Effects Of Different Management Measures On Soil Water And Nitrogen Transport And Crop Growth In The Loess Plateau,China

The cultivated area in the dry farming tableland area of the Loess Plateau accounts for 1/3 of the total area,which is an important grain-producing area and a typical rain-fed agricultural area in the northwestern region.The main problems faced by agricultural production are less rainfall and uneven seasonal distribution,more fertilization but low utilization rate.Therefore,water and nutrients are the keys to limiting the high and stable yield of crops.In this paper,the continuous cropping system of winter wheat and spring maize in rainfed farmland was selected as the research object.Different conservation tillage measures were set in the Loess Plateau of Wangdonggou small watershed in Changwu County,Shaanxi Province,carried out field experiment for two years.Firstly,7 treatments were selected in wheat fields and 6 treatments were selected in maize fields to analysis soil nitrate accumulation and water transport in 2016-207.Then,the changes about soil temperature,water content,and NO3--N and crop development of six treatments in maize field were analyzed in 2017-2018.So that the effects of different farmland management measures on soil temperature,water,fertilizer,and crop production were studied to improve water and fertilizer use efficiency and increase crop yield,and to provide a theoretical basis for selecting farmland management measures suitable for sustainable production in the region,the main research results are as follows:1 In the 2016-2017 growing year,compared with conventional tillage(NP)in the wheat field,NP with potassium fertilizer(NPK)and NP with biochar(NB)had no significant effect on soil water replenishment and consumption.The NO3--N of NPK was concentrated in 0-100 cm,and cumulative peak accounted for only 20.2%of NP.While NB was concentrated in 0-20 cm and had no cumulative peak.And the NO3--N accumulation of them in 0-300 cm significantly decreased 66.0%and 73.2%.Mulching were significantly effected on soil water replenishment and consumption,the water replenishment of NP with plastic film mulching in growing period(NPFGT),plastic film mulching in fallow period(NPFFT),and plastic film mulching in the whole year(NPFWT)significantly increased 32.7%,43.1%,and 43.5%.while the consumption of NPFFT increased significantly 2.0 times in 0-300 cm compared with NP respectively.The NO3--N of NPFFT,NPFWT,and NPFGT were concentrated in 0-200,0-100,and 0-20 cm,and cumulative peak of NPFFT and NPFWT accounted for only 77.1%and 37.8%of NP,while NPFGT had no cumulative peak.And the NO3--N accumulation of them in 0-300 cm significantly decreased 19.2%,59.7%,and 78.7%.In addition,the biomass,yield,and water use efficiency of NPFGT and NPFWT significantly increased 56.4%and 66.3%,20.0%and 18.9%,and 24.3%and 15.2%,while the water use efficiency of NPFFT significantly decreased 22.7%compared with NP.NPFGT and NPFWT improved soil water status and significantly increased yield,and NPFGT was the best treatment to reduce the leaching and accumulation of NO3--N.NPB and NPK cannot improve soil water status,but they all effectively reduced the leaching and accumulation of NO3--N.While NPFFT not only significantly reduces water use efficiency and yield,but also fails to alleviate the leaching and accumulation of NO3--N.2 In the 2016-2017 and 2017-2018 growing year,the soil water had gone through water replenishment,consumption,and recharge.During the first water replenishment period(fallow-tasseling),soil water was mainly replenished to the deep below 100 cm.The replenishment of no-tillage with plastic film mulching(NF),straw mulching(NS),and straw-plastic film mulching(NSF)was significantly increased 17.1,25.3,and 31.6 mm compared with no-tillage(NT).During the water consumption period(tasseling-filling),soil water was mainly consumed from 0-200 cm.The consumption of NS,NF,NT with biochar(NB),and NSF were significantly increased 19.7,26.4,27.6,and 41.7 mm compared with NT.During the second water replenishment period(filling-maturing),soil water was mainly replenished to the deep above 100 cm.The replenishment of NF and NB significantly increased 2.7 and 6.4 times,while NS significantly decreased 75.0%compared with NT in 2017-2018 growing year.The soil NO3--N transport of NS and NB were concentrated in 0-100 and 200-300 cm,which NO3--N accumulation were significantly decreased 26.5%and 45.2%compared with NT in maturing period,and NS had obvious cumulative peaks.While NSF and NF were concentrated in 0-40 cm,which NO3--N accumulation were significantly decreased 62.5%and 70.5%,and had no cumulative peaks.In addition,the biomass and water use efficiency of NB significantly increased 18.4%and 15.6%over the two years compared with NT.And the biomass,yield and water use efficiency of NF and NSF significantly increased 43.4%and 49.2%,43.4%and 50.5%,and 37.2%and 44.2%,and nitrogen uptake,LAI,and rainfall use efficiency were significantly increased 1.7 times.Moreover,the soil temperature of NS was decreased 1.3-2.1 0C in the early growth period(0-85 day),while NF was increased 0.6-1.5 0C compared with NT in 2017-2018 growing year.And the evapotranspiration of NSF,NS,and NF significantly decreased 12.0,19.3,and 32.5 mm in fallow period compared with NT,while NB was significantly decreased 28.4 mm in growth period.Combined with two-year maize field experiment,NS could improve soil water condition but reduced soil temperature,yield did not increase significantly,and it could not effectively alleviate NO3--N leaching and accumulation.NB,NF,and NSF can improve nitrogen utilization,but NB cannot effectively improve soil water and temperature conditions,and the yield increase was not significant,while NF and NSF improved soil temperature,water and crop growth status,it significantly increased water use efficiency and yield.