Effect of Reduced Iron Chelate Fertilization on Photosynthesis, Stress Parameters, and Yield of Mandarin Trees

The objective of this work was to analyze the effect of reducing Fe chelate fertilization (50% and 25% reduction) on soil nutrient content and on different physiological and biochemical parameters in mandarin leaves. The reduction in Fe fertilization efficiently decreased soil Fe content, even in the short-term, without affecting leaf Fe or chlorophyll contents. Reduced iron fertilization increased the accumulation of certain heavy metals in mandarin roots, indicating potential implications for phytoremediation. It is well-established that disturbances of foliar Fe homeostasis can impair the photosynthetic process. Nevertheless, reduction in Fe supply did not negatively affect photosynthetic performance (based on chlorophyll fluorescence parameters), nor did it influence the stress levels of the trees, as indicated by lipid peroxidation. In addition, reduced iron fertilization did not alter peroxidase activity, which is considered a biochemical marker of Fe nutrition in plants. Finally, mandarin production was evaluated over two consecutive years, with no significant variations among the different iron treatments, whereas only minor differences were observed in fruit quality. Overall, these results indicate that reducing Fe fertilization is a feasible strategy, as it does not adversely affect the physiological processes or yield of mandarin trees. Furthermore, this agricultural practice can enhance nutrient use efficiency, thereby contributing to the reduction in soil and aquifer contamination while providing economic benefits to farmers.