Evapotranspiration and drought responses in nursery chestnut (Castanea spp.): a first assessment of cultivar-specific crop and stress coefficients

Plants water uptake ability and soil water availability are a key determinant of growth, physiological functioning and survival of young woody plants, particularly under nursery conditions. For species such as Castanea spp. the ability to manage irrigation precisely and assess cultivar drought tolerance are increasingly important under the pressures of climate change and water scarcity. Two years old plants of two Euro-Japanese chestnut cultivars ( C. crenata × C. sativa ), CA07 (‘Marsol’) and CA74 (‘Maraval’), were subjected for 20 days to three irrigation regimes: 100% (CT), 60% (MT) and 30% (ST) of relative soil water content. Several morpho-physiological parameters were monitored during the experiment and evapotranspiration models were obtained at hourly and daily time scale. CA07 seemed to have a greater tolerance to drought in the medium term, showing smaller reductions in height growth (−67% vs −73%), stomatal conductance (−89% vs −90%), leaf chlorophyll content index (−9.1% vs −9.9%) and evapotranspiration under severe water stress (CA07 vs CA74, ST treatment relative to the control at the end of the experiment); however, CA07 also exhibited a marked depletion of leaf soluble sugar content (−65% vs −22%). Evapotranspiration modelling allowed to study how chestnut plants regulate water loss throughout the day. Moreover, crop coefficients and stress coefficients were estimated for the first time in Castanea spp. These results could contribute to setting up more efficient irrigation, rationally managing water stress levels during periods of drought, and better help growers in the choice of varieties according to the environmental conditions expected in the orchard.