Effects Of Artificial Grasslands On Soil Quality And Soil Moisture Of Farmland In Semi-Arid Areas

Due to long-term mechanical cultivation,fertilizer use and improper land management,large areas of agricultural land are suffering from serious degradation.Natural restoration(fallow farmland)and artificial measures(crop rotation,green manure cultivation,etc.)are the main strategies to improve soil quality and achieve the sustainable development of modern agriculture.Compared with natural restored grassland,artificial grassland has higher vegetation coverage,plant height and biomass yield,which can quickly achieve vegetation restoration in abandoned land and soil erosion areas,thus better protecting ecological environment.In order to explore the effects of different artificial grasslands on soil quality and soil moisture in farmland,this study studied the five artificial grassland,as well as the farmland in Loess Plateau.The variation rules of aboveground biomass,underground biomass and water use efficiency of different artificial grassland were systematically studied.The effects of different artificial grassland on soil moisture,soil infiltration rate and soil quality were analyzed,and the main factors affecting soil infiltration rate were discussed.Furthermore,this study compared the effectiveness of different artificial grasslands on improving farmland soil quality.The main conclusions were as follows:(1)There were significant differences in the effects of different artificial grasslands on root distribution characteristics.Among them,the root diameter of Bromus inermis(B.inermis)and Trifolium repens(T.repens)were mostly 0-2 mm,while the root diameter of Miscanthus sinensis(M.sinensis)and Medicago sativa(M.sativa)were mostly larger than 4.5 mm.And the root diameter of Panicum virgatum(P.virgatum)were equally distributed.The aboveground biomass of artificial grasslands increased with the increasing cultivation years,and tended to be stable after 3-4 years.Panicum virgatum and M.sinensis had the highest aboveground biomass and water use efficiencies.Appropriate drought stress could improve the water use efficiency of P.virgatum and M.sinensis.(2)The soils in P.virgatum and M.sinensis were mostly not desiccated during the 3-5 years of cultivation.The soils in B.inermis and T.repens were mostly in the state of no desiccation to moderate desiccation.However,M.sativa was moderately and severely desiccated in deep soils.Some of the soils in M.sativa was even extremely desiccated,and a dry soil layer appeared at 150-400 cm soil depth.(3)Artificial grassland could increase soil water holding capacity,soil porosity,soil aggregate and soil organic carbon content.Among them,B.inermis,T.repens and P.virgatum significantly improved soil quality of farmland.(4)Artificial grassland could significantly increase soil infiltration rate.The initial infiltration rate of M.sativa was significantly higher than that of other grasslands,while the infiltration rate of B.inermis and T.repens was significantly higher than that of other grasslands at the late infiltration stage.(5)Initial soil infiltration rate was mainly affected by initial soil water content.Stable soil infiltration rate was mainly affected by soil geometric mean diameter and total porosity.The increase of root volume percentage of 0-2 mm root diameter could significantly improve soil geometric mean diameter,capillary porosity and organic carbon content.However,the increase of root volume percentage of 2-4.5mm root diameter could reduce soil capillary porosity and total porosity.On the whole,the soil infiltration rate of artificial grassland was mainly determined by the initial soil water content and root distribution characteristics.There was a significant negative correlation between the initial soil infiltration rate and the initial soil water content.With the increase of infiltration time,the influence of soil initial moisture content on infiltration rate gradually decreased,and the influence of root systems on infiltration rate gradually increased.Artificial grassland could improve soil quality and soil infiltration performance of fallow farmland,and thus affecting the rainfall-soil moisture conversion process in semiarid areas.The effectiveness of artificial grassland on improving farmland soil quality varied with grassland types.Panicum virgatum has high biomass yield and low water consumption.And its roots could increase soil porosity,organic carbon content and infiltration rate,and improve soil structure.Our results suggested that the cultivation of artificial grassland(especially P.virgatum)could be considered as a proper agricultural management measure to improve soil quality and achieve the sustainable development of modern agriculture in semiarid areas.