Yield of soybean and corn intercropping and quality of mixed silage in farming-pastoral ecotones with nitrogen fertilization

The effect of nitrogen fertilization and its rate of application on the agronomic traits, crop yield, and mixed silage quality of farming-pastoral ecotones that use intercropping has yet to be determined. To address this, maize and soybean intercropping systems were evaluated using a two-factor random block design. Herein, the main factor was maize and soybean intercropping (M2S3), maize monoculture (MM), and soybean monoculture (SS), while the secondary factor was comprised of three nitrogen levels: N₁ (0 kg·ha⁻¹), N₂ (150 kg·ha⁻¹), and N₃ (300 kg·ha⁻¹). Therefore,, nitrogen application was found to change the agronomic traits and yield of soybeans, increasing the fresh yield by 12.97%～14.79%. Soybean intercropping had a significant effect on plant height, bottom pod height, and number of main stem nodes (P < 0.05). The application of nitrogen improved plant height, ear height, stem diameter, and the maize yield, while intercropping had a significant impact on stem diameter and yield, but no effect on plant or ear height (P > 0.05). Reducing the nitrogen level achieved the same results as constant nitrogen application. Secondly, nitrogen application increased the crude protein content by 6.36%～6.63% and the crude fat content by 7.11% of mixed silage, but had no significant impact on the crude ash or starch content. The acid detergent fiber and neutral detergent fiber contents showed a decreasing trend with nitrogen application, and the nutritional components achieved better results under N₂ treatment. A comprehensive analysis of agronomic traits, yield, and nutritional components revealed that nitrogen applied at a rate of 150 kg·ha⁻¹ under intercropping mode was the most suitable for soybean and corn crops. The results suggest that a ratio of 4 ꞉ 6 and 2 ꞉ 8 for soybean and corn mixed silage, respectively, would be optimal for high-yield, efficient cultivation, and high-quality feed in farming-pastoral ecotones.