Crop sequence intensification: Meta‐analysis of soil organic carbon and aggregate stability in Argentina

Abstract

Intensification of crop sequence (ICS) has been proposed as a key field practice to preserve soil health and achieve more sustainable agricultural systems. However, the effects of ICS are site-specific and vary according to soil characteristics, climatic conditions, the duration of the crop sequencing and the types of crop involved. Soil aggregate stability (AS) and soil organic carbon (SOC) stock are useful indicators of soil health as they are closely linked to diverse soil services and functions and are sensitive to management practices. We performed a meta-analysis of 33 studies to analyse the impact of ICS on SOC stock and AS in field experiments in the central-eastern region of Argentina. Our results showed that ICS increased SOC stock and AS, with an overall mean change of 7% and 22%, respectively. Fine-textured soils showed the greatest SOC stock increase (12%), comparable to the increase observed in coarse-textured soils (11%); in medium-textured soils this increase was less than half (5%). Coarse-textured soils had the greatest increase in AS (32%), followed by medium-textured and fine-textured soils, which also showed notable improvements (25% and 19%, respectively). Greater diversity of crops resulted in larger increases in both AS and SOC. ICS generated a larger increase of SOC stock in the soil surface (0–10 cm) than in the subsurface (10–20 cm), whereas the opposite was found for AS. Long-term studies (≥9 years) had the greatest effect on AS and SOC stock. Regression analysis revealed that the initial carbon stock influenced SOC stock results following ICS, increases being greater when initial carbon stock contents were smaller. Introducing gramineous species into the crop sequence was associated with a greater improvement of AS and SOC stock. Finally, the mean rate of carbon sequestration from ICS in all the studies amounted to 0.28 Mg ha−1 yr−1. Overall, ICS is a useful strategy for improving SOC storage and AS in this region, though results may vary according to soil characteristics and management practices.