Abstract
Monitoring plant water status is relevant for the sustainable management ofirrigation under water deficit conditions. Two treatments were applied to an early-maturingnectarine orchard: control (well irrigated) and precise deficit irrigation (PDI, based on soilwater content thresholds). Moderate water deficits generated by PDI were assessed bycomparing terrestrial: stem water potential (Ψstem) and gas exchange parameters, with remote:canopy temperature, normalized difference vegetation (NDVI), and soil adjusted vegetationindex (SAVI), plant water status indicators. The Ψstem was the only indicator that showedsignificant differences between treatments. NDVI and SAVI at the postharvest period wereappropriate indexes for estimating winter pruning, although they did not serve well as plantstress indicator. Vapor pressure deficit along with Ψstem values were able to predict remotesensing data. Ψstem and canopy to air temperature difference values registered the highestsignal intensity and NDVI the highest sensitivity for detecting water deficit situations. Theresults suggest that care should be taken when using instantaneous remote indicators toevaluate moderate water deficits in deciduous fruit trees; more severe/longer water stressconditions are probably needed. The proposed PDI strategy promoted water saving whilemaintaining yield, and could be considered a promising tool for semi-arid agrosystems.
Highlights
Efficient irrigation of horticultural crops using technologies that enable the better husbandry of scarce freshwater resources has been increasingly studied in recent years, because irrigated agriculture is the largest user of freshwater worldwide [1]
The annual amounts of water applied in the growing season (2017/2018), measured by the in-line water meters were 420.4 mm and 251.6 mm for the control and precise deficit irrigation (PDI) treatments, respectively, meaning that the soil deficit imposed in the PDI treatment represented a mean water reduction of about 40%
The current work showed that in early-maturing nectarine trees submitted to moderate deficit irrigation, Ψstem is a valuable robust indicator for detecting water stress; it needs to be considered together with Vapor pressure deficit (VPD) for comparison with remote sensing data to reveal spatial patterns of water stress
Summary
Efficient irrigation of horticultural crops using technologies that enable the better husbandry of scarce freshwater resources has been increasingly studied in recent years, because irrigated agriculture is the largest user (up to 70%) of freshwater worldwide [1]. Peach and nectarine trees have high irrigation requirements, especially during dry and hot seasons [4,5], when irrigated orchards are frequently subjected to drastic reductions in the water supply. This situation is aggravated in early-maturing cultivars with their high water needs during the summer postharvest interval [6,7]. To optimize water use and save water, deficit irrigation (DI) practices can be used since they minimize any impact on fruit yield and quality, while reducing excessive vegetative growth [2,8]
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