Behavior of castorbean cultivars intercropped with cowpea and grain sorghum.

Abstract

Castorbean (Ricinus communis L.) is an oil seed plant grown in different regions of Brazil. In the Northeast of Brazil castorbean is usually grown under rain fed conditions intercropped with cowpea, bean or corn. A field study was performed to evaluate two castorbean cultivars, (BRS 149 Nordestina and BRS 188 Paraguaçu) intercropped with cowpea (Vigna unguiculata (L.) Walp) and grain sorghum (Sorghum bicolor (L) Moench). The study took place in Quixadá county, state of Ceará, Brazil, at Lavoura Seca farm. The experimental design was in a complete randomized blocks with eight treatments and four replications. The treatments consist on the combination of the two castorbean cultivars with either sorghum or cowpea. The yield in kg.ha-1 and the yield components of castorbean, sorghum and cowpea were measured for crop performance evaluation, individually. Land equivalent ratio (LER) was used for intercrop evaluation. It was observed a general decrease in the productivity of all crops intercropped. Sorghum was responsible for the highest decrease in castorbean yield. The Nordestina cultivar was more adversely affected by the sorghum competition than Paraguaçu cultivar. Castorbean yield was composed of seeds from primary, secondary and tertiary racemes. The number of fruit/raceme, the seed/fruit relation and the weight of 100 seeds were reduced in the tertiary racemes. Intercrop caused a reduction in the weight of 100 castorbean seeds. In general, the intercropped systems were more efficient than the single ones, according to the LER. The LER values varied from 1.08 to 1.45.