Trickle Irrigation Requirements for Strawberries in Coastal California

Controlled trickle irrigation applications in commercial strawberry [ Fragaria xananassa Duch. ‘Heidi’] plantings in coastal California were used to estimate crop coefficients (K c ) relating applied water requirements to reference evapotranspiration (ET o ) and Class A pan evaporation (E pan ). The value of K c increased with foliar growth during spring and leveled off at a relatively constant maximum through summer and early autumn. Since rates of ET o averaged 13% higher than E pan , lower K c values were recommended for irrigation schedules based on ET o than for schedules based on E pan . The value of maximum K c for ET o scheduling was fixed between 0.45 ≤ K c ≤ 0.7, whereas the limits for E pan scheduling were 0.55 ≤ K c ≤ 0.8. Upper K c limits were established by scheduling small volume irrigations only as necessary to maintain favorable soil moisture conditions. Harvest results and soil matric potential measurements indicated that irrigations scheduled at the lower K c limits could lead to production loss. An evaluation of grower irrigation practices showed that current applied water rates could be reduced significantly by scheduling irrigations with recommended K c values.