Annual–Perennial Forage Mixtures Improve Forage Productivity and Soil Quality in Patchily Degraded Cultivated Pastures Under Grazing Management

ABSTRACT Patchy degradation of cultivated pastures under long‐term grazing is a serious issue limiting grassland productivity. The use of annual and perennial legume–grass mixtures, which offer complementary functional advantages, may provide a practical reseeding‐based approach for improving patchily degraded cultivated pastures; however, limited information is available on how patch size influences the performance of different mixture ratios under grazing management. This study evaluated the effects of different seeding ratios between a perennial forage mixture (D: Dactylis glomerata L. + Trifolium repens L.) and an annual forage pastures mixture (Y: Secale cereale L. + Vicia villosa Roth) on the improvement of patchily degraded cultivated pastures in southwestern China. A nonreseeded control (CK) and five D:Y reseeding ratios, including 10:0 (D), 0:10 (Y), 3:7 (D3Y7), 5:5 (D5Y5), and 7:3 (D7Y3), were established in two relative patch‐size classes, namely smaller degraded patches (1–2 m 2 ) and larger degraded patches (> 2.5 m 2 ), under practical grazing and fertilization management, to assess their effects on forage productivity, soil physicochemical properties, soil enzyme activities, and soil quality index (SQI). The results showed that annual–perennial mixed sowing generally improved forage aboveground biomass (AGB) and soil quality compared with the CK and monoculture treatments. After two consecutive years of reseeding, D5Y5 produced the highest AGB and SQI in smaller patches, whereas D3Y7 performed best in larger patches. Random forest analysis indicated that the proportion of annual forage in both patch types was mainly associated with soil ammonium nitrogen (NH 4 + ‐N) and nitrate nitrogen (NO 3 − ‐N). In smaller patches, soil urease activity (URE) was the only significant factor affecting AGB, while belowground biomass (BGB) was mainly influenced by NO 3 − ‐N and URE. In large patches, AGB was mainly affected by NH 4 + ‐N, NO 3 − ‐N, and total nitrogen, whereas BGB was mainly influenced by NH 4 + ‐N, β‐glucosidase, and soil water content. These findings indicate that, as patch size increases, the regulation of forage productivity shifts from a limited number of dominant factors to a broader set of soil nutrient and enzyme‐related variables. Overall, annual–perennial legume–grass mixtures provide a practical reseeding‐based approach for improving forage productivity and soil fertility in patchily degraded cultivated pastures under grazing management.