Effects of Planting Time and Fertilizer Application on the Productivity of Intercropped Cowpea and Maize in a Sub-humid Zone

Abstract

The effects, on the performance of intercropped maize (Zea mays L.) And cowpea (Vigna unguiculata (L) (Walp.) of varying the planting time of cowpea after maize, varying the planting date of simultaneous maize-cowpea intercropping, and applying fertilizer to the intercrop were studied in two field experiments in Njala (7 6' N, 12 5' W 55 m a.s.l.) Two cowpea cultivars were used, a local erect and determinate cultivar (Temne Local), and an improved semi-determinate cultivar (Tvu 1190), both of which are widely grown in Sierra Leone. Growth and yield of cowpea were strongly influenced by intercropping. Cowpea seed yield was significantly (P<0.05) higher in simultaneous intercropping than in staggered intercropping in which the yields of both cultivars were depressed consistently as sowing was delayed after maize. On average, staggered intercropping depressed cowpea yield by 58%, relative to the corresponding sole crop yields. However, in simultaneous intercropping cowpea yield was reduced by only 32%. Maize yield was significantly (P<0.01) depressed only when intercropped with Tvu 1190, and only when the cowpea was planted two or three weeks after maize. On the other hand, when both cowpea cultivars were planted four or five weeks after maize, maize yield was higher (46%) in intercrop than in sole crop. Total productivity measured by LER was greater in simultaneous intercropping than in staggered intercropping. Fertilizer application in simultaneous intercropping resulted in significantly (P<0.01) higher yields than in the non-fertilized treatment for both cowpea and maize, although sole cowpea did not respond to fertilizer application. LERs were greater than unity for most of the planting dates when fertilizer was applied. The results are interpreted as indicating greater overall productive advantage for simultaneous maize-cowpea intercropping than staggered intercropping, and a scope for significant positive response of simultaneous maize cowpea intercropping to improved management in the sub-humid tropics.

UNISWA Research Journal of Agriculture, Science and Technology Vol 3 (2) 2000: pp 54-62