Comparison of sources with different solubilities for Mn supply and retranslocation along with soybean development

Foliar sprays with micronutrients are widely employed in agricultural production as an alternative to improve soil fertilization and plant nutritional status. We hypothesized that less water-soluble sources of manganese (Mn; MnCO3) could serve as a slow-release source compared to a water-soluble source (MnSO4.H2O). Our goal here was to evaluate Mn-sources (MnSO4.H2O and MnCO3) and rates (150; 250; 350; and 450 g ha(-1)) sprayed in the 3(rd) and 4(th) trifoliate leaflets of soybean growing in clayey and sandy soil under controled conditions. In phenological stages V7 (vegetative period) and R1 (reproductive period), dry matter, height, the diameter of the stem, and Mn-content in the shoot, stem, and in the trifoliate leaflets were determined. Results showed that the application of Mn resulted in an augmented Mn-content in the 3(rd) and 4(th) trifoliate leaflets (sandy) and the 3(rd) and 5(th) trifoliate (clayey). The MnSO4.H2O promoted Mn-retranslocation from the 3(rd)/4(th) trifoliate to the stem and the 5(th)/6(th) trifoliate. However, MnCO3 was accumulated in the 3(rd)/4(th) trifoliate. The Mn-rates presented a linear response in sandy soil and quadratic response in clayey soil. Clayey soil was characterized by the higher Mn-contents in the stem, while sandy soil presented the higher Mn-contents in the 3(rd), 4(th), 5(th), and 6(th) trifoliate. Our results suggest that MnSO4.H2O is more effective in increasing Mn-content in soybean leaves during plant development due to the Mn-retranslocation to sink organs (5(th)/6(th) trifoliate leaflets and shoot).

Automated summary

The research compared the effects of water-soluble manganese sources and less water-soluble manganese sources sprayed on soybean leaves, and found that MnCO3 accumulated more in trifoliate leaflets while MnSO4.H2O had better redistribution effects.