Grazing management of cultivated grassland with different weed proportions optimizes soil nutrient status and improves forage yield and nutritional quality

Abstract

Context

Grassland utilization methods and weed management are critical strategies for optimizing soil ecology and sustainable forage productivity in cultivated grasslands. However, the mechanisms by which grazing/mowing and weed proportions influence forage productivity, soil nutrient cycling, and ecosystem stability through interspecific complementarity and competition are not well understood, particularly in arid agroecosystems with interannual climate variability. To address this, a three-year field experiment was conducted in the arid inland region of Northwest China to evaluate the effects of different grassland utilization methods and weed-to-forage ratios on soil nutrients, forage yield, and nutritional quality in two mixed cultivated grasslands.

Methods

A three-year field experiment was conducted in the arid inland region of Northwest China, including two grassland utilizations (grazing and mowing), three weed ratios (weed biomass: forage biomass = 4: 6, 2: 8, 0: 10) for two mixed cultivated grasslands (Medicago sativa +Bromus inermis, Festuca arundinacea + Bromus inermis), to evaluate their effects on the soil nutrients, productivity and nutritional quality of cultivated grasslands. Key plant physiological and soil biochemical indicators were measured, including yield composition, crude protein, ether extract, soil available potassium, alkali-hydrolyzable nitrogen, urease and alkaline phosphatase activities.

Results

The results showed a 6.28 %-36.14 % higher forage yield in grazing grassland than mowing grassland. The forage yield decreased with the increase in weed proportion. Moreover, the yield stability of Festuca arundinacea + Bromus inermis grassland was better than that of Medicago sativa + Bromus inermis grassland. The crude protein and ether extract contents of Medicago sativa, Festuca arundinacea and Bromus inermis in mixed cultivation grassland decreased with the increase in weed proportion. Grazing significantly increased the crude protein and ether extract contents of the pastures. Soil available potassium and alkali-hydrolyzable nitrogen in the surface layer (0–10 cm) were significantly higher in grazing grassland than mowing grassland. In 2024, the activities of urease and alkaline phosphatase in grazing grassland were higher by 26.77 %-95.80 % and 6.72 %-33.46 % than mowing grassland, respectively. Correlation analysis revealed negative relationship of forage yield and crude protein content with acid detergent fiber and neutral detergent fiber, while positive correlation between yield and crude protein content. In addition, urease was positively correlated with temperature and rainfall.

Conclusion

Overall, grassland utilization through grazing and maintaining a lower weed to pasture ratio enhances soil nutrients, forage yield, and nutritional quality. This research establishes a scientific foundation for efficient management of cultivated grasslands, improving productivity and optimizing soil nutrient dynamics in arid regions.