RESPONSE OF WHEAT GENOTYPE NIA-SUNDAR TO VARYING LEVELS OF NITROGEN AND PHOSPHORUS

Field experiments were conducted to study the effect of various nitrogen (N) and phosphorus (P) levels and ratios on yield and yield components of wheat during 2009-10 and 2010-11 at Nuclear Institute of Agriculture, Tando Jam, Sindh, Pakistan Four levels of N (0, 120, 150 and 180 kg ha^-1) and nine levels of P (0, 30, 40, 45, 60, 80, 90, 110 and 135 kg P2O5 ha^-1) in ten combinations were applied in different ratios (i.e. 4:1, 4:2 and 4:3). Results indicated that the agronomic parameters like plant height, spike length, number of tillers and 1000-grain weight, biological and grain yield were influenced significantly by the application of N and P. The maximum biological yield of 11.4 tons ha^-1 was recorded with 180 kg N and 135 kg P2O5 ha^-1, which was statistically at par with 11.3 tons ha^-1 produced with 150 kg N and 110 kg P2O5 ha^-1. However, the maximum grain yield of 5.6 tons ha^-1 was produced with 150 kg N and 110 kg P2O5 ha^-1. The yield trend in both years clearly indicated that application of N and P2O5 in 4:3 ratios improved their utilization efficiency for the test genotype NIA-Sundar. Nitrogen uptake by wheat genotype was escalated from 38.6 to 174.9 kg ha-1 when N application rate was increased from 120 to 180 kg ha^-1. Phosphorus harvest also increased linearly with the corresponding increase in P2O5 application rate. The highest P uptake of 18.0 kg ha^-1 was recorded with 110 kg P2O5 ha^-1 and the lowest (3.6 kg ha^-1) in the control treatment. It can be concluded that application of 150 kg N and 110 kg P2O5 ha^-1 remained the optimum dose for exploiting the yield potential of wheat variety NIA-Sundar.