EFFECT OF NATIVE AND FERTILIZER ZINC ON DRY-MATTER YIELD AND ZINC UPTAKE BY WHEAT (TRITICUM-AESTIVUM L) IN UDIC USTOCHREPTS

Twenty experiments were conducted on cultivators' fields to study the Zn nutrition of wheat as influenced by native and fertilizer Zn in an extensive soil series (Rarha-Udic Ustochrept) of Kanpur, Uttar Pradesh, India. The cultivar of wheat used was 'Sonalika' and the Zn rates applied to all the experiments were none, 1.25, 2.50 and 5.00 kg Zn ha-1. Application of 5.00 kg Zn ha-1 resulted in a significant increase in the wheat dry matter yield, Zn concentration and uptake of Zn by the crop in soils testing DTPA-Zn below 0.60 ppm; the magnitude of the response showed a decrease with an increasing DTPA-Zn status of the soil. The requirements of fertilizer Zn for optimum grain yield were 6.32 and 2.52 kg ha-1 in soils of low (below 0.60 ppm) and medium (0.60-1.00 ppm) DTPA-Zn status, respectively. Recovery of fertilizer Zn was higher in low Zn soils and vice versa. The DTPA-Zn status of soil and Zn concentration in the leaf showed a high degree of relationship with percentage grain yield. The critical limit of DTPA-Zn and Zn content of the third leaf of 45-day-old plants for predicting the response of wheat to applied Zn was computed to be 0.60 and 18.4 ppm, respectively.