Canopy conductance of hazelnut orchards appeared insensitive to irrigation regimes
The hazelnut (Corylus avellana L., ‘Tonda Gentile delle Langhe’ (TGL)) remains one of the most appreciated nut trees by the food industry. Its production has been expanded world-wide to allow extensive plantations. Still TGL is known to be highly sensitive to climate outside of Piemonte, Italy. Its moisture sensitivity is expressed as a rigid stomata behavior with stomata closing in the early morning at a vapor pressure deficit of the atmosphere (VPD) of 10 hPa. We hypothesized that because of its sensitivity to VPD, TGL would have a limited benefit from increasing the irrigation regime because of the small impact in the total canopy conductance and on carbon assimilation and yield. We monitored six TGL hazelnut trees during two growing seasons in San Sebastian, Chile. We measured climatic parameters, sap flow, and soil water content in two irrigation treatments, T100 (standard irrigation) and T200 (doubled irrigation). Our result showed that the response of sap flow to VPD remained consistent in the two treatments. The sap flow density in T200 was significantly higher than T100, but the diurnal canopy conductance was >17% in T200 respect to T100 only in a restricted interval of VPD, i.e., 4-12 hPa around a peak of 7 hPa. Our results suggested that doubled irrigation caused an increase in canopy conductance only in few climatic circumstances. These results suggest that benefits from increased irrigation occur only at low VPD. In such conditions, stomata are more prone to gas exchanges and carbon sequestration, a proxy for crop yield.
Gaia Pasqualotto won an ISHS Young Minds Award for the best poster at the IX International Symposium on Irrigation of Horticultural Crops in Italy in June 2019.
Gaia Pasqualotto, Università degli Studi di Padova, Dept. TESAF, viale dell'università 16, 35020 Legnaro, PD, Italy, e-mail: email@example.com
The article is available in Chronica Horticulturae