Effects Of Microbial Agents On N₂O Emissions And Fertility Improvement Of Reclaimed Soi

Reclaimed land is an important reserve land resource,but usually the soil structure is poor,and the organic matter and nutrient content are low.Increasing the application of organic fertilizers is a key way to quickly improve soil productivity,but it will cause large emissions of greenhouse gases such as nitrous oxide（N₂O）.Inoculation of plant rhizosphere growth promoting bacteria（PGPR）with N₂O reduction function can not only reduce greenhouse gas emissions,but also promote crop growth and improve land fertility.In this study,a laboratory-preserved strain of Achromobacter denitrificans YSQ030 was used as a test strain to explore its effect on N₂O emission in reclaimed soil,and real-time fluorescence quantitative PRC was used to explore its effect on key functional genes of nitrogen cycling.Then four N₂O reducing bacteria were collected in the laboratory:Azospirillum sp.TSA2S,Pseudomonas stutzeri.NRCB010,Achromobacter denitrificans.YSQ030,Bacillus subtilis.NRCB002 as test strains.The emission reduction and growth promotion characteristics of these strains were evaluated by soil microcosmic experiment and indoor potting simulation test,and finally the characteristics of these strains on soil fertility improvement after matching were evaluated by field in situ experiment.The main conclusions are as follows:（1）Achromobacter denitrificans YSQ030 was selected for soil microcosmic experiment.After applying commercial organic-inorganic fertilizer and sheep manure organic fertilizer,YSQ030 fungi were inoculated into reclaimed soil,which significantly reduced soil N₂O emissions,and the maximum emission reduction efficiency reached 90%and 30%,respectively.It could increase the copy number of nos Z I and nos Z II genes in soil,and inoculation with YSQ030 fungi after application of sheep manure organic fertilizer could increase soil nitrate nitrogen and ammonium nitrogen content.（2）Under soil microcosmic conditions,compared with the control without inoculation,inoculation of Azospirillum sp.TSA2S,Pseudomonas stutzeri.NRCB010,Achromobacter denitrificans.YSQ030,Bacillus subtilis.NRCB002 were inoculated into reclaimed soil after application of organic-inorganic fertilizer.All of them significantly reduced soil N₂O emissions,with emission reduction rates of 63%,62%,71%and 60%,respectively,and also increased soil nitrate nitrogen and ammonium nitrogen content.（3）Under indoor simulation conditions,soybean potting test was carried out by using reclaimed soil.Compared with the non-vaccination control,soil N₂O emissions were significantly reduced after vaccination with TSA2S,NRCB010,YSQ030 and NRCB002,and the emission reduction rates were 75%,81%,70%and 65%,respectively.After inoculation with four N₂O reducing bacteria,the growth range of soybean seedlings plant height,aboveground fresh weight and underground fresh weight was YSQ030>TSA2S>NRCB010>NRCB002,and vaccination with TSA2S,NRCB010 and YSQ030 could significantly increase the leaf width of soybean seedlings,and the growth range was TSA2S>YSQ030>NRCB010.（4）Compared with the control without fertilization,after inoculation with TSA2S,NRCB010,NRCB002 and YSQ030 mixed bacterial solution after applying sheep manure organic fertilizer and commercial organic-inorganic fertilizer,soil p H increased by nearly 0.2and 0.5 units,conductivity increased by 46%and 50%,organic matter content increased by6%and 30%,alkaline hydrolyzable nitrogen content increased by 31%and doubled,and available potassium content increased by 35%and 70%.The available phosphorus content increased by nearly 3 times and 3.5 times,the total nitrogen content increased by 76%and more than 1 times,the total phosphorus content increased by 25%and 53%,and the total potassium content increased by 35%and 47%.