Effects of corn (Zea mays L.) stover removal and leaching on soil test and whole plant K+ levels in corn and K+ fertilization/highinput treatments on soybean using site-specific management to increase soybean (Glycine max) production in South Dakota

Potassium is important for crop production. Corn stover removal has the potential to reduce exchangeable and soluble soil potassium (K+) needed for optimal plant growth as well as grain yield. An experiment was conducted in Aurora, SD, USA, to observe the effects of corn stover removal on water soluble and exchangeable soil test K+ (STK) levels and corn grain yields across a five-year period. Abundant K+ reserves were recorded between the initial and final sampling periods. While corn grain yields were affected by removing corn biomass, exchangeable and solution K+ levels were relatively unaffected by stover removal.;Potassium fertilizer has the potential to mitigate yield decreases associated with corn stover removal. An on-farm cooperation amongst producers who have had an extensive history of corn stover removal was initiated. Two K + fertilization rates were spread across half-mile strips in spring 2014; 250 lbs K2O and 0 lbs K2O. Initial (spring) and final (fall) soil sampling quantified STK values. Stomatal conductance and tissue sampling indicated K+ fertilization influences on crop physiology and K+ concentrations, respectively. Yield monitor data from treatment strips were cleaned and analyzed. Yield difference maps were generated through statistical software programs to examine yield responses to K+ fertilizer. While yield increases were not economically sufficient, a wide degree of in-field variability existed between sampling periods and points, site locations, and season.;Nitrogen (N) fertilization has the potential to increase soybean grain yield. On-farm cooperators applied nitrogen fertilizer in the encapsulated urea nitrogen (ESN) form in two rates across half-mile strips at R1 growth stage in July 2014; 0 lbs N/acre and 75 lbs N/acre strips (replicated at least twice per field). Spatial variability in yield responses across soil topography and elevations was seen. While yield gains were statistically significant after applying ESN, economic analysis proved applications of ESN on soybean at R3 to be uneconomical in some localities while advantageous in others.;Offsite K+ movement may occur following precipitation after corn physiological maturity, presumably through leaching off of corn biomass material. Whole corn plant portions were collected and tested for K+ following rainfall event. The portion of K+ leached relative to total plant K+ concentration indicated that corn stover biomass has great offsite movement, occurring as a function of rainfall inch rather than cumulative rainfall amounts.