Efficiency of Soil Applied Boron When Co-Granulated with Potash on Alfalfa and Soybean.

Today’s high-yield cropping systems have placed a bigger demand on soils to provide micronutrients in order to maximize yield. Following zinc (Zn), boron (B) is the second most deficient micronutrient in North America. The use of bulk blends containing dry granular B with potash (MOP [0-0-60]) has increased in recent years. Application challenges of MOP+B blends can lead to uneven nutrient distribution of B and encourages application rates in excess of crop nutrient needs. A source or mechanism to more evenly spread and increase the efficiency of B uptake is needed. Aspire™ (0-0-58-0.5B) is a recently developed fertilizer that combines both K and B in every granule. Co-granulating a micronutrient with a macronutrient has been shown to improve micronutrient application uniformity, though its effect on yield has not been evaluated. The objective of this study was to determine the effect of B source and rate on alfalfa (Medicago sativa) and soybean (Glycine max). Twenty small-plot replicated trials were conducted in alfalfa over four years (2013-16) and thirty-one soybean trials were conducted over three years (2013-15). Averaged across all sites-years of alfalfa, the Aspire treatment yielded more dry matter yield (13.7 MT ha^-1) than any of the MOP+B blends (13.53 to 13.72 MT ha^-1) including those receiving higher B application rates. Aspire applied to soybean yielded 3,901 kg ha^-1 compared to other MOP+B treatments which ranged in yield from 3,702 to 3,814 kg ha^-1. Results indicate that the co-granulated Aspire fertilizer provided a more even application of B, resulting in more yield, and with less total B than MOP+B blend in both alfalfa and soybean cropping systems.