Eficiência do uso do nitrogênio afetada pelos indicadores físicos do solo

Abstract

Soil cover maintenance can be a valid alternative for compactness reduction and nutrient leaching in tropical soils. The nitrogen use efficiency (NUE) can be defined as the ratio between the productivity achieved and the dose of nitrogen applied. Alley cropping system with tree legumes may be a suitable management option to increase the NUE. The objective of this work was to evaluate the effect of the use of residues of tree legumes on the NUE and its relation with physical indicators of soil quality. The experiment was carried out in an alley cropping system implanted in 2009 in the eastern region of Maranhão, Brazil. Two tree species of high quality of residues were sown: leucaena and gliricidia and two tree species of low quality of residues: clitoria and acacia. Between the years 2010 to 2018 corn was sown between the rows of tree legumes and under its straw. In 2018, 10 treatments were established, which consisted of combinations of legumes with or without urea fertilization. Doses of the legume combinations were determined to provide 150 Kg N ha-1 via plant residues. Corn plants were collected at tasseling and maturity to determine the N content and NUE calculation. After harvest, the soil samples were collected with volumetric ring and the penetration resistance was determined with a digital penetrometer. Among the physical indicators of soil quality only penetration resistance showed differences between treatments, with the highest values in the control treatments. In general, the control treatments presented lower nitrogen accumulation and nitrogen use efficiency, as a result of the greater compactness of soil and lower levels of organic matter. Soil cover with residues of tree legumes increases the nitrogen accumulation and nitrogen use efficiency through improvements in the soil physical characteristics.