Studies on the effect of zinc supply on growth and nutrient uptake in pecan

Zinc (Zn) deficiency is a nutrient disorder observed in pecan (Carya illinoinensis Wangenh. K. Koch) under field conditions, and can cause distorted leaf growth and severe rosetting of shoots. Conducting Zn studies with pecan in the field have been problematic because Zn nutrition is difficult to control. In this study, Zn nutrient disorders were induced in greenhouse-grown pecan seedlings using hydroponic culture. Zinc efficiency was compared in two pecan seedstocks, 'Stuart' and 'Curtis' by evaluating growth response, nutrient uptake, and leaf nutrient analysis. Zinc deficiency symptoms appeared in plants grown in the absence of Zn after six weeks. Deficiency symptoms were characterized by interveinal mottling, followed by interveinal chlorosis, interveinal necrosis, and marginal purling. Symptoms were confined to the youngest most distal three to five leaves. Differences in Zn efficiency between the two seedstock were observed. Stuart exhibited more severe deficiency ratings than Curtis. Zinc supply also had a differential effect on the foliar concentration and content of Zn and other nutrient. Stuart seedstocks grown under minus Zn vs. plus Zn conditions exhibited significantly higher foliar concentration of phosphorus (P), calcium (Ca), magnesium (Mg), and copper (Cu), while Curtis leaves contained significantly higher manganese (Mn) and lower sulfur (S). Results of this study concur with the observed frequency of Zn deficiencies of the cultivars in the field, i.e., Stuart shows Zn deficiency more frequently then Curtis. This study verifies that in pecan, there are genotypic differences in Zn efficiency, and that hydroponic culture can be utilized for screening and selection.