Relationships between yield and leaf nutrient contents in peach trees: Early nutritional status diagnosis

The objective was to determine to what extent foliar nutrient contents in different stages of the vegetative cycle are related to yield. The study was conducted on 180 peach trees (Prunus persica, L. Batsch) in several orchards located in the Ebro Basin. Leaf sampling (at 60, 90, 120, 150, and 180 days after full bloom) and crop harvesting were carried out individually on each of the 180 trees. Leaf samples were analyzed for N, P, K, Ca and Mg. The relationships of mineral analysis data (nutrient contents and their ten binary ratios) with yield were explored by applying three different calculation procedures. First, we analyzed the degree of significance of the differences in nutrient contents and binary ratios between two blocks of trees, separated according to yield level. This degree of significance was highest for leaf samples taken 60 and 120 days after full bloom, although the differences in K content and N/P and Ca/Mg ratios were not significant 120 days after full bloom. Second, we analyzed the correlations between mineral analysis data (nutrients and nutrient ratios) and yield. The best correlation coefficients were found for samples taken 60 and 120 days after full bloom. Again, samples taken 60 days after full bloom had a better performance than samples taken at a later stage. Third, we used multiple covariance studies to obtain a mathematical expression reflecting the effect of nutrient contents on yield. This type of analysis indicated again that the best time to take samples was 60 days after full bloom. Therefore, we conclude that the nutrient contents of the leaves and their ten binary ratios at 60 and 120 days after full bloom are the factors best related to yield in our study. Furthermore, all three calculation procedures showed that using samples taken 60 days after full bloom may offer significant advantages over samples taken at a later stage, thus opening the possibility to establish an early diagnosis of the nutritional status of peach trees.