Development of a Portable Electro-Mechanical Educational Model for Variable Rate Center Pivot Irrigation Technology

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.

Non-negligible factors in low-pressure sprinkler irrigation:droplet impact angle and shear stress

Droplet shear stress is considered as an important indicator that reflects soil erosion in sprinkler irrigation more accurately than kinetic energy,and the effect of droplet impact angle on the shear stress cannot be ignored.In this study,radial distribution of droplet impact angles,velocities,and shear stresses were investigated using a two-dimensional video disdrometer with three types of low-pressure sprinkler(Nelson D3000,R3000,and Komet KPT)under two operating pressures(103 and 138 kPa)and three nozzle diameters(3.97,5.95,and 7.94 mm).Furthermore,the relationships among these characteristical parameters of droplet were analyzed,and their influencing factors were comprehensively evaluated.For various types of sprinkler,operating pressures,and nozzle diameters,the smaller impact angles and larger velocities of droplets were found to occur closer to the sprinkler,resulting in relatively low droplet shear stresses.The increase in distance from the sprinkler caused the droplet impact angle to decrease and velocity to increase,which contributed to a significant increase in the shear stress that reached the peak value at the end of the jet.Therefore,the end of the jet was the most prone to soil erosion in the radial direction,and the soil erosion in sprinkler irrigation could not only be attributed to the droplet kinetic energy,but also needed to be combined with the analysis of its shear stress.Through comparing the radial distributions of average droplet shear stresses among the three types of sprinklers,D3000 exhibited the largest value(26.94-3313.51 N/m^(2)),followed by R3000(33.34-2650.80 N/m^(2)),and KPT(16.15-2485.69 N/m^(2)).From the perspective of minimizing the risk of soil erosion,KPT sprinkler was more suitable for low-pressure sprinkler irrigation than D3000 and R3000 sprinklers.In addition to selecting the appropriate sprinkler type to reduce the droplet shear stress,a suitable sprinkler spacing could also provide acceptable results,because the distance from the sprinkler exhibited a highly significant(P<0.01)effect on the shear stress.This study results provide a new reference for the design of low-pressure sprinkler irrigation system.

2009—2018年毛乌素沙地圆形农田发展及其对土地规划的启示

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.