularly maintain and/or replace irrigation

motors and pumpsmany producers do notrealize that pumping plant inefficiency can sig-


36/176

36 | Irrigation

able 5. Depth o irrigation water applied over time atvarious irrigation system capacities.

Cumulative Inches Applied

GPM/Acre

Daily Weekly 30Days

45Days

60Days

90Days

2.0 0.11 0.74 3.2 4.8 6.4 9.5

2.5 0.13 0.93 4.0 6.0 8.0 11.9

3.0 0.16 1.11 4.8 7.2 9.5 14.33.5 0.19 1.30 5.6 8.4 11.1 16.7

4.0 0.21 1.48 6.4 9.5 12.7 19.1

4.5 0.24 1.67 7.2 10.7 14.3 21.5

5.0 0.27 1.86 8.0 11.9 15.9 23.9

6.0 0.32 2.23 9.5 14.3 19.1 28.6

7.0 0.37 2.60 11.1 16.7 22.3 33.4

8.0 0.42 2.97 12.7 19.1 25.5 38.2

9.0 0.48 3.34 14.3 21.5 28.6 43.0

10.0 0.53 3.71 15.9 23.9 31.8 47.7

Approximate minimum irrigation capacity to water grain sorghum at ullE; reduced irrigation capacities can still be managed to produce high yield-ing sorghum using timely application o irrigation.


37/176


38/176

38 | Irrigation

to limited, timely irrigation, so producers shouldconsider this aspect based on net return compared

to crops like cotton or corn where productioncosts are significantly higher.

Failure to consider cost o irrigation or the poten-tial return based on avorable commodity pricescan lead to unortunate unintended consequences: Producers select and plant longer-season

hybrids and/or higher seeding rates that canoutstrip rainall and irrigation capacity.

Upon realizing the lack o return in someseasons or sorghum irrigation, producersreduce or even stop irrigation.

Ten the field is lef more susceptible tosignificantly reduced production potentialbecause the hybrid maturity is too long andthe seeding rate is much too high.

ips or Furrow Irrigation(From Irrigating Sorghum in South and SouthCentral exas, Charles Stichler)Furrow irrigation is best timed according to theplants stage o growth. Furrow irrigation and timing

is not as exact as sprinkler irrigation. I urrow irri-gation is managed well, most water applications willbe about 3 to 4 inches per irrigation. A good guideis to apply irrigations at key growth stages i there isno rain and additional soil moisture is needed: I the soil profile is ull at planting, the stored soil

moisture should supply the water requirementsuntil the first irrigation at the reproductive stage.

Te onset o the reproductive stage is 35 to


39/176

Irrigation |39

40 days afer planting. One 4-inch urrowirrigation will last the 25 days until flag lea.

At flag lea or boot stage, two 3-inch irriga-tions about 2 weeks apart will last until sofdough in the grain fill period.

Te last irrigation will maximize yield, but isgenerally not economical and does not payor the water. One 3- or 4 inch-irrigation isneeded beginning at sof dough to completegrain fill, which will take approximatelyanother 3 weeks to physiological maturity.

Using this schedule, the appropriate amounto irrigation water will be applied during eachgrowing period i rainall is not received. Ithose amounts are totaled or the entire grow-ing period, the amount need by the crop willapproximate the ollowing:

6-8 in. rainall or pre-irrigationto fill the soil profile i totally dry+

4 in. 30 days afer planting+

6 in. in two 3-in. irrigations

at flag lea or boot stage+

3 in. at sof dough=

19-21 in. o total water

Te 19 to 21 inches o irrigation is the amount owater needed to produce a crop without stress.Te total amount needed will vary somewhat


40/176

40 | Irrigation

depending on weather conditions such as heat,humidity, cloud cover and wind.

Common Mistakes in Grain SorghumIrrigation and Water Usage

Growers need to avoid these common mistakes affect-ing water usage in South exas (Charles Stichler): Waiting too long to put on the first irriga-

tion. Te head begins to orm about 35 daysafer planting. I the plant is stressed duringthis period, the number o potential seedsper head will be reduced.

Irrigating too late. Do not irrigate or yieldafer the sof dough stage. Also do not irri-gate afer the plants have reached physiologi-cal maturity, which is up to 45 days aferflowering or at black layer. Afer that point,the individual seeds umbilical cord is

sealed off and stops unctioning. It will notgain any more weight afer this event, whichoccurs at about 30% moisture.

Over-planting. For ull irrigated production, donot exceed 70,000 to 80,000 established plantsper acre; dryland production should not exceed50,000 to 60,000 established plants per acre andeven this is likely too high when soil moistureis limited and drought occurs. Over-plantingreduces head size, increases the chance o char-coal rot and lodging, increases plant competition

and increases water use with little increase inyield. Proper irrigation management is criticalor profitable yields. I you pay attention to timely


41/176

Irrigation |41

and adequate irrigation, you can keep costs to aminimum while maximizing production.

Summary o op ips or GrainSorghum Irrigation

Statewide exas AgriLie Extension Service andexas AgriLie Research staff Begin the sorghum season with significant

water reserves in the soil profile. Tis is bestaccomplished by maximizing off-season pre-cipitation capture with minimum tillage andresidue management practices. Pre-plantirrigation is not generally recommended orsorghum because o reduced efficiency othe applied water (which makes the waterexpensive).

In arid and droughty conditions, low eleva-tion precision application (LEPA) irrigation

coupled with urrow diking and drag hosesis an excellent means to conserve water andmaximize economic return on grain sorghum.

Irrigate immediately ollowing planting toimprove germination, plant stand and soil-water reserves.

Critical in-season irrigation periods are neargrowing point differentiation (i dry), early tomid-boot stage and early in the grain fill stage.Under limited water conditions, any amount owater during these periods will be beneficial.

Preerence should be given to applying waterearly during critical crop stages, especiallyin limited water conditions. Stress caused


42/176

42 | Planting Irrigation | 42

by lack o water prior to and during the bootstage and grain-fill stages will define lower

yield capacity that cannot be overcome withadequate or excess water during subsequentplant growth stages.

Smaller, timely applications are recom-mended or sorghum under deficit irrigationto encourage uniorm growth conditions. Aslittle as 6 inches o timely irrigation wateron sorghum can significantly increase yieldsand profitability.

Irrigation termination should occur ol-lowing the sof dough stage under typical

seasonal conditions. On an on-going basis, know how much it

costs you to pump or deliver 1 acre-inch oirrigation.

Avoiding excessive plant populations abovewhat is appropriate or the environment andthe projected irrigation level ensures better,more efficient use o irrigation.


43/176


44/176

44 | Planting

indirect means o estimating when soil tem-peratures are likely sufficient to not impede

good adequate sorghum stand establish-ment. Sorghum seedlings can recover roma reeze. However, cold soil temperaturesduring germination can significantly reducegermination, stand, early season vigor andthis can negatively affect a crop well into thegrowing season.

2. Agronomic Delay Rule #1: i the averagesoil temperature has not reached a five-dayaverage o at least 60F at two inch depth,although an ideal temperature or quick ger-mination and establishment grain sorghumis near 65F. Te minimum soil temperatureat the desired planting depth or germinationand emergence o sorghum is about 55F(expect slow growth).

3. Practical Te single risk o early seedingsand subsequent mediocre stand establish-ment, especially in coastal exas, may still bea better bet to minimize the combination omultiple potential riskssorghum midge, a

trend toward hotter temperatures, especiallyat night, later in the cropping season duringflowering and grain fill, and storm damage atthe end o the cropping season.

Prolonged wet periods early in the season

during the planting window can be quiterisky or grain sorghum, especially along thecoast, and in soils that have poor drainage.So in the mind o many producers i you can


45/176

Planting | 45

plant now, when fields are dry, in spite oless than optimum temperature conditions,

you may need to plant anyway. What willyou do i you have two weeks or more o wetfields that delay sorghum planting? Stay withsorghum? I so, reduce maturity? Or evenchange crops?

Long-term weather orecasts: 10-day ore-casts have improved their prediction o long-term temperature trends and cold ronts.Tese may simpliy your planting plans. Iyou are planting early and see no indicationo a orthcoming cool down, then you can

better plant with confidence, and might evenbe able to reduce your seeding rate since youcan assume a higher percentage o seeds arebecoming established plants. On the otherhand prediction o coastal climate or rainallconditions is less precise than or continentalclimates, so recognizing rainall trends in thenext 10 days is more difficult along the coast.

Reduced rainall, beginning in June, or theCoastal Bend to Lower Rio Grande Val-leyearlier plantings are more likely receive

rainall during grain fill. Cool soil temperatures or grain sorghum versus

cotton: Grain sorghum and cotton actually havesimilar optimum soil temperature requirements,but early season cooling is potentially muchmore detrimental to cotton stand establishment,especially as some cotton seed has poor coldgermination vigor, which can affect the crop wellinto the cropping season.


46/176

46 | Planting

4. Practical I you plant very early when coolsoil temperatures are a risk contact your seed

dealer or any hybrids that may have bettercool soil germination and vigor.

You can view local soil temperatures at:

http://cwp.tamu.edu, a weather network

or soil temperatures, rainall and severalother useul tools that cover the region romWeslaco north through the Coastal Bend tothe Upper Gul Coast as well additional sitesin Uvalde and Williamson Co.

http://researcharm.tamu.edu/test.txt, theexas A&M University research arm in theBrazos Bottoms west o College Station.

http://www.ars.usda.gov/Research/docs.htm?docid=9697 contains current daily soiltemperatures rom emple (six inch depth),

but only historical data or soil temps at Riesel. Te exas Potential Evapotranspiration Net-

work, http://texaset.tamu.edu, offers com-prehensive weather inormation at numerousSouth and Central exas sites, but does notprovide soil temperature inormation.

Have you had trouble with sickly seedlings andpoor early season vigor in your sorghum crop? Iso, then consider your planting date. Increasingyour seeding rate to overcome this may be a prac-

tical solution, but this is not good agronomics oryour sorghum crop. Normally, a sorghum cropis not worth planting too early unless the risk oan early planting is outweighed by actors at and


47/176

Planting | 47

afer flowering and maturity (midge, heat, slowdrydown, increased potential storm damage).

Are you requently dealing with significant sor-ghum midge damage or possible poor grain fill?Sometimes early planting cant be accomplisheddue to cool conditions or especially wet fields. Idelays in planting are increasing your problems

with midge or harvest issues, then consider howyou can move plantings orward slightly, or per-haps shorten maturity. (We note, however, thatin South and Central exas there are typicallyonly a ew days difference in the hal-bloom datesor medium-early, medium and medium-longhybrids.) Te Lower Rio Grande Valley, CoastalBend and Gul Coast regions have about a two tothree week window or planting when consider-ing the average last reeze (which is sporadic inSouth exas) and flowering to minimize midge

issues (able 6).

Tis window is much narrower or the regionrom Uvalde to Guadalupe County whereproducers must weigh the risk o either earlyplanting and cool soil temperatures (and a late

reeze) versus anticipated midge potential.ables 6 and 7 suggest a practical justificationor planting dates based on the window betweenearly cool conditions and planting to minimizesorghum midge potential. What are actual

suggested planting dates or different regions oSouth & Central exas? ables 8 and 9 provideexas AgriLie suggested planting dates andtypical plant by dates based on agronomics,


48/176


49/176

Planting | 49

able 7 Notes: 30-year averages rom exas Almanac, 2008-2009.Early planting still requires minimum thresholds or soil temperature. An addi-tional 1-week delay will significantly diminish early season planting concerns butmight increase risk rom sorghum midge or heat depending on location and year.

exas AgriLie Research Crop esting trials in South exas have ound themost common range o days to hal bloom or medium-long and medium grainsorghum hybrids o 71 to 76 days rom planting. Hal bloom @ 75 days is used asa conservative value in this calculation to determine at what point in a typical yearyou could expect to plant to minimize significant sorghum midge potential. For2006-2009, average days to hal-bloom was only 2 days shorter or a medium vs.medium-long. Reer to the insect chapter or a chart on estimated flower-by datesor sorghum midge in exas.

yield potential, crop saety, etc. Tese are, in act,mostly similar to the previous tables. Since exasAgriLie hybrid trial data reports that there areor the most part only small differences in cropdevelopment rom planting to bloom in Southand Central exas, you may use the same dura-tion or medium-early, medium, and medium-

long maturities.

Keep in mind that local experience is worth alot in terms o optimum planting dates. I youhave a planting date that is working or you, ora hybrid that is working or you at the plant-

ing dates you use, then be slow to change yourplanting. Due to the rainall and soil plantingconditions that sorghum producers routinely aceat planting time, i the window is open to plant,because field conditions are avorable, then youmay choose to err on the side o planting early toensure that you arent set back by a prolonged wetspell (although that wet spell does not do yoursorghum any good).


50/176

50 | Planting

able7.Ave

ragelastspringfreeze,

earlyplantingdatescenarios,andprojectedsafeplantingdatesformedium-longandmed

ium

hybridsinCentral&Northexas.

Location

Lastaverage

springfreeze

Earliestsuggestedp

lanting

basedonlastaveragespring

freeze

Approx.Plantbydateformedium

&medium-longhybridstomini-

mizesorgh

ummidge

argetFlowerbydateto

minimizesorghum

midge

Georgetown

3/5

3/19

4/5

6/20

Cameron

3/7

3/21

4/5

6/20

Waco

3/12

3/26

4/10

6/25

Waxahachie

3/14

3/28

4/15

6/30

McKinney

3/21

4/4

4/15

6/30

Sherman

3/22

4/5

4/15

6/30

(abovedatess

et75daysbeforelastcolumn)

30-yearaveragesromTexasAlmanac,2008-2009.

Earlyplanting

stillrequiresminimumthresholdsorsoiltemperature

.Anadditional1-weekdelaywillsignificantlydiminish

earlyseasonplantingconcernsbut

mightincrease

riskromsorghummidgeo

rheatdependingonlocatio

nandyear.

TexasAgriLieResearchCropTestingtria

lsinCentralTexashaveou

ndthemostcommonrange

odaystohalbloomorm

edium-longandmediumgrain

sorghumhybridso71to76daysromplanting.Halbloom@75day

sisusedasaconservativevalueinthiscalculationtode

termineatwhatpointinat

ypical

yearyoucould

expecttoplanttominimize

significantsorghummidge

potential.For2006-2009averagedaystohal-bloomw

asonly2-3daysshorteror

amedium

vs.medium-long.Reertotheinsectchapterorachartonestimatedflower-bydatesorsorghum

midgeinTexas.


51/176

Planting | 51

Suggested Final Planting Dates: Late-Season Planting?

In contrast to the above agronomic planting datesuggestions, on a rare occasion a late-planted sor-ghum crop (possibly a double crop) may be con-sidered. Tere is little concern about being able tomature a late-planted sorghum crop anywhere in

South and Central exas or plantings to July 1 andeven mid-July to the south; however, end-o-the-season actors like midge, drought, tropical stormsand poor drying conditions (and or Central andespecially North exas, muddy fields) can greatly

reduce the practicality and economic return o alate crop. Perhaps you have tried it beore. Somearmers simply say it does not work well.

South exasLate grain sorghum may occurwhen another crop ails, wheat is harvested, but

it is risky due to insufficient rainall. However, itwill make modest yields i rain is sufficient. Donot plant so late that heads will not dry.

Central and North exasWhere rare later fieldsmay be planted into late June, a cutoff date should

allow the sorghum to reach black layer 1-2 weeksbeore your areas average killing rost (or sincethat data is harder to find, 2-3 weeks prior tothe average first reeze, or example, Sherman,11/11; McKinney, 11/14; Waxahachie, 11/18).Tis allows or sorghum maturation withoutsignificant risk to yield or test weight i a rost orreeze occurs up to 10 days earlier than average.In practical terms, though you can mature a late


52/176

52 | Planting

able 8. Range o suggested early (6 to 10-day range),preerred, and last (5-day range) suggested planting dates

or grain sorghum hybrids in South exas. Agronomical-ly, optimum dates or stand establishment in many yearsmay trail suggested early dates by 1 to 2 weeks. Te win-dow between early planting dates (cool conditions) andlate planting (potential or sorghum midge, hot weatherand drought during flowering & grain fill, and rain &tropical storm damage prior to harvest) is unortunately

sometimes less than one month.South exasRegions

Suggestedearly plantingdate limits

Plantingdatepreerredtarget

Suggestedfinalplantingdate limits

Lower Rio

GrandeValley

1/21-1/30 1/31-2/10 2/15-2/20

Costal Bend 2/15-2/21 2/22-3/5 3/15-3/20

Upper GulCoast

2/25-3/4 3/5-3/15 3/25-3/30

San Antonio

Region

(Gonzales toUvalde)

3/5-3/10 3/10-3/20 3/20-3/25

Agronomic suggestions crowd the last average reeze dateor the Uvalde region (March 10, able 4-1) yet sorghummidge on the back side pinches preerred planting dates in

this region to a narrow range. Use o extended 7-10 dayweather orecast or this region is strongly encouraged,more so than other regions.


53/176

Planting | 53

able9.Rangeofsuggestedearly(6to

10-dayrange),prefe

rredandlast(5-day

range)suggestedplanting

datesforgrainsorg

humhybridsinCen

tral&Northexas.

Agronomically,optimumdatesforstan

d

establishmentinmanyyearsmaytrailsuggestedearlydatesby1to2weeks.T

ewindowbetweenearly

plantingdates(coolconditionsandlastspringfreeze,seeable4-2)andlateplanting(potentialfor

sorghummidge,ho

tweatheranddroughtduringflowering

&grainfill)isunfo

rtunatelysometimesless

thanonemonth.

Central&North

exasRegions

Suggestedearly

plantingdatelimits

Plantingdatepre-

ferredtarget

Sugg

estedfinalplanting

date

limits,primarycrop

LowerBlacklands

(GeorgetowntoWaco)

3/10-3/15

3/15-3/2

5

3/31-4/5

CentralBlacklands

(WacotoDallasarea)

3/15-3/25

3/26-4/5

4/15-4/20

NorthernBlackland

s

(DallastoRedRiver

)

3/25-4/4

4/5-4/15

4/21-25

Somedoublecroppingm

ayoccurinCentral&North

Texas.Laterplantingscan

assumesorghummidgeriskandpossibledrydownissu

esinthe

alliplantedmid-Juneor

later.


54/176

54 | Planting

sorghum crop, can you harvest it? Harvestabilityis the key consideration or late season sorghum.

Fog, all rains, high humidity and muddy fieldsthat may not dry or months, requently intererewith grain sorghum harvest or late-plantedsorghum. Tese issues lead to poor dry downleading to long harvest delays, increased lodgingpotential, sucker heading, eral hog damage, etc.For these reasons, concluding late planting by: July 1 in South exas, a medium or medium-

early maturity hybrid may enable harvestwhen drying conditions are still avorable.

For North exas, late June plantings can

mature adequately, but harvest issues aresignificant. Local exas AgriLie staff in thenorthern Blacklands suggest that plantingsafer June 1, though easily matured, aceharvest timing during the wet all monthswhen fields might never dry sufficiently toachieve harvest.

Does planting date affect grain sorghum hybridgrowth? Yes. Although some hybrids tiller more thanothers, the same hybrid planted in any location inexas over a period o time (six weeks and more) willlikely have more tillers early in the season. Tis ismost likely triggered by cool conditions. illering,though largely regarded as a common and even essen-tial acet o grain sorghum production, can sometimesdiminish a crop because it sets too many tillers early

in the season then drought occurs, and then the cropsheads per acre is too high to fill very well and yieldscan actually be diminished because o tillering.


55/176

Planting | 55

Grain Sorghum Seeding Rates

Planting: Seeds per Acre versus Pounds per Acreexas AgriLie has long recommended thatsorghum producers base planting on seeds peracre rather than pounds per acre. Grain sorghumseed can vary widely in seed size, ofen 12,000to 18,000 seeds per pound with 13,000 to 16,000

being most common. I you have to use seednumber per pound (e.g., you have a plate planterrather than an air-vacuum planter) check theseedtag first or choose about 14,500 or 15,000.I you assume 14,500 seeds per pound but the

seed was actually 16,500 then you have effectivelyincreased the seeding rate 14% (germination andemergence will probably be similar).

Calculating seeding rates can be done two ways.

Seeding rate:

For example:

Seeds (or plants) per oot:

For example:

55,000 seeds X 38 inches

43,560 sq. f. per acre 12 in.= 4 seeds/oot o row

arget seeding rate X Row spacing

43,560 sq. f. per acre 12 in.= Seeds/oot o row

43,560 sq. f. X 12 in. X 3.5 seeds

acre 38 in. Foot o row

= 48,145 seeds/A

43,560 sq. f. X 12 inches X Seeds

Acre Row spacing(in.) Foot o Row=Seeds/A


56/176

56 | Planting

IP: exas AgriLie ound that grain sorghumseeding rate varied by approximately 20% on

individual rows o an air-vacuum planter. Evena new planter had significant differences in seeddrop that needed correction. Beore plantingseason arrives check your seed drop at both lowand high rates to ensure you are planting yourtarget seeding rate. Use able 10 to help deter-mine an approximate seed drop or each row overa pre-determined length such as 50 eet.

Seeding Rate General Guidelines

Guiding principle-less is more!Tis principle

has long guided grain sorghum seeding rates,especially or rained production when droughtconditions are a regular occurrence. Lower seed-ing rates can produce higher yields when droughtyconditions prevail and you are begging or a

rain. Lower plant populations are suited to thesedrought conditions preserving more moisture perindividual plant, thus reducing the plants stresslevel. Moisture and yield potential is conservedas less moisture is used to produce unneededstems and leaves while the crop is better able to

wait extra days until that next rain you are hopingor. Furthermore, anywhere in exas, high plantpopulations or the production environment, willenhance the development o charcoal and otherstalk rots in drought-stressed plants, leading to

lower yield and significant lodging potential.Reduced seeding rate is perhaps the key or man-aging grain sorghum production risk anywhere inexas, unless you have ull control o irrigation.


57/176

Planting | 57

Sorghum plants are very water efficient and havethe ability to compensate considerably in grain

yield with respect to growing conditions andplanting rates. I soil moisture is limiting, grainyield will be greater i plant population is lower.Furthermore, i soil moisture is avorable due toirrigation or adequate rainall, there is a level oplant population above which no additional grainyield will be achieved rom an increase in plantpopulation. I a modest plant population is usedor an area typically limited by adequate moistureand above average rainall is received, sorghumplants can adjust their grain numbers and weight

considerably to compensate or the improvedgrowing conditions.

Depending upon soil moisture conditions,recommended seeding rates vary between 30,000and 80,000 plants per acre or South exas. Dont

be too quick to assume that your productionconditions merit the highest end o this range.Under limited moisture conditions, 2 to 4 plantsper oot or 38-inch row spacings will normallyuse all available soil moisture (able 12). Irrigatedsorghum perorms better with no more than80,000 plants per acre (this would require ullirrigation).

Furthermore, exas AgriLie field tests in theCorpus Christi area examined greatly reduced

grain sorghum seeding rates. Yields in the areawere maintained by seeding as little as 1/3 othe highest seeding rates that some commercialseed companies recommend, thus reducing


58/176

58 | Planting

able10.

Rowspacin

gandseedsperacre

andtheresultingseedsperfoot.

Forairvacuum

plantersyourplanterbooklistsboththes

eedsperacreandre

sultingseedsperfootincombi-

nationwiththeneede

dplantersettingsto

achieveyourtargetedseeddrop.

Planter

Row

W

idth

(inches)

Linear

RowFeetper

acre

argetSeed

ingRateperAcrefo

rSouth&Centralexas

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

Seedsperfootofrow

40

13,068

2.3

3.1

3.8

4.6

5.4

6.1

6.9

7.7

38

13,756

2.2

2.9

3.6

4.4

5.1

5.8

6.5

7.3

36

14,520

2.1

2.8

3.4

4.1

4.8

5.5

6.2

6.9

30

17,424

1.7

2.3

2.9

3.4

4.0

4.6

5.2

5.7

20

26,136

1.1

1.5

1.9

2.3

2.7

3.1

3.4

3.8

15

34,848

0.9

1.1

1.4

1.7

2.0

2.3

2.6

2.9

10

52,272

0.6

0.8

1.0

1.1

1.3

1.5

1.7

1.9


59/176

Planting | 59

85%

2

5,500

34,000

42,500

51,0005

9,500

68,000

76,500

85,000

(C

ommonwhenwater

andsoiltemperature

areavorableorirrig

ationisusedtoestab

lishthe

crop.)

67%

2

0,000

27,000

33,500

40,0004

7,000

53,500

60,500

67,000

(Somewhatlessavorab

lesoil,moisture,and

environmentalcond

itionsincludingearlyplantingin

coolerconditions.)

Linearrow-eetperacre=43,560sq.f.peracredividedbytherowwidthineet.

Extensionencouragesproduc

erstothinkintermsoSeedDropperacre,notpounds

peracreorplantsperacre

.Withair

vac

uumplantersseedsizeshou

ldnotaffectplanting,butn

oteseedsperpoundonyourseedbagsanalysistag.


60/176

60 | Planting

production costs and insulating against potentialcharcoal and stalk rot development.

IP: Have you ever had a seed salesman or seedcompany tell you: No, that is too high a sorghumseeding rate? I so, they have your sorghum cropand your best interests in mind. You should con-sider being their customer a long time. Some seed

company websites recommend as much as 10 lbs.per acre or grain sorghum production withoutsaying anything about your rainall, irrigationlevel, etc. No sorghum production area in the U.S.requires such an excessive seeding rate! A rate inthis range is potentially 150,000 seeds per acrethat almost sounds like a decent hay crop!

Reducing Seeding Rate when Stored SoilMoisture is Low

As noted in other sections, too high seeding rateleads to problems in grain sorghum. Te primaryconcerns are drought and the subsequent poten-tial or charcoal and stalk rots hence lodging. Istored, soil moisture is low or poor (in contrastto planting moisture) and exas AgriLie recom-

mends that you immediately reduce your seedingrate by at least 10,000 seeds per acre. Tat wouldhopeully be more than 10% and as much as a 20%reduction in your seeding rate. Tis is one way tomanage (reduce) risk in your sorghum crop.

As in able 11, the driest region with the lowestaverage rainall o the sorghum production areain South and Central exas is the region west and


61/176

Planting | 61

southwest o San Antonio in Uvalde, Medina,Zavala and Frio counties. Annual rainall

approaches 20 inches and is lower in some years.Tis calls or the reduced seeding rates more sothan other areas covered in this handbook asplant population can too easily outstrip availablewater. Te goal or this region is to make a crop,not a mistake (too high seeding rate), to providethe producer the best possible chance or a mod-est yield in spite o prolonged dry conditions.able 11 below notes a five-year trial in whichlower populations were sufficient to meet theyield potential o the conditions.

Why are some rained exas grain sorghum fieldsseeded at more than 100,000 seeds per acre?It is the practice in some areas o exas in theUpper Gul Coast to use seeding rates that maygo up to 120,000 seeds per acre and as high as

140,000 seeds per acre on the best ground wherehigh inputs are used. No exas AgriLie testshave ever reported significant yield increasesrom these excess seeding rates. In contrast, theconclusion o numerous exas AgriLie trials hasnoted that reduced seeding rates, even lower thanthose suggested in able 11, have maintainedyield potential on par with higher seeding rates.

Do relatively inexpensive sorghum seed costsaffect seeding rate?Yes. Farmers ofen cite the

act that sorghum seed is inexpensive as a reasonwhy they do not bother with reducing seed-ing rates. Inexpensive seed costs mean that aproducer is not concerned much by using a high


62/176

62 | Planting

able 11. Suggested seeding rate targets and resulting plantpopulations or South & Central exas. Lower seeding rates aresuggested a) when stored soil moisture is low at planting, b) or laterplantings when soil temperatures are up (stand establishment willbe much improved), and c) i you have a history o drought thatmay lead to potential lodging rom overpopulation. In contrast,early planting subject to cool wet conditions could lead to a standestablishment in the 50-60% range thus the higher end seeding rateis suggested or those conditions.

exas Region

argeted

Plant Pop.

argeted Seedling

Rate to AchievePlant Population

Lower Rio Grande Valley & Coastal Bend

Irrigated (limited) 60,000-70,000 70,000-80,000

Rained 50,000-60,000 60,000-70,000

Rained, low storedsoil moisture

40,000-50,000 50,000-60,000

Upper Gulf Coast

Rained 70,000-80,000 80,000-95,000


60,000-70,000 70,000-80,000

San Antonio Region

Irrigated 60,000-70,000 70,000-80,000

Rained 40,000-50,000 50,000-60,000


30,000-40,000 40,000-50,000

Central & North

Texas

Rained, particularlyearly plantings

60,000-70,000 70,000-80,000

Rained, with later

plantings and/or lowstored soil moisture

50,000-60,000 60,000-70,000


63/176

Planting | 63

seeding rate i planting early in cool conditions

so that he will still have an adequate stand. I seedcosts were two or three times higher, high seed-ing rates would be reduced to agronomic ratesand producers would likely be more hesitant toplant early in cold conditions.

Planter Row Spacing and Seeding RateDepending on the area predominant row spacingis 30 inch, 36 inch, 38 inch or 40 inch rows. Aew producers use 15 inch or 20 inch rows onoccasion by either drilling or using an inter-

plant planter. Research in San Patricio Countyand emple shows increased yields with 30 inchrow spacing versus wider rows. Making rows 30inches instead o 38 to 40 inches can help shadethe soil aster and reduce weed growth.

Further research in the Coastal Bend and Uvalde(able 13) regions has shown that narrower rowspacing (or example 19 inch versus 38 inch) has

able 12. Dryland sorghum seeding rate results romfive years o testing at Uvalde (38 rows) demonstrate

the lack o benefit o excessive seeding rates (courtesyCharles Stichler, ormer Extension agronomist, Uvalde).

Plants per Acre

Estimated Seed per

Acre @ 75%

Establishment Yield (lbs ac-1)

27,000 36,000 2,360

41,000 55,000 2,750

55,000 73,000 2,640

76,000 101,000 2,570


64/176

64 | Planting

airly consistently produced slightly higher yields(seeding rate held the same).

One exas AgriLie test in the Corpus Christiarea ound that grain sorghum yields increased10 to 26% by planting narrow rows (less than 20inches) compared to conventional row spacing(38-40 inches), except under severe drought

(where lower seeding rate likely would have astronger impact). All tests were held at the sameseeding rate or narrow and conventional rows.

Sorghum plants are more efficient when eachplant is given space to intercept sunlight and

competition between plants is minimized. Inaddition, closer spacing (i.e., double row ornarrow rows) will promote shading o the soilsurace to reduce evaporation losses and provideweed suppression.

able 13. Irrigated sorghum seeding rate and row spacingrom five years o testing at Uvalde demonstrate the po-tential advantage o narrow row spacing in grain sorghum(Courtesy Charles Stichler, ormer Extension agronomist,

Uvalde).Plants/A Estimated

Seeds/A at 75%Establishment

Yield(lbs/A -1) Rowspacing

26 38

27,000 36,000 3,560 2,910

41,000 55,000 4,080 3,03055,000 73,000 4,790 3,200

76,000 101,000 4,810 3,730


65/176

Planting | 65

IP: We recommend you do not increase yourtarget plant population per acre i you move rom

wider row spacing to narrower rowslet the sor-ghum plant compensate or you in the field lest youerr by raising seeding rate too much. Furthermore,maintaining the same seeding rate guards againstthe potential effects o over-populating a field.

For narrow row seeding, a planter perhaps with asecond set o planter boxes (e.g., Kinze interplantplanter) is preerred, but i you use a drill ollowthese guidelines: Consider plugging 1 o 2 or 1 o 3 holes to

ensure that you can lower the seeding rate,especially i drilling (calibrate the drill,dont just assume the settings are accurate,especially since seed size varies). Te valueo good seed placement with a planter underadverse conditions to ensure a stand at lowseeding rates may make drilling undesirable.

I using a drill, increase seeding rate no morethan 10% over what you would use with aplanter only i you expect reduced standestablishment due to decreased desirability

o seed placement with a drill. By all means avoid overseeding on nar-

row rows. I you bump the seeding rate upsubstantially thinking you might have troublegetting a stand but all the seeds come up dueto a good rain you immediately and irrevers-ibly have too many plants per acre in a cropthat will have higher susceptibility to drought.


66/176

66 | Planting

IP: Where ever you arm in exas, i youare having doubts about whether you need to

increase your seeding rate, dont do it! Apartrom a stand ailure or major insect damage youwill rarely i ever see a South exas sorghum fieldthat was too thin or its production environment.

CAUION: Over Seeding Equals Speeding! Iyou drive too ast at the risk o your saety andwell being, the police or highway patrol will stopyou and you are cited or ailure to control speed.Likewise, in grain sorghum production speedingis akin to ailure to control seeding rate!, and the

risk is to your sorghum crops yield potential andyour balance sheets bottom line.

Likewise, in grain sorghum production speedingis akin to ailure to control seeding rate!, and therisk is to your sorghum crops yield potential and

your balance sheets bottom line.

Seeding Rate May be more Important thanHybrid Selection

You can spend a lot o time selecting a good

hybrid choice, but you can quickly undo yourhybrids potential by seeding too high. Tis doesnot diminish the importance o hybrid selection,but serves as a reminder to ensure seeding ratedecisions are given your best effort.


67/176

Planting | 67

Successully Seeding Your Selected GrainSorghum Hybrid

Consider these IPS to ensure success: Ensure that sorghum seed sits on good moisture. ypical sorghum seeding depth is near 1.0-

1.5 inches, but 2.0 inches can lead to emergence problems

and a spindly seedling. Sorghum can emergein a hurry in a couple o days rom 1 inchdepth i conditions are warm.

Tere is no substitute or local producer expe-rience; i youve had trouble getting sorghum

to emerge, ask your neighbors or suggestions. Particularly in rained production, minimize

possible soil crusts by dragging dry soil backover the seed row to reduce drying and bak-ing o the soil i hot weather prevails. Tiswill enhance seedling emergence.


68/176

68 | Fertilization

FERTILIZATION

Grain sorghum production in exas ranges romlow input rain-ed production to high-input ullirrigation. Hence soil nutrient status is highly

variable. Crop rotation and the requent pro-ducer practice to ertilize only when a certain

crop is in rotation means that residual ertilitymay be more important. Likewise, tillage andertilizer placement practices will affect the nutri-ent use efficiency o grain sorghum.

Soil esting

Many producers do not realize the extent oresearch and testing that is behind the processo analyzing soil samples or nutrients and thesubsequent recommendations they generate. Arealistic goal or many producers is to take a soil

sample every three years.

Different Philosophies o Soil estRecommendations

Tere are two common approaches to soil ertility

recommendations or the same crop and produc-tion conditions. Each has its own merits and canbe used successully although these approachescan generate recommendations that seeminglyare at odds with each other.1. Provide what the crop needs or current-year

production. Based on your yield goal, yourcurrent soil nutrient status and that nutri-ents projected availability to your crop, add


69/176


70/176

70 | Fertilization

erent recommendations. Although, labs within agiven region o the country tend to have uniorm

testing procedures, this is not always the case. Forexample, there are different tests or soil P (soilpH may dictate which one should be used). Labsmay use a different extractant or the soil, or oncethey have obtained the extract or nutrient analy-sis may use a different method o measuring thenutrient in the extract which could be affected byother constituents in the sample. Tese differ-ences lead to different test values o nutrientsmeasured in your soil.

Different ertilizer recommendations

As noted above there are differences in thephilosophy o soil testing. Provided the soil test

value or a particular nutrient is the same, thenbuild-and-maintain would likely have a higher

ertilizer recommendation. Tis philosophy maybe the normal approach to recommendations bya test lab. Apart rom differences in philosophythe calibration curves plotting nutrient require-ment or a unit o yield are not necessarily thesame. One lab may recommend 2 lbs o N per

hundred weight o sorghum yield goal, whereasanother recommends 2.5. Or, a particular labsrecommendations might include additions ordeductions to their calculation that are notactored in by a different lab.

IP: When your soil test lab, ertilizer dealer,crop consultant or other third party providesertilizer recommendations, do the ollowing:


71/176

Fertilization | 71

Ask about their philosophy o soil test recom-mendations as noted in Nos.1 and 2 above.

Furthermore, i you are receiving ertilizer appli-cation recommendations without the benefito soil test results, then ask about the guidelinesused in arriving at those recommendations.

Finally, i you receive recommendationswithout having even provided a yield goalthen you need to question the recommenda-tions closely to ensure that at least a mini-mum agronomic basis and not a pure salesmotive alone is guiding ertilizer plans.

exas A&M University Soil esting Lab

Te College Station lab provides complete ee-based services or soil, plant tissue and wateranalyses. exas AgriLie testing across exas ongrain sorghum (as well as other crops) orms the

basis or soil test recommendations or samples.For more inormation on services, submittalorms (including the Soil Profile N orm dis-cussed below) and how to collect and submitrepresentative samples visit http://soiltesting.tamu.edu/. A key soil test procedure that exas

A&M uses, which is now a common standardacross many labs, is the Mehlich III extract-ant. Soil test numbers (but not necessarily therecommendations) using this method comparedto other procedures will vary, especially or P.

Te Mehlich III test is better suited or the variedsoil types across exas. Te test has been key toimproving P recommendations or the state.


72/176

72 | Fertilization

IP: When choosing a soil test lab, inquire i thelab is accredited by a state agency or certifica-

tion board, a participant in the North AmericanProficiency esting program, or some othertesting standard guidelines. Tis ensures that thelab meets recognized standards and practices thatare oundational or providing you with good test

values and recommendations.

IP: I you already use or consider using a soiltest lab that is ar removed rom the region orstate where your soil was sampled, call them toensure they can provide you with results basedon suitable test procedures and recommenda-tions or your soil type and your crop (especiallyi your crop is not grown in that state).

Sorghum Nutrient RequirementsNitrogen

You cant get something from nothing for very long

Occasionally in exas, particularly where rainall islower (especially less than 20 inches), armers mayertilize grain sorghum minimally or not at all,even or nitrogen. o some extent this just-get-byattitude resulted rom low grain sorghum prices,but it may also reflect poor attitudes and the lacko success on the part o many producers due totoo-high seeding rates and little thought in hybridselection. Sorghum indeed responds to nitrogen.

Nitrogen(N) is by ar the most important nutri-ent or sorghum to maximize production. Formaximum yields relative to the available water, N


73/176

Fertilization | 73

able 14. Approximate nutrient uptake and removal bygrain sorghum per acre or major nutrients.

Nutrient Uptake Nutrient Removal

Yield N PO KO N PO KO

----------------------- Pounds per Acre -------------------

2,000 60 21 55 30 15 8

4,000 120 42 110 60 30 16

6,000 180 63 165 90 45 24

8,000 240 84 220 120 60 32

10,000 300 105 275 150 75 40

Nutrient uptake at the rate (per cwt.) o 3.0 N, 1.1 P2O5, 2.75 K2O. Nutrient

uptake is the total taken up by the crop grain and above ground vegetation.Tese numbers should be used only as general guideline (Potash & PhosphateInstitute). Nutrient removal at the rate (per cwt.) o 1.5 N, 0.75 P2O5, 0.4 K2O

should not be lacking or grain development willbe reduced. Te long-standing general N nutri-ent requirement or exas grain sorghum is:

N requirement:2 lbs actual N (soil or ertilizer) per acre per 100lbs o yield goal

Tus a 5,000-pound grain yield would need

about 100 lbs o N per acre. In exas this hasofen been presentederroneouslyto produc-ers as the amount o N ertilizer to add withoutacknowledging available soil N. However, theexas A&M University soil test lab recom-

mends using the above rule but correctly deductnitrate-N rom a soil test in the top 6 inches asnoted below.


74/176

74 | Fertilization

exas A&M Recommendation:(Fertilize 2 lbs actual N/acre per 100 lbs o yield

goal) - (soil N at 0-6 in.)

Hence or the same yield goal noted above, butwith a soil test report showing 9 ppm NO3-N ora 6-inch deep sample (which is about 2 millionlbs o soil), the calculated N ertilizer addition is:

Fertilizer N to add:(2 lbs N/acre)X(50 cwts/A yield goal)(2 X 9ppm) = 82 lbs N/acreTis N recommendation, particularly when the

soil N is deducted, is more conservative (lower)that what is normally generated in other statessuch as Kansas or Oklahoma which each usea more complicated ormula or include otheradjustments, but AgriLie Extension recommends

exas producers maintain the simple rule othumb above. When soil test inormation is notavailable this rule will help producers at a mini-mum to be in the range o meeting the sorghumsN requirement or good yield.

Soil Profile N est rom exas A&MSampling and Crediting Soil N Below 6 in.

Ideally soil testing or N would use a 24 inchesdepth sample (in contrast to 6 inches or P, whichis largely in the surace, or the standard depth

noted above in most soil tests). Research inseveral areas o exas across several crops is re-quently showing a significant amount o N below


75/176


76/176

76 | Fertilization

Under center pivot irrigation, N ertilizer maybe applied several times during the early part o

the growing season. Due to the convenience opivot-applying N especially in the High Plains, upto 20% o N might be held back until afer GPD,but Extension recommends that the final N beapplied no later than boot stage which is about 60days afer germination or a ull-season hybrid andno later than about 50 days or a medium maturityhybrid. About 70% o the needed N or a grainsorghum crop is already in the plant at boot stage.

Because N is relatively mobile in the soil, ertil-izer placement is not as critical or N as it is ormost other nutrients. Nitrate-nitrogen, NO3-N,the orm most available to grain sorghum, willmove with water and can be readily brought intocontact with crop roots or quick absorption.

Ammonium-nitrogen (NH4, also availableto plants) is positively charged and is held bynegatively-charged clay and organic matter par-ticles in the soil until converted by soil bacterialaction into the nitrate orm. Te conversion romammonium to NO3-N in the soilnitrification

is most likely to occur when fields are arable.When fields are water-logged, nitrate can beconverted to nitrogen gasdenitrificationandlost rom the soil by volatilization.

Guidelines or Surace Applied N Fertilizer

Ammonium-based ertilizers are more suscep-tible to volatilization losses when applied to


77/176

Fertilization | 77

the soil surace i no rain or irrigation occurs.Tree key actors reduce the effectiveness o the

surace-applied N leading to volatilization losses,particularly when acting together: Moist or wet soil pH is greater than 7 Increased temperature, windy conditions

Extension always recommends where possiblethat producers using broadcast N ertilizer applyto dry soil. Furthermore, applying N prior to apredicted rain or scheduled irrigation is particu-larly advantageous.

Starter Fertilizer and Salt InjuryPotentialSuggestions or Grain Sorghum

Starter ertilizer application or sorghum is asound practice in exas. Even i soil tests likephosphorus (P) are in the medium range, oneo the purposes o starter ertilizer or N and Pis to kick-start or stimulate growth right aferemergence. Starter ertilizer research, especially inKansas has shown that rooting and early growthis promoted by starter ertilizer applications in

the 2 inch x 2 inch configuration (rom the seed,2 inches to the side and 2 inches below). Starterertilizer can be applied with the seed, the so-called pop-up ertilization, but at rates much lessthan the 2 inch x 2 inch placement. A commonconcern is potential salt injury and ammonia dam-age i the rate o starter ertilizer is too high. Salt injury comes rom N, potassium (K),

and sulur (S).


78/176

78 | Fertilization

Pounds per acre o N+K+S applied willdetermine injury potential, but K and S

ertilization is much less common than N assoil K is high in most exas soils (acid soilsthe likely exception) and S is sufficient.

N ertilizers that contain or readily orm ammo-nia, NH3, can be toxic to seed (see below).

Phosphorus ertilizer (e.g., triple superphos-phate, 0-46-0, etc.) does not cause injuryto seedlings, but most P ertilizers used inexas contain N (e.g. 11-52-0, 10-34-0), soollow the below guidelines or N (able 16).

able 15. Suggested maximum ertilizer salt amounts(lbs. N-K2O-S/acre) or seed row ertilizer placement,row spacing, and soil type.

Loamy-Clayey Soil Sandy Soil

--------- Row spacing (inches) -----------FertilizerPlacement

15 20 30 40 15 20 30 40

Pop-up(w/ seed)

10-15 8-12 5-8 6 10 8 5 4

2 x 2pattern

80 60 40 30 40 30 20 15

More salt-orming N and K ertilizers can beapplied to loamy and clay based soils than tosandy soils. Narrower row spacings allow moreN and K as well. Pop-up starter ertilizer rates

are much lower than starter ertilizer 2 inchesrom the seed. I the total amount o N ertil-izer applied to your sorghum is 60 lbs N and A,and you are on 20-inch rows, than the entire


79/176

Fertilization | 79

dose could be applied as a 2 in. X 2 in. starter onloamy and clayey soils. However, in most cases,

the balance o the N ertilizer will have to be sid-edressed. Tis can be as 32-0-0 either dribbled orknied in 6 to 10 inches off the row without thethreat o injury, applied through a pivot or usinga broadcast spreader.

Some starter N ertilizers have potential orinjury rom ammonia (NH3) because theyeither contain NH3 or an N orm that quicklyconverts to NH3 gas. Tis is primarily a concernwith pop-up ertilization. For pop-up applica-tions with the seed producers should avoid ureaammonium nitrate (32-0-0 or 28-0-0), mixtureso 32-0-0 and ammonium thiosulate (28-0-0-5S), solid urea (46-0-0), mono-ammoniumphosphate or MAP (11-52-0) and diammoniumphosphate DAP (18-46-0).

For sample calculations as well as additional rowspacings consult Starter and In-Furrow Fertilizer& Salt Injury Potential, (Bronson) at http://lub-bock.tamu.edu/sorghum

Phosphorus (P2O5)It is difficult to gauge needed P requirementsor grain sorghum or any crop without soil testinormation or P in the 0-6 inch depth. able 17notes soil test P levels and their relative designa-

tion such as very low, low and moderate (20-50ppm, a very wide range). Soil test P levels above50 ppm are high. Using the Mehlich III soil test


80/176

80 | Fertilization

method, the crop response in most o exas toertilizer P is inconsistent between 30 to 40 ppm

(the transition zone o soil P response), and mea-surable yield differences are not demonstratedabove 40 ppm soil P.

When growing conditions are cool or wetearly in the season, especially where producers

might be planting early to minimize sorghummidge potential, seedlings may show temporaryP-deficiency symptoms. Tis particular situation,as well as P nutrition in general, lends itsel wellto either banded or in-urrow application o P.Fertilizer P itsel is not salt orming or toxic toplants at higher levels o P. See comments aboveon allowable banded and pop-up P ertilizer rateswhen N is a component o the P ertilizer.

Since soil P is relatively immobile or ixed

in most exas soils, placement in a concen-trated orm is particularly important in lowto medium testing soils. Research has shownthat plants obtain a higher proportion o theirneeded P rom soil reserves. Only about 30% oapplied P is used by the crop ollowing ertil-

ization in the current year, even though it mayhave been banded.

exas AgriLie does not offer a general rule othumb or P2O5 needs or grain sorghum like wedo or nitrogen. However, when soil test P levelsare very low, tables rom several states extensionsoil test guidelines cite a P2O5 requirement orertilizer that is approximately 50% N (and 40%


81/176

Fertilization | 81

or low soil test P, 25% or moderate soil test P).Tis would reflect the act that much P comes

rom residual sources.

IP: I you do not know your soil P status, arewithout a soil test, but are willing to band P thenconsider

South & Central Texas SORGHUM production handbook.pdf

Documents

Transcript of South & Central Texas SORGHUM production handbook.pdf