Soybean Responses to Potassium Placement and Tillage Alternatives following No‐Till

Abstract

More information is needed about optimum potassium (K) fertilizer placement for soybean [Glycine max (L.) Merr.] production in no‐till fields. This study was conducted at two locations in Ontario, Canada, from 1998 to 2000 to examine soybean responses to K placement methods and tillage systems on soils with a 5‐ to 7‐yr no‐till history and medium to high soil‐test K levels. Fertilizer K treatments (15‐cm deep banding in fall, 7.5‐cm shallow banding in spring, surface broadcast in fall, and a zero K control) were compared in three conservation tillage systems (fall zone‐till, fall disk, and no‐till). The K fertilizer rate was 100 kg ha−1 for all but the control treatment. Soybean row widths (76 or 38 cm) varied with tillage systems, and soybean rows were positioned above K fertilizer bands if applicable. Yield responses to K application occurred in the fall zone‐till and no‐till systems on some medium‐ to high‐testing soils. There was no significant leaf K or seed yield advantage to band placement compared to surface broadcasting, and to fall zone‐till or fall disk systems relative to no‐till, for soybean of similar row width. Neither leaf K nor seed yield was negatively affected by degree of soil K stratification. Despite vertical soil K stratification after continuous no‐till, there was no significant leaf K or yield benefit to replacing narrow‐row, no‐till soybean systems (involving surface K fertilizer application) with wide‐row zone‐till or no‐till systems (involving deep banding of K), or with narrow‐row, fall disk systems (involving surface‐applied, but tillage‐incorporated K).