Fertilizer Zn needs of rice (Oryza sativa L.) as influenced by native soil Zn in Udic Ustochrepts of the Indo-Gangetic plains
Keywords:Fertilizer Zn, DTPA-Zn, Rice, Yield response, Zn uptake, Critical limit, Udic Ustochrepts
AbstractSeventeen experiments were conducted on farmers' fields to study the effect of native Zn on the fertilizer Zn needs of rice in an extensive soil series (Rarha; Udic Ustochrepts) of Kanpur, Uttar Pradesh, India. Rice (cv. Saket-4) was grown with four rates of fertilizer Zn (0, 1.25, 2.5 and 5 kg Zn ha-1) in the soils of varying DTPA-Zn status. Application of 5 kg Zn ha-1 resulted in significant increases in the dry matter yield (grain + straw), Zn concentration, and uptake of Zn by the crop in soils having DTPA-Zn less than 0.60 ppm; the magnitude of the response decreased with increasing DTPA-Zn status of the soil. Fertilizer Zn needs for optimum grain yield were 7.10 and 3.73 kg ha-1 in soils of low (<0.60 ppm) and medium (0.61-1.00 ppm) DTPA-Zn status. Recovery of fertilizer Zn was higher in low Zn soils compared to high Zn soils. DTPA-Zn status of the soil and Zn concentration in the third leaf of 45-day-old plants showed a highly significant correlation with percentage grain yield. The critical limits of DTPA-Zn and leaf-Zn for predicting response of rice to fertilizer Zn were 0.80 and 26.5 ppm, respectively.