To combat the problem of residual film pollution and ensure the sustainable development of agriculture in oasis areas,a field experiment was carried out in 2019 at the Wuyi Farm Corps Irrigation Center Test Station in...To combat the problem of residual film pollution and ensure the sustainable development of agriculture in oasis areas,a field experiment was carried out in 2019 at the Wuyi Farm Corps Irrigation Center Test Station in Urumqi,Northwest China.Four types of biodegradable mulches,traditional plastic mulchs and a control group(bare land;referred to as CK)were compared,including a total of six different treatments.Effects of mulching on soil water and heat conditions as well as the yield and quality of processing tomatoes under drip irrigation were examined.In addition,a comparative analysis of economic benefits of biodegradable mulches was performed.Principal component analysis and gray correlation analysis were used to evaluate suitable mulching varieties for planting processing tomatoes under drip irrigation.Our results show that,compared with CK,biodegradable mulches and traditional plastic mulch have a similar effect on retaining soil moisture at the seedling stage but significantly increase soil moisture by 0.5%-1.5%and 1.5%-3.0%in the middle and late growth periods(P<0.050),respectively.The difference in the thermal insulation effect between biodegradable mulch and plastic mulch gradually reduces as the crop grows.Compared with plastic mulch,the average soil temperature at 5-20 cm depth under biodegradable mulches is significantly lowered by 2.04°C-3.52°C and 0.52°C-0.88°C(P<0.050)at the seedling stage and the full growth period,respectively,and the water use efficiency,average fruit yield,and production-investment ratio under biodegradable mulches were reduced by 0.89%-6.63%,3.39%-8.69%,and 0.51%-6.33%(P<0.050),respectively.The comprehensive evaluation analysis suggests that the black oxidized biological double-degradation ecological mulch made from eco-benign plastic is the optimal film type under the study condition.Therefore,from the perspective of sustainable development,biodegradable mulch is a competitive alternative to plastic mulch for large-scale tomato production under drip irrigation in the oasis.展开更多
Studies on coupled transfer of soil moisture and heat have been widely carried out for decades. However, little work has been done on red soils, widespread in southern China. The simultaneous transfer of soil moisture...Studies on coupled transfer of soil moisture and heat have been widely carried out for decades. However, little work has been done on red soils, widespread in southern China. The simultaneous transfer of soil moisture and heat depends on soil physical properties and the climate conditions. Red soil is heavy clay and high content of free iron and aluminum oxide. The climate conditions are characterized by the clear four seasons and the serious seasonal drought. The great annual and diurnal air temperature differences result in significant fluctuation in soil temperature in top layer. The closed and evaporating columns experiments with red soil were conducted to simulate the coupled transfer of soil water and heat under the overlaying and opening fields’ conditions, and to analyze the effects of soil temperature gradient on the water transfer and the effects of initial soil water contents on the transfer of soil water and heat. The closed and evaporating columns were designed similarly with about 18 °C temperatures differences between the top and bottom boundary, except of the upper end closed or exposed to the air, respectively. Results showed that in the closed column, water moved towards the cold end driven by temperature gradient, while the transported water decreased with the increasing initial soil water content until the initial soil water content reached to field capacity equivalent, when almost no changes for the soil moisture profile. In the evaporating column, the net transport of soil water was simultaneously driven by evaporation and temperature gradients, and the drier soil was more influenced by temperature gradient than by evapo- ration. In drier soil, it took a longer time for the temperature to reach equilibrium, because of more net amount of transported water.展开更多
Simulation models of heat and water transport have not been rigorously tested for the red soils of southern China. Based on the theory of nonisothermal water-heat coupled transfer, a simulation model, programmed in Vi...Simulation models of heat and water transport have not been rigorously tested for the red soils of southern China. Based on the theory of nonisothermal water-heat coupled transfer, a simulation model, programmed in Visual Basic 6.0, was developed to predict the coupled transfer of water and heat in hilly red soil. A series of soil column experiments for soil water and heat transfer, including soil columns with closed and evaporating top ends, were used to test the simulation model. Results showed that in the closed columns, the temporal and spatial distribution of moisture and heat could be very well predicted by the model, while in the evaporating columns, the simulated soil water contents were somewhat different from the observed ones. In the heat flow equation by Taylor and Lary (1964), the effect of soil water evaporation on the heat flow is not involved, which may be the main reason for the differences between simulated and observed results. The predicted temperatures were not in agreement with the observed one with thermal conductivities calculated by de Vries and Wierenga equations, so that it is suggested that Kh, soil heat conductivity, be multiplied by 8.0 for the first 6.5 h and by 1.2 later on. Sensitivity analysis of soil water and heat coefficients showed that the saturated hydraulic conductivity, KS, and the water diffusivity, D(θ), had great effects on soil water transport; the variation of soil porosity led to the difference of soil thermal properties, and accordingly changed temperature redistribution, which would affect water redistribution.展开更多
A coupled water and heat transport mode is established based on the Richards equation to study water flow and heat transport in soil during freezing process. Both the finite difference and finite element method are us...A coupled water and heat transport mode is established based on the Richards equation to study water flow and heat transport in soil during freezing process. Both the finite difference and finite element method are used in the discretization, respectively. Two different computer programs are written and used to simulate an indoor unidirectional frozen test. The freezing depth, freezing rate and temperature variation are compared among lab tests, finite difference calculation simulation and finite element calculation simulation. Result shows that: the finite difference method has a better performance in freezing depth simulation while the finite element method has a better performance in numerical stability in one-dimensional freezing simulation.展开更多
Coupled transfer of soil water and heat in closed columns of homogeneous red soil was studied under laboratory conditions. A coupled model was constructed using soil physical theory, empirical equations and experiment...Coupled transfer of soil water and heat in closed columns of homogeneous red soil was studied under laboratory conditions. A coupled model was constructed using soil physical theory, empirical equations and experimental data to predict the coupled transfer. The results show that transport of soil water was affected by temperature gradient, and the largest net water transport was found in the soil column with initial water content of 0.148 m3 m-3. At the same time, temperature changes with the transport of soil water was in a nonlinear shape as heat parameters were function of water content, and the changes of temperature were positively correlated with the net amount of water transported. Numerical modelling results show that the predicted values of temperature distribution were close to the observed values, while the predicted values of water content exhibited limited deviation at both ends of the soil column due to the slight temperature changes at both ends. It was indicated that the model proposed here was applicable.展开更多
In this paper, based on the basic equations of water flow and heat transfer, the hydrothermal coupling model is established.The numerical model was realized in COMSOL Multiphysics software, and simulation results are ...In this paper, based on the basic equations of water flow and heat transfer, the hydrothermal coupling model is established.The numerical model was realized in COMSOL Multiphysics software, and simulation results are compared with the experimental results of Watanabe and Wake(2008) to verify the effectiveness of the model. Through the calculation, we can obtain the dynamic changes of heat and water fluxes, thermal and hydrological properties, matric potential and temperature gradient in unsaturated freezing soil; and these variables are unmeasurable in practice.展开更多
The objective of this study was to clarify the effect of crop root on soil water retentivity and movement to improve the crop growth environment and irrigation efficiency. To simulate soil water movement considering t...The objective of this study was to clarify the effect of crop root on soil water retentivity and movement to improve the crop growth environment and irrigation efficiency. To simulate soil water movement considering the crop root effect on the physical properties of soil, a numerical model describing the soil water and heat transfers was introduced. Cultivation experiments were conducted to clarify the effect of the crop root on soil water retentivity and verify the accuracy of the numerical model. The relationship between soil water retentivity and the root content of soil samples was clarified by soil water retention curves. The soil water content displayed a high value with increasing crop root content in the high volumetric water content zone. The experimental results indicated that the saturated water content increased with the crop root content because of the porosity formed by the crop root. The differences of the soil water retentivity became smaller when the value of the matric potential was over pF 1.5. To verify the accuracy of the numerical model, an observation using acrylic slit pot was also conduced. The temporal and spatial changes of the volumetric water content and soil temperature were measured. Soil water and heat transfers, which considered the effect of the crop root on the soil water retentivity clarified by the soil water retention curves, were simulated. Simulated volumetric water content and temperature of soil agreed with observed data. This indicated that the numerical model used to simulate the soil water and heat transfer considering the crop root effect on soil water retentivity was satisfactory. Using this model, spatial and temporal changes of soil water content were simulated. The soil water condition of the root zone was relatively high compared with the initial conditions. This indicated that the volumetric water condition of the root zone increased with the soil water extraction and high soil water conditions was maintained because the soil water retentivity of root zone increased with the root effect.展开更多
The objective of this study is to evaluate the difference of the soil water management in mango orchards between the varieties of “Irwin” in Japanand “Nam Dok Mai” inThailand. Field observations were conducted in ...The objective of this study is to evaluate the difference of the soil water management in mango orchards between the varieties of “Irwin” in Japanand “Nam Dok Mai” inThailand. Field observations were conducted in mango orchards in Okinawa, Japan and Phrao, Thailand to clarify the water management practices. Measurement of the hourly soil water content in Phrao indicated that the irrigation was scarce and the volumetric water content in the soil was maintained almost constant. in the flowering season. This can be the farmers’ practice for flower induction. After the flowering season, irrigation was frequent in order to produce the large fruit. In the harvest season, the soil water content was relatively high because of frequent irrigation and rainfall. In Okinawa, the volumetric water content was maintained at the same level in a relatively deep layer. The result at the5 cmdepth indicated that the farmer carefully controlled the soil water content. In the flowering season, the soil water content was relatively low. While the orchard was managed empirically, the volumetric water content near the soil surface was maintained over 25% during the harvest season. This result indicates that the farmer performed the good soil water management to enhance mango fruit quality even without technical measurement. A numerical model describing the soil water and heat transfers was introduced to predict the farmer’s empirical soil water management in Okinawa. Using the meteorological data in March 2010, the irrigation regime was predicted using the simulated soil water content. In the flowering season, the farmer irrigated when the soil surface water content reached 14%. Based on this criterion for the empirical soil water management, the simulation result indicated that the farmer irrigated four times in this period. The numerical model presented here can be useful for evaluating the differences in water management practices of local farmers.展开更多
基金the Scientific and Technological Innovation Team Project in Key Areas(2019CB004)the Water-Saving Irrigation Experiment Project(BTJSSY–201911)of Xinjiang Production and Construction Corps,China。
文摘To combat the problem of residual film pollution and ensure the sustainable development of agriculture in oasis areas,a field experiment was carried out in 2019 at the Wuyi Farm Corps Irrigation Center Test Station in Urumqi,Northwest China.Four types of biodegradable mulches,traditional plastic mulchs and a control group(bare land;referred to as CK)were compared,including a total of six different treatments.Effects of mulching on soil water and heat conditions as well as the yield and quality of processing tomatoes under drip irrigation were examined.In addition,a comparative analysis of economic benefits of biodegradable mulches was performed.Principal component analysis and gray correlation analysis were used to evaluate suitable mulching varieties for planting processing tomatoes under drip irrigation.Our results show that,compared with CK,biodegradable mulches and traditional plastic mulch have a similar effect on retaining soil moisture at the seedling stage but significantly increase soil moisture by 0.5%-1.5%and 1.5%-3.0%in the middle and late growth periods(P<0.050),respectively.The difference in the thermal insulation effect between biodegradable mulch and plastic mulch gradually reduces as the crop grows.Compared with plastic mulch,the average soil temperature at 5-20 cm depth under biodegradable mulches is significantly lowered by 2.04°C-3.52°C and 0.52°C-0.88°C(P<0.050)at the seedling stage and the full growth period,respectively,and the water use efficiency,average fruit yield,and production-investment ratio under biodegradable mulches were reduced by 0.89%-6.63%,3.39%-8.69%,and 0.51%-6.33%(P<0.050),respectively.The comprehensive evaluation analysis suggests that the black oxidized biological double-degradation ecological mulch made from eco-benign plastic is the optimal film type under the study condition.Therefore,from the perspective of sustainable development,biodegradable mulch is a competitive alternative to plastic mulch for large-scale tomato production under drip irrigation in the oasis.
基金Project supported by the National Natural Science Foundation ofChina (No. 40171047) and the Doctoral Foundation of NationalEducation Ministry China
文摘Studies on coupled transfer of soil moisture and heat have been widely carried out for decades. However, little work has been done on red soils, widespread in southern China. The simultaneous transfer of soil moisture and heat depends on soil physical properties and the climate conditions. Red soil is heavy clay and high content of free iron and aluminum oxide. The climate conditions are characterized by the clear four seasons and the serious seasonal drought. The great annual and diurnal air temperature differences result in significant fluctuation in soil temperature in top layer. The closed and evaporating columns experiments with red soil were conducted to simulate the coupled transfer of soil water and heat under the overlaying and opening fields’ conditions, and to analyze the effects of soil temperature gradient on the water transfer and the effects of initial soil water contents on the transfer of soil water and heat. The closed and evaporating columns were designed similarly with about 18 °C temperatures differences between the top and bottom boundary, except of the upper end closed or exposed to the air, respectively. Results showed that in the closed column, water moved towards the cold end driven by temperature gradient, while the transported water decreased with the increasing initial soil water content until the initial soil water content reached to field capacity equivalent, when almost no changes for the soil moisture profile. In the evaporating column, the net transport of soil water was simultaneously driven by evaporation and temperature gradients, and the drier soil was more influenced by temperature gradient than by evapo- ration. In drier soil, it took a longer time for the temperature to reach equilibrium, because of more net amount of transported water.
基金Project supported by the National Natural Science Foundation ofChina (No. 40171047) and the Doctoral Foundation of NationalEducation Ministry China
文摘Simulation models of heat and water transport have not been rigorously tested for the red soils of southern China. Based on the theory of nonisothermal water-heat coupled transfer, a simulation model, programmed in Visual Basic 6.0, was developed to predict the coupled transfer of water and heat in hilly red soil. A series of soil column experiments for soil water and heat transfer, including soil columns with closed and evaporating top ends, were used to test the simulation model. Results showed that in the closed columns, the temporal and spatial distribution of moisture and heat could be very well predicted by the model, while in the evaporating columns, the simulated soil water contents were somewhat different from the observed ones. In the heat flow equation by Taylor and Lary (1964), the effect of soil water evaporation on the heat flow is not involved, which may be the main reason for the differences between simulated and observed results. The predicted temperatures were not in agreement with the observed one with thermal conductivities calculated by de Vries and Wierenga equations, so that it is suggested that Kh, soil heat conductivity, be multiplied by 8.0 for the first 6.5 h and by 1.2 later on. Sensitivity analysis of soil water and heat coefficients showed that the saturated hydraulic conductivity, KS, and the water diffusivity, D(θ), had great effects on soil water transport; the variation of soil porosity led to the difference of soil thermal properties, and accordingly changed temperature redistribution, which would affect water redistribution.
基金the support and motivation provided by National 973 Project of China (No. 2012CB026104)National Natural Science Foundation of China (No. 41171064)
文摘A coupled water and heat transport mode is established based on the Richards equation to study water flow and heat transport in soil during freezing process. Both the finite difference and finite element method are used in the discretization, respectively. Two different computer programs are written and used to simulate an indoor unidirectional frozen test. The freezing depth, freezing rate and temperature variation are compared among lab tests, finite difference calculation simulation and finite element calculation simulation. Result shows that: the finite difference method has a better performance in freezing depth simulation while the finite element method has a better performance in numerical stability in one-dimensional freezing simulation.
基金Project (No. 49671050) supported by the National Natural Science Foundation of China.
文摘Coupled transfer of soil water and heat in closed columns of homogeneous red soil was studied under laboratory conditions. A coupled model was constructed using soil physical theory, empirical equations and experimental data to predict the coupled transfer. The results show that transport of soil water was affected by temperature gradient, and the largest net water transport was found in the soil column with initial water content of 0.148 m3 m-3. At the same time, temperature changes with the transport of soil water was in a nonlinear shape as heat parameters were function of water content, and the changes of temperature were positively correlated with the net amount of water transported. Numerical modelling results show that the predicted values of temperature distribution were close to the observed values, while the predicted values of water content exhibited limited deviation at both ends of the soil column due to the slight temperature changes at both ends. It was indicated that the model proposed here was applicable.
基金financial support from the National Natural Science Foundation of China (Grant No. 41371092)partially supported by the Scientific Research Starting Foundation for Re turned Overseas Chinese Scholars, Ministry of Educa tion (Grant No. 20100528), China+2 种基金the State Key Labo ratory of Frozen Soil Engineering (SKLFSE201402)the National Key Scientific and Technological Project of Henan Province Office of Education, China (Grant No. 14B170007)and the Doctoral Scientific Fund Project of Henan Polytechnic University (Grant No. 648347)
文摘In this paper, based on the basic equations of water flow and heat transfer, the hydrothermal coupling model is established.The numerical model was realized in COMSOL Multiphysics software, and simulation results are compared with the experimental results of Watanabe and Wake(2008) to verify the effectiveness of the model. Through the calculation, we can obtain the dynamic changes of heat and water fluxes, thermal and hydrological properties, matric potential and temperature gradient in unsaturated freezing soil; and these variables are unmeasurable in practice.
文摘The objective of this study was to clarify the effect of crop root on soil water retentivity and movement to improve the crop growth environment and irrigation efficiency. To simulate soil water movement considering the crop root effect on the physical properties of soil, a numerical model describing the soil water and heat transfers was introduced. Cultivation experiments were conducted to clarify the effect of the crop root on soil water retentivity and verify the accuracy of the numerical model. The relationship between soil water retentivity and the root content of soil samples was clarified by soil water retention curves. The soil water content displayed a high value with increasing crop root content in the high volumetric water content zone. The experimental results indicated that the saturated water content increased with the crop root content because of the porosity formed by the crop root. The differences of the soil water retentivity became smaller when the value of the matric potential was over pF 1.5. To verify the accuracy of the numerical model, an observation using acrylic slit pot was also conduced. The temporal and spatial changes of the volumetric water content and soil temperature were measured. Soil water and heat transfers, which considered the effect of the crop root on the soil water retentivity clarified by the soil water retention curves, were simulated. Simulated volumetric water content and temperature of soil agreed with observed data. This indicated that the numerical model used to simulate the soil water and heat transfer considering the crop root effect on soil water retentivity was satisfactory. Using this model, spatial and temporal changes of soil water content were simulated. The soil water condition of the root zone was relatively high compared with the initial conditions. This indicated that the volumetric water condition of the root zone increased with the soil water extraction and high soil water conditions was maintained because the soil water retentivity of root zone increased with the root effect.
文摘The objective of this study is to evaluate the difference of the soil water management in mango orchards between the varieties of “Irwin” in Japanand “Nam Dok Mai” inThailand. Field observations were conducted in mango orchards in Okinawa, Japan and Phrao, Thailand to clarify the water management practices. Measurement of the hourly soil water content in Phrao indicated that the irrigation was scarce and the volumetric water content in the soil was maintained almost constant. in the flowering season. This can be the farmers’ practice for flower induction. After the flowering season, irrigation was frequent in order to produce the large fruit. In the harvest season, the soil water content was relatively high because of frequent irrigation and rainfall. In Okinawa, the volumetric water content was maintained at the same level in a relatively deep layer. The result at the5 cmdepth indicated that the farmer carefully controlled the soil water content. In the flowering season, the soil water content was relatively low. While the orchard was managed empirically, the volumetric water content near the soil surface was maintained over 25% during the harvest season. This result indicates that the farmer performed the good soil water management to enhance mango fruit quality even without technical measurement. A numerical model describing the soil water and heat transfers was introduced to predict the farmer’s empirical soil water management in Okinawa. Using the meteorological data in March 2010, the irrigation regime was predicted using the simulated soil water content. In the flowering season, the farmer irrigated when the soil surface water content reached 14%. Based on this criterion for the empirical soil water management, the simulation result indicated that the farmer irrigated four times in this period. The numerical model presented here can be useful for evaluating the differences in water management practices of local farmers.