生物炭对东北黑土持水特性的影响

Effect of biochars on water retention properties of northeast region black soils

为探究生物炭对东北黑土持水特性的影响,系统研究3种添加比例(2%、5%、10%)、3种粒径(0.25、0.5、1mm)的杨木炭和竹炭对3种质地东北黑土(壤土、砂壤土、砂土)田间持水量和含水率的影响规律,构建添加生物炭黑土的水分特征曲线,并采用Van-Genuchten和Broods-Corey模型进行拟合。结果表明:生物炭能显著提高不同质地东北黑土的持水能力,黑土的田间持水量与生物炭的添加比例呈显著正相关,而与生物炭的粒径呈负相关,0.5mm和1mm粒径的生物炭对黑土田间持水量的影响差异不显著,杨木炭显著优于竹炭,0.25mm、10%添加比例的杨木炭对东北黑土持水能力的提高效果最优,壤土、砂壤土、砂土3种质地黑土的田间持水量和饱和含水率分别可提高64.97%、66.42%、69.39%和47.60%、38.93%、31.18%;Van-Genuchten模型能更精确的模拟添加生物炭黑土的水分特征曲线,最佳离心时间为100min,三次函数曲线能够较好的拟合添加生物炭黑土的体积含水率与离心吸力之间的多元动态关系,为生物炭对各种质地东北黑土水分运动规律的深入研究提供理论依据。

The water retention capacities and organic matter content of valuable black soil is decreasing year by year with unreasonable farming and excessive dependence on chemical fertilizers and pesticides continuously.Black soil erosion is serious and black soil layer is less and less.It is urgent to protect black soil resource.Biochar is recognized gradually in recent years for improving soil structure,soil water retention capacity and crop yield,and for reducing surface runoff and soil erosion as a soil conditioner.However,most researches focus on the improvement in the acidic soil and sandy soil with less organic matter because of the high pH of biochar and the relative good fertility of black soil.The application of biochar in black soil in northeast region is relatively rare.The water retention capacity improvement is one of the important indexes to characterize the physical and chemical properties of black soil.In this paper,the effects of biochars including poplar wood carbon and bamboo carbon on the water retention properties of loamy soil,sandy loam and sandy soil were studied systematically with three different addition ratios(2%,5%,10%)and three different particle sizes(0.25,0.5,1 mm)of biochars.The water characteristic curves of different northeast black soils added with biochars were studied by the centrifugation method,and were fitted by the models of Van-Genuchten and Broods-Corey.The results showed that the field capacity and the saturated moisture content of loamy soil,sandy loam and sandy soil all increased significantly because of biochars addition.The field capacity of black soils increased significantly with the increase of addition ratios of biochars,but decreased with the increase of particle sizes of biochars.However,an insignificant difference in 0.5 and 1 mm particle sizes was achieved.The effects of poplar wood carbon on the water retention properties of black soils were superior to those of bamboo carbon,significantly.The particle size of 0.25 mm and addition ratio of 10%was optimum for poplar wood carbon to achieve high water retention capacities of northeast black soils.Under optimum condition,the field capacity and the saturated moisture content increased by 64.97%and 47.60%for loamy soil,66.42%and 38.93%for sandy loam,and 69.39%and 31.18%for sandy soil,respectively.Furthermore,the effect of grain size distribution of black soil itself on its water retention properties was significant.A negative relationship was between soil field capacity and sand particle content of soil.However,the soil field capacity increased significantly with the increase of the silt and clay particle content of soil.Loamy soil has the largest water holding capacity,followed by sandy loam.The water holding capacity of sandy soil was the smallest.Moreover,the water characteristic curves of three black soils with biochar addition decreased gradually with thethe increase of centrifugal time and suction.Van-Genuchten model fitted the water characteristic curves of three black soils,more precisely.All the fit goodness of cubic curves simulating the relationship of soil volume moisture content and suction were more than 0.99.Centrifugation time of 100 min was optimum.The results in this study provided good insight into the effects of biochars on the water retention properties of different black soils in the northeast region.