Chlorination has been recognized as an efficient and economically favorable method for treating clogging in drip emitters caused by biological growth during sewage application. Further important criteria for determini...Chlorination has been recognized as an efficient and economically favorable method for treating clogging in drip emitters caused by biological growth during sewage application. Further important criteria for determining an optimal chlorination scheme are the different responses of crops to the chloride added into the soil through chlorination. During two seasons in 2008 and 2009, field experiments were conducted in a solar-heated greenhouse with drip irrigation systems applying secondary sewage effluent to tomato plants to investigate the influences of chlorine injection intervals and levels on plant growth, yield, fruit quality, and emitter clogging. Injection intervals ranging from 2 to 8 wk and injection concentrations ranging 2-50 mg L-1 of free chlorine residual at the end of the laterals were used. For the 2008 experiments, the yield from the treatments of sewage application with chlorination was 7.5% lower than the yield from the treatment of sewage application without chlorination, while the yields for the treatments with and without chlorination were similar for the 2009 experiments. The statistical tests indicated that neither the chlorine injection intervals and concentrations nor the interactions between the two significantly influenced plant height, leaf area, or tomato yield for both years. The qualities of the fruit in response to chlorination were parameter-dependent. Chlorination did not significantly influence the quality of ascorbic acid, soluble sugar, or soluble acids, but the interaction between the chlorine injection interval and the chlorine concentration significantly influenced the levels of soluble solids. It was also confirmed that chlorination was an effective method for reducing biological clogging. These results suggested that chlorination is safe for a crop that has a moderate sensitivity to chlorine, like tomato, and can maintain a high level of performance in drip irrigation systems applying sewage effluent.展开更多
Drip-irrigation is increasingly applied in maize （Zea mays L.） production in sub-humid region. It is cdtical to quantify irrigation requirements during different growth stages under diverse climatic conditions. In t...Drip-irrigation is increasingly applied in maize （Zea mays L.） production in sub-humid region. It is cdtical to quantify irrigation requirements during different growth stages under diverse climatic conditions. In this study, the Hybrid-Maize model was calibrated and applied in a sub-humid Heilongjiang Province in Northeast China to estimate irrigation requirements for drip- irrigated maize during different crop physiological development stages and under diverse agro-climatic conditions. Using dimensionless scales, the whole growing season of maize was divided into diverse development stages from planting to maturity. Drip-irrigation dates and irrigation amounts in each irrigation event were simulated and summarized in 30-year simulation from 1981 to 2010. The maize harvest area of Heilongjiang Province was divided into 10 agro-climatic zones based on growing degree days, arid index, and temperature seasonality. The simulated results indicated that seasonal irrigation requirements and water stress during different growth stages were highly related to initial soil water content and distribution of seasonal precipitation. In the experimental site, the average irrigation amounts and times ranged from 48 to 150 mm with initial soil water content decreasing from 100 to 20% of the maximum soil available water. Additionally, the earliest drip-irrigation event might occur during 3- to 8-leaf stage. The water stress could occur at any growth stages of maize, even in wet years with abundant total seasonal rainfall but poor distribution. And over 50% of grain yield loss could be caused by extended water stress during the kernel setting window and grain filling period. It is estimated that more than 94% of the maize harvested area in Heilongjiang Province needs to be irrigated although the yield increase varied （0 to 109%） in diverse agro-climatic zones. Consequently, at least 14% of more maize production could be achieved through drip-irrigation systems in Heilongjiang Province compared to rainfed conditions.展开更多
Understanding bacterial transportation in unsaturated soil is helpful for reducing and avoiding pathogenic contamination that may be induced by irrigation with reclaimed waste water and for developing better irrigatio...Understanding bacterial transportation in unsaturated soil is helpful for reducing and avoiding pathogenic contamination that may be induced by irrigation with reclaimed waste water and for developing better irrigation management practic-es. Experiments were conducted to study the transport of a typical bacterium,Escherichia coli （E. coli）, in a sandy and a sandy loam soil under different application rates and input concentrations. A 30° wedge-shaped plexiglass container was used to represent one twelfth of the complete cylinder in the experiments. The apparent cylindrical application rate varied from 1.05 to 5.76 L h–1 and the input concentration ofE. coli from magnitude of 102 to 107 colony-forming unit （CFU） mL–1. For a given volume of water applied, an increase in application rate resulted in an increase in the wetted radius and a decrease in the wetted depth. In the sandy loam soil, the water spread out in a circular-arc shaped saturated zone on the surface, and the ultimate saturated entry radius increased with the application rate. An increasing application rate of water suspended bacteria alowed a more rapid transport of bacteria, thus acceleratingE. coli transport rate and resulting in a larger distributed volume ofE. coli for both soil types. For the sandy soil, more than 70% of theE. coli that was de-tected within the entire wetted volume concentrated in the range of 10 cm from the point source, and the concentration of E. colidecreased greatly as the distance from the point source increased. More than 98% of theE. coli was detected in a range of 5 cm around the saturated wetted zone for the sandy loam soil. For both soil types tested, an extremely high concentration ofE. coli was observed in the proximity of the point source, and the peak value increased with an increased input concentration. In principle, using an emitter with relative lower application rate would be effective to restrictE. coli transport. To reduce bacterial concentration in the sewage eflfuent during wastewater treatment is important to decrease the risk of soil contamination caused by irrigation with sewage eflfuent.展开更多
The dynamics of water and salt in soil were monitored in the 2010 and 2011 growing seasons of cotton to evaluate the salinity risk of soil under drip irrigation in arid environments for different management practices ...The dynamics of water and salt in soil were monitored in the 2010 and 2011 growing seasons of cotton to evaluate the salinity risk of soil under drip irrigation in arid environments for different management practices of drip system uniformity and irrigation amount. In the experiments, three Christiansen uniformity coefficients （CU） of approximately 65, 80, and 95% （referred to as low, medium, and high uniformity, respectively） and three irrigation amounts of 50, 75, and 100% of full irrigation were used. The distribution of the soil water content and bulk electrical conductivity （ECb） was monitored continuously with approximately equally spaced frequency domain reflectometry （FDR） sensors located along a dripline. Gravimetric samples of soil were collected regularly to determine the distribution of soil salinity. A great fluctuation in CU of water content and ECb at 60 cm depth was observed for the low uniformity treatment during the irrigation season, while a relatively stable variation pattern was observed for the high uniformity treatment. The ECb CU was substantially lower than the water content CU and its value was greatly related to the water content CU and the initial ECb CU. The spatial variation of seasonal mean soil water content and seasonal mean soil bulk electrical conductivity showed a high dependence on the variation pattern of emitter discharge rate along a dripline for the low and medium uniformity treatments. A greater irrigation amount produced a significantly lower soil salinity at the end of the irrigation season, while the influence of the system uniformity on the soil salinity was insignificant at a probability level of 0.1. In arid regions, the determination of the target drip irrigation system uniformity should consider the potential salinity risk of soil caused by nonuniform water application as the influence of the system uniformity on the distribution of the soil salinity was progressively strengthened during the growing season of crop.展开更多
Chlorination is usually an economical method for treating clogging in drip emitters during sewage application. Appropriate assessment of the responses of soil and crop is essential for determining an optimal chlorinat...Chlorination is usually an economical method for treating clogging in drip emitters during sewage application. Appropriate assessment of the responses of soil and crop is essential for determining an optimal chlorination scheme. During 2008 to 2009, field experiments were conducted in a solar-heated greenhouse for tomato drip irrigated with secondary sewage effluent, to investigate the influences of chlorine injection intervals and levels on soil chemical properties and nitrogen uptake. Injection intervals ranging from two to eight weeks and injection concentrations ranging from 2 to 50 mg L-1 were used. A salinity factor and a nutrient factor were extracted from the pool of the nine soil chemical constituents using factor analysis method. The results demonstrated that chlorination practices increased the residual Cl in the soil, resulting in an increased salinity factor, especially for the frequent chlorination at a high injection concentration. Chlorination weakened the accumulation of nutrients factor in the upper soil layer. Nitrogen uptake of the tomato plants also was inhibited by the increased salinity in the upper soil layer caused by high chlorination levels. In order to reduce the unfavorable effect on soil chemical properties and nitrogen uptake, chlorination scheme with concentrations of lower than 20 mg L-1 was recommended.展开更多
The aim of drip fertigation is synchronising the application of water and nutrients with crop requirements, and maintaining the proper concentration and distribution of nutrient and water in the soil. The wetting patt...The aim of drip fertigation is synchronising the application of water and nutrients with crop requirements, and maintaining the proper concentration and distribution of nutrient and water in the soil. The wetting patterns and nutrient distributions under drip fertigation have been proved to be closely related to the fertigation strategies. In order to find out the critical factors that affect the nutrient distribution under different drip fertigaiton strategies, a computer simulation model HYDRUS2D/3D was used to simulate the water and nitrate distribution for various fertigation strategies from a surface point source. Simulation results were compared with the observed ones from our previous studies. A 15° wedge-shaped plexiglass container was used in our experiment to represent one-twenty-fourth of the complete cylinder. The height of container is 40 cm, and the radius is 41 cm. The ammonium nitrate solution was added through a no. 7 needle connected to a Mariotte tube with a flexible hose. The soil water content, nitrate and ammonium concentrations were measured. The comparison of simulated and observed data demonstrated that the model performed reliably. The numerical analysis for various fertigation strategies from a surface point source showed that：（1） The total amount of irrigation water, the concentration of the fertilizer solution and the amount of pure water used to flush the pipeline after fertilizer solution application are the three critical factors influencing the distribution of water and fertilizer nitrogen in the soil.（2） The fresh water irrigation duration prior to fertigation has no obvious effect on nitrate distribution. The longer flushing time period after fertigation resulted in nitrate accumulation closer to the wetting front. From the point of avoiding the possibility of nitrate loss from the root zone, we recommended that the flushing time period should be as shorter as possible.（3） For a given amount of fertilizer, higher concentration of the fertilizer applied solution reduces the potential of nitrate leaching in drip irrigation system. While, lower concentration of the fertilizer solution resulted in an uniform distribution of nitrate band closer to the wetted front.展开更多
Field experiments were conducted to investigate the effects of nonuniformity of sprinkler fertigation and the amount of fertilizers applied through fertigation on nitrogen uptake and crop yield during two growing seas...Field experiments were conducted to investigate the effects of nonuniformity of sprinkler fertigation and the amount of fertilizers applied through fertigation on nitrogen uptake and crop yield during two growing seasons of winter wheat in 2002-2003 and 2003-2004 at an experimental station in Beijing. In the experiments, the seasonal averaged Christiansen irrigation uniformity coefficient （CU） varied from 72% to 84%. Except for the fertilizer applied before planting, fertilizer was applied with the sprinkler irrigation system with a seasonal averaged CU for fertigation varied from 71% to 85%. Three levels of fertilizer applied varying from 0 to 180 kg N ha^-1 were used in the experiments. The experimental results demonstrated that sprinkler fertigation uniformity had insignificant effects on nitrogen uptake and crop yield for the uniformity range tested. Also, the influence of fertilizer applied through sprinkler fertigation on crop yield was minor, while the total nitrogen content for stem and nitrogen uptake increased with increasing fertilizer applied.展开更多
基金financially supported by the National Natural Science Foundation of China (50779078)
文摘Chlorination has been recognized as an efficient and economically favorable method for treating clogging in drip emitters caused by biological growth during sewage application. Further important criteria for determining an optimal chlorination scheme are the different responses of crops to the chloride added into the soil through chlorination. During two seasons in 2008 and 2009, field experiments were conducted in a solar-heated greenhouse with drip irrigation systems applying secondary sewage effluent to tomato plants to investigate the influences of chlorine injection intervals and levels on plant growth, yield, fruit quality, and emitter clogging. Injection intervals ranging from 2 to 8 wk and injection concentrations ranging 2-50 mg L-1 of free chlorine residual at the end of the laterals were used. For the 2008 experiments, the yield from the treatments of sewage application with chlorination was 7.5% lower than the yield from the treatment of sewage application without chlorination, while the yields for the treatments with and without chlorination were similar for the 2009 experiments. The statistical tests indicated that neither the chlorine injection intervals and concentrations nor the interactions between the two significantly influenced plant height, leaf area, or tomato yield for both years. The qualities of the fruit in response to chlorination were parameter-dependent. Chlorination did not significantly influence the quality of ascorbic acid, soluble sugar, or soluble acids, but the interaction between the chlorine injection interval and the chlorine concentration significantly influenced the levels of soluble solids. It was also confirmed that chlorination was an effective method for reducing biological clogging. These results suggested that chlorination is safe for a crop that has a moderate sensitivity to chlorine, like tomato, and can maintain a high level of performance in drip irrigation systems applying sewage effluent.
基金supported by the Key Technology R&D Program of China during the 12th Five-year Plan period (2014BAD12B05)the National Natural Science Foundation of China (51479211, 51621061)the Chinese Scholarship Council (201506350059)
文摘Drip-irrigation is increasingly applied in maize （Zea mays L.） production in sub-humid region. It is cdtical to quantify irrigation requirements during different growth stages under diverse climatic conditions. In this study, the Hybrid-Maize model was calibrated and applied in a sub-humid Heilongjiang Province in Northeast China to estimate irrigation requirements for drip- irrigated maize during different crop physiological development stages and under diverse agro-climatic conditions. Using dimensionless scales, the whole growing season of maize was divided into diverse development stages from planting to maturity. Drip-irrigation dates and irrigation amounts in each irrigation event were simulated and summarized in 30-year simulation from 1981 to 2010. The maize harvest area of Heilongjiang Province was divided into 10 agro-climatic zones based on growing degree days, arid index, and temperature seasonality. The simulated results indicated that seasonal irrigation requirements and water stress during different growth stages were highly related to initial soil water content and distribution of seasonal precipitation. In the experimental site, the average irrigation amounts and times ranged from 48 to 150 mm with initial soil water content decreasing from 100 to 20% of the maximum soil available water. Additionally, the earliest drip-irrigation event might occur during 3- to 8-leaf stage. The water stress could occur at any growth stages of maize, even in wet years with abundant total seasonal rainfall but poor distribution. And over 50% of grain yield loss could be caused by extended water stress during the kernel setting window and grain filling period. It is estimated that more than 94% of the maize harvested area in Heilongjiang Province needs to be irrigated although the yield increase varied （0 to 109%） in diverse agro-climatic zones. Consequently, at least 14% of more maize production could be achieved through drip-irrigation systems in Heilongjiang Province compared to rainfed conditions.
基金financially supported by the National Natural Science Foundation of China(51339007)
文摘Understanding bacterial transportation in unsaturated soil is helpful for reducing and avoiding pathogenic contamination that may be induced by irrigation with reclaimed waste water and for developing better irrigation management practic-es. Experiments were conducted to study the transport of a typical bacterium,Escherichia coli （E. coli）, in a sandy and a sandy loam soil under different application rates and input concentrations. A 30° wedge-shaped plexiglass container was used to represent one twelfth of the complete cylinder in the experiments. The apparent cylindrical application rate varied from 1.05 to 5.76 L h–1 and the input concentration ofE. coli from magnitude of 102 to 107 colony-forming unit （CFU） mL–1. For a given volume of water applied, an increase in application rate resulted in an increase in the wetted radius and a decrease in the wetted depth. In the sandy loam soil, the water spread out in a circular-arc shaped saturated zone on the surface, and the ultimate saturated entry radius increased with the application rate. An increasing application rate of water suspended bacteria alowed a more rapid transport of bacteria, thus acceleratingE. coli transport rate and resulting in a larger distributed volume ofE. coli for both soil types. For the sandy soil, more than 70% of theE. coli that was de-tected within the entire wetted volume concentrated in the range of 10 cm from the point source, and the concentration of E. colidecreased greatly as the distance from the point source increased. More than 98% of theE. coli was detected in a range of 5 cm around the saturated wetted zone for the sandy loam soil. For both soil types tested, an extremely high concentration ofE. coli was observed in the proximity of the point source, and the peak value increased with an increased input concentration. In principle, using an emitter with relative lower application rate would be effective to restrictE. coli transport. To reduce bacterial concentration in the sewage eflfuent during wastewater treatment is important to decrease the risk of soil contamination caused by irrigation with sewage eflfuent.
基金supported by the National Natural Science Foundation of China (50979115)
文摘The dynamics of water and salt in soil were monitored in the 2010 and 2011 growing seasons of cotton to evaluate the salinity risk of soil under drip irrigation in arid environments for different management practices of drip system uniformity and irrigation amount. In the experiments, three Christiansen uniformity coefficients （CU） of approximately 65, 80, and 95% （referred to as low, medium, and high uniformity, respectively） and three irrigation amounts of 50, 75, and 100% of full irrigation were used. The distribution of the soil water content and bulk electrical conductivity （ECb） was monitored continuously with approximately equally spaced frequency domain reflectometry （FDR） sensors located along a dripline. Gravimetric samples of soil were collected regularly to determine the distribution of soil salinity. A great fluctuation in CU of water content and ECb at 60 cm depth was observed for the low uniformity treatment during the irrigation season, while a relatively stable variation pattern was observed for the high uniformity treatment. The ECb CU was substantially lower than the water content CU and its value was greatly related to the water content CU and the initial ECb CU. The spatial variation of seasonal mean soil water content and seasonal mean soil bulk electrical conductivity showed a high dependence on the variation pattern of emitter discharge rate along a dripline for the low and medium uniformity treatments. A greater irrigation amount produced a significantly lower soil salinity at the end of the irrigation season, while the influence of the system uniformity on the soil salinity was insignificant at a probability level of 0.1. In arid regions, the determination of the target drip irrigation system uniformity should consider the potential salinity risk of soil caused by nonuniform water application as the influence of the system uniformity on the distribution of the soil salinity was progressively strengthened during the growing season of crop.
基金financially supported by the National Natural Science Foundation of China(50779078 and 50909101)
文摘Chlorination is usually an economical method for treating clogging in drip emitters during sewage application. Appropriate assessment of the responses of soil and crop is essential for determining an optimal chlorination scheme. During 2008 to 2009, field experiments were conducted in a solar-heated greenhouse for tomato drip irrigated with secondary sewage effluent, to investigate the influences of chlorine injection intervals and levels on soil chemical properties and nitrogen uptake. Injection intervals ranging from two to eight weeks and injection concentrations ranging from 2 to 50 mg L-1 were used. A salinity factor and a nutrient factor were extracted from the pool of the nine soil chemical constituents using factor analysis method. The results demonstrated that chlorination practices increased the residual Cl in the soil, resulting in an increased salinity factor, especially for the frequent chlorination at a high injection concentration. Chlorination weakened the accumulation of nutrients factor in the upper soil layer. Nitrogen uptake of the tomato plants also was inhibited by the increased salinity in the upper soil layer caused by high chlorination levels. In order to reduce the unfavorable effect on soil chemical properties and nitrogen uptake, chlorination scheme with concentrations of lower than 20 mg L-1 was recommended.
基金financially supported by the Non-Profit National Research Institute,Ministry of Finance of China(IARRP-2012-202-3)the Special Fund for Agro-scientific Research in the Public Interest,China(201203077-04-05)
文摘The aim of drip fertigation is synchronising the application of water and nutrients with crop requirements, and maintaining the proper concentration and distribution of nutrient and water in the soil. The wetting patterns and nutrient distributions under drip fertigation have been proved to be closely related to the fertigation strategies. In order to find out the critical factors that affect the nutrient distribution under different drip fertigaiton strategies, a computer simulation model HYDRUS2D/3D was used to simulate the water and nitrate distribution for various fertigation strategies from a surface point source. Simulation results were compared with the observed ones from our previous studies. A 15° wedge-shaped plexiglass container was used in our experiment to represent one-twenty-fourth of the complete cylinder. The height of container is 40 cm, and the radius is 41 cm. The ammonium nitrate solution was added through a no. 7 needle connected to a Mariotte tube with a flexible hose. The soil water content, nitrate and ammonium concentrations were measured. The comparison of simulated and observed data demonstrated that the model performed reliably. The numerical analysis for various fertigation strategies from a surface point source showed that：（1） The total amount of irrigation water, the concentration of the fertilizer solution and the amount of pure water used to flush the pipeline after fertilizer solution application are the three critical factors influencing the distribution of water and fertilizer nitrogen in the soil.（2） The fresh water irrigation duration prior to fertigation has no obvious effect on nitrate distribution. The longer flushing time period after fertigation resulted in nitrate accumulation closer to the wetting front. From the point of avoiding the possibility of nitrate loss from the root zone, we recommended that the flushing time period should be as shorter as possible.（3） For a given amount of fertilizer, higher concentration of the fertilizer applied solution reduces the potential of nitrate leaching in drip irrigation system. While, lower concentration of the fertilizer solution resulted in an uniform distribution of nitrate band closer to the wetted front.
基金the National Natural Science Foundation of China (50179037).
文摘Field experiments were conducted to investigate the effects of nonuniformity of sprinkler fertigation and the amount of fertilizers applied through fertigation on nitrogen uptake and crop yield during two growing seasons of winter wheat in 2002-2003 and 2003-2004 at an experimental station in Beijing. In the experiments, the seasonal averaged Christiansen irrigation uniformity coefficient （CU） varied from 72% to 84%. Except for the fertilizer applied before planting, fertilizer was applied with the sprinkler irrigation system with a seasonal averaged CU for fertigation varied from 71% to 85%. Three levels of fertilizer applied varying from 0 to 180 kg N ha^-1 were used in the experiments. The experimental results demonstrated that sprinkler fertigation uniformity had insignificant effects on nitrogen uptake and crop yield for the uniformity range tested. Also, the influence of fertilizer applied through sprinkler fertigation on crop yield was minor, while the total nitrogen content for stem and nitrogen uptake increased with increasing fertilizer applied.
