In recent years, the use of fertigation technology with center pivot irrigation systems has increased rapidly in the North China Plain (NCP). The combined effects of water and nitrogen application uniformity on the gr...In recent years, the use of fertigation technology with center pivot irrigation systems has increased rapidly in the North China Plain (NCP). The combined effects of water and nitrogen application uniformity on the grain yield, water use efficiency (WUE) and nitrogen use efficiency (NUE) have become a research hotspot. In this study, a two-year field experiment was conducted during the winter wheat growing season in 2016–2018 to evaluate the water application uniformity of a center pivot with two low pressure sprinklers (the R3000 sprinklers were installed in the first span, the corresponding treatment was RS;the D3000 sprinklers were installed in the second span, the corresponding treatment was DS) and a P85A impact sprinkler as the end gun (the corresponding treatment was EG), and to analyze its effects on grain yield, WUE and NUE. The results showed that the water application uniformity coefficients of R3000, D3000 and P85A along the radial direction of the pivot (CUH) were 87.5, 79.5 and 65%, respectively. While the uniformity coefficients along the traveling direction of the pivot (CUC) were all higher than 85%. The effects of water application uniformity of the R3000 and D3000 sprinklers on grain yield were not significant (P>0.05);however, the average grain yield of EG was significantly lower (P<0.05) than those of RS and DS, by 9.4 and 11.1% during two growing seasons, respectively. The coefficients of variation (CV) of the grain yield had a negative correlation with the uniformity coefficient. The CV of WUE was more strongly affected by the water application uniformity, compared with the WUE value, among the three treatments. The NUE of RS was higher than those of DS and EG by about 6.1 and 4.8%, respectively, but there were no significant differences in NUE among the three treatments during the two growing seasons. Although the CUH of the D3000 sprinklers was lower than that of the R3000, it had only limited effects on the grain yield, WUE and NUE. However, the cost of D3000 sprinklers is lower than that of R3000 sprinklers. Therefore, the D3000 sprinklers are recommended for winter wheat irrigation and fertigation in the NCP.展开更多
The Mu Us dune field in China has become a focal region for research of the prevention and control of desertification.Agricultural practices in this area have been modernized in recent years,evidenced by the developme...The Mu Us dune field in China has become a focal region for research of the prevention and control of desertification.Agricultural practices in this area have been modernized in recent years,evidenced by the development of Center Pivot Irrigation(CPI)farmlands.However,the impacts of CPI farmlands on combating desertification remain poorly understood.This study chose the southeastern part of the Mu Us dune field as a study area to investigate the variations of CPI farmlands from 2009 to 2018 and the influencing factors.The results showed growth trends in both the number and the area of these CPI farmland units over the period.The areas of meso-and micro-scale CPI farmland units stabilized over time to mainly 0-0.2 km2 and 0.2-0.4 km2,respectively;Topography,temperature,and geological substratum were preliminarily identified as the major natural factors driving the development of the CPI farmlands.Within the context of varied stakeholders,the potential for soil erosion,and damage to natural vegetation,the current study suggests that strict management of CPI farmland is required through effective long-term planning and land-use policies.The results of this study can assist in realizing the sustainable development of agriculture and its ecological significance in dune field areas.展开更多
Agricultural irrigation is a primary user for freshwater withdrawal. Irrigation plays an important role in crop production, as it provides the benefit of reducing the effects of prolonged dryness and erratic precipita...Agricultural irrigation is a primary user for freshwater withdrawal. Irrigation plays an important role in crop production, as it provides the benefit of reducing the effects of prolonged dryness and erratic precipitation. Center pivot irrigation system is the most common irrigation system in agriculture. As the center pivot irrigation system ages, the system could develop a leaking joint, clogged sprinklers, and physical damage. This can cause areas of non-uniformity that can lead to under- or over-irrigated in some areas of the land, resulting in excess energy use and cost, wasting resources, and environmental impacts. Thus, it is important to evaluate the performance of a center pivot irrigation system regularly to maximize return on investments and minimize wasting resources. This study focuses on evaluating the impacts and benefits of improved center pivot irrigation distribution uniformity by performing distribution uniformity evaluations pre- and post-retrofit. This study also focused on demonstrating an unmanned aerial vehicle (UAV) to assess the performance of the center pivot irrigation system in two irrigated farmlands. The Coefficient of Uniformity (CU), Distribution Uniformity (DU), and Scheduling Coefficient (SC) were calculated based on the catch can test data. The values were utilized to evaluate water and energy savings from the improved coefficients. The team has found that replacing sprinkler packages increased the CU from 78 to 89 and the DU from 77 to 82, and reduced the SC from 1.3 to 1.2 in Field A. In Field B, replacing sprinkler packages increased the CU from 73 to 91 and the DU from 62 to 84 and reduced the SC from 1.6 to 1.2. The estimated water savings in Field A due to the reduced scheduling coefficient was approximately 151,000 liters/hectare/year, with consideration of the corn and soybean rotation field in Michigan. The estimated water savings in Field B was 608,000 liters/hectare/year. The data from this demonstration study showed the value of distribution uniformity evaluation and retrofit of irrigation systems. This information will encourage farmers and agricultural industries to consider performing more distribution uniformity evaluations, ultimately improving irrigation water use efficiency and supporting sustainable water management in agriculture.展开更多
Center pivot irrigation systems usually apply a relatively uniform amount of water to fields that are often inherently variable, which could lead to significant waste of water and energy. To address this issue, our te...Center pivot irrigation systems usually apply a relatively uniform amount of water to fields that are often inherently variable, which could lead to significant waste of water and energy. To address this issue, our team is now developing an Intelligent Center Pivot (ICP) by integrating sensor-based irrigation scheduling with variable rate irrigation technology. However, before this technology can be applied in commercial production, it is necessary to educate growers about its practicality and potential benefits. The objective of this study was to develop a portable tabletop intelligent center pivot model (ICPDemo) to demonstrate and promote adoption of the ICP technology. This paper describes an ICPDemo constructed in 2014, including the design specifications, electro-mechanical design, control strategy, and performance. The ICPDemo has performed according to design specifications and is successfully being used to demonstrate the benefits and effectiveness of ICP technology for irrigation scheduling.展开更多
Maintaining the homogeneity of soil nitrogen(N)and plant vigor across agricultural fields is a major concern for farmers and agricultural scheme planners,particularly fields that are irrigated through pressurized syst...Maintaining the homogeneity of soil nitrogen(N)and plant vigor across agricultural fields is a major concern for farmers and agricultural scheme planners,particularly fields that are irrigated through pressurized systems,such as center pivots.Therefore,this study was carried out on a 30 hm2 potato field located 650 km south of Riyadh,the capital city of the Kingdom of Saudi Arabia,to investigate the impacts of the center pivot irrigation distribution uniformity on the crop development and the spatial distribution of residual soil N.Irrigation performance test was designed to investigate water application rate and distribution uniformities.The overall water application uniformity coefficients(Cu),determined through Christiansen(Cud)and Heerman(CuH)methods,were determined at 81.29%and 80.64%,respectively.However,the overall water distribution uniformity(Du)was determined at 70%.A considerable variability in the distribution uniformity of irrigation water was observed across the experimental field(a Du value of 67%over the medium spans compared to a Du value of 88%over the inner spans).Results of this study showed a linear correlation between the irrigation water distribution uniformity and the soil N(R^(2)=0.88).On the other hand,the vegetation cover distribution,indicated by the Cumulative Normalized Difference Vegetation Index(CNDVI),was not found to be much responsive to the irrigation distribution uniformity(R^(2)=0.11).A time series of successive NDVI maps extracted throughout the potato crop growth stages showed a consistent trend in the distribution of NDVI across the field,with R2 values that ranged between 0.25-0.73.展开更多
An indoor experiment with a fixed spray plate sprinkler(FSPS) of 36-grooved plate D3000 was conducted to evaluate the discharge-pressure relationship,wetted diameter,effective width,and water application rate in this ...An indoor experiment with a fixed spray plate sprinkler(FSPS) of 36-grooved plate D3000 was conducted to evaluate the discharge-pressure relationship,wetted diameter,effective width,and water application rate in this research.In addition,a field experiment with a center pivot system equipped with the same measured FSPS was carried out to investigate the radial and circular uniformity under different cycle times and settings of the percent-timer.A package of nozzles numbering from #9(1.79 mm) to #33(6.55 mm) was tested with a nozzle elevation of 1.2 m and a 20-psi pressure regulator.The results showed that the wetted diameter and average application rate increased with nozzle size,but the effective wetted width and peak instantaneous application rate had no significant relationship with nozzle size.The simulated application rate of the center pivot system using the measured water distribution data of single FSPS was in good agreement with the measured result,which verified that the improved measurement procedure and modified nozzle sizing equation of the D3000 sprayhead in this paper were correct.Reducing the percent-time cycle time from 60 s to 40 s resulted in a slight increase in the radial uniformity coefficients,with an average of 1.09% to 1.17%,while there was no significant influence on the circular uniformity coefficients.展开更多
Cross-spring pivots, formed by crossing two identical flexural beams at their midpoint, have been broadly used in precision engineering and aerospace fields. Many researches have been conducted on modeling and analysi...Cross-spring pivots, formed by crossing two identical flexural beams at their midpoint, have been broadly used in precision engineering and aerospace fields. Many researches have been conducted on modeling and analysis of cross-spring pivots. However the influence of application position and magnitude of the external loads on the load-rotation and parasitic motion characteristics has not yet been discussed. In order to reveal the effect of the external loads, this paper develops the accurate load-rotation and center shift models of cross-spring pivots, with generalized planar loads applied including bending moment, horizontal and vertical forces. Firstly, by using the energy method, the load-displacement models of the pivot are derived with the assumption of small rotational angles. Based on the models, the influence of generalized planar loads on the load-rotation relationship is discussed, which shows that both application position and magnitude of the vertical and horizontal forces influence the load-rotation behaviors. Then the accurate center shift expressions of the pivot with generalized planar loads are developed, which shows that the rotational angle is the dominant term for both components of the center shift while the vertical and horizontal forces are small. Finally, the accuracy of the proposed model is validated by finite element analysis（FEA）. Comparing the model data with the results obtained from FEA, the relative error of the load-rotation is less than 6% even if the rotational angle reaches 20°; the relative errors of the two components of center shift are less than 5% and 10% respectively when the rotational angle reaches 10°. The proposed model and analytical conclusions can be used to analyze and preliminarily design the compliant mechanisms containing cross-spring pivots.展开更多
基金The research was supported by the National Key Research and Development Program of China(2017YFDO201502)the National Natural Science Foundation of China(51621061 and 51939005)+1 种基金the Science and Technology Open Cooperation Project of Henan Province,China(172106000015)the Open Fund of NationalEngineering Laboratory of Crop Stress Resistance Breeding,China(NELCOF20190104).
文摘In recent years, the use of fertigation technology with center pivot irrigation systems has increased rapidly in the North China Plain (NCP). The combined effects of water and nitrogen application uniformity on the grain yield, water use efficiency (WUE) and nitrogen use efficiency (NUE) have become a research hotspot. In this study, a two-year field experiment was conducted during the winter wheat growing season in 2016–2018 to evaluate the water application uniformity of a center pivot with two low pressure sprinklers (the R3000 sprinklers were installed in the first span, the corresponding treatment was RS;the D3000 sprinklers were installed in the second span, the corresponding treatment was DS) and a P85A impact sprinkler as the end gun (the corresponding treatment was EG), and to analyze its effects on grain yield, WUE and NUE. The results showed that the water application uniformity coefficients of R3000, D3000 and P85A along the radial direction of the pivot (CUH) were 87.5, 79.5 and 65%, respectively. While the uniformity coefficients along the traveling direction of the pivot (CUC) were all higher than 85%. The effects of water application uniformity of the R3000 and D3000 sprinklers on grain yield were not significant (P>0.05);however, the average grain yield of EG was significantly lower (P<0.05) than those of RS and DS, by 9.4 and 11.1% during two growing seasons, respectively. The coefficients of variation (CV) of the grain yield had a negative correlation with the uniformity coefficient. The CV of WUE was more strongly affected by the water application uniformity, compared with the WUE value, among the three treatments. The NUE of RS was higher than those of DS and EG by about 6.1 and 4.8%, respectively, but there were no significant differences in NUE among the three treatments during the two growing seasons. Although the CUH of the D3000 sprinklers was lower than that of the R3000, it had only limited effects on the grain yield, WUE and NUE. However, the cost of D3000 sprinklers is lower than that of R3000 sprinklers. Therefore, the D3000 sprinklers are recommended for winter wheat irrigation and fertigation in the NCP.
基金National Natural Science Foundation of China(41901094)National Natural Science Foundation of China(41930641)Fundamental Research Funds for the Central Universities(GK202103148)。
文摘The Mu Us dune field in China has become a focal region for research of the prevention and control of desertification.Agricultural practices in this area have been modernized in recent years,evidenced by the development of Center Pivot Irrigation(CPI)farmlands.However,the impacts of CPI farmlands on combating desertification remain poorly understood.This study chose the southeastern part of the Mu Us dune field as a study area to investigate the variations of CPI farmlands from 2009 to 2018 and the influencing factors.The results showed growth trends in both the number and the area of these CPI farmland units over the period.The areas of meso-and micro-scale CPI farmland units stabilized over time to mainly 0-0.2 km2 and 0.2-0.4 km2,respectively;Topography,temperature,and geological substratum were preliminarily identified as the major natural factors driving the development of the CPI farmlands.Within the context of varied stakeholders,the potential for soil erosion,and damage to natural vegetation,the current study suggests that strict management of CPI farmland is required through effective long-term planning and land-use policies.The results of this study can assist in realizing the sustainable development of agriculture and its ecological significance in dune field areas.
文摘Agricultural irrigation is a primary user for freshwater withdrawal. Irrigation plays an important role in crop production, as it provides the benefit of reducing the effects of prolonged dryness and erratic precipitation. Center pivot irrigation system is the most common irrigation system in agriculture. As the center pivot irrigation system ages, the system could develop a leaking joint, clogged sprinklers, and physical damage. This can cause areas of non-uniformity that can lead to under- or over-irrigated in some areas of the land, resulting in excess energy use and cost, wasting resources, and environmental impacts. Thus, it is important to evaluate the performance of a center pivot irrigation system regularly to maximize return on investments and minimize wasting resources. This study focuses on evaluating the impacts and benefits of improved center pivot irrigation distribution uniformity by performing distribution uniformity evaluations pre- and post-retrofit. This study also focused on demonstrating an unmanned aerial vehicle (UAV) to assess the performance of the center pivot irrigation system in two irrigated farmlands. The Coefficient of Uniformity (CU), Distribution Uniformity (DU), and Scheduling Coefficient (SC) were calculated based on the catch can test data. The values were utilized to evaluate water and energy savings from the improved coefficients. The team has found that replacing sprinkler packages increased the CU from 78 to 89 and the DU from 77 to 82, and reduced the SC from 1.3 to 1.2 in Field A. In Field B, replacing sprinkler packages increased the CU from 73 to 91 and the DU from 62 to 84 and reduced the SC from 1.6 to 1.2. The estimated water savings in Field A due to the reduced scheduling coefficient was approximately 151,000 liters/hectare/year, with consideration of the corn and soybean rotation field in Michigan. The estimated water savings in Field B was 608,000 liters/hectare/year. The data from this demonstration study showed the value of distribution uniformity evaluation and retrofit of irrigation systems. This information will encourage farmers and agricultural industries to consider performing more distribution uniformity evaluations, ultimately improving irrigation water use efficiency and supporting sustainable water management in agriculture.
文摘Center pivot irrigation systems usually apply a relatively uniform amount of water to fields that are often inherently variable, which could lead to significant waste of water and energy. To address this issue, our team is now developing an Intelligent Center Pivot (ICP) by integrating sensor-based irrigation scheduling with variable rate irrigation technology. However, before this technology can be applied in commercial production, it is necessary to educate growers about its practicality and potential benefits. The objective of this study was to develop a portable tabletop intelligent center pivot model (ICPDemo) to demonstrate and promote adoption of the ICP technology. This paper describes an ICPDemo constructed in 2014, including the design specifications, electro-mechanical design, control strategy, and performance. The ICPDemo has performed according to design specifications and is successfully being used to demonstrate the benefits and effectiveness of ICP technology for irrigation scheduling.
文摘Maintaining the homogeneity of soil nitrogen(N)and plant vigor across agricultural fields is a major concern for farmers and agricultural scheme planners,particularly fields that are irrigated through pressurized systems,such as center pivots.Therefore,this study was carried out on a 30 hm2 potato field located 650 km south of Riyadh,the capital city of the Kingdom of Saudi Arabia,to investigate the impacts of the center pivot irrigation distribution uniformity on the crop development and the spatial distribution of residual soil N.Irrigation performance test was designed to investigate water application rate and distribution uniformities.The overall water application uniformity coefficients(Cu),determined through Christiansen(Cud)and Heerman(CuH)methods,were determined at 81.29%and 80.64%,respectively.However,the overall water distribution uniformity(Du)was determined at 70%.A considerable variability in the distribution uniformity of irrigation water was observed across the experimental field(a Du value of 67%over the medium spans compared to a Du value of 88%over the inner spans).Results of this study showed a linear correlation between the irrigation water distribution uniformity and the soil N(R^(2)=0.88).On the other hand,the vegetation cover distribution,indicated by the Cumulative Normalized Difference Vegetation Index(CNDVI),was not found to be much responsive to the irrigation distribution uniformity(R^(2)=0.11).A time series of successive NDVI maps extracted throughout the potato crop growth stages showed a consistent trend in the distribution of NDVI across the field,with R2 values that ranged between 0.25-0.73.
基金supported by the China Key Technological Special Project of National Tenth Five-Year Plan (Grant No.2002AA2Z4161)Program for Changjiang Scholars and Innovative Research Team in University (Grant No.IRT0657)Program for Beijing Key Subject of Hydrology and Water Resources
文摘An indoor experiment with a fixed spray plate sprinkler(FSPS) of 36-grooved plate D3000 was conducted to evaluate the discharge-pressure relationship,wetted diameter,effective width,and water application rate in this research.In addition,a field experiment with a center pivot system equipped with the same measured FSPS was carried out to investigate the radial and circular uniformity under different cycle times and settings of the percent-timer.A package of nozzles numbering from #9(1.79 mm) to #33(6.55 mm) was tested with a nozzle elevation of 1.2 m and a 20-psi pressure regulator.The results showed that the wetted diameter and average application rate increased with nozzle size,but the effective wetted width and peak instantaneous application rate had no significant relationship with nozzle size.The simulated application rate of the center pivot system using the measured water distribution data of single FSPS was in good agreement with the measured result,which verified that the improved measurement procedure and modified nozzle sizing equation of the D3000 sprayhead in this paper were correct.Reducing the percent-time cycle time from 60 s to 40 s resulted in a slight increase in the radial uniformity coefficients,with an average of 1.09% to 1.17%,while there was no significant influence on the circular uniformity coefficients.
基金supported by National Natural Science Foundation of China(Grant Nos. 50975007, 51105014)PhD Programs Foundation of Ministry of Education of China(Grant No. 20091102110023)China Postdoctoral Science Foundation(Grant No. 20100480179)
文摘Cross-spring pivots, formed by crossing two identical flexural beams at their midpoint, have been broadly used in precision engineering and aerospace fields. Many researches have been conducted on modeling and analysis of cross-spring pivots. However the influence of application position and magnitude of the external loads on the load-rotation and parasitic motion characteristics has not yet been discussed. In order to reveal the effect of the external loads, this paper develops the accurate load-rotation and center shift models of cross-spring pivots, with generalized planar loads applied including bending moment, horizontal and vertical forces. Firstly, by using the energy method, the load-displacement models of the pivot are derived with the assumption of small rotational angles. Based on the models, the influence of generalized planar loads on the load-rotation relationship is discussed, which shows that both application position and magnitude of the vertical and horizontal forces influence the load-rotation behaviors. Then the accurate center shift expressions of the pivot with generalized planar loads are developed, which shows that the rotational angle is the dominant term for both components of the center shift while the vertical and horizontal forces are small. Finally, the accuracy of the proposed model is validated by finite element analysis（FEA）. Comparing the model data with the results obtained from FEA, the relative error of the load-rotation is less than 6% even if the rotational angle reaches 20°; the relative errors of the two components of center shift are less than 5% and 10% respectively when the rotational angle reaches 10°. The proposed model and analytical conclusions can be used to analyze and preliminarily design the compliant mechanisms containing cross-spring pivots.
