Grasses and legumes intercropping can be an attractive alternative for phytomass supply to crop rotation systems; however, information about its decomposition and macronutrient release dynamics is scarce. Thus, the objective of this work was to evaluate the persistence of dry matter, nutrient, carbon and silicon release of pigeonpea and millet intercropping, with and without mechanical fragmentation of straw. The experiment was arranged as a 2x6 factorial in randomized block design, with four replications. First factor consisted of two straw managements (without and with fragmentation) and second consisted of six sampling times (0, 18, 32, 46, 74 and 91 days after management (DAM)). The fragmentation of straw did not alter decomposition and release of N, P, K, Ca, Mg and S, and the maximum daily release of these occurred between 0 and 18 DAM. At 91 DAM at least 80% of all macronutrients were released to the soil. Potassium was released faster, leaving only 1.4% of the total amount accumulated in the straw at 91 DAM, on average of the managements with and without mechanical fragmentation. Silicon was the most slowly released from the straw, still leaving 69% of the total amount accumulated in the straw at 91 DAM. The C/Si ratio is suggested as a tool to evaluate the degradation of straw.
Cajanus cajan; Pennisetum glaucum; recycling; decomposition rate; straw management; cover crop
