Irrigation of apples in a humid climate in wet and dry years

Irrigation field experiments were conducted from 2015 to 2017 at 2 locations in southern New York State (Hudson) and western New York State (Geneva), USA. At each site we managed irrigation quantity using a modified Penman-Monteith transpiration model (Cornell apple irrigation model) We assessed tree growth and tree stress, and crop yield, fruit size with irrigation and no irrigation.
In 2015 at Geneva the cumulative water balance showed that water supply from rainfall was sufficient to meet water requirement by the tree for the whole season, whereas at Hudson, water requirement exceeded supply from rain from August through October.
In 2016 both at Geneva and at Hudson, water balance showed that water requirement exceeded supply from rain from June through October.
In 2017 both at Geneva and Hudson, water supply from rainfall was sufficient to meet water requirement by the tree for the whole season, with the highest cumulative rainfall values of the last three years.
At Geneva we did not detect differences in stem water potential between irrigated and non-irrigated trees in 2015 or 2017 but significant differences were observed in 2016 while at Hudson there were significant differences all three years.
We consider that tree stress starts with stem water potential decreases below about -1.6 MPa.
Trees at Geneva did not reach this stress level in any of the three years of the study but at Hudson they reached this level in two of the three years.
As a consequence, fruit size was not affected by lack of irrigation at Geneva in any of the 3 years but was reduced at Hudson in each of the three years.

IX International Symposium on Irrigation of Horticultural Crops

T.L. Robinson, J. Lordan, P. Francescatto

Malus × domestica, transpiration, water supply, stem water potential, yield, fruit size

https://doi.org/10.17660/ActaHortic.2022.1335.59