Onken, Arthur

Thomas, Grant W.

Valentine, James H.

Welch, Charles D.

Texas A&amp;M Repository

L-742Crop Fertilization on Texas High Plains SoilsJames H. Valentine, Arthur Onken, Charles D. Welchand Grant W. Thomas*The High Plains of Texas is an isolated broadpiedmont apron shown in figure 1. Soils vary insurface texture from loamy sands in the southwestto clay loams and silty clay loams in the northeast.The High Plains region encompasses about 19 mil-lion acres. About 7.8 million acres are in croplandof which approximately 5.3 million are irrigated.The irrigated cropland includes an estimated82,500 acres of improved pasture..Soil CharacteristicsThe High Plains soils vary greatly, not only inmorphological characteristics but in native fertilityand potential productive capacity. However, allare similar in that they have developed under agrass vegetation in sub-humid climate.*Area extension soil chemist and assistant professor of soilchemistry at South Plains Research & Extension Center,Lubbock; Extension soil chemist and professor of soil chem-istry, Texas A&M University, College Station.Figure 1. Locatian af High Plains region.12.4As a result of limited preCIpItation, very littlelime has leached from these soils. A zone of limeaccumulation (calcium carbonate) has developedat depths of 2Y2 to 5 feet. pH values above 7 gen-erally prevail.Mineral deposits from which the soils devel-oped were high in potassium. Therefore, soilscontain relatively high amounts of exchangeablepotassium even under extended periods of culti-vation.Wind erosion is a problem, especially in thesandier regions. Wind can remove substantialamounts of topsoil and alter the productive capa-city of the soil if control measures are not taken.Hardpans occur occasionally where the soils areirrigated and have not been deep-plowed for severalyears. For these reasons, soil management prac-tices to improve the physical condition of thesesoils is highly important in crop production on theHigh Plains.Soil Fertility StatusBecause of soil characteristics, past fertilizationand cropping practices, fertility levels vary widelyfor High Plains soils. This is illustrated by thesoil test summary data in Table 1.The response and return from applied nutri-ents is dependent on the level of the availablenutrient in the soil. Infonnation in the soil nutri-ent levels indicates probable responses primarilyfrom nitrogen, (estimated from organic mattercontent and other infonnation) and phosphorusand, to a lesser degree, from potassium. Such gen-eral infonnation is useful to county agents, ferti-lizer industry personnel and others but does notprovide specific information to the individualproducer concerning fertilization of his soil. Todetermine nutrient levels for individual fields,representative soil samples should be tested every2 to 3 years for soils used intensively.Texas A&M University • Agricultural Extension Service • John E. Hutchison, Director • College StationTable 1. Percentage distribution of High Plains soils in fiveranges for pH, organic matter, phosphorus and potassiumPercentage of samples at each levelSoil test Organic Phos- Potas- Soil pH Per-level* matter phorus sium range centVL 28 36 0 Below 6.6 1L 64 22 0 6.6·7.3 9M 8 18 1 7.4 • 7.8 35H 0 19 4 7.9 - 8.3 50VH 0 5 95 8.4 • 9.7 5*Soil test summary data from Texas Agricultural Extension ServiceSoil Testing Laboratories.N, P205 and K20 for Maior CropsAlthough High Plains soils are relatively highin native fertility compared with other areas, theconcept that nitrogen is the only element neededfor s~stained high production is not valid, espe-cially under irrigation.Nitrogen is generally the first nutrient to be-come deficient. This is the element required inthe largest amount for field crops other thanlegumes. Phosphorus is the second fertilizer nutri-ent limiting production and potassium, third.Because of the range in nutrient levels, soil testsare the best means of determining the present levelof available nutrients and amounts of plant nutri-ents to apply. The expected yield is influencedby numerous management and cultural practicesas well as climatic conditions. Tables 2-8 presentthe amounts of N, P20 5 and K20 suggested undervarying nutrient levels (shown by soil tests) andfor varying expected yields.Many additional factors are considered in arriv-ing at fertilizer use suggestions shown on the soiltest report. If information on a soil test reportdiffers from these general guides, an error is notnecessarily indicated. Refer questions to countyagricultural agents or the Soil Testing Laboratory.To use these tables, determine the soil test levelfor the nutrient in the left column and read acrossto the expected yield column for the rate of nutri-ent. For example, using Table 2, a soil with alow (L) level of nitrogen, a low (L) level ofphosphorus and a very high (VH) level of potas-sium would show a 60-60-0 per acre for an expectedyield of two bales of cotton.Calcium, Magnesium and SulfurHigh Plains soils are generally high in calciumand magnesium; thus, deficiencies have not beenreported. These two elements predominate on theclay fractions and are responsible for the alkalinecondition (up to pH 8.3) of most soils. HigherpH values are generally caused by sodium accumu-lations. Sulfur, the third secondary element, alsooccurs in irrigation water in sulfate form. SomeTable 2. Application rates of nutrients for cotton-three production levels under irrigation and one for drylandSoil test Expected yield-l "12 baIe I A. Expected yield-2 balelA. Expected yield-2 "12 balelA. Dryland (sandylevel* N P2011 1<20 N P2011 1<20 N P205 1<20 lands only)VL 60 60 60 80 80 80 100 100 80 30-30-30L 40 40 40 60 60 60 80 80 60 20-20-20M' 20 20 20 40 40 40 60 60 40 0-0-0H 0 0 0 0 0 0 0 0 0 0-0-0VH 0 0 0 0 0 0 0 0 0 0-0-0*Texas A&M University soil testing methods and calibrations.Table 3. Application rates of nutrients for grain sorghum-three production levels under irrigation1 and drylandExpected Expected Expected DrylandSoil test yield-4000 Ib./A. yield-6000 Ib./A. yield-8000 Ib./A.a (Sandy lands only)level 2 N P2011 K20 N P20 11 K20 N P2011 K20 N P205 K20VL 80 40 80 120 60 100 160 80 120 30 20 20L 60 40 60 100 40 80 140 60 100 20 20 20M 40 0 0 80 20 60 120 40 80 0 0 0H 0 0 0 40 0 40 80 0 40 0 0 0VH 0 0 0 0 0 0 0 0 0 0 0 0.1For sandy soils and others that take water rapidly, apply about half the N and all the P20 5 and 1<20, where needed, preplant. Side-dress remainder of N within 35 days after crop is up being careful to avoid root pruning.2Texas A&M University soil testing methods and calibrations.aFor expected yields in excess of 8,000 pounds, increase the N rate by 20 pounds of N for each 1,000 pounds.Table 4. Application rates of nutrients for corn-two productionlevelsExpected ExpectedSoil test yield-l 00 bu./A. yield-ISO bu./A.level* N p.o. K.O N P.O. K.oVL 120 80 120 180 80 140L 100 60 100 140 60 120M 80 40 80 100 40 100H 40 0 40 60 0 60VH 0 0 0 0 0 0*Texas A&M University soil testing methods and calibrations.fertilizers are formulated with various sulfur ma-terials. For these reasons, a general need for sulfuras a plant nutrient has not been shown and is notanticipated. The extent to which this elementwill give yield responses is under study.MicronutrientsBecause numerous soil conditions affect theavailability of micronutrients and differences incrop requirement, no general need for additions ofTable 5. Application rates of nutrients for alfalfa maintenance--three production levelsExpected Expected ExpectedSoil test yield--4 tan/A. yield-6 ton/A. yield-8 ton/A.levels' N' P.O. K.o N' P.O. K.O N' P.O. K.OVL 0 60 120 0 100 160 0 140 200L 0 40 80 0 80 120 0 120 160M 0 40 40 0 60 80 0 100 120H 0 0 0 0 40 40 0 80 80VH 0 0 0 0 0 0 0 40 40'Texas A&M University soil testing methods and calibrations.'Include 20·30 pounds of N per acre for new plantings.TABLE 6. Application rates of nutrients for wheat-three production levels with moderate grazing'Soil Expected Expected Expectedtestyield--40 bu./A. yield-60 bu./A. yield-80 bu./A.level' N P.O. KoO N P.O. KoO N P.O. K.OVL 80 40 40 120 50 50 140 60 60L 60 20 20 100 40 40 120 50 50M 40 0 0 60 30 30 100 40 40H 0 0 0 40 0 0 60 0 0VH 0 0 0 0 0 0 0 0 03020oooDryland(Sandy lands only)20oooo20oooo'For sands apply all the p.o. and KoO and part of the N preplant. Topdress remainder of N ahead of joint stage. For clays, all thefertilizer may be applied before planting.'Texas A&M Universtiy soil testing methods and calibrations.'Texas A&M Universtiy soil testing methods and calibrations.'Apply 60·80 pounds N, all the P.O. and half the KoO whereK.O rates are heavier than 80 pounds in the spring ahead ofirrigation. Apply remainder of nitrogen in 50-70 pound incre-ments after each time grazed down or cut. Remove cattle beforefertilizing and defer grazing for at last a week after irrigationis complete.'Texas A&M University soil testing methods and calibrations.'Should be divided into 40-60 pound applications with oneapplication preplant and an additional similar application aftereach time cut or grazed down and just ahead of irrigation.micronutrients is indicated. Of the seven elementsin this group, only iron and zinc presently are con-sidered important. Iron deficiency, as character-ized by yellowing between the veins of sorghum, iscommon on high-lime soils. Zinc deficiency hasbeen observed on cotton in isolated areas high inlime, in areas that have received applications ofphosphate sufficient to produce very high levelsand in cut areas where topsoil has been removed.Soil test values for pH, calcium and phosphorusgive some indication as to the probability of defi-ciencies of iron and zinc; however, past historyand close observation for deficiency symptoms inthe field offer the best guide. Research studiesare underway with these and other micronutrients.See Extension leaflets, L-721 and L-723, availablefrom your county agricultural agent, for a morecomplete discussion about zinc and iron.Conversion FactorsThe phosphorus and potassium contents of fer-tilizers are guaranteed as percent P205 and K20.Soil test values are also reported in these terms.However, plant analyses results usually are re-ported as percentages of the element. For this rea-son, the following factors are presented for use inconverting from one form to the other.From P205 to P multiply by 0.44From P to P20 5 multiply by 2.29From K20 to K multiply by 0.83From K to K20 multiply by 1.20Cooperative Extension Work in Agriculture and Home Economics, Texas A&M University and the United States Departmentof Agriculture cooperating. Distributed in futherance of the Acts of Congress of May 8, 1914, as amended, and June 30, 1914.5M-5·68

Crop Fertilization on Texas High Plains Soils.

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Crop Fertilization on Texas High Plains Soils.

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Crop Fertilization on Texas High Plains Soils.

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