Higher microbial activity improved rhizosphere soil aggregation of Lolium multiflorum throughout the crop cycle

Abstract

Plant roots can modify the stability of soil aggregates in the rhizosphere and the surrounding bulk soil. Italian ryegrass (Lolium multiflorum) is known to improve soil aggregation through processes related to microbial activity, but these dynamics vary throughout the crop cycle. This study aims to correlate microbial activity with soil aggregate stability, determined by turbidimetry (readily-dispersible clay and mechanically-dispersible clay), in the rhizosphere and bulk soil of Italian ryegrass at 86, 113, 141, and 168 days after sowing. Results showed that the rhizosphere soil was significantly more stable, with 85–154 % lower dispersed clay than the bulk soil. Furthermore, aggregate stability increased (i.e., dispersed clay decreased) throughout the crop cycle, in tandem with a general increase in microbial parameters such as β-glucosidase, acid phosphatase, and glomalin-related soil protein. Aggregate stability was strongly correlated (R2 = 0.17–0.53; p<0.01) with these microbial parameters. In conclusion, Italian ryegrass effectively enhances soil aggregation and microbial activity, particularly in the rhizosphere, making it a valuable crop for improving soil health.