Nitrogen Soil Tests under Conditions of No-Fertilizer and Fertilizer Application

An evaluation of soil test procedure for mineralizable nitrogen has been made under non-fertilized and fertilized situations by fitting various regression functions on yield of cereal crops of bajra (pearl millet), rice and wheat. Nitric acid potential appeared to be universally applicable to these crops under the former condition and ammonium nitrate potential in fertilized situation. The performance of each method in the two situations was quite different. Further, these methods were examined in the light of their relationship with crop yields using various statistical models. It was found that multiple quadratic function gave better R² values in comparison to others.