Agronomic and biological efficiency in the castor bean intercropped with cowpea or maize

ABSTRACT

The aim of this study was to evaluate the agronomic and biological efficiency of intercropping the castor bean with cowpea or maize. The research was carried out at the Lavoura Seca Experimental Farm, of the Federal University of Ceará, in Quixadá, in the State of Ceará, Brazil. Plants of the castor bean cv. BRS Energy were evaluated intercropped with cowpea cv. Setentão (I) or with maize cv. BRS 206 (II). The treatments consisted of combinations of two crops at two densities (5,000 and 10,000 castor bean plants per hectare; 20,000 and 40,000 intercropped plants per hectare), and two single crops, which were distributed into four randomised blocks. Crop productivity, land-use efficiency, competition index and the minimum requirements of the intercropped plants were evaluated. Productivity data were submitted to analysis of variance and mean values were compared by contrasting. Biological indices were interpreted from the partial values ​​for land-use efficiency plotted on a Cartesian plane. The cropping systems affected productivity in the castor bean, cowpea and maize. An effect was also seen from the intercropping and population densities of the castor bean and intercrops on the indices of land-use efficiency and competition. Intercropping reduces productivity in the castor bean and the intercrops; between the cowpea and castor bean, intercropping is efficient in land use. When intercropping castor bean with maize, efficient land-use is only seen for the largest populations of the oilseed. Intercropping the castor bean with the cowpea, the dominant crop is influenced by crop density, whereas maize is more competitive than the castor bean.

Key words:
Ricinus communis; Vigna unguiculata; Zea mays; Biodiesel