Multifactorial Nutrient Interactions Contribute to Mouse-Ear Symptoms in Greenhouse-Grown ‘Giles’ Pecan Seedlings

Mouse ear (ME) is a growth disorder that poses a significant challenge in pecan seedlings. This study investigates nutrient uptake as a potential cause of ME disorder in 6-month-old ‘Giles’ pecan seedlings grown in soilless media. Based on visual observations, seedlings were categorized into normal leaves (control) and ME groups. Nutrient analysis of leaf samples showed that nickel concentrations were critically low, and copper levels were excessively high in both groups. ME-affected leaves had higher levels of phosphorus, zinc, sulfur, and magnesium, along with lower nitrogen compared with normal leaves. The nutrient analysis of soilless media indicated that media from ME seedlings had significantly higher levels of most nutrients including sodium, potassium, calcium, chloride, nitrate, and sulfate, compared with media from normal seedlings. The electrical conductivity (EC) of ME group media was also significantly higher. These findings support a multifactorial model of ME, in which limited nickel availability interacts with imbalance of other nutrients in the leaves. In this study, elevated EC, along with increased levels of calcium, chloride, sulfate, and magnesium in the media, may exacerbate the deficiency and contribute to the ME symptoms observed in pecan seedlings. Overall, our results suggest that ME symptoms arise from a complex interplay of deficiencies, toxicities, and disrupted nutrient uptake dynamics. These findings highlight the need for comprehensive nutrient management, including micronutrient balancing and substrate optimization, to prevent ME during the early developmental stages of pecan seedlings grown in greenhouse conditions.