Mineralizac¸a&tild;o do nitrogeˆnio de plantas de cobertura, solteiras e consorciadas, depositadas sobre um solo com histo´rico de cultivo de cebola

Abstract

The decomposition of winter cover plants on the soil surface can increase nitrogen (N) availability during the onion crop cycle. The objective of this study was to evaluate N mineralization of cover plant litter, intercropeed or not, in a soil with a history of onion plantation. Soil was collected, prepared, placed in acrylic containers. Dry mass of black oats, rye, oilseed radish, black oats + oilseed radish and rye + oilseed radish were added into soil surface and incubated for 90 days. Soil was sampled and contents of total N, NO3--N and NH4+-N were determined at time zero and at 18, 36, 54, 72 and 90 days after incubation. Values of mineral N, net mineral N, mineralized N and total N - mineralized N were espe´calculated. The highest contents of NH4+-N were found in the soil with the deposition of oilseed radish litter and rye + oilseed radish intercrop. The greatest contents of NO3--N and mineral N from 36 to 90 days after incubation and of mineralized N from 18 to 92 DAI were found in the soil with the rye + oilseed radish litter deposition. Mineralization rate was positive in all soil samples with deposition of rye and oilseed radish litter, and black oats + oilseed radish and rye + oilseed radish intercrops, and negative on 18 and 72 days after incubation in the soil with deposition of black oats litter. The oilseed radish litter and rye + oilseed radish intercrop displayed the greatest potential for mineralization.