| With the rapid development of China's agricultural production, fertilizer application rate increased year after year, large amounts of fertilizer entered into the environment, caused many environmental problems, has caused government and the public's attention, so as soon as possible to find substitutes for chemical fertilizers, thus reducing the chemical environment risk is an important way. As a nitrogen fixing and carbon reducing crop, leguminous green manure played an important role in improving soil fertility and reducing nitrogenous fertilizer usage. Over the years, Loess Plateau'soil fertility was inadequate, also had a long time and a wide area traditional summer fallow period. In this paper, field experiment and nylon mesh bag decomposition experiment were carried out to investigate the effect of leguminous green manure in summer fallow period on soil biological indicators properties and to reveal the mechanism of improving soil fertility.1. Compared to the fallow treatment, green manure could improved soil invertase, urease, phosphatase, arylsulfatase and dehydrogenase activity.In most cases, huai bean and soybean could activated soil enzyme activity. Nitrogenous fertilizer application could inhibit soil enzyme activity. GM, Nitrogenous fertilizer and their interaction had significant or remarkably significant influence on soil enzyme activities; Correlation analysis showed that soil invertase, urease, phosphatase, arylsulfatase and dehydrogenase and TEI can evaluate the soil fertility improvement effect of GM. Enzyme activities increased in the second year and Enzyme activities in the 5-20cm soil layer was significantly higher than that of 20-40cm soil layer.2. Green Manure could significantly increase the number of bacteria, fungi and actinomycete, huai bean had a most obvious effect in the no nitrogen fertilizer level. In the treatment of nitrogen application, due to the impact of the interaction, different green manure had different effect. Huai bean treatment had a high total number of microorganisms, followed by soybean.3. Green Manure can significantly increased microbial biomass carbon and nitrogen content, different green manure treatments showed a greater difference, huai bean and soybean showed higher microbial biomass C and N values. Microbial biomass carbon and nitrogen ratio analysis showed that huai bean had higher microbial biomass carbon and nitrogen ratio than the other green manures. Correlation analysis showed that soil microbial biomass carbon and nitrogen were significantly correlated. Green Manure could significantly increase the soil respiration, and huai bean had a best effect. There had a lower soil respiratory quotient under the huai bean than other green manures.4. After the four green manure applied into the soil, in the first month its dry matter decomposition rate can reach to 50%, then entered a slow decomposition period. The accumulated decomposition rate of carbon can reach to 50% in the first 18 days. At the end of the End of the experiment Astragalus Adsurgens Pall and hairy vetch had higher decomposition rate of carbon than sweet clover and Grain Amaranth. Nitrogen release of four green manure were fast, the cumulative release rate of sweet clover, Grain Amaranth, Astragalus Adsurgens Pall and hairy vetch were 62.8%, 59.1%, 53.2%, 60.3% respectively in the first four days; Phosphorus release characteristics were different in the preliminary days, but ultimately sweet clover and Grain Amaranth had slightly decomposition rate of phosphorus than Astragalus Adsurgens Pall and hairy vetch. Potassium Release features of four green manure were more consistent, that was release quickly in the early time then entered the stagnation period which was different from carbon, nitrogen and phosphorus. |
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