Effects Of Green Manure Returning On Maize Yield And Greenhouse Gas Emissions In Yellow Soil Of Karst Mountainous Area

Green manure is not only an important natural organic fertilizer,but also an indispensable part of modern ecological agriculture.The study was conducted on the yellow soil corn field in karst mountain area of Guizhou Province.The treatment of winter leisure+local conventional fertilization（CK）,winter alfalfa returning to field+fertilizer reduction by 20%（AL+CF80）,winter alfalfa returning to field+fertilizer reduction by 40%（AL+CF60）,winter arrow tongue pea returning to the field+fertilizer reduction by 20%（VS+CF80）,winter arrow tongue pea returning to the field+fertilizer reduction by 40%（VS+CF60）were used,In order to select the planting mode of reducing and increasing fertilizer efficiency,and provide a theoretical basis for planting green manure in winter fallow field of yellow soil in karst mountainous area of Guizhou Province.The main results are as follows:（1）Green manure+nitrogen fertilizer reduced application soil showed an acidification trend,and organic matter,total phosphorus and available phosphorus content showed an upward trend.Vervet pea+nitrogen fertilizer reduced microbial biomass nitrogen was the highest in the jointing and harvest period of AL+CF80treatment.Reduced application of green manure+nitrogen fertilizer reduced soil microbial groups and abundance,which decreased with the increase of fertilization,and the horizontal community composition of bacterial genus changed.The community structure was mainly affected by organic matter,total phosphorus and catalase（P<0.05）.（2）The total nitrogen content in the stems during the three growth periods was the highest in the jointing stage,and showed a trend of decreasing and then increasing.The total phosphorus decreased with the growth of maize.The AL+CF80 treatment had the largest ear length,ear diameter,1000-grain weight and yield.The return of green manure+reduced nitrogen fertilizer had a tendency to increase the yield.Among them,the treatment of AL+CF80 was the most obvious,which was 20.1%higher than that of CK.（3）The soil CH₄ emissions are all negative values,indicating that the soil has a CH₄ sink function,and the AL+CF80 treatment has the highest CH₄ absorption,which is-23.03 g/m².CO₂ emissions showed seasonal changes.The CO₂ emissions of VS+CF60 treatment were significantly lower than AL+CF80 and AL+CF60treatments（P<0.05）.CO₂ emissions are extremely significantly correlated with soil temperature,microbial biomass carbon nitrogen,ammonium nitrogen,and acid phosphatase activity（P<0.01）,with explanations of 14.8%,16.2%,15.5%,and 18.1%,respectively.（4）The cumulative CO₂ emissions from soil ranged from 601.61 to 798.32 g/m²,and the cumulative CO₂ emissions showed a decreasing trend with the decrease of fertilization.The cumulative emission of CH₄ was-23.03～-1.41 mg/m²,CK was the highest,followed by VS+CF80 treatment,which was significantly higher than other treatments（P<0.05）.Compared with CK,except for the treatment of AL+CF60,the GHGI of the green manure+nitrogen reduction treatment has a tendency to decrease.In summary,AL+CF80 and VS+CF80 have a promoting effect on soil fertility and corn yield,and the intensity of greenhouse gas emissions is lower than that of local traditional fertilization,it shows that planting alfalfa and arrowhead pea green manure in winter fallow fields can reduce nitrogen fertilizer and increase efficiency in yellow soil maize fields in karst mountainous areas.