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Fluid Journal : Fluid Journal 2002-2004
3 Fluid Journal Winter 2003 on a high extractable K Loring silt loam were unaffected by soil applied K, while CT yields on a high K Lexington silt loam were increased by broadcasting 30 lbs/A of K2O. NT cotton yields on both soils were increased by broadcasting 60 lbs/A of K2O, which was higher than the currently recommended K fertilization rate. Foliar K applications did not increase yields on these two high K soils. Four-year average CT and NT yields on the low extractable K Memphis silt loam were increased by broadcasting 120 lbs/A of K2O. This fertilization rate was the highest used in the research and was higher than that recommended for cotton production. Foliar K applications increased yields for both tillage systems on this low extractable K soil. Foliar K fertilization Foliar K fertilization of cotton was evaluated as a supplement to soil K for increasing yields. Effects of solution pH on K uptake and yields were also evaluated in other studies. An acid buffer surfactant was included in the studies and increased K uptake on a Lexington silt loam. K concentration increased in leaves collected one, three, and seven days after foliar K application of potassium nitrate plus an acid buffered surfactant (pH 5.5). Yields were also increased by these foliar K applications. Additional research included varied solution pH levels (unbuffered at pH 9.0 and buffered solutions at pH 6.0 and 4.0). Buffering to pH 4.0 increased four- year average lint yields compared with yields when the foliar solutions were buffered to high pH levels. Buffering foliar solutions to an acid pH range improved foliar K uptake and yields. Phosphorus fertilization Surface broadcasting P appeared to be an effective application method for NT cotton on a low P testing Loring silt loam. Broadcasting 40 lbs/A of P2O5 was sufficient for improved yields. A combination of broadcasting 40 lbs/A of Figure 2. Effect of varying nitrogen rates on yield of ultra-narrow row produced cotton. 630 700 770 840 910 980 1050 1120 1190 0 30 60 90 120 150 N rate-lbs/A Yield-lbs/A 1999 2000 Table 2. Nitrogen rate and method of placement for NT cotton production on three silt loam soils at Milan, Jackson, and Ames Plantation N rate Loring* Memphis** Lexington** lbs/ABIBI BI ---------------------lint yield (lbs/A)--------------------- 0 660 733 970 30 900 878 866 904 1,229 1,207 60 1,143 1,164 946 934 1,371 1,248 90 1,111 1,280 1,044 932 1,356 1,342 120 1,145 1,301 1,023 954 1,365 1,232 * 1994-1997 ** 1996-1997 B = broadcast I = injection P2O5 plus 60 lbs/A of K2O produced highest yields over five years on this low P testing soil. Dr. Howard is professor emeritus, Plant and Soil Science Department, University of Tennessee Agricultural Experiment Station, Jackson, Tennessee.
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