| Degradation problems such as wind erosion,sandy and nutrient barren agricultural lands in the dry northwest are present.Leguminous green manure crops are important measures to slow down topsoil erosion and fertilize the soil.Therefore,in this study,three common legume green manures(arrow end pea-J,mung bean-L,and hairy crop-M)were used in the northwest region,and three monocropping(J,L,M)and four mixed crop(JL,JM,LM,JLM)cropping patterns were set up to measure multiple effective nutrients in the soil and enzyme activities driving the turnover of carbon,nitrogen,and phosphorus nutrients in the soil during the planting and ploughing down periods of legume green manures;DTOPSIS method with entropy weighting was applied to evaluate the fertilization effect of different cropping patterns and to screen legume green manure cropping patterns suitable for fertilization of northwest sandy farmland.To provide a theoretical basis and data support for soil fertilization in the northwest sandy land.The main results are as follows:1.the leguminous green manure planting significantly increased the soil ammoniacal N content in mixed and monoculture patterns,with the enhancement effect ranked as LM>JL>JLM>JM>L;L,M,JL,JM and LM treatment groups were able to significantly increase soil organic carbon content,and the enhancement effect was ranked as JM>JL>LM>M>L;After green manure ploughing down,the activity of chitinase,which is involved in organic matter decomposition,was significantly enhanced,and the enhancement effect was ranked as JM>JL>M>LM>L>JLM>J.The comprehensive evaluation results of DTOPSIS showed that JL and M were suitable green manure treatment groups for planting in sandy farmland in the northwest drylands.2.Both monocrop and mixed cropping patterns enhanced functional bacterial groups such as nitrogen fixation,heterotrophic,denitrification,fermentation and nitrification during the legume green manure planting period;soil bacterial diversity showed an overall decreasing trend after legume green manure ploughing down,but the soil bacterial community structure differed more among treatment groups during the ploughing down period,and functional bacterial groups such as methylotrophic,nitrate denitrification,chemoheterotrophy and chitinous degradation were prominently enriched in each treatment group during the ploughing down period.The results of Spearman and random forest model analysis showed that the β-diversity of soil bacteria,WD2101 soil group of Planctomycetota and Nitrosomonadaceae family were the key indicators to enhance the multifunctional index of soil nutrients.3.Compared with the leguminous green manure planting period,the soil fungal diversity showed a decreasing trend and the fungal community structure changed significantly during the leguminous green manure ploughing down period.The prediction of fungal community function indicated that the potential function of soil fungal community under legume green manure cultivation pattern was saprotroph fungi,but the functional groups of soil fungi in different legume green manure fertilization patterns did not demonstrate a consistent pattern;the results of Spearman and random forest model analysis indicated that β-diversity of soil fungi,Ascobolaceae and Didymellaceae were key indicators for enhancing the multifunctional index of soil nutrients. |
