DIVERSIFICAÇÃO DO CULTIVO DE PLANTAS DE COBERTURA E SUA INFLUÊNCIA NA CICLAGEM DE NUTRIENTES E PRODUTIVIDADE DA SOJA

Abstract

For the no-tillage system, it is essential that the soil has crop residues in quantity and quality. The aim of this study was to evaluate the biomass production of cover crops, the dynamics of crop residues decomposition and nematode suppression, and the agronomic performance of soybean cultivated in succession. The study was conducted for three years (2018, 2019 and 2020) in two locations (Rio Verde - GO and Montividiu - GO). The treatments evaluated were soybean production systems sown under different biomasses of cover crops 1) mix (Pennisetum glaucum, Crotalaria spectabilis and Urochloa ruziziensis), 2) millet (Pennisetum glaucum), 3) crotalaria (C. spectabilis), 4) U. ruziziensis, 5) U. brizantha cv. Marandu and 6) U. brizantha cv. BRS Paiaguás. The variable evaluated were: the biomass production and the speed of decomposition and release of nutrients from the crop residuos, the population of nematodes, agronomic variables and the grain yield on different crop residuos of cover plants. The production systems affected the amount of dry matter (DM) produced, with Pennisetum glaucum and U. brizantha cv. Marandu obtained the highest DM values during the three years for Montividiu and Rio Verde, respectively. The lowest DM values were for C. Spectabilis, being 2,899 and 2,451 kg ha-1, 5,992 and 5,544 kg ha-1 and 1,271 and 823 kg ha-1 for the first, second and third years for Montividiu and Rio Verde, respectively. The cover crops influenced the population of Helicotylenchus in the soybean root only in Montividiu, where the lowest population was observed in the straw of Pennisetum glaucum. The mix treatment (C. spectabilis, Pennisetum glaucum and U. ruziziensis) appears as an option when there is an intention to use C. spectabilis in the system, as it provided higher amounts of DM compared to single C. spectabilis. As for the speed of nutrient release, C. spectabilis was the cover crop with the shortest half-life, being 65 days for N, 119 days for P, 12 days for K, 73 days for Ca, 48 days for the Mg and 178 days for S. The mix treatment (C. spectabilis, Pennisetum glaucum and U. ruziziensis) had a longer half-life than C. spectabilis, in addition to being the treatment that provided the highest productivity of 5,635 kg ha-1 of soybean, highlighting the advantages of diversifying cover plant species through intercropping, in order to extract greater benefits.