Appropriate application of organic fertilizer enhanced yield, microelement content, and quality of maize grain under a rotation system

Maize (Zea mays L.), as a cornerstone crop, is integral to both livestock feed and human nutrition. However, the effects of long-term manure application on maize yield, micronutrient levels, and nutritional quality under a maize-soybean rotation system have not been fully elucidated. This study investigates the impact of long-term manure application on maize yield, the micronutrients content of grains, and grain nutritional quality in a maize-soybean rotation. Our results indicate that consistent manure application significantly enhances maize yield. Compared to the long-term chemical fertilizers only, the addition of manure increased the Fe, Mn, Cu, and Zn concentrations of the grains. In addition, the highest grain protein concentration was observed when treated with manure. Concentrations of protein fractions such as globulins, gliadins, and glutenins were found to be higher with a low manure application (13.5 t ha⁻¹) compared to high manure application (27 t ha⁻¹). The optimum increments in essential amino acids (EAA) and the ratios of essential to nonessential amino acids (EAA/NAA) was observed under low manure addition treatment. Collectively, incorporating manure into a long-term maize-soybean crop rotation not only escalates yields but also critically enhances the nutritional profile of maize grains through an increase in micronutrients and by promoting balance of proteins and amino acids within the grain. In the long run, low manure addition is more conducive to improving the nutritional quality of grains under crop rotation systems.