Thurmond, R. V.

Texas A&amp;M Repository

R. V. THURMOND. EXTENSiONAGRICULTURAL ENGINEER-IRRIGATIONTexas A. & M. College SystemI RRIGATIOO IS A MEANS of maintaining a con-tinuous supply of available moisture in theplant root zone of the soil thr~ughout the grow-ing season. When the soil moisture is allowedto reach the permanent wilting percentage,plants wilt and growth is restricted. If thiscondition is reached, the irrigator has waitedtoo late. Where large acreages are irrigated.several days may be required to cover the entireacreage; consequently, irrigation must be start-ed soon enough to arrive at the last portionof the field bef6re its available water hasbeen exhausted.By inspecting soil moisture conditionsat regular intervals and at several depths, theL-355How to EstimateSoi/Moisture by Feelirrigator obtains information as to the rateat which moisture is being used by crops fromdifferent soil depths. This provides a basisfor determining when and how much water toapply. For most crops, irrigation should bestarted when about 50 percent of the availablemoisture in the soil root zone is depleted.A practical method of estimating theavailable soil moisture is to ta~e a smallamount of soil: squeeze it in the hand so asto form a ball; then refer to the chart onthe reverse side for a description of the feeland appearance of different textured soils forvarious moisture percentages.So 11 textureSandy (coarae)Sandy. loam (11 ght)WATER HOLDING CAPACITY OF DIFFERENT TEXTURED SOILSAvailable water - Inches per foot of depth• • 1/2'" 1•••• 1 - 1 1/2Silt and clay lo'ams (medium) •Clays (heavy) •••••••TOO 'DRY• 1 1/2 - 2• 2 - 2 1/2IDEALFEEL CHART FOR ESTIMATING SOIL MOISTUREFEEL OR APPEARANCE OF SOILSDEGREE OFMOISTUREDryLowFairExcellentIdealToo wetPERCENT USEFULSOIL MOISTUREREMAININGo50 or less50 to 7575 to fieldcapacityAt fie ldcapacityAbove fieldcapacityCOARSEDry, loose, single-gr ained, flowsthrough finger s.Still appears tobe dry; will notform a ball withpressure.·Same as coarsetexture under50 or less.Tends to sticktogether slightly;sometimes forms avery weak ballunder pressure.Upon squeezing,no free waterappears on soilbut wet outlineof ball is lefton hand.Free water apepears when soilis bounced inhand •LIGHrDry, loose, flowsthrough finger s.Still appears tobe dry; will notform a ball..Tends to ballunder pressurebut se ldom wi 11hold together.Forms weak ball,b r e ak seas il y ,wi 11 not slick.Same as coar se.Free water wi 11be released withkneading.MEDIUMPowdery, dry,sometimes slight-ly crusted buteasi ly breaks downinto powderycondition.Somewhat crumbly,but will holdtogether frompressure.·Forms a ball,somewhat plastic;will sometimesslick slightlywith pressure.Forms a ball andis very pliable;slicks readily ifrelatively highin clay.Same as coarse.Can squeeze outfree water.HEAVY - VERY HEAVYHard, baked,cracked; sometimeshas loose crumbson surface.Somewhat pliable;will ball underpressure.·Forms aball; willribbon out be-tween thumb andforefinger.Easily ribbonsout betweenfinger s., has aslick feeling.Same as coarse.Puddles and freewater forms onsurface.• Ball is formed by squeezing a handful of soil very firmly with fingers.Cooperative Extension Work in Agriculture and Home Economics. The Texas A. & M. College System and theUnited States Department of Agriculture cooperating. Distributed in furtherance of the Acts of Congressof May 8, 1914, as amended, and June 30, 1914.

How to Estimate Soil Moisture By Feel.

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How to Estimate Soil Moisture By Feel.

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How to Estimate Soil Moisture By Feel.

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Texas A&amp;M Repository

Texas A&M Repository