The effects of the inoculation of bacterial microorganisms (Pseudomonas sp. and Bacillus sp.) on soil quality, aerial biomass and nutritional quality of native grasses under field conditions in the Peruvian highlands

Abstract

Peruvian highland ecosystems cover approximately 22 million hectares and provide key ecosystem services that support human well-being and food security. Soil functioning in these ecosystems largely depends on the activity of microbial communities. This study evaluated the effects of Pseudomonas sp. and Bacillus sp. inoculation on soil chemical properties, aerial biomass production, and nutritional quality of Festuca dolichophylla, Jarava ichu and Cinnagrostis vicunarum. A field experiment was conducted at 4379 m a.s.l. in the central Peruvian highlands. Bacterial inoculation increased soil organic matter and nitrogen availability in plots dominated by J. ichu and F. dolichophylla inoculated with Bacillus sp., compared to non-inoculated controls. Higher soil phosphorus content was observed in C. vicunarum pastures inoculated with Pseudomonas sp. In terms of biomass production, significant increases were recorded in C. vicunarum under both bacterial inoculations and in F. dolichophylla associated with Bacillus sp., while J. ichu showed higher yields with Pseudomonas sp. In addition, bacterial inoculation improved forage nutritional quality, particularly total protein, calcium, and phosphorus contents in J. ichu, highlighting species-specific plant–microorganism interactions. Overall, the inoculation of beneficial bacteria represents a promising and environmentally sustainable strategy to improve soil quality, forage productivity, and nutritional value in native highland grasslands, contributing to more resilient rangeland systems and the conservation of ecosystem services.