Effect of Dose and Residence Time of Neem-Leaf Dust as Nitrification Inhibitor on N-Transformation in Maize Soil

Abstract

To increase the recovery of fertilizer nitrogen, reduction in the leaching loss of nitrate-N became a major challenge in nitrogen management in soil. A greenhouse experiment was conducted with maize to study the effect of dose of neem-leaf dust on transformation of nitrogen and the period of efficacy as nitrification inhibitor in a Vertic Epiaquept. The treatments comprised of neem-leaf dust @ 0, 500, 750 and 1000 mg kg⁻¹ of soil at three frequencies, e.g., once at basal (0), in two equal splits at basal and 30 days after sowing and in three equal splits at 0, 30 and 60 days after sowing. Higher values of ammonium-N (7.2–10%) at all stages of sampling in neem-leaf treated soil than their corresponding control proved neem leaf as an effective nitrification inhibitor. Barring few exceptions, transformation/decrease in amino acid-, hexosamine-, total hydrolysable- and total-N was governed by the rate and frequency of neem-leaf dust application. Irrespective of dose and frequency of neem-leaf application there was a net build up of total non-hydrolysable-N. Both dose and frequency of neem-leaf dust application independently had a significant positive impact on dry matter yield and nitrogen uptake by maize. Application of neem-leaf dust at the rate of 600 mg kg⁻¹ of soil in two equal splits was found to be the best combination for dry matter production as well as nitrogen nutrition of maize.