Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/30/2000
Publication Date: N/A
Interpretive Summary: Precision crop management potentially can greatly improve irrigation management and water use efficiencies. It is presently used in rain-fed agriculture and with sprinkler irrigation systems capable of applying different amounts of water and chemicals to separate areas within an irrigated field. This work examines how precision crop management concepts might be applied to surface irrigation. Field experiments on a surface- irrigated field were performed. Findings showed that yield differences within the field were strongly influenced by irrigation water application uniformity. To reduce the influence of water uniformity on yields, surface irrigation systems need to be designed as separate management zones within the field. Managing smaller, individual irrigation sets, rather than broadly managing the total field should provide overall improvement for surface irrigation. This information is important to irrigation system design engineers ,irrigation consultants, and farmers for understanding ho precision management can improve the overall performance of surface irrigation systems. Those who benefit from this research are irrigation designers, irrigation consultants and farmers.
Technical Abstract: For surface irrigation, it is difficult to manage inputs at extremely fine scales. However, site-specific management on the scale of an irrigation set can potentially provide improvements in overall management compared to irrigating areas on the order of hundreds of hectares. The purpose of this work is to examine the precision farming concept as it might be applied to surface irrigation and to determine associated limitations and research needs. Cotton experiments were conducted on a level basin irrigation field in 1987, 1988, and 1994 in Arizona. Various soil and water parameters were evaluated for their contribution to the cotton yield variability using GIS software and other statistical methods. Spatial variations in yield were not well correlated between years. Less than 25% of the variation was explained between any of the years. None of the correlations between yield variability and the parameters elevation, sand content, and field capacity were significant in a consistent manner. Distribution uniformity (DU), which is a measure of the variability of the water application, was highest in 1987 and lowest in 1988. The variability of yield was lowest in 1987, which corresponded with the best irrigation uniformity. Producers may need to rethink the way in which they manage individual irrigation sets and border sizes to eliminate DU as a factor in yield variability. If capital investment or physical limitations prevent improvement of DU, then the expected water distribution pattern should be considered in defining management zones.