Selecting the Right Leaves for Sampling

Josh McGill Nutrition, Tip of the Week

By Jamie D. Burrow and Tripti Vashisth

With the increased cost and limited availability of fertilizer, purchasing decisions are more important now than ever. Collecting the right leaves for sampling is the first step to making fertilizer decisions. Leaf samples should consist of 100 leaves that are 4- to 6-month-old spring flush leaves taken from nonfruiting branches.

Leaves for Sampling

Leaf nutrient concentrations vary between nonfruiting and fruiting branches. When leaf-sampling methods were established, many factors went into where leaves should be collected from on the tree. One key factor was samples should be consistently collected from either nonfruiting or fruiting branches. Methods and interpretations were created based on consistency and the ease of leaf collection. University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) recommendations are based on leaf nutrient concentrations from nonfruiting branches.

When sampling, all leaves should be from nonfruiting branches. Due to the variability of leaf nutrient concentration between branch types, consistency is key to obtaining an accurate analysis. It is also critical to not collect leaf samples from both nonfruiting and fruiting branches. Mixing leaf samples can skew the leaf analysis and lead to inadequate fertilization.

Recently, there have been questions about the leaf sampling methods on HLB-affected trees. Since the current recommendations are based on healthy trees, should the sampling methods be different for HLB-affected trees? Early research has indicated macronutrients (nitrogen, phosphorus and potassium) in HLB-affected trees follow the same pattern of healthy trees with lower nutrient concentrations in fruiting branches than in nonfruiting branches. Secondary macronutrient (calcium, magnesium) leaf concentrations in HLB-affected trees are generally higher in fruiting branches than nonfruiting branches, which is the same as healthy trees.

The continuation of this nutrition research project on HLB-affected trees will help to solidify how nutrient concentrations vary between nonfruiting and fruiting trees and aid in determining leaf sampling recommendations for HLB-affected trees.

Collecting leaves from both nonfruiting and fruiting branches or only fruiting branches can skew the nutrient results and lead to unnecessary fertilizer purchases. Consistent leaf sampling from nonfruiting branches will provide the most accurate leaf analysis and aid in making appropriate fertilizer decisions.

Jamie D. Burrow is a UF/IFAS Extension program manager, and Tripti Vashisth is an associate professor, both at the UF/IFAS Citrus Research and Education Center in Lake Alfred.

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