Abstract:
To ameliorate the impact of soil phosphorus (P) deficiency on cowpea, the use of P-based
fertilizers is recommended. Plant zinc (Zn) is an essential nutrient required by plants in a wide range
of processes, such as growth hormone production and metabolism. However, a negative association
between plant Zn content and high P application has been reported in some crops. There are few
reports about soil P application and plant Zn content relationship on cowpea. Thus, this study
investigated the response of cowpeas to three P rates in the screenhouse (0, 1.5, and 30 mg P/kg) and
field (0, 10, and 60 kg P2O5/ha) and their effects on plant P and Zn content, biomass, and grain yield.
In the screenhouse, shoot and root dry weights, and shoot P and Zn content were measured. Shoot
dry weight, grain yield, grain P, and Zn contents were determined from field plants. Higher rates of
P led to increased shoot biomass and grain yield of the field experiment but were not associated with
a significant change in shoot or grain Zn content. There was not a significant correlation between
grain yield and Zn content in high soil P (p < 0.05). The effect of higher P application on reduced
plant Zn contents may be genotype-dependent and could be circumvented if genotypes with high Zn
content under high soil P are identified.
