Soybean Response to Polyhalite As a K and S Source in Northern São Paulo State, Brazil.

Soybean is the most important crop grown in Brazil, with a projected production in 2015-2016 of 99 million metric tons. Soybean is the largest user of potassium fertilizers accounting for 35 % of the total K₂O used in Brazil. The objective of the present study was to evaluate polyhalite as a fertilizer for soybean in northern São Paulo State, Brazil, comparing the current 0-18-18 and 4-30-10 blends for soybean made with MOP as the K source with the same blends made with polyhalite+MOP as the K sources. Field studies were conducted within Northern São Paulo State, Brazil on an Oxisol (Typic Hapludox). The results suggest that polyhalite in soils can supply K to plants in sufficient quantities compared to other K source fertilizers as MOP. Therefore, farmers may consider polyhalite as an option to supply K and S, as well as some micronutrients to soybean and as long term benefits associated with gypsum application. It is imperative to explore polyhalite as a new source of K based fertilizers, not only to be an alternative for traditional K fertilizers, but also to provide other nutrients including Ca, Mg, S, Fe, Zn, Ni, Cu, and Mn. Little data is available regarding its plant nutritional properties and comparison to other potassium fertilizers.