Produção de matéria seca e marcha de absorção de nitrogênio, fósforo e potássio em Crotalaria juncea e Crotalaria spectabilis

There are several benefits in the cultivation of Crotalaria spp., including high levels of biomass production and N accumulation, nutrient cycling and antagonistic activity against some nematodes. However, information on nutritional demand is still scarce for these species. This study aimed to determine the dry matter production and macronutrient uptake in shoots of Crotalaria juncea and Crotalaria spectabilis. Two experiments (one for each species) were carried out in a randomized block design, with three replications, assessing thirteen harvest times for C. juncea and ten for C. spectabilis. After each harvest, the samples were dried, weighed and submitted to laboratory analysis, in order to determine the nutrient contents in different parts of the plant. The nutrient accumulation on the shoots, for both species, occurred in the order K > N > P, being the stem the main organ of nutrient accumulation. Also for both species, the export of nutrients by the grains followed the order N > K > P. The maximum dry matter accumulation occurred at 135 and 104 days after emergence (DAE), respectively for C. juncea and C. spectabilis, while the production of viable seeds, in both species, had already begun at 90 DAE. KEYWORDS: Green manure, nutrient accumulation, phytomass.