| Aiming at the problems of serious soil erosion,decline of land productivity and the unreasonable use of massive crop straw,etc..take the slopping farm land of black soil region as the research object,crop stalk biochar and the soybean which is the local main grain plant as the experiment materials,under the condition of the combinations of artificial rainfall and natural rainfall,experiments indoor and outdoor,experiment and computer simulation,a series experimental researches were conducted by means of runoff plots in Hongxing state farm,Beian county,Heilongjiang province and Wanjia experimental base which is belong to the Institute of water conservancy research of Heilongjiang province respectively,including the researches on influence of biochar application on farm land productivity under the condition of the biochar applied every year from 2015 to 2017 and the biochar applied only in the first year from 2016 to 2018.The results showed that:The influences of different biochar amount and the years of biochar applied on soil structure were different.With the increases of the amount and the years,soil bulk densities and the total soil porosities were getting lower and higher respectively.Appropriately applying biochar could make the soil aggregation stability and GSSI increase.The soil aggregation stabilities were better when the biochar applied for 2 years and 3 years with 50 t/hm2 biochar;the GSSI should be biggest when 2 years biochar apply with the amount of 56.75 t/hm2.In addition,when accumulated amount of biochar apply was the same,multi-apply was better than onetime-apply for soil structure improvement.Biochar apply made the soil water adsorption capacity and the soil water availability increases,but the soil water adsorption capacity was not increased continuously with the increases of the amount and the years,when accumulated amount of biochar applied was too high,instead it the soil water repellency should be increase.6 years biochar apply with the amount of 12.00 t/hm and 6 years with 3.70 t/hm2 should made soil water capacity and maximal effective soil water content reach the highest.When 2 years biochar applied with the amount of 55.76 t/hm,1 year with 63.20 t/hm2 and 4 years with 142.48 t/hm2,available N,available P and available P should reach the highst level respectively.The synthetical fertility of soil for 2 years and 3 years biochar applied with the amount of 25 t/hm2 and 2 years with 50 t/hm2 were higher than 1 year with 50 t/hm2,75 t/hm2 and 100 t/hm2.In addition,the biochar apply could make the spatial distribution of soil fertilities more uniform,the problem of soil fertilities un-uniform distribution from up-slope to down-slope could be solved.Biochar aplply also had the influences on soil water dynamic parameter and soil water redistribution,but the influence degree was different with the amount and the years of biochar applied.soil water characteristic curve displaced upward obviously with the increases of the amount and years.When the soil water content was same,with the increases of the amount and the years,unsaturated soil hydraulic conductivity was getting increase.Biochar apply could increase the specific water capacity of soil,improve soil water supply capacity.The layers which the soil water moved to was getting deeper,the duration of soil water redistribution was getting longer.HYDRUS-1D model can be used for simulation of unsaturated soil water movement under the condition of biochar application in slopping farm land of black soil region.The Influence of biochar on soil water dynamics mainly in soil layer of 0-60cm.In the year when the biochar applied,soil water contents and soil water storage in 0-100cm soil layer were all getting higher with the amount of biochar increase,but the effects in the treatments with lower amount of biochar were better than that with larger amount after 2 and 3 years.The biochar apply.The soil water storage could be reached highest level when 3 years biochar continuously applied with the amount of 44.99 t/hm2.A suitable biochar apply could improve the growth of soybean,but this effect was getting increase first and then decrease with the amount of biochar increase,and the yield of soybean and WUE in the interval of 3 years were also changed like it.Continuously biochar apply for 5 years with the amount of 33.1952 t/hm2 was the best for soybean yield,and the 2 years with the amount of 55.8430 t/hm2 was best for WUE.Biochar apply could reduce the amount of the runoff and the soil erosion,but the effects of them were different with the amount and years of biochar apply increase.Treatment B75 in the year when biochar applied was the best one for runoff control,but B50 for continuously biochar apply for 2 and 3 years was the best,and the effects of runoff control in the treatments with higher biochar content were lower than that with lower biochar content.Treatment B50 in the year when biochar applied and 2 years continuously biochar apply was the best one for sediment control,and for 3 years continuously apply the treatment B25 was the best.The best biochar apply modes for runoff control and sediment control were the 2 years continuously biochar apply with the biochar amount of 65.7419 t/hm2 and the 2 years continuously biochar apply with the biochar amount of 53.4167 t/hm2 respectively.With the years after biochar apply increase,the influences of biochar on soil physical and chemical properties were getting lower.The affecting period of biochar on soil bulk density,total soil porosity,soil capillary porosity,noncapillary porosity,GSSI,stability of soil water-stable aggregates,maximum content of soil available water,saturated soil water content,wilting water content soil water capacity,available K,available N,available P,total organic carbon and index of comprehensive soil fertility were 5 years,7 years,4 years,12 years,4-5 years,3-4 years,3-4 years,5-6 years,5-6 years,6-7 years,4 years,4 years,5 years,3 years and 5-6 years respectively.With the years after biochar apply increase,the influences of biochar on soil water dynamic parameter were getting lower,soil water characteristic curve for the treatments with biochar were all located above that without biochar in 2016-2018,but the curves were moving lower with the years after biochar apply increase.Biochar apply was beneficial for soil water transmission.unsaturated soil hydraulic conductivity in the year when biochar applied was highest,and then the influence was getting weaker with the years increase.With the years after biochar apply increase,the influence on soil water redistribution and soil water increase rate were all getting lower.The soil water storage in the treatments with biochar were all higher than the treatments without biochar in 2016-2018,but the differences between the 2 treatments was declined in logarithmic function with the years increase,after 5-6 years of biochar application,the differences should be almost disappeared.With the years after biochar apply increase,the effects of biochar on water-saving and yield-increasing were declined in exponential function.The plant height,stem diameter and leaf area index of soybean in the treatments with biochar were all better than that without biochar,but the best one was in the year when the biochar applied.The increase rate of yield and WUE of soybean were all declined in exponential function with the years after biochar application.The effect of water-saving for the treatment with 75 t/hm2 biochar could be maintained about 4 years.With the years after biochar apply increase,the effects of biochar on surface runoff reduction rate and sediment reduction rate were declined in exponential function,and the influence of the years after biochar applied on annual runoff depth was greater than on annual sediment production,The effect of runoff and sediment control for the treatment with 75 t/hm2 biochar could be maintained 2-3 years.With the years after biochar apply increase,the effects of biochar on land productivity was declined in exponential function.According to the evaluation of land productivity based on Copula evaluation method,2 best biochar application mode had been proposed,one is 2 years continuously biochar apply with the amount of 50 t/hm2,another one is that 75 t/hm2 biochar can be applied every 4 years. |
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