Effect of nitrification inhibitors and their combinations on yield and quality of Brassica chinensis and analysis of their inhibitor residue in soil

A hyocaust plot experiment was employed to study the effects of three different nitrification inhibitors and their combinations on yield and quality of Brassica chinensis.A similar fluctuant pattern on vegetable nitrate contents during the growing period of B.chinensis was observed when different nitrification inhibitors were added to urea.The nitrate in vegetable decreased,by 8.34%-65.60% on average.After harvest,it decreased by 13.21%-70.86%.As compared to the control,the yield and contents of nitrate,chlorophyll,carotenoid and vitamin C of B.chinensis increased by 3.45%-59.42%,13.21%-70.86%,0.15%-27.41%,2.30%-29.15%,and 26.00%-131.97%,respectively.At the same time,the nitrogen,phosphorus and potassium in the plant increased in varying degrees.The Nitrification InhibitorⅠwas found to be the best among three inhibitors tested,when they were added individually to urea.The combinations of the Nitrification Inhibitor I and other inhibitors were also better than those of the others.The best combination was found to be Nitrification InhibitorsⅠ+Ⅱ+Ⅲ.Significant portion(i.e.,89.93%) of the Nitrification Inhibitor I was degraded,67 days after the fertilization.