Precision overhead irrigation is suitable for several Central Valley crops

Abstract

Overhead systems are the dominant irrigation technology in many parts of the world, but they are not widely used in California even though they have higher water application efficiency than furrow irrigation systems and lower labor requirements than drip systems. With water and labor perennial concerns in California, the suitability of overhead systems merits consideration. From 2008 through 2013, in studies near Five Points, California, we evaluated overhead irrigation for wheat, corn, cotton, tomato, onion and broccoli as an alternative to furrow and drip irrigation. With the exception of tomato, equal or increased yields were achieved with overhead irrigation. Many variables are involved in the choice of an irrigation system, but our results suggest that, with more research to support best management practices, overhead irrigation may be useful to a wider set of California farmers than currently use it.A 1976 Scientific American article called center-pivot irrigation "perhaps the most significant mechanical innovation in agriculture since the replacement of draft animals by the tractor" (Splinter 1976). Patented in 1952 by Frank Zybach, a farmer in eastern Colorado, center-pivot systems are automated, precision irrigation water application machines typically made up of seven or eight connected pipes with drop hoses and sprinkler nozzles that rotate in a line around a pivot point. Linear move systems are similar but apply irrigation water in a straight line across a field. Together, center-pivot and linear move systems are known as overhead, or mechanized, irrigation systems and are the most prevalent form of irrigation system in the United States (NASS 2013). They account for the irrigation of 50.4% of total U.S. irrigated acreage.In Nebraska, the state with the highest crop acreage under irrigation, 70,000 overhead systems are used on more than 7.2 million acres -87% of the state's total irrigated land -and the remaining gravity irrigation systems are being rapidly replaced by overhead systems because of overhead systems' superior application precision and yield benefits (Pfeifer and Line 2009). In California, by contrast, roughly 350 overhead systems irrigate about 150,000 acres, just 2% of the state's total irrigated acreage. Technology adoptionSeveral factors may have contributed to the slow rate of adoption of overhead irrigation in California.First, difficulties encountered by early adopters of the technology led to overhead systems gaining an undeserved reputation for being unable to keep up with California's high crop evapotranspiration demands, losing unacceptably large amounts of water to evaporation, and being prone to getting stuck in muddy fields. While successful installations of center-pivot systems in recent years show that the technology can in fact work well in California, these negative perceptions persist.Incomplete coverage by center-pivot systems is another issue. With a standard center-pivot system, roughly 20%, or 33 acres, of a typical 160-acre (quarter section) field is unirrigated. ...

The Policy Enabling Environment for Climate Smart Agriculture: A Case Study of California

“…With California's dry climate, fast-growing population, and relatively strong policies to protect ecosystems and the environment, agriculture's competition for water is increasingly strained. Agriculture remains the largest single-sector water user (Hanak et al, 2016), even though California's farms have continually improved in water use efficiency over the past five decades (Mitchell et al, 2016). Relevant to water management, predicted climate changes for the state include warming temperatures-which will increase crop-water demands, earlier snowmelt, increasing frequency and severity of extreme weather events (e.g., storms, floods, droughts), and sea level rise, which may contribute to saltwater intrusion into freshwater resources and salinization of low elevation lands in the Central Valley (Weare, 2009;Marston and Konar, 2017); (Pathak et al, 2018).…”

Modelling impacts of precision irrigation on crop yield and in-field water management

“…Various authors have recently investigated the potential for PI in outdoor agriculture based on field experimentation (García Morillo et al 2015;Haghverdi et al 2016;Mitchell et al 2016). In this study, an integrated modelling approach involving the coupling of a deterministic water/irrigation application model (WAM) with a biophysical crop model (Aquacrop) ) was developed and used to simulate the impacts of irrigation heterogeneity caused, for example, due to wind drift, irrigation system pressure variation and/or sprinkler overlapping on crop growth and yield at the field scale.…”