Effects of diammonium phosphate and potassium application and deflowering on yield and quality of coepea (Vigna unguiculate (L) Walp) leaves

Abstract

Two experimients were carried out during the short rains of 1992 and the long rains of 1992 and the long rains of 1993 at the University of Nairobi’s Kabete Campus Field Station to study the effects of; (i) diammonium phosphate (DAP) and potassium fertilizers application on yield and crude fibre content and (ii) DAP and potassium fertilizers application and deflowering on yield and leaf senescence of cowpea leves. For the first experiment, 16 treatments which were a factorial combination of four fertilizer rates each of DAP and potassium were used in a completely randomized design (CRD) experiment with 3 replications. For the second experiment, there were 32 treatments which were a factorial combination of four rtes each of DAP and potassium and deflowering or not in a CRD experiment with 3 replications. Diammonium phosphate application significantly increased the fresh leaf yield during the season only. Potassium application had no significant effect on fresh yield during both seasons. The interaction between phosphorus and potassium was not significant. Diammonium phosphate and potassium application or their interaction had no significant effect on cowpea leaf numbers and leaf senescence in both seasons. Deflowering significantly (P≤0.01) increased both fresh leaf yield and leaf number and decreased leaf senescence in both seasons. The interaction between DAP application and deflowering for leaf senescence during both seasons significant during both seasons. Diammonium phosphate application and deflowering reduced leaf senescence. The interaction between potassium application and deflowering was only significant during the first season when potassium application and deflowering reduced leaf senescence. The interaction between potassium application and deflowering was only significant during the first seasn when potassium application and deflowering reduced leaf senescence. The interaction between potassium and phosphorus application for leaf sensence was not significant in both seasons. Diammonium phosphate and potassium application did not significantly affect crude fibre content. However, leaf fibre content increased significantly with increasing plant age