COWPEA YIELD RESPONSE TO FERTILIZER AND WATER

Seed and dry matter yields were determined under varied NPK (1:2:2) fe rtilizer and water rates on the field using a line source sprinkler sy stem for cowpea, Vigna unguiculata, L. Walp, var. Ife brown. Yields in creased with increasing fertilizer and applied water, but became depre ssed at 240 kg/ha of fertilizer application. Multiple regression showe d that the optimum combination of fertilizer and water for the maximum cowpea seed yield of 1.58 t/ha was found to be 120 kg/ha and 340 mm; respectively. The highest dry matter yield of 6.12 t/ha was produced w ith 235 kg/ha of fertilizer and 205 mm of water. Substantial reduction s of fertilizer input from the optimum to minimum requirements did not appreciably decrease cowpea yields. However, only minor reductions of applied water could be made without adversely affecting yields.