Effects of important ecological measures on plant diseases and soil microbial communities in the Hulunber Grassland

Introduction Ecological management measures can influence plant diseases, forage production, soil nutrients, and microbial communities, but their integrated effects in natural meadow grasslands remain unclear. This study evaluated the effects of mowing twice per year, microbial agent application, and organic fertilizer application in the Hulunber natural grassland. Methods Field plots were subjected to mowing twice per year (MT), microbial agent application (MA), and organic fertilizer application (OF), with untreated plots serving as the control (CK). Plant community and disease surveys, soil physicochemical analyses, and high-throughput sequencing were combined to assess treatment effects on plant community characteristics, foliar fungal diseases, soil nutrients, and soil microbial communities. Results MA significantly increased plant community cover, whereas MT significantly reduced community height. MT increased fresh and hay forage yields by 89.26% and 85.62%, respectively, and OF also significantly increased forage yield. Leaf spot was the predominant plant disease, with peak incidence occurring in August. MA and MT significantly reduced community pathogen load, and MT produced the strongest reduction, decreasing community pathogen load by 56.60% relative to CK. At the functional-group level, MA and MT reduced pathogen loads in grasses and sedges, while all treatments reduced pathogen loads in legumes by 47.52%–65.33%. MA increased soil total nitrogen; MT increased total nitrogen, ammonium nitrogen, and soil organic carbon; and OF increased soil organic carbon. OF increased fungal alpha diversity, while bacterial diversity and community composition differed among treatments. MT increased the relative abundance of Fusarium , whereas MA, MT, and OF decreased the relative abundance of Alternaria . Discussion Mowing twice per year and microbial agent application showed greater potential for reducing foliar fungal disease, whereas organic fertilizer mainly improved forage production, soil organic carbon, and fungal diversity. These findings provide an ecological basis for management strategies that balance disease reduction, forage production, and soil microbial conservation in meadow grasslands.