Effect of some Heterocyclic Synthetic Nitrogen Regulators for Increasing the Efficacy of Urea in Paddy-wheat Crop Rotation

Abstract

In developing countries urea is the major source of nitrogen, but it is a matter of concern that one-third of urea (30-35%) is only utilized by the plants and the rest two-third (65-70%) is lost by volatilization, denitrification, leaching and absorbed in lower profiles of the soil. Due to this farmers suffer a great economic loss and have to face the polluted environment and contaminated water. This wasteful loss of nitrogen can be controlled to a certain extent

by application of some heterocyclic nitrogen regulators like pyrazoles and isoxazoles. The isoxazole regulators can control urea hydrolysis and denitrification, and increase N-uptake and apparent N-recovery by formation of nitrogen complexes in soil which can be easily adsorbed by growing plants. The present investigation was carried out in a IARI farm soil (Typic Haplustept) and urea fortified with different synthetic isoxazole compounds for N-regulation. The study indicated that the test regulators (at 5% of the fertilizer level) significantly retarded the nitrification of soil applied urea. In vitro studies have revealed that whereas 75% soil applied urea-N got converted to nitrate-N within a week's time, the use of test chemicals delayed the urea transformation for 10-14 days to achieve the same level of

nitrate-N. These regulators not only increased the dry matter yield by 20-25% over control, but their application along with fertilizer also increased the apparent -N recovery by 20-40% in both paddy and wheat crops. The use of these chemicals was not detrimental to soil health. These nitrification regulators retarded the conversion of ammoniacal-N to nitrate-N without accumulation of nitrite-N, which is supposed to be toxic to the plants.