Dinâmica do potássio no sistema soja-milho na região Médio Norte do Mato Grosso

Abstract

The potassic fertilizer recommendations are almost entirely made thinking only of the culture that is the field, not being taken into account the predecessor and successor culture. The nutrients in crop residues represent a reserve for subsequent crops, with important knowledge of the absorption capacity and nutrient cycling culture, and efficient fertilization should be done thinking of the system as a whole. The study was conducted in North East state of Mato Grosso, in the municipalities of Sinop and Sorriso, in order to evaluate the behavior of potassium in the soil, plant debris and the influence of potassium fertilization in soybean-corn system. Two studies were conducted; (1) The effect of potassium doses (0, 40, 80, 160 and 320 kg ha-1 K2O) in soybean-corn system for two years, we evaluated the chemical changes in the soil, and its influence on absorption nutrients and grain yield and dry matter of brachiaria. The first year of corn had increased grain yield influenced by doses, was observed in all crops increased K concentration and decrease in Ca and Mg in plant materials, and it is found that high doses of K provoke strong leaching of the element up to 60 cm depth: (2) decomposition and release of nutrients from corn straws, braquiária and the consortium of these, and behavior of the soil. The corn had the highest dry matter yield and the consortium the largest accumulation of nutrients per hectare, the single braquiária in turn presented the highest decomposition rate and the highest percentage of nutrient release. Ca and Mg elements released from straw were retained in the first 5 cm, since the K moved in the soil profile reaching up to 40 cm deep.