| Farmland set-aside is often regarded as an effective treatment for farmland self-recovery and sustainable utilization.It is widely used in cultivated land management.Fallowing contains short-term set-aside practices and long-term setaside practices.In many studies,long-term set-aside has been proven to have good ecological and environmental benefits,and which was widely used in farmland ecosystem protection.However,it is worth noting that long-term set-aside may lead to a decline in grain output of cultivated land,which could affect regional food supply.The short-term set-aside can reduce the risk of food security,and it can also be utilized to maintain the sustainable utilization of farmland.However,there are few studies on short-term set-aside in domestic and foreign,especially on soil microbiology.Therefore,this study constructed different short-term set-aside management practices.Determining the ecological benefits of short-term set-aside practices,based on the changes of soil microbial characteristics.Through the above study,the management implications of shortterm farmland set-aside are obtained.This study constructed four short-term set-aside management methods,and set three levels of water-fertilizer management for each recuperation management method.In addition,the study set sorghum arable land under local traditional farming management as a control group.The four types of short-term rest management methods constructed by this research include:(1)the way of native vegetation set-aside;(2)using Alfalfa and Elymus to jointly establish a pasture set-aside management;(3)taking into account the management costs of farmers,choosing soybeans mixed with corn to build a crop-oriented set-aside mode;(4)taking into account ecological benefits and low-cost,choose alfalfa and corn mixed sowing to build crop-pasture set-aside mode.The three levels of water-fertilizer management set by this research include:(1)no management,no water and fertilizer management;(2)irrigation management,a certain amount of irrigation in the early fallow period;(3)farm manure management,applying a certain amount of farmers on the basis of irrigation.In this study,the analysis of short-term set-aside through microbial indicators showed that soil microbial indicators are more sensitive to changes during farmland set-aside.Moreover,it can be combined with soil physical and chemical properties to obtain more information on arable land quality.The main conclusions obtained in this paper are as follows:(1)During short-term set-aside,microbial diversity and community structure showed significant differences in the early stages,but physicochemical properties and microbial biomass carbon-nitrogen showed significant differences in the later stages of set-aside.As a result,the microbial community structure became more stable over time.At the end of the rest period,the analysis results of soil physical and chemical properties show that pasture vegetation without management led to a lack of nitrogen,and that crop-pasture vegetation set-aside in three levels of water-fertilizer management may also lead to insufficient nitrogen supply.Nevertheless,the supply of nitrogen was guaranteed in crop vegetation with manure.The effect of short-term farmland set-aside on soil microbial biomass carbon is significant,especially in native vegetation and crop-pasture vegetation under irrigation management,and pasture vegetation with farm manure management.In terms of microbial biomass nitrogen,irrigation management can enhance it,and native vegetation with farm manure management can also increase it significantly.(2)According to the main effects of vegetation and water-fertilizer management,the native vegetation has accelerated the consumption of ammonium nitrogen,and irrigation management has also caused its consumption and loss.Inorganic carbon was significantly accumulated under no management conditions,and it is also accumulated in irrigation management.Under no management conditions,available potassium was accumulated.But in the management of farm manure,the available potassium was more absorbed by vegetation.Combined with ammonium nitrogen content,we can know that the increase of microbial biomass nitrogen may benefit from the conversion of ammonium nitrogen by the soil microbiota.In terms of microbial diversity,changes in arable land management measures in the short term are difficult to affect the microbial community diversity.But in the pasture vegetation with irrigation management,a significant decline in microbial diversity has occurred.There was a certain risk in the pasture vegetation with irrigation management,and it is necessary to continue to observe its changes in subsequent studies.(3)In terms of the nitrogen cycle,crop set-aside could strengthen some microbial communities associated with nitrogen fixation,which represents a positive effect on nitrogen accumulation.Irrigation management increases microbial biomass nitrogen and inhibits genera associated with nitrogen consumption,which indicated potential nitrogen accumulation benefits.In addition,irrigation management also inhibits phosphatase-related genera.In terms of the decomposition ability of organic matter,irrigation showed a significant inhibitory effect,and the effect also presented in crop-pasture set-aside.In terms of soil-borne disease resistance,the positive effect of no management is most pronounced,while irrigation management is less effective in it.In terms of promoting vegetation growth,most set-aside management has a growth-promoting effect,and only pasture set-aside with irrigation and fertilization fails to produce the effect.(4)Pasture set-aside practices is considered not suitable for short-term set-aside.Native set-aside under no management showed less ecological benefits than native set-aside with irrigation or fertilization.Native set-aside witout management may be more suitable for long-term set-aside.The crop set-aside with farmyard manure improved different kinds of farmland ecological benefits,such as the ability of organic matter decomposition,disease resistance,and growth promotion.Crop-pasture set-aside with irrigation could increase soil microbial biomass carbon and nitrogen content..(5)Based on the analysis of the cost and local agricultural policy,the crop-pasture vegetation were more suitable for short-term set-aside.The cost of crop-pasture set-aside with irrigation and farm manure management were lower.If the purpose is to increase the microbial biomass carbon and nitrogen content,crop-pasture vegetation with irrigation is also more favorable.For crop vegetaton,set-aside with farm manure is a necessary chosen to improve ecological benefits of farmland and its cost is higher than crop-pasture vegetation.Therefore,the crop-pasture vegetation could be spreaded for short-term set-aside in our study area.Moreover,the management practices should be adapted to local farmland conditions according to farmers' requirements.Choosing a low-cost set-aside management is more conducive to farmers' support for farmland set-aside projects. |
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