Response of fruit yield, fruit quality, and water productivity to different irrigation levels for a microsprinkler-irrigated apple orchard (cv. Fuji) growing under Mediterranean conditions

Irrigation management strategies based on soil-plant-climate interactions are the key to improving water productivity and maintaining optimum yield and quality for apple orchards growing under Mediterranean conditions where water availability for irrigation is significantly decreasing. Thus, an experiment was carried out to investigate the effect of different irrigation levels on the yield, fruit quality, and water status of microsprinkler-irrigated apple trees (Malus domestica 'Fuji') located in a Mediterranean region in the central part of Chile. Four irrigation treatments were applied to a commercial orchard during the 2011/12 and 2013/14 growing seasons as follows: 125%, 100%, 75%, and 50% of actual evapotranspiration (ETa). Fruit yield (Y), crop load (fruits per tree, FP), fruit size (fruit weight (FW) and fruit diameter (FD)), fruit quality (firmness (FF), contents of soluble solids (SS), and starch (ST)), water productivity (WP), midday stem water potential (psi(stem)), and water stress integral (WSI) were measured in each growing season. The results indicate that trees at 125% and 100% ETa reached an average psi(stem) near -1.0 MPa, whereas trees at 75% and 50% ETa reached psi(stem) similar to -1.5 MPa. With the exception of FP, irrigation treatment had significant effects on Y, FW, FD, FF, SS, ST and WP. In this regard, the apple trees irrigated at 50% ETa produced fruits with the highest SS, FF, and WP, but the Y and fruit size (FW and FD) were significantly reduced because of severe water stress (average psi(stem) ranged from -1.35 to-1.88 MPa). Apple trees with the 100% and 125% ETa treatments produced higher Y, FW, and FD than those with the 75% ETa treatment. In addition, the irrigation amount for apple trees irrigated at 125% ETa was 15% greater than for those irrigated at 100% ETa, but the yield and fruit quality were similar in both treatments. Finally, this study suggested that irrigation scheduling based on 100% ETa and psi(stem) closed to -1.5 MPa could be a suitable strategy for microsprinkler-irrigated apple (cv. Fuji) orchards growing in Mediterranean climate areas.

Automated summary

Irrigation management strategies based on soil-plant-climate interactions are crucial for improving water productivity and maintaining optimum yield and quality for apple trees grown under Mediterranean conditions. The experiment showed that different irrigation levels had significant effects on fruit yield, quality, and water status. Apple trees irrigated at 50% ETa produced fruits with the highest soluble solids, firmness, and water productivity, but had lower yield and fruit size due to severe water stress. Irrigation scheduling based on 100% ETa and stem water potential of approximately -1.5 MPa may be suitable for microsprinkler-irrigated apple orchards in Mediterranean climate areas.