Potassium Placement Effects on Yield and Seed Composition of No‐Till Soybean Seeded in Alternate Row Widths

Optimum K fertilizer placement for no‐till soybean [ Glycine max (L.) Merr.] yield and quality in wide‐row production systems may not be appropriate for narrow‐row systems. Potassium fertilizer placement and row width effects on no‐till soybean were evaluated from 1998 through 2000 on a continuous no‐till soil with low, but stratified, soil‐test K. Four K fertilizer placements of surface broadcast, 76‐cm band width, 38‐cm band width, and zero K were compared at a single rate of 100 kg K ha −1 for soybean planted in 76‐, 38‐, and 19‐cm row widths. Broadcast K application significantly increased leaf K concentrations in all 3 yr. Band placement increased soybean leaf K more than surface broadcast in 2 of 3 yr. Band placement increased yield 10 to 15% in 76‐ and 38‐cm rows, compared with zero K, while seed yield was not significantly improved by surface broadcasting in any row‐width system. Within the 19‐ and 38‐cm row width systems, soybean rows positioned midway between the K fertilizer bands had lower K uptake and productivity than soybean rows seeded above the K bands. Banded K also increased seed K concentrations and accumulation more than broadcast application in 76‐ and 38‐cm row widths. Seed oil concentrations were increased by band placement, and were often positively correlated with leaf K, seed K, and seed yield. Potassium banding was superior to surface broadcasting for plant K nutrition, yield, and seed oil concentrations in both wide and intermediate row‐width systems, but not in narrow‐row soybean production, on low soil‐test K fields.