Effects Of Urea Combined With Nitrification Inhibitor On Lawn Growth And Soil Nitrification

Lawn is a type of green space,and it is the main vegetation of urban greening and sports grounds.Excessive use of nitrogen fertilizer in the lawn leads to air and water pollution.It is necessary for the healthy development of lawn industry to formulate reasonable fertilization technology.Nitrification is the main way of soil nitrogen conversion,which is closely related to nitrogen loss and efficient fertilizer use.Nitrification inhibitors are chemical substances that can inhibit the rate of nitrification.It reduces the loss of nitrogen by reducing the accumulation of nitrate nitrogen,thereby improving fertilizer utilization.Therefore,the application of nitrification inhibitors is one of the important means to improve the nitrogen utilization efficiency while reducing fertilization.The purpose of this study is to explore the effects of different urea dosages combined with nitrification inhibitors on lawn growth and soil nitrification.Firstly,in this experiment,turfgrass bluegrass was used as the material,and dicyandiamide(DCD)was applied with different fertilizer amounts.The experiment used field potting methods,and analyzed the effects of different treatments on the growth of lawn,soil inorganic nitrogen content,and nitrification inhibition rate.Secondly,DCD and 3,4-dimethylpyrazole phosphate(DMPP)were selected as nitrification inhibitors to evaluate the inhibitory effect of urea dosing with different nitrification inhibitors.The experiment was carried out under indoor constant temperature conditions.The effects of different treatments on soil nitrogen mineralization potential,mineralization rate constant,nitrification rate,nitrification inhibition rate and nitrogen-conversion related enzyme activities were analyzed,so as to compare the inhibitory effects of the two nitrification inhibitors.The main results are as follows:1.In the field pot experiment with urea combined with 2 g·m-2 DCD,the lawn grew better treated with 15 g·m-2 urea(U15).Lawn growth was not affected with the application of10 g·m-2 urea combined with DCD treatment(U10D)and 15 g·m-2 urea combined with DCD treatment(U15D).It was inhibited under the 20 g·m-2 urea with DCD(U20D)treatment compared to the 20 g·m-2 urea with DCD(U20)treatment alone.The content of ammonium nitrogen in soil treated with U20 D treatment was significantly increased,and the content of nitrite nitrogen treated with U15 D treatment was significantly reduced.The nitrification inhibition rate of each treatment was 5.02%-46.92%.Comprehensive consideration,U15 D treatment has a better effect on maintaining lawn growth and reducing soil nitrate.2.In the indoor constant temperature culture experiement of urea combined with twonitrification inhibitors,the addition of 10-30 mg·kg-1 DCD under the treatment of 150mg·kg-1 urea(N150)and 200 mg·kg-1 urea(N200)significantly inhibited soil nitrogen mineralization.The addition of 1-3 mg·kg-1 DMPP only had an inhibitory effect on soil nitrogen mineralization under N200 fertilization.The net nitrification rate decreased significantly of DCD treatment combined with N150 and N200 fertilization,and it significantly decreased of DMPP treatment combined with N150 fertilization.The inhibition rate of soil nitrification of urea combined with DCD treatment was 55%-173.94%,and it was25%-60% of urea combined with DMPP treatment.Comparing the two nitrification inhibitors,the addition of DCD has better inhibition effect on nitrogen mineralization and nitrification,and the inhibition effect is more stable.Under the N200 fertilization rate,the higher the DCD dosage,the better the effect.3.The urease activity of each treatment was higher on the 7th day of culture.The nitrate reductase(NAR)activity of each treatment decreased to the minimum at the end of the culture(day 35).Neither nitrification inhibitor has a significant effect on soil urease,ammonium monooxygenase(AMO)or NAR activity.In the treatment of urea combined with DCD,the nitrification inhibition rate was significantly negatively correlated with urease activity(P < 0.05).In the treatment of urea combined with DMPP,nitrogen mineralization potential and net nitrification rate were significantly positively correlated(P < 0.01).