potassium guidelines for field crops in new york - Purdue Agriculture

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Potassium Guidelines for Field Crops in New York. Second Release. June 12, 2003.This set of equations implies that if the soil test K level is higher than 150% of the “A”value of a specific soil management group, the potassium requirement becomes zero. Ifthe soil test K level between 100 and 150% of the “A” value, the potassium requirementis 20 lbs per acre K 2 O. At low soil K levels, a maximum K 2 O recommendation rate is set(Table 3). For crop establishment and topdressing potassium, manure can be used tosupply the entire requirement. Appendix Table B shows the K recommendations for eachof these crops by Cornell Morgan soil test K level. The recommendations in this Table Bare rounded to the nearest 5 lbs.5.2 SoybeansThe K recommendations for soybeans are soil management group and soil testspecific as outlined in Table 4.Table 4: Potassium recommendations (lbs K 2 O/acre) for soybeans.CNAL Morgan extractable KSoil Management Grouplbs K/acre I, II III IV, V, VI269 0 0 05.3 Established stands of alfalfa, alfalfa grass, and alfalfa birdsfoot trefoilThe potassium recommendations for established stands of alfalfa (ALT), alfalfagrass (AGT) and alfalfa birdsfoot trefoil (ABT) are derived using the followingequations:Soil management group I:K recommendation (lbs K 2 O/acre) = [{(ypa * 40) – SoilTestK} / 0.6] – 120[8]Soil management group II:K recommendation (lbs K 2 O/acre) = [{(ypa * 40) – SoilTestK} / 0.6] – 100[9]16
Potassium Guidelines for Field Crops in New York. Second Release. June 12, 2003.Soil management group III:K recommendation (lbs K 2 O/acre) = [{(ypa * 40) – SoilTestK} / 0.6] – 80[10]Soil management group IV:K recommendation (lbs K 2 O/acre) = [{(ypa * 40) – SoilTestK} / 0.6] – 60[11]Soil management group V and VI:K recommendation (lbs K 2 O/acre) = [{(ypa * 40) – SoilTestK} / 0.6] – 40[12]In these equations, ypa is the soil specific alfalfa yield potential in tons/acre (12%moisture) and SoilTestK is the lbs CNAL Morgan extractable K/acre. Soil type specificyield potentials for alfalfa can be found in Appendix Table C.5.4 Established grasses, intensively managed grass, and native grass pasturePotassium recommendations for established and intensively managed grass (GIT)and established grasses (GRT) and native grass pasture (PNT) are derived from those fortopdressing alfalfa (ALT):GIT K recommendation (lbs K 2 O/acre) = 0.8 * ALT K recommendationsGRT/PNT K recommendation (lbs K 2 O/acre) = 0.66 * ALT K recommendations[13]Derivations for potassium recommendations for established alfalfa were discussed insection 5.3.5.5 Spring barley, winter barley, oats, and wheatPotassium requirements for spring barley (BSP), winter barley (BWI), oats (OAT)and wheat (WHT) are calculated using the following general K requirement equation:If SoilTestK > 165, K 2 O recommendation = 0 K 2 O/acreIf SoilTestK > 80 but = 165, K 2 O recommendation = 20 lbs K 2 O/acreIf SoilTestK = 80, K 2 O recommendation = (110-STK) * 0.7 lbs K 2 O/acre [14]In this equation, SoilTestK is the amount of CNAL Morgan extractable K in lbs/acre. Therecommendations for these crops do not depend on soil management group and becomezero for soil with soil test K levels of 166 lbs/acre or higher. Appendix Table D shows theK recommendations (rounded to the nearest 5 lbs of K 2 O) for these crops as a function ofsoil test K level.17
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