Floral analysis for Satsuma mandarin (Citrus unshiu Marc.) nutrient diagnosis based on the relationship between flowers and leaves

• This paper studied the relationships between nutrient concentrations of Satsuma mandarin flowers and leaves.
• It was put forward that floral analysis could be an earlier nutrient diagnosis method for citrus reticulata.
• The critical values for Satsuma mandarin floral diagnosis were calculated.

Foliar analysis is usually adopted for nutrient diagnosis in fruit trees, particularly citrus trees, but the results are only applicable in the subsequent year. Flowers are a precursor to fruit, and their nutrients should have a direct effect on the yield and fruit quality of a tree. A field experiment was conducted to research the relationship between the nutrient concentrations of flowers and leaves to determine whether flower analysis could be used for nutrient diagnosis in the Satsuma mandarin (Citrus unshiu Marc.). The point observation method was adopted. Flower and leaf samples were collected from 616 trees in 77 sampling locations in April and September. N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, B and Mo concentrations in the flower and leaf samples were analyzed. The regression analyses between the nutrient concentrations in the flowers and leaves were performed. The results showed that the K, Mn, Cu, Ca and B concentrations in the citrus flowers were significantly correlated with those in the leaves. The N, P, K, Cu and Zn concentrations in the citrus flowers were higher than those in the leaves, whereas the Ca, Mg, Mn and B concentrations were lower in the flowers. Higher coefficients of variation were observed for most of the nutrient concentrations of the citrus flowers, indicating a sensitive response to nutritional status changes. Regression analyses and grade standards showed the flower critical concentrations of K, Ca, Cu, Fe and B to be 2.08%, 0.56%, 13.80 mg/kg, 69.90 mg/kg and 33.20 mg/kg, respectively. These results suggest that floral analysis could be used as an early method of nutrient diagnosis for Satsuma mandarin (Citrus unshiu Marc.).