Irrigation management based on soil matric potential improves water use efficiency of field-grown strawberries in California

Abstract

Faced with climate change and the intensification of crop production, water is expected to be increasingly in demand worldwide. Focus is now on increasing water use efficiency (WUE) of crops as influenced by irrigation management practices. Common methods for irrigation scheduling in open-field strawberry production are based on the estimation of crop evapotranspiration (ET) and on soil moisture measurements. Although studies have reported that tension (ѱ)-based irrigation management presented a good potential of optimizing WUE, the capacity of this method to improve WUE has not always been clearly demonstrated. This study aimed at comparing WUE of two irrigation management methods, the conventional and the ѱ-based approaches, in strawberry crop in California. Conventional irrigation treatments included both the standard grower procedure and managements based on evapotranspiration (ET) of the crop (50, 75 and 100% ET). Irrigation management based on tension measurements used irrigation thresholds that varied from -8 to -35 kPa. Multiple linear regressions determined using data from 5 growing seasons and 8 sites in field strawberry production in California and describing relationships between (1) marketable yield and ѱ achieved before irrigations and (2) water use (WU) and ѱ at irrigation initiation, considering the management method, were used. WUE was calculated as the ratio of predicted marketable yield by predicted WU values at specific ѱ thresholds deduced from the regression lines. A cost-benefit analysis was also conducted to assess the economic effectiveness of increasing WUE based on a deficit irrigation strategy. Results show that tension-based irrigation management improves WUE compared to conventional irrigation management. For a same amount of water used, WUE is increased by 7.5 to 8.3%. For a same average ѱ threshold achieved before irrigations, tension-based irrigation management improves WUE from 33 to 93% compared to conventional practices. This study demonstrates that (1) tension-based irrigation management improves WUE in strawberry crop in California, regardless of the production region and soil type, and that (2) water savings associated with deficit irrigation strategies generate little benefits compared to yield losses associated with such a practice.