Irrigation of pistachio in Italy: Ten years of observation

In Basilicata, Italy an experiment has been carried out to determine the long term effects of various irrigation regimes on pistachio trees. The experimental field was planted in 1987 with Pistacia integerrima grafted with cultivar Larnaka. The irrigation treatments replaced 75, 50, 25, and 0 % of daily evaporation (class A evaporimeter). Growth patterns indicated that irrigation equal to 50 % of evaporative demand could support trunk growth equal to that in the fully irrigated treatment. Flower production in irrigated treatments was two years earlier than in non-irrigated trees. Irrigation also caused greater branch growth, both in the presence and in the absence of the inflorescence. This phenomenon was beneficial in reducing alternate bearing, which is especially strong in non-irrigated plants. Production data demonstrate that irrigation increases fresh and dry kernel yield and has no effect on the hull to kernel ratio.