Actavia 0 Abid, M. Ahmed, N. Qayyum, M.F. Shaaban, M. Rashid, A. 2013 2013-11-30 505-510 The objectives of present study were to determine the residual and cumulative effects of zinc (Zn) fertilizer on cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) in a silt loam Typic Haplocambid soil (< 0.05 mg/kg diethylenetriaminepentaacetic acid (DTPA)-Zn). The study comprised of two years field experiments where first cotton crop received zinc sulphate (ZnSO₄∙H₂O) at five rates (0, 5, 7.5, 10, 12.5 kg Zn/ha) in a randomized complete block design with four replications. After harvest, each plot was divided into two sub-plots. To study the residual effect, one sub-plot of all plots did not receive Zn fertilizer for the subsequent crops; however, the other sub-plot received all Zn rates for 2005-06 wheat, 2006 cotton, and 2006-07 wheat. Fresh applied, residual as well as cumulative Zn application significantly (P ≤ 0.05) increased crops production for both experimental years. Residual effect of 5.0 kg Zn/ha optimized the 2006 cotton yield; however, wheat productivity was optimized with residual effect of 7.5 kg Zn/ha in 2005-06 and of 10.0 kg Zn/ha in 2006-07. Optimum yield of both crops was attained with a lesser fresh-applied and residual Zn rate than cumulative Zn rate. Total Zn uptake by wheat (134.9-289.6 g/ha) was much greater than by cotton (92.3-192.5 g/ha). It is concluded that one application of 7.5 kg Zn/ha proved adequate for optimizing two cycles of the cotton-wheat production system. Two-year repeated use of 5.0-7.5 kg Zn/ha did not depress crop yields. 11 59