The Effect And Microbiological Mechanism Of Nitrification Inhibitor In Blocking Nitrate Leaching In Vegetable Soil Of Alkaline Purple Soil

Reducing reactive nitrogen losses in vegetable production systems is an important procedure in optimizing nitrogen fertilizer management,reducing environmental costs and achieving sustainable agricultural development.A large number of studies have shown that nitrogen fertilizer combined with nitrification inhibitors is an effective measure to improve crop productivity and reduce the reative nitrogen loss.However,there is a lack of systematic research on the application effects of different nitrification inhibitors on Chinese vegetable production in China.Therefore,the meta-analysis method was used to systematically quantify the impact of three nitrification inhibitors including dicyandiamide（DCD）,3,4-dimethylpyrazole phosphate（DMPP）and2-chloro-6-（trichloromethyl）pyridine（NP）on vegetable yield,plant nitrogen uptake,nitrogen use efficiency and reactive nitrogen loss（N₂O emission,nitrate leaching）in China.In addition,taking vegetable soil of the alkaline purple soil in southwest China and the above three nitrification inhibitors as the research objects,the soil incubation trial and soil column leaching trial were conducted to compare inhibitory effect of different types and dosages of nitrification inhibitors on the soil nitrification process and the effect of blocking nitrate leaching in alkaline purple vegetable soil,and to select the best type of nitrification inhibitor and dosage.While The real-time fluorescence quantitative technology was used to preliminarily clarify the microbiological mechanism of different types of nitrification inhibitors blocking the nitrate leaching in alkaline purple vegetable soil.The results of this study have important reference significance for the widespread promotion of nitrification inhibitors in Chinese vegetable production systems.The main results are as follows:（1）Our results showed that nitrogen fertilizer combined with nitrification inhibitor coul significantly increase vegetable yield by 9.2%,plant nitrogen uptake by 10.4%and nitrogen use efficiency by 11.2%,while reducing nitrate leaching by 25.4%and nitrous oxide emissions by 28.4%through meta-analysis.Among the different types of nitrification inhibitors,NP had the highest effect on the yield-increasing effect and the reduction effect of nitrous oxide emission,which were16.1%and 32.0%,respectively,followed by DMPP and DCD.Nitrification inhibitors had the most significant effects on increasing vegetable yield（14.7%）and reducing nitrous oxide emissions（36.8%）when nitrogen fertilizer rate was less than 200 kg N ha^-1.In neutral and alkaline vegetable soils,the yield-increasing effect and reducing effect on nitrous oxide emission of nitrification inhibitors were larger than those in acidic soils.The nitrification inhibitor had better effect the yield-increasing effect and reducing effect on nitrous oxide emission under the conditions of open field cultivation,root vegetables and leafy vegetables.Principal component analysis（PCA）showed that soil total nitrogen content and soil p H were the main factors that promoted the increasing of vegetable yields and drove nitrous oxide emissions under the application of nitrification inhibitors.In general,nitrogen fertilizer combined with nitrification inhibitors can effectively improve the production efficiency of vegetables and reduce the reactive N loss.（2）Our results showed that three nitrification inhibitors could significantly inhibit the conversion of ammonium nitrogen to nitrate nitrogen in vegetable soil of alkaline purple soil through the soil incubation trial;On the 14th day,DCD,DMPP and NP treatments significantly reduced soil apparent nitrification rates by 42.1%,28.7%and 26.8%,respectively,compared with ammonium sulfate application alone.DCD and NP had obvious dosage effects on the inhibition of soil nitrification,but DMPP had no obvious dosage effects.In general,DMPP had a better inhibitory effect on the nitrification process of alkaline purple soil than DCD and NP.Considering the environmental benefits brought by the nitrification inhibitor dosage,the recommended application dosage of DCD,DMPP and NP were 10%,1.0%and 1.0%of the pure nitrogen rate,respectively,for the vegetable soil of alkaline purple soil.The results of real-time fluorescence quantitative technology showed that DMPP and NP inhibited the soil nitrification process by inhibiting the gene abundance of AOA and AOB,while DCD only inhibited soil nitrification by inhibiting the gene abundance of AOB,and the inhibitory effect of DMPP and NP on AOA and AOB greater than DCD.（3）Combined with ¹⁵N tracer technology,the soil column leaching trial was conducted.The results showed that the DCD,DMPP and NP treatment with the optimal recommended amount was26.3%,30.6%and 19.2%lower than that in ASN treatment（ammonium added sulfate application alone）,respectively.The effect of DMPP on inhibiting nitrate leaching is better than that of DCD and NP.At the same time,this three kinds of nitrification inhibition significantly inhibited the activity of ammonia monooxygenase（AMO）,among which DMPP had stronger inhibitory effect on AMO activity than DCD and NP.During the experiment,DMPP significantly inhibited the abundance of AOA and AOB,and the inhibitory effect was higher than that of DCD and NP;DCD and NP had a significant inhibitory effect on AOB but not on AOA.In conclusion,compared with DCD and NP,DMPP has a better effect on the promotion and application of vegetable production in the southwestern alkaline purple soil area.