Effect of P on nodulation, N harvest index and growth correlations between nodulation and other plant parts in cowpea under well-watered and dryland conditions

Beneficial effects of nutrients like P and Zn on growth and nitrogen partitioning of cowpea both under irrigated (pot) and dryland (field) conditions were investigated. Under adequate soil moisture, P had increased growth, N accumulation, N harvest index and yield, whereas such responses were lacking under field conditions. The interrelationships between nodulation and other plant parts had significant positive correlations. The higher correlation between nodule number and leaf area than that between nodule dry matter and leaf area indicate requirement of some factors other than assimilate supply for initiation of nodules.