Fertilizer Requirement Characterization Based on the Stoichiometric Ratio of Rabbiteye Blueberry Leaves

In this study, a novel fertilization measurement strategy was constructed by combining stoichiometric ratio, photosynthetic rate, and photosynthetic area. In this study, the theoretical fertilizer requirement of nitrogen (N), phosphorus (P), and potassium (K) per 10 d at flowering (S1), fruiting (S2), young fruiting (S3), and fruit expansion (S4) stages was calculated based on the ecological stoichiometric ratio of leaves, photosynthetic rate, and photosynthetic area. Four fertilization gradients of 1-fold (1F), 5-fold (5F), 10-fold (10F), and 15-fold (15F) of the theoretical fertilizer requirement were set up at the four developmental stages to investigate the specific effects of different NPK fertilization rates on the nutrient contents of blueberry leaves. In the stoichiometric ratio study of blueberry leaves, the leaf stoichiometric ratios were in the desirable range under most treatments, with the S1-5F, S2-15F, S3-5F, and S4-5F treatments being the best, resulting in a more efficient nutrient utilization of blueberries, better maintenance of the internal nutrient status of the plant, and less wastage of fertilizers. Of the 16 fertilization treatments, eight treatments had C:N ratios, nine treatments had C:P ratios, and 14 treatments had C:K ratios in the desirable range. In addition, the leaf N:P, N:K, and K:P ratios of all fertilization treatments fluctuated within the suitable range, which indicated that the stoichiometric ratio-based fertilization method could promote the blueberry plants to maintain nutrient balance and efficiently maintain their internal stability. In conclusion, this study verified the feasibility of this fertilization method, and provided new fertilization ideas and theoretical support for the field of fruit tree cultivation.