Philip’s two-term infiltration equation has been widely used to infer soil saturated hydraulic conductivity(Ks),the accuracy of which is usually influenced by the size of infiltration rings and soil conditions.Previo...Philip’s two-term infiltration equation has been widely used to infer soil saturated hydraulic conductivity(Ks),the accuracy of which is usually influenced by the size of infiltration rings and soil conditions.Previous studies have primarily focused on exploring the ring-size dependence of Ks estimations under specific soil conditions(e.g.,soil isotropy and/or uniform initial water content).This study aimed to provide a comprehensive analysis by systematically considering eight heterogeneous and anisotropic soils with nonuniform initial water contents.Specifically,we examined the validity of Philip’s infiltration equation as well as the recently proposed two forms(i.e.,infiltration and time forms)of Parlange’s infiltration equation both theoretically and in practical applications of double-ring infiltration.Then the time form of Parlange’s equation was applied to infer Ks using double-ring infiltrometer measurements with different combinations of six inner ring diameters(10,20,40,80,120,and 200 cm)and three buffer index(defined as the ratio of the difference between inner and outer ring diameters to the outer ring diameter)values(0.20,0.33,and 0.50).For each infiltrometer set,20 stochastic Ks fields were randomly generated by adopting five standard deviation values(0.1,0.3,0.5,0.7,and 0.9).Furthermore,we investigated the effects of five horizontal correlation lengths(30,60,150,300,and 600 cm)on Ks estimations.The results demonstrated that Parlange’s equation,compared to Philip’s equation,was more universal in describing the cumulative infiltration relationship for the test soils.The combination of inner ring diameter and buffer index of 40 cm and 0.2,respectively,which satisfied most of the practical requirements for determining Ks in the Soil Water Infiltration Global(SWIG)database was optimal.When the horizontal correlation length exceeded a threshold(i.e.,150 cm in our study),the inner ring diameter was required to increase to 80 cm.Our findings contribute to accurate Ks estimations of different soils using double-ring infiltrometers.展开更多
氮肥施用是引起土壤酸化的主要原因之一,酸性环境促进紫色母岩的风化过程,并影响紫色母岩风化产物的理化性质,然而氮肥施用对风化产物的盐基离子和酸缓冲容量(pH Buffer Capacity,pHBC)的影响尚不明晰.因此,以蓬莱镇组(J_(3)p)紫色泥岩...氮肥施用是引起土壤酸化的主要原因之一,酸性环境促进紫色母岩的风化过程,并影响紫色母岩风化产物的理化性质,然而氮肥施用对风化产物的盐基离子和酸缓冲容量(pH Buffer Capacity,pHBC)的影响尚不明晰.因此,以蓬莱镇组(J_(3)p)紫色泥岩为研究对象,设置3组氮肥施用水平(280,560,840 kg/hm^(2))以及不施肥处理(CK),通过淋溶试验模拟母岩风化,以探明氮肥施用对紫色泥岩风化产物盐基离子及pHBC的影响.结果表明:与CK处理相比,氮肥施用处理下风化产物的化学蚀变指数(Chemical Index of Alteration,CIA)增加0.9%~4.7%,且风化产物的CIA随施肥水平的增加而呈现先增加后减小的趋势.氮肥施肥处理下风化产物的pHBC较CK处理降低4.0%~8.9%,且风化产物的pHBC随氮肥施用水平的增加呈现先减小后增加的趋势.风化产物的交换性盐基离子、水溶性盐基离子和盐基离子的淋失总量表现为:Ca^(2+)>Mg^(2+)>Na^(+)>K^(+),且风化产物的二价盐基离子(Ca^(2+)和Mg^(2+))含量远高于一价盐基离子含量(K^(+)和Na^(+)).基于多元线性逐步回归分析和结构方程模型分析结果表明:氮肥施用对风化产物水溶性K^(+)(R^(2)=0.75)和Na^(+)(R^(2)=0.99)含量存在显著负效应(p<0.05),而水溶性K^(+)和Na^(+)含量对风化产物pHBC(R^(2)=0.44)存在正效应,进而导致氮肥施用对风化产物pHBC存在负效应,这可能是氮肥施用影响风化产物pHBC的主要机制之一.研究结果表明:为了紫色土肥力的可持续发展,紫色土区域的氮肥施用量应小于280 kg/hm^(2).展开更多
基金supported by the National Natural Science Foundation of China(Nos.42107066 and 42007004)the Natural Science Foundation of Jiangsu Province,China(No.BK20201105)。
文摘Philip’s two-term infiltration equation has been widely used to infer soil saturated hydraulic conductivity(Ks),the accuracy of which is usually influenced by the size of infiltration rings and soil conditions.Previous studies have primarily focused on exploring the ring-size dependence of Ks estimations under specific soil conditions(e.g.,soil isotropy and/or uniform initial water content).This study aimed to provide a comprehensive analysis by systematically considering eight heterogeneous and anisotropic soils with nonuniform initial water contents.Specifically,we examined the validity of Philip’s infiltration equation as well as the recently proposed two forms(i.e.,infiltration and time forms)of Parlange’s infiltration equation both theoretically and in practical applications of double-ring infiltration.Then the time form of Parlange’s equation was applied to infer Ks using double-ring infiltrometer measurements with different combinations of six inner ring diameters(10,20,40,80,120,and 200 cm)and three buffer index(defined as the ratio of the difference between inner and outer ring diameters to the outer ring diameter)values(0.20,0.33,and 0.50).For each infiltrometer set,20 stochastic Ks fields were randomly generated by adopting five standard deviation values(0.1,0.3,0.5,0.7,and 0.9).Furthermore,we investigated the effects of five horizontal correlation lengths(30,60,150,300,and 600 cm)on Ks estimations.The results demonstrated that Parlange’s equation,compared to Philip’s equation,was more universal in describing the cumulative infiltration relationship for the test soils.The combination of inner ring diameter and buffer index of 40 cm and 0.2,respectively,which satisfied most of the practical requirements for determining Ks in the Soil Water Infiltration Global(SWIG)database was optimal.When the horizontal correlation length exceeded a threshold(i.e.,150 cm in our study),the inner ring diameter was required to increase to 80 cm.Our findings contribute to accurate Ks estimations of different soils using double-ring infiltrometers.
文摘氮肥施用是引起土壤酸化的主要原因之一,酸性环境促进紫色母岩的风化过程,并影响紫色母岩风化产物的理化性质,然而氮肥施用对风化产物的盐基离子和酸缓冲容量(pH Buffer Capacity,pHBC)的影响尚不明晰.因此,以蓬莱镇组(J_(3)p)紫色泥岩为研究对象,设置3组氮肥施用水平(280,560,840 kg/hm^(2))以及不施肥处理(CK),通过淋溶试验模拟母岩风化,以探明氮肥施用对紫色泥岩风化产物盐基离子及pHBC的影响.结果表明:与CK处理相比,氮肥施用处理下风化产物的化学蚀变指数(Chemical Index of Alteration,CIA)增加0.9%~4.7%,且风化产物的CIA随施肥水平的增加而呈现先增加后减小的趋势.氮肥施肥处理下风化产物的pHBC较CK处理降低4.0%~8.9%,且风化产物的pHBC随氮肥施用水平的增加呈现先减小后增加的趋势.风化产物的交换性盐基离子、水溶性盐基离子和盐基离子的淋失总量表现为:Ca^(2+)>Mg^(2+)>Na^(+)>K^(+),且风化产物的二价盐基离子(Ca^(2+)和Mg^(2+))含量远高于一价盐基离子含量(K^(+)和Na^(+)).基于多元线性逐步回归分析和结构方程模型分析结果表明:氮肥施用对风化产物水溶性K^(+)(R^(2)=0.75)和Na^(+)(R^(2)=0.99)含量存在显著负效应(p<0.05),而水溶性K^(+)和Na^(+)含量对风化产物pHBC(R^(2)=0.44)存在正效应,进而导致氮肥施用对风化产物pHBC存在负效应,这可能是氮肥施用影响风化产物pHBC的主要机制之一.研究结果表明:为了紫色土肥力的可持续发展,紫色土区域的氮肥施用量应小于280 kg/hm^(2).
