Rotating intercrops in continuous maize cultivation: effect on the soil macronutrient content and aggregate stability

This study investigated whether intercrops from different botanical families can mitigate soil degradation in a continuous maize cultivation system. Maize was grown together with species from the Fabaceae, Poaceae, and Brassicaceae families, while inter-row loosening and weed mulching were used as control treatments. The results showed that soil aggregate stability was influenced more by meteorological conditions than by the intercrop rotations. The most consistent positive effect on aggregate stability was observed in the rotation of blue-flowered alfalfa, common oat, and spring camelina. Over the three-year period, soil chemical properties remained stable. The content of mobile phosphorus increased by 20–45%, potassium slightly decreased, and magnesium remained at a high fertility level. The comprehensive evaluation index identified weed mulching and diversified intercrop rotations–particularly blue-flowered alfalfa-common oat-spring camelina, crimson clover-annual ryegrass-spring oilseed rape, and Persian clover-spring barley-oilseed radish–as the most effective treatments for improving soil quality. Maize and intercrop rotation systems were found to maintain soil fertility under continuous cropping conditions, although climatic variability remained the dominant factor influencing soil structure. Earlier establishment of intercrops is recommended to improve moisture utilisation and canopy development, and future research should explore a broader range of species combinations to enhance long-term soil sustainability.