Water Supply on Grafted Stone Pine: Effects on Growth and Mating

The pine nut, the seed of the stone pine, is highly valued in local cuisine and dietetics for its nutritional qualities. These nuts still come from forest stands, which results in their limited and irregular presence on the market. Domesticating the species through orchard management practices could increase its production. In this context, two irrigation schedules were tested in a grafted stone pine orchard that was planted in 2009 and has been under drip irrigation since 2011. Water needs were calculated weekly using the water balance method (ETc-P). The treatments considered were as follows: T1, irrigation from April to the end of summer; T2, irrigation from April to the end of June; and T0, rainfed as the control. Monitoring of the pines, considering vegetative and reproductive responses, was carried out from 2015 (7th leaf) to 2023. T1 and T2 increased primary and secondary growth and resulted in higher strobili production compared to T0. The tree’s ability to sustain the reproductive load was enhanced under irrigation versus rainfed treatment. The longest irrigation schedule increased productivity. However, when the environmental cost of supplying twice as much water in the Mediterranean region—an annual average of 900 m3 ha−1 (T2) versus 1900 m3 ha−1 (T1)—is considered, the overall assessment changes. The irregularity of stone pine mating was not prevented by a regular water supply, but it was mitigated, promoting sustainable production.