Adoption and adaptation of scientific irrigation scheduling: trends from Washington, USA as of 1998

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Scientific irrigation scheduling (SIS) is defined as the use of crop evapotranspiration data and soil moisture sensors to accurately determine when and how much to irrigate. Three surveys were conducted during 1997 and 1998 to determine the status of and direction for SIS in Washington. According to the survey results, nine private consultants were contracted to perform irrigation scheduling on nearly 120,000 ha per year. Conservation districts, county extension, and the national resource conservation service assisted producers in scheduling irrigation on an additional 6000 ha in a year. Two-hundred and four producers reported scheduling 26,750 ha of irrigation on their own and 6000 ha with consultants. At a minimum, the combined acreage reported in these surveys indicates an 18% adoption rate of SIS. However, the actual adoption rate is much greater if the self-implementation rate for the 200 producers is representative of the entire state. Survey results also indicated that potatoes and tree fruit account for more than half of the acreage being scheduled. The main reason producers were willing to pay for irrigation scheduling is to insure the quality of high-value crops. Energy savings became important when water needed to be lifted a considerable distance; however, water conservation, high yield, fertilizer savings, and non-point pollution reduction were considered secondary benefits. Center-pivots were the most likely irrigation systems to be scheduled and a considerable proportion of drip and solid-set sprinklers were scheduled, but a very small proportion of furrow systems and set-move sprinklers were scheduled. Over 75% of the survey respondents have personal computers and 50% have modems but less than 5% are using their computers to schedule irrigation. However, when examining the group producers who irrigate more than 405 ha, 33% are using their computers to schedule irrigation. Since computers and communication technology are available “on-farm”, and producers are showing a willingness to implement SIS on their own, Washington State University (WSU) has developed the Washington Irrigation Scheduling Expert (WISE) software and a web-based information system. Self-implemented SIS also requires increased producer knowledge along with training for potential vendors. Therefore, WSU is continuing traditional SIS educational efforts such as on-farm testing of soil moisture sensors, workshops, field days, publications and newsletters. Conversely, WSU has stopped providing full-service SIS demonstrations that compete with existing services, require intensive labor, and affect a limited number of producers. Agri-business is employing a similar strategy as self-service SIS providers have increased by seven companies since the 1998 survey.