Variation in Nitrification Inhibition Activity of Neem Leaves Collected from Different Locations of Lucknow (India)

This study was carried out to assess the variation in nitrification inhibition (NI) activity of neem leaves obtained from trees growing in same agroclimate. The study was accomplished in the year 2012, in Lucknow city of Uttar Pradesh State of India. Dried leaves of four neem trees growing at different locations within Lucknow were screened for their NI potential. Treatments comprised of 6 combinations of urea-N and inhibitors as urea with dried leaf powder of New Hyderabad (NH) location tree, urea with dried leaf powder of Gomti Nagar (GN) location tree, urea with dried leaf powder of Hazratganj (HG) location tree, urea with dried leaf powder of Indira Nagar (IN) location tree, urea alone (without any inhibitor) and control (without urea-N and without any inhibitor). Concentrations of NH4+-N and NO3--N present in soil were quantified on 1,3,7,14,21 and 28 day/s after treatment (DAT) by standard methods. Significant difference was observed in NI potential, as high concentration of NH4+-N was maintained during experimental period when dried leaf powder of NH location tree was used whereas low concentration of NH4+-N was obtained with the leaves of HG location tree. In the first week leaves of NH location tree, showed 90% NI which remained 56.98% till the third week, whereas it was least for HG by the third week, i.e., about 23%. Leaves obtained from NH location tree proved to be the best inhibitor for nitrification amongst all treatments. Further, growth response of seedlings of Hordeum vulgare (barley) was used as a biological check of soil nutritive value with the supplementation of dried leaf powder of four trees individually. NH location tree leaves treated soils were found to be the best with respect to growth parameters of barley. Study gives an indication for pre-screening of trees growing in different locations for better results at commercial levels.