Decomposition and release of nutrients from crop residues on soybean-maize cropping systems

Abstract

Nutrients found in residues from agricultural cultures are important reserves for subsequent crops. The objective was to assess the decomposition and release of nutrients from different crop residues for subsequent soybean cultivation. The study was conducted in Mid-Northern Mato Grosso State, Brazil. The residual straw of cropping systems - maize, brachiaria and maize/brachiaria consortium - were sampled, weighted, disposed in litter bags and then distributed on the soil. The adopted experimental design followed the completely randomized arrangement with three repetitions. Treatments were determined based on harvest time, which was performed every 14 days within 140 days for maize, and within 154 days for brachiaria and for the consortium. The remaining dry matter and nutrients content, and half-time life were evaluated. Maize showed the highest straw dry matter yield (14,176 kg ha-1), and the consortium recorded the biggest nutrient accumulation per hectare (K=172.2; N= 141.7 and Ca=56.0 kg ha-1). Brachiaria straw presented the fastest decomposition rate (85%) and the highest nutrient release (K=99%; N=92%; Mg=98% and Ca=90% of total initial content). The total K released reached 150 kg ha-1, which can fit the needs of soybean crops.