Crop intensification influences water infiltration and microbial activity in agricultural soils from the southeast of the Argentinean Pampas

Low crop diversification in highly productive areas has led to declines in total organic carbon (TOC) in soil, essential nutrients for plant’s growth and microbial diversity/activity. This could have an impact on the movement of water in the soil profile and, consequently, on the production of crops. To address these challenges there is growing support for crops intensification, which involves increasing the number/variety of crops throughout the year. The purpose of this study was to assess the influence of crop intensification on the initial infiltration of water in the upper layer of the soil profile and the activity/abundance of soil microorganisms involved in the turnover of TOC and phosphorus (P). Three crop regimes were assessed in a long-term experiment established in the southeast of the Argentinean Pampas: without intensification (Monocrop: soybean), intensified (Cover crop: CC [oat]/soybean) and Rotation (CC [oat]/soybean-corn-wheat). Soil in the Monocrop regime exhibited the highest sorptivity values and a lower TOC, suggesting a higher initial rate of water entry into the profile, which could break down soil aggregates. Under rotation, the highest infiltration rate was recorded, which would guarantee more water flow into the profile. Intensified soils showed the highest total glomalin content and root colonization with arbuscular mycorrhizal fungi (AMF), which are known to contribute to plant nutrient uptake and growth and soil aggregate stability. Trichoderma abundance and their P-solubilizing capacity were also higher under Rotation, which could favor AMF activity. Correlation analysis revealed a significant positive correlation between sorptivity and glomalin under Rotation. Our study suggests that soils from the Argentinean south-eastern Humid Pampas under crop intensification promote soil water storage and maintenance of soil structure in the upper layers compared to Monocrop, which could be attributed —at least in part— to a greater microbiological activity and TOC content.