a b s t r a c tEffective and adapted criteria for irrigation scheduling are required to improve yield and water use efficiency (WUE) and reduce the environmental impacts associated with water and nutrients losses by runoff and leaching. In this study, field-scale experiments were conducted at four commercial strawberry production sites with contrasting soil and climatic conditions. Within each site, the influence of different soil matric potential-based irrigation thresholds (IT) on yield and WUE was evaluated. Matric potentialbased irrigation management was also compared with common irrigation practices used by producers in each site's respective areas. At Site 1 (silty clay loam; humid continental (Dfb) climate), an IT of −15 kPa improved yields by 6.2% without any additional use of water relative to common irrigation practices. At Site 2, with similar soil and climatic conditions, the irrigation treatments did not affect yield and the matric potential-based management decreased WUE relative to common practices. However, the results suggested that maintaining the soil matric potential lower than −9 kPa could induce stressing conditions for the plants. At Site 3 (sandy loam; Mediterranean (Cs) climate), the best yield and WUE were obtained with an IT of −8 kPa and suggested that WUE could be further improved by implementing high-frequency irrigation. At Site 4 (clay loam; Mediterranean (Cs) climate), results suggested that an IT between −10 and −15 kPa could optimize yield and WUE, and matric potential-based irrigation considerably reduced leaching under the root zone relative to common practices. Considering the results from all sites, an IT of −10 kPa appears to be adequate as a starting point for further optimizing irrigation under most field conditions.

Understanding latitudinal adaptation of switchgrass (Panicum virgatum L.) and Miscanthus (Miscanthus× giganteus J. M. Greef & Deuter ex Hodk. & Renvoize) to the southern Great Plains is key to maximizing productivity by matching each grass variety to its optimal production environment. The objectives of this study were: (1) to quantify latitudinal variation in production of representative upland switchgrass ecotypes (Blackwell, Cave-in-Rock, and Shawnee), lowland switchgrass ecotypes (Alamo, Kanlow), and Miscanthus in the southern half of the US Great Plains and (2) to investigate the environmental factors affecting yield variation. Leaf area and yield were measured on plots at 10 locations in Missouri, Arkansas, Oklahoma, and Texas. More cold winter days led to decreased subsequent Alamo switchgrass yields and increased subsequent upland switchgrass yields. More hot-growing season days led to decreased Kanlow and Miscanthus yields. Increased drought intensity also contributed to decreased Miscanthus yields. Alamo Electronic supplementary material The online version of this article

Although California is experiencing permanent water deficits compensated by irrigation, the state accounts for more than 90% of total strawberry production in the United States. There is a critical need to optimize yield and crop water productivity (CWP), as influenced by irrigation management. Although studies have reported that irrigation management based on soil matric potential (ѱ) has the potential to increase yield and CWP compared to conventional practices, the cost of this technology may be a limiting factor for some growers. In this study, we assessed the cost-effectiveness of wireless tensiometer technology (WTT) for field-grown strawberries in California in comparison with the conventional irrigation management. As a second step, we evaluated the costeffectiveness of deficit irrigation. Using data from eight sites, we calculated multiple linear regressions (MLR) to describe the relationship between: (1) fresh market yield and average soil matric potential reached before irrigation initiation (ѱ irr) and (2) water use and ѱ irr. Based on MLR results, we evaluated the technical performance of each irrigation management method and conducted an economic analysis. Our results showed that adopting a precise irrigation scheduling tool such as WTT is cost-effective and leads to water savings relative to conventional irrigation. Our results also revealed that any water savings associated with a deficit irrigation strategy are costly for strawberry growers.

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