Effects of different roostertree (Calotropis procera) amounts and spatial arrangements on the performance of the beet-cowpea intercropping system

Intercropping of beet with cowpea-vegetable is increasing in the State of Rio Grande do Norte, Brazil. However, its management requires scientific information and technologies pertaining to space arrangement and adequate fertilization with roostertree. The present study evaluated the agronomic/biological performance of the beet and cowpea-vegetable intercropping system with different amounts of roostertree and spatial arrangements of the component cultures. We established a 4 × 3 factorial completely randomized design with four blocks. The first factor was the amount of roostertree biomass incorporated into the soil (20, 35, 50, and 65 t ha-1 in dry matter), while the second was the spatial arrangement of beet rows alternated with cowpea rows (2:2, 3:3, and 4:4). We evaluated the total, commercial, and classified productivities of beet roots, as well as the number of green pods per m2, green and dry pod productivities, the number of green grains per pod, the weight of 100 green grains, and green and dry grain productive of cowpea. The agronomic efficiency of the intercropping system was evaluated by the land equivalent ratio, productive efficiency index, and score of the canonical variable z. The results showed no significant interactions among the amounts of roostertree biomass and spatial arrangements for any evaluated trait or agronomic index. The highest agronomic efficiency of the intercropping system was obtained with 65 t ha-1 of roostertree biomass and the 2:2 spatial arrangements.