Response of no-till soybean [Glycine max (L.) Merr.] to timing of preplant and foliar potassium applications in a claypan soil
2005
Nelson, K.A. | Motavalli, P.P. | Nathan, M.
Potassium availability in agronomic crops has recently decreased due to periodic drought conditions, soil compaction, reduced K applications, lower frequency of soil testing, and higher K fertilizer requirements because of increasing corn (Zea mays L.) yields and larger soybean Glycine max (L.) Merr acreage. Little research has evaluated the effects of foliar K applications on low to medium soil test K claypan soils, which are susceptible to drought and surface compaction. Field research was conducted in 2001 and 2002 to determine soybean response to foliar-applied K fertilizer compared with a preplant application and evaluate the cost-effectiveness of these treatments. Potassium fertilizer (K2SO4) was either broadcast-applied at 140, 280, and 560 kg K ha(-1) as a preplant application or foliar-applied at 9, 18, and 36 kg K ha(-1) at the V4, R1-R2, and R3-R4 stages of soybean development. Soybean grain yield increased 727 to 834 kg ha(-1) when K was foliar-applied at 36 kg ha(-1) at the V4 and R1-R2 stage of development in 2001 and 2002. Foliar-applied K at the R3-R4 stage of development increased grain yield but not as much as V4 or R1-R2 application timings. Treatment cost-effectiveness ranked preplant K at 280 kg ha(-1) = preplant K at 140 kg ha(-1) > preplant K at 560 kg ha(-1) = V4 or R1-R2 foliar-applied at 36 kg ha(-1). Foliar K did not substitute for preplant K in this research; however, foliar K may be a supplemental option when climatic and soil conditions reduce nutrient uptake from the soil.
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