Zinc studies in Zimbabwean soils: Effect of lime and phosphorus on growth, yield, and zinc status of maize

Greenhouse and field experiments were carried out to assess the effect of applying different levels of lime, phosphorus (P), and zinc on the growth, yield, and zinc status of maize. Liming was observed to improve yield when the soil pH was below 4.8 (0.01M CaCl2), but there was generally no yield benefit for liming when the soil pH was above pH 5.0. In greenhouse experiments, applications of 120 to 240 kg P2O5/ha were observed to increase yield significantly. In the field experiments, yields were variable due mostly to weather stress. Yield response to zinc application was observed in soils which were either limed or had recieved 240 kg P2O5/ha. Liming and P applications reduced zinc concentration in maize plants. The increase in CEC with P application was found to be strongly correlated with the decrease in plant tissue zinc. The “dilution”; effect, often advanced as an explanation for reduced zinc concentration in plants where P application was made, was explored and did not explain the reduced zinc concentration in plants.