How much can Zn or Fe fertilization contribute to Zn and Fe mass concentration in rice grain? A global meta-analysis

Abstract

Zinc (Zn) and iron (Fe) deficiency remain global public health problems. While much information is available in the literature on the effect of fertilization with Zn and Fe on the concentration of these micronutrients in rice grain, the absence of a quantitative synthesis of previous studies constitutes an important knowledge gap. Here we report the first global meta-analysis based on 816 records from 56 publications. Compared with a no Zn control, soil-applied fertilizer (0.5–50 kg ha−1, 12.2 ± 0.48 kg ha−1 on average) increased Zn mass concentration by 3.33 ± 0.72 mg kg−1 on average while foliar-applied fertilizer (0.12–24 kg ha−1, 2.88 ± 0.24 kg ha−1 on average) resulted in an average increase of 7.76 ± 0.80 mg kg−1. Combined soil and foliar application of Zn (soil: 1.3–50 kg ha−1, 16.3 ± 0.72 kg ha−1 on average; foliar: 0.49–24 kg ha−1, 1.63 ± 0.33 kg ha−1 on average) increased mass concentration by 13.0 ± 0.81 mg kg−1. Foliar application of Fe (0.13–1.8 kg ha−1, 0.33 ± 0.07 kg ha−1 on average) increased grain Fe mass concentration by 9.62 ± 4.18, while grain Fe mass concentration was not significantly affected by the application of Fe to the soil (5.32 ± 4.34 mg kg−1) or combined soil and foliar Fe application (5.37 ± 4.32 mg kg−1). The greatest increases in grain Zn mass concentration were obtained with foliar applications at ripening stage and with more than two foliar applications combined with a basal soil Zn application. No significant relationship was found between grain yield and grain Zn or Fe mass concentrations. Thus, our findings indicate that combined soil and foliar application of Zn fertilizer and foliar application of Fe fertilizer can efficiently enhance rice grain Zn and Fe mass concentration, respectively. This knowledge can be used to design effective fertilization strategies for enhancing nutritional quality of rice.

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