Yield and Uptake Response of Corn to Zinc, as Influenced by Phosphorus Fertilization

Zinc deficiency has been reported after P fertilization of corn (Zea mays L.), but reasons for this deficiency are not clear. A field experiment was conducted for 3 years from 1970 to 1973 with a fixed wheat-corn rotation to determine the effect of P and Zn fertilization on corn yield, uptake, and translocation of Zn, and to evaluate the parameters that would monitor best the P-Zn interaction in corn. Five rates of P (0, 22, 44, 66, and 88 kg of P/ha), and four rates of Zn (0, 11, 22, and 44 kg of Zn/ha) were applied to P and Zn-deficient soil (Ustipsamments) using a split-plot design (with P in the main plots and Zn in the subplots). P was applied to all the six crops and Zn only to the first and second crops. Optimum response of corn to P was observed at 44 kg of P/ha. The high P supply beyond the optimum P rate produced severe Zn-deficiency symptoms in treatments without added Zn and a significant decrease in grain and stover yields. This resulted from a significant decrease of Zn and a significant increase of P concentration in the shoots of the plant with a high P supply. An increase in the supply of Zn alleviated its deficiency symptoms, significantly increased Zn concentration and its uptake and resulted in a significant increase in growth and yield. The requirement of Zn increased at high (66 to 88 kg/ha) rates of P fertilization. The main effect of P on Zn utilization by corn was to reduce the rate of Zn entry into the roots and induce zinc deficiency. The P-Zn disorder was better related with P/Zn ratio in the soil and in different parts of the corn plant than either with the P or Zn content of the tissues and soil. Values of P/Zn greater than 7.5 in the soil, 245 in grain, 130 in stover, 150 in the leaves (of 25-day-old plants) indicated a severe Zn deficiency in corn and a highly significant response to its application. The P/Zn values 4 to 7.5 in the soil, 150 to 245 in the grain, 90 to 130 in the stover, and 100 to 150 in the leaves indicated moderate Zn deficiency or response to its application.