Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/30/2005
Publication Date: 11/1/2005
Citation: Sadler, E.J., Evans, R.G., Stone, K.C., Camp Jr, C.R. 2005. Opportunities for conservation with precision irrigation. Journal of Soil and Water Conservation. 60(6):371-379. Interpretive Summary: While precision agriculture has mostly emphasized variable-rate nutrients, seeding, and pesticide application, several groups have studied variable-rate irrigation to see if managing irrigation amount differently in different places in a field could have potential for economic or environmental benefits. So far, the research has proven that the equipment can be built to do precision irrigation, but economics are not favorable under current prices and costs. However, with increased attention to water shortages, conservation has become a higher priority than before. This paper explores the potential for saving irrigation water, both in a general discussion and in some specific examples. Where amounts of water that can be saved can be estimated, it appears that from 10-15% of the irrigation water can be conserved, on average, with individual years being outside that range. The general discussion and the specific examples suggest that the opportunity exists for water conservation using precision irrigation and that this should be explored for a representative range of conditions.
Technical Abstract: Precision agriculture has mostly emphasized variable-rate nutrients, seeding, and pesticide application. At several research sites, variable-rate irrigation equipment has been developed to explore the potential for managing irrigation spatially. The modifications to commercial machines are relatively straightforward, but costly. Economic analyses have not been positive at current grain price: water cost ratios. However, with increased attention to conservation of water during drought or with increased contention for environmental, recreational, municipal, and industry use, conclusions regarding profitability may change. Regulatory constraints may shift decisions about variable-rate irrigation as well. The objectives of this paper are to 1) define and describe site-specific irrigation, 2) discuss the opportunities for conservation using site-specific irrigation, and 3) present case studies where quantitative results have been obtained. One of these, a 3-year experiment using a site-specific center pivot explored spatially varying irrigation production functions for corn. These equations allow computation of the irrigation water use at both maximum yield and maximum profit, and by difference, the potential savings. Results from this study and other case studies provide estimates of the potential for water conservation using precision irrigation that range from marginal to nearly 50% in single-year cases and average from 8-20%, depending on the previous irrigation management strategy employed.