Effects of preharvest drip-irrigation scheduling on strawberry yield, quality and growth
Strawberry (Fragaria x ananassa Duch) cultivars, Oso Grande and Camarosa were grown in the field from July 1999 to May 2000 in order to investigate the effectiveness of preharvest drip-irrigation management on fruit yield, quality (i.e. soluble dry matter, fruit size), leaf macro-nutrient composition and normal growth parameters. All plots were irrigated uniformly until 2 weeks before harvest. Differential treatments were then imposed ranging from a complete cut-off of irrigation to full irrigation through the harvest period. Preharvest drip-irrigation management treatments were (i) complete irrigation cut-off, dry (D), (ii) normal irrigation based on class A pan and percentage cover (C), (iii) 75% of normal irrigation, C (IR1), (iv) 50% of normal irrigation, C (IR2), and (v) 25% of normal irrigation, C (IR3). Normal irrigation (control, C) was created by irrigating plants once every 2 days at 100% A pan (Epan) evaporation. No irrigation (D) and IR3 treatments caused reductions in most parameters measured, except water-soluble dry matter concentrations (SDM) in fruit compared with other treatments. There were no significant differences between C, IR1, and IR2 treatments in normal growth parameters or leaf nutrient composition. Fruit size and SDM were both significantly affected by late-season irrigation management; individual fruit weight was significantly reduced and SDM increased even in the IR2 and IR3 treatments compared with control values. Fruit yield was not affected significantly by reduced water application except in the D treatment. These results clearly indicate that reduced preharvest irrigation was partially detrimental; a small reduction in irrigation (IR1) had little or no effect but 50% or less of normal irrigation, while not reducing overall fruit yield, resulted in smaller fruits.