Assessing the effects of fertilisation on the yield, protein, and oil content of soybean seeds: a metadata analysis

For a comprehensive study on balancing yield and grain composition, a meta-analysis of 48 peer-reviewed studies evaluated the effects of soil and foliar fertilization on soybean ( Glycine max L.) yield, protein, and oil content. The metadata includes fertilizer type, application method, yield (kg ha ⁻¹ ), and concentration of protein (%) and oil (%). The data show that foliar and soil N fertilization increased grain yield by 13.7% and 14.2%, respectively (p < 0.05), compared to the control. However, it did not significantly affect the protein (38.4 ± 3.4%) or oil (20.2 ± 2.3%) content. High variability in experimental designs and the underrepresentation of foliar strategies make it difficult to draw broad conclusions. These findings showed the need for standardized field and controlled trials to balance increased yield with quality and to guide nutrient management.