Effects Of Nitrification Inhibitors On Nitrogen Loss And Microbial Effects In Greenhouse Tomato Production System

In current greenhouse vegetable production,low utilization and serious losses of nitrogen?N?caused great waste of resources and negative environmental effects.With combined indoor aerobic incubation and ¹⁵N box simulation experiment,using ¹⁵N isotope tracer technology and 16S rDNA high throughout sequencing method,this study determined the pathway,loss characteristics and microbial mechanism of fertilizer N under the control of nitrification inhibitor dicyandiamide?DCD?and 3,4-dimethylpyrazole phosphate?DMPP?.Nitrogen management and nitrification inhibitor regulation scheme for controlling nitrogen loss in greenhouse vegetables'field were constructed.Provided scientific basis and certain technical support for reducing greenhouse gas emissions from greenhouse vegetables'field and improving nitrogen use efficiency.The main results are as follows:?1?Under the condition of 60%field water holding capacity,the effects of applying DCD and DMPP were significantly better than those of 40%and 80%field water holding capacity.The application of DCD and DMPP under the condition of water content can delay the peak time of NH₄⁺-N content in soil by 2 days,and reduce the NO₃^--N content by19.05%⁴0.97%,and nitrification inhibition rate reached 79.21%and 55.97%by applying20%DCD and 2%DMPP respectively.Application of 10%,20%DCD or 1%,2%DMPP can significantly reduce soil N₂O emissions by 50.7%⁵5.9%,and reduce the N-type gas loss rate by 35.86%⁴0.44%.?2?Analysis of abundance of ammonia-oxidizing microbes in soil showed that the application of DCD had no significant effect on the abundance of ammonia-oxidizing microbial population,but the application of DMPP increased the abundance of ammonia oxidizing archaea?AOA?population and decreased the abundance of ammonia oxidizing bacteria?AOB?population.?3?Under the same amount of nitrogen,the application of 15%DCD of pure N increased the biomass of tomato fruit,stem and leaf,meanwhile the plant biomass increased significantly by 51.09%,which was better than the application of 1%DMPP.Nitrogen application with 15%DCD or 1%DMPP increased the absorption of ¹⁵N in tomato fruit by 64.16%and 3.52%respectively,and the utilization rate of ¹⁵N increased by75.67%and 27.12%respectively.?4?Compared with traditional nitrogen application,the yield of reduced nitrogen application decreased to a certain extent,but the difference of yield between traditional nitrogen application and nitrogen combined with 15%DCD or 1%DMPP were not significant,indicating that nitrogen application combined with nitrification inhibitors ensure that tomato yield is not affected.Under the condition of equal nitrogen,the nitrogen application combined with nitrification inhibitors can increase the Vc content of tomato fruit by 54.34%⁴5.43%,the soluble solid content by 17.54%²5.52%,the nitrate content by 16.89%³3.79%,which obviously improved the tomato fruit quality.?5?Compared with traditional nitrogen application,the nitrogen residue in the soil decreased by 32.99%⁵7.89%,and the leaching loss of NO₃^--N in the lower layer soil decreased 17.85%³4.87%after reduced nitrogen fertilization or nitrogen reduction combined with inhibitors.The effect of applying DCD with 15%of pure N content was most pronounced.During the growth period of tomato,compared with traditional nitrogen application,the reduction of nitrogen or combined with inhibitors reduced soil N₂O emissions by 18.37%⁵2.90%,and the total gas loss of nitrogen decreased by 6.30%²2.77%.The effect of applying DCD with 15%of pure N was the most obvious.?6?Further analysis of the microbial population in the soil showed that the application of nitrification inhibitors only reduced the abundance of AOB in the soil by 35.61%⁶0.54%,but there were no significant effects on the abundance,diversity and population structure of soil microbes.Therefore,the application of nitrification inhibitors is an environmentally friendly nitrogen regulation measure.To conclude,optimization of nitrogen application combined with DCD?application of nitrogen fertilizer 480 kg N/hm²,combined with DCD of 15%of pure N?is a regulation measure to effectively reduce nitrogen loss and increase nitrogen use efficiency in greenhouse tomato production,which can achieve a win-win situation for the economy and the environment.