Current Research
Briefs

 

Project Description and Benefits: Areas within a field can require different quantities of irrigation due to variations in soil texture, depth of soil, and the effect of topography on rainfall runoff (lower elevations benefiting, or suffering, from runoff from higher elevations). Also, water wells in the Texas High Plains typically lack the capacity to fully meet the evapotranspiration demand of most crops. Therefore, the non-uniform distribution of irrigation (variable-rate irrigation or VR) based on topography and water holding capacity of the soil profile could better utilize both rainfall and irrigation water and improve water use efficiencies. Also, crops could benefit by changing irrigation amounts at points along a pivot lateral as the relationships among soil chemical properties, pest infestations, production inputs, and crop yields are determined. For example, disease or insect pests associated with excess water can reduce yields at identifiable locations in a field. A reduction in irrigation at these sites may reduce these pests, thereby maintaining an economic yield with little or no chemical treatment, prevent the spread of the pest into non-infected areas, and reduce water requirements.   Construction of a site-specific irrigator will help determine the potential for improving production efficiencies using precision agriculture.

Accomplishments: A standard 1360-ft center pivot was delivered to the Helms research site in March 2000. A VR LEPA application system has been constructed on the distal 480 feet of the pivot lateral (Spans 6, 7, and 8). The VR irrigator is composed of: a water delivery network including valves,pressure regulators, pipes, nozzles and irrigation applicators a programmable control system that can change flow rates along the pivot lateral as frequently as every three degrees (70 feet) around the 360o pivot circumference a pressure control system at the water source that regulates pressure in pipelines and pivot as the total irrigation volume changes with time. The largest control area will be less then 0.1 acre resulting in over 2000 water/chemical control areas under this 133-acre pivot at completion. Irrigation amounts ranging from 40 to 140% of the base irrigation rate can be applied in each control area. These amounts can be changed with newly developed software as needs dictate.   Plans and Goals: We will complete construction of the first 480-foot section of the VR irrigator and initiate field tests in the spring of 2001. Additional sections will be built in the future. An experiment comparing production efficiencies of site-specific versus conventionally irrigated corn will be conducted beginning the summer of 2001. Options that may improve equipment performance will be investigated and methods to incorporate low-volume chemigation will be explored.