Comparison of Different Plant Sap, Conventional Leaf, and Soil Nutritional Analyses in Citrus Groves under Citrus Greening Conditions

Over the past decades, Florida’s citrus production has faced significant challenges, including hurricanes and devastating diseases such as citrus greening (Huanglongbing, HLB). One strategy commonly used to help reduce tree stress under both abiotic and biotic pressures is nutrient management. However, the effectiveness of these practices relies on accurate testing to confirm trees are receiving the proper nutrient levels. Plant sap analysis is an emerging technology that offers real-time insights into nutrient flow within the plant, but its reliability on fruit tree systems when compared with conventional plant and soil nutrient analyses remains largely understudied. To evaluate this, a 2-year study was conducted in a commercial citrus grove in Vero Beach, FL, using 12-year-old ‘Ray Ruby’ grapefruit ( Citrus × paradisi ) trees grafted on ‘Sour Orange’ ( Citrus × aurantium ) rootstock. Nutrient levels were assessed using conventional soil and leaf tissue analysis, alongside two sap analysis methods. All methods showed consistent results for total nitrogen, which remained within or slightly above the optimal range. However, results for phosphorus varied: conventional methods indicated sufficient levels, whereas sap analysis revealed a deficit. For potassium, sap analysis indicated a surplus, whereas conventional methods suggested levels were in or below the optimal range. Similar inconsistencies were observed in micronutrient data. These findings highlight the potential of sap analysis but also underscore the need for further validation before widespread adoption.