The effect of irrigation on chestnut physiology and production (Castanea sativa)

This study aims to evaluate the influence of irrigation on the chestnutRSQUOs physiology, nut calibre and yield. The study was carried out during 2015 and 2016, in a chestnut orchard of the 'Judia' cultivar, located in Braganca in the northeast of Portugal. Two irrigation systems were installed in 10 trees each: drip (TI) and micro-sprinkler (SI). Irrigation was triggered when stem water potential fell below -1.2 MPa. Ten other sample trees were kept in rainfed conditions (NI). From June to October the stem water potential, chlorophyll fluorescence, photosynthetic and transpiration rates were monitored and production per tree was weighted. The total mean amount of water furnished was of 470 and 925 m3 ha-1 in 2015 and 2016, respectively. On both years the photosynthetic and transpiration rates were higher for irrigated trees (8.6 µmol CO2 m-2 s-1 and 1.9 mmol H2O m-2 s-1) than for non-irrigated ones (7.6 µmol CO2 m-2 s-1 and 1.8 mmol H2O m-2 s-1). Chestnut production was 26% higher for irrigated trees with 48.2 kg tree-1 and nut size was smaller in non-irrigated trees (93 nuts kg-1) than for the irrigated ones (75 nuts kg-1). Despite of these differences the climatic conditions, particularly the hotter temperatures in 2016, affected production and nut size. From 2015 to 2016 production decreased 16, 27 and 33% for SI, TI and NI, respectively. Nut size also decreased 90, 45 and 24% for NI, TI and SI, respectively, when the temperature sum (May-October) varied from 2348 to 2504°D. The introduction of irrigation in the chestnut orchard is beneficial but temperature plays an important role in the tree physiology and production.