Water stress for a long period before harvest and crop load effects on marketable yield and consumer acceptance of nectarine

摘要

Under water shortage growers may need to adjust horticultural practices to optimize yield and fruit quality. This study explores the reduction of crop load as a technique to mitigate water stress considering marketable yield and consumer acceptance as the most relevant traits. Commercial irrigation (CI) and deficit irrigation (DI) for a long period before harvest was applied to a late-maturing nectarine ('Nectalady') in 2011 and 2012. In both years, midday stem water potential (midday SWP) in CI trees was around - 0.85 MPa while in DI trees the values ranged between -1.50 and -1.80 MPa. In the experiment, CI and DI were combined with three crop loads: low crop load (LCL, 85 fruits/tree) in 2011, and medium crop load (MCL, 150 fruits/tree) and commercial crop load (CCL, 230 fruits/tree) in 2012. Under CCL and MCL conditions, DI reduced marketable yield due to a significant reduction of the number of fruits that can be commercialize (fruit size higher than 65 mm). DI combined with LCL slightly reduced fruit size but not marketable yield. Reducing crop load by 60% (from 230 to 85 fruits/tree) maintained fruit size to the standard of marketable yield despite the water stress. Fruit thinning did not affect consumer acceptance of fruit, but it was slightly increased under DI in the first pick each year. The benefit of DI on consumer acceptance may have been observed because trees did not experienced midday SWP below -1.80 MPa for the extended period of water shortage (35 and 53 days in 2011 and 2012, respectively). For the levels of midday SWP experienced in this study (1.50 to -1.80 MPa), marketable yield was more sensitive to water stress than consumer acceptance. Consequently, growers do not need to worry about fruit quality, but crop load adjustments should be done to maintain marketable yield.