Acúmulo e liberação de potássio em sistema de produção sob plantio direto no cerrado matogrossense

Abstract

Cover crops used in the off-season, under no-tillage system, have different extraction and nutrient efficiency capacities. The phytomass production, its persistence on the soil and then its decomposition are primordial for the study in the cycling of plant essential nutrients, such as potassium, second nutrient that is required in larger amounts by soybean crop. The objective of this study was to demonstrate the use of species in the safrinha to promote potassium cycling. The experiment was conducted in the year 2015, including a harvest and a second crop, at the Federal University of Mato Grosso (UFMT), Campus de Rondonópolis, in a randomized block design with nine production systems, and four replications. The treatments were: S1- Pousio no tillage (PD); S2 - Fallowing in conventional tillage system (PC); S3 - Crotalaria spectabilis; S4 - Corn + C. spectabilis; S5 - Pennisetum. glaucum; S6 - Urochloa. ruziziensis; S7 - Sunflower + U. ruziziensis; S8 - Vigna unguiculata and S9 - Corn + U. ruziziensis. The evaluations were carried out on flowering, senescence and just before desiccation of management in October 2016, and repeated at 15, 30, 60, 90 and 120 days after the desiccation of management (DAD) for soybean sowing. At the time of desiccation of pre-sowing of soybean, the consortium sunflower + U. ruziziensis presented the highest accumulation of K, while the lowest accumulation was found in the fallow. The treatment C. spectabilis obtained the shortest half-life (7 days) and the Vigna unguiculata had the longest half-life (28 days). The sunflower has high K soil extraction capacity and low export index for grain formation. C. spectabilis has a faster release of K because its C/N (Carbon / Nitrogen) ratio is low.