Manejo da adubação nitrogenada em cobertura no sistema de consórcio de feijão-comum (phaseolus vulgaris l.) E mamona (ricinus communis l.)

Abstract

Intercropping is a very common procedure in Brazil, especially in small farms. The actual advantage of this technique compared to monoculture, nevertheless, becomes more evident when the cultures involved present different requirements for available resources, concerning either quality, amount or period of that demand. In addition to that, the cultures involved will only reach satisfactory yeld if couting on knowledge on their factual nutritional needs, with special focus on particular requirements of each of the especies involved. Therefore, this work aims to assess agronomic and nutritional features of common bean and castor bean intercropped, under different topdress nitrogen doses, in Brazilian savanna (cerrado), in the state of Goiás. The randomized block designed was applied, arranged in 2 X 2 X 4 factorial design + 4 additional treatments. Three repetitions were performed. Treatments consisted on two cultivars of common bean (Pontal and Pérola) and two cultivars of castor bean (Energia and Paraguaçu), intercropped and combined with four topdress nitrogen doses (0, 50, 100 and 200 kg ha-1). Four additional treatments involved the combinations of the cultivars of common bean and castor bean, under the unique nitrogen dose of 40 kg ha-1, which is recommended by literature for both cultures under covered monoculture. We conclude that leaf contents of nitrogen, potassium, calcium, magnesium and sulfur of common bean, while intercropped with castor bean, were influenced by topdress nitrogen doses. On the other hand, castor bean, while intercropped with common bean, presented foliar contents of nitrogen, magnesium and sulfur responding to the different treatments. Leaf nutrient contents in common bean and castor bean, under both intercropping and monoculture, were not affected by treatments. Maximum grain yelds of common beans, 1074.2 kg ha-1 for the cultivar Pontal and 989.9 kg ha-1 for the cultivar Pérola, were reached under 137.8 e 128.5 kg ha-1 of topdress nitrogen, respectively. For castor bean, maximum grain yeld, 1417.9 kg ha-1, was reached by the cultivar Paraguaçu, under 98.5 kg ha-1 of topdress nitrogen. The cultivar Energia had its maximum grain yeld, 1243.5 kg ha-1, verified under 106.0 kg ha-1 of topdress nitrogen.