Comparative efficacy of natural and synthetic nitrification inhibitors for nitrogen release in alkaline calcareous soils.

Nitrogen (N) fertilizer use efficiency seldom exceeds 50% and the surplus N is either escapes to the atmosphere or enters groundwater in the forms of ammonia, or nitrous oxide, nitrates, hampering air, water, and soil quality. Managing N transformations from N fertilized soils are thus vital to enhance nitrogen use efficiency (NUE) and decreasing N losses. The use of nitrification inhibitors (NIs) is a tested strategy to manage nitrification, the first step towards N loss in the form of nitrates and nitrous oxides in the soil. The current study was conducted to evaluate the influence of neem oil (Azadirachta indica) coated prilled urea (NOCU) and pomegranate (Punica granatum) leaf extract coated prilled urea (PLECU) in comparison with dicyandiamide (DCD) blended urea; for mineral N (NH4-N and NO3-N) release in soil, nitrification inhibition (NIH), and apparent nitrification rate (NIR). The results indicated that maximum nitrification inhibition (NIH) (26-64%) was shown by DCD followed by the NOCU in the range of (15-50%) and the least NIH (4-39%) was indicated by PLECU. However, the maximum apparent nitrification rate (NIR) of 73% was calculated in urea only treatment, and the lowest NIR of 32% was shown by DCD. Dicyandiamide showed maximum NIH than other treatments followed by NOCU, and the least NIH was observed in treatment receiving PLECU. Hence, it is recommended that these substances could be used successfully for the slow release of N by manipulating N transformations in the soil, and enhanced N efficiency can be achieved in agroecosystems. The results warrant further field studies considering various soil and crop-related parameters in different agroecological zones. [ABSTRACT FROM AUTHOR]