POLIHALITA COMO FONTE DE POTÁSSIO NA ADUBAÇÃO DO SISTEMA DE SUCESSÃO SOJA–MILHO

Abstract

In Brazil, the main grain production system is soybean-corn, and potassium chloride (KCl) is the main fertilizer source used in management of potassium fertilization, due to scarcity of options on the market. Polyhalite is a natural fertilizer, which can be made available as granule. In addition to K, it has a lower solubility and saline effect than KCl and has S, Ca, and Mg in its composition. In this context, this paper aimed to evaluate such sources in the K management for soybean and corn fertilization cultivated in succession. The study was carried out in a distrophic Red-Yellow Latosol with a sandy texture. The experiment was in a randomized block design, and treatments were done by a combination of K sources (KCl, polyhalite, and KCl/Polyhalite blend), provided in total dose before soybean sowing, or splitted before soybean and before corn, in addition to a control treatment without potassium fertilization. No differences were observed in soybean grain yield, even though the polyhalite treatments had showed higher grain weight values. For corn, the control treatment had a productivity of 160 bags ha-1, what is similar to the amount produced in parts of the region with uncorrected soil. The other treatments showed higher values, even when blending about 200 bags ha-1 of KCl/Poli. The control treatment had lower grain yield (12,387 Kg ha-1) whereas the highest yield was found when blending 14,715 Kg ha-1. The exclusive use of polyhalite as a K source resulted in positive balances of Ca, S, and Mg. The benefits of using polyhalite in cropping systems, either in exclusive use or blendind with KCl, can enable the anticipation of potassium fertilization, even in a lighter textured soil.

Keywords: Glycine max. Zea mays. Nutrient balance. Potassium chloride.