Some measures of reducing leaching loss of nitrates beyond potential rooting zone

Summary

Seven sites in two long-term fertility experiments progressing at PAU Farm Ludhiana were selected on the basis of fertilizer treatments they were receiving. Soil samples were obtained upto 225 cm depth at 15 cm interval and nitrate was estimated from them by phenol disulphonic acid method. In the first experiment, to each of the three sites, equal amount of N was applied. When phosphorus and potassium were added at the rate of 26.2 kg P/ha and 24.9 kg K/ha, there was little NO₃ ^--N left in the profile for leaching, and where no P and K was added, lot of NO₃ ^- was left in the profile unutilized. Graphs for P₁₃K₂₅ treatment were in between the two extremes. Perhaps by balanced fertilization roots become proportionately efficient absorbers and little amount of nutrients is left, which is not absorbed. In the second experiment, supply of NPK to all the three treatments was increased or decreased from the recommended dose in a proportionate manner. This resulted in a nitrate distribution pattern similar to that of control treatment where no N was applied and thus strengthened the case for balanced fertilization.