NITROGEN NUTRITION MANAGEMENT AND FERTILIZER USE EFFICIENCY IN WHEAT UNDER DIFFERENT SOIL CONDITIONS

Abstract

Nitrogen fertilizers are the major input being used for crop production especially for wheat in Pakistan. However, wheat yields are low, almost stagnant and nitrogen use efficiency is poor. Efforts are underway to improve wheat production and enhance nitrogen use efficiency. In this connection, different studies were carried out. In one study in which the effect of mixed NH/- Nand N03- -N nutrition was investigated, it was found that wheat yield (VM: \~il ) and nitrogen utilization efficiency significantly improved when mixed NH4 +- Nand N03- -N in 50:50 ratio was used as compared to when these sources were used alone. It was further observed that balanced nitrogen nutrition was helpful to overcome the adverse effect of drought and salt stress. In another study on the effect of nitrogen carrier and dicyandiamide (DCD), it was found that nitrogen sources significantly affected the wheat yield and nitrogen use efficiency. Calcium ammonium nitrate (CAN) was found to be the most efficient nitrogen source followed by a!Jll11onium sulphate and urea. Use of . . L'vfr>- ~+M 90) . DCD WIth CAN unproved wneaJA YIeld by 29 per cent and plant nItrogen recovery by 34 per cent. This is because DCD inhibited nitrification process and maintained an ideal NH/- N : N03- -N ratio in the soil where CAN was used. However, DCD was not helpful to improve efficiency of urea and ammonium sulphate, because of inhibition of nitrification process with the result ammoniacal nitrogen dominated in the soil when these fertilizers were used. Dominant1; presence of this nitrogen fonn disturbed the ideal balance of NH/- N : N03- -N ratio of 50:50. Therefore, no improvement in wheat yield and nitrogen use efficiency was registered. As regard the effect of gypsum and nitrogen sources on wheat yield and nitrogen utilization it was observed that the use of gypsum improved wheat yield from 30 per cent to 46 per cent and plant nitrogen recovery [Tom 25 per cent to 39 per cent. Improved nitrogen use efficiency was attributed to reduction in soil pH and ammonia volatilization losses. In another study potassium helped to improve efficiency