Insufficient spring irrigation increases abnormal splitting of pistachio nuts

Abnormal pistachio nuts, known as "early-split nuts," have both the hull and shell split while still on the tree, exposing the kernel to invasion by insects and molds. Deficit irrigation of pistachio trees in April and May resulted in substantial increases in the formation of early-split nuts in late summer, while extreme deficit irrigation in July and August resulted in decreased formation. However, deficit irrigation during the period of shell hardening, mainly in June, did not affect early-split formation.