Water infiltration and soil structure related to organic matter and its stratification with depth

Soil organic matter is a key attribute of soil quality that impacts soil aggregation and water infiltration. Two soils (Typic Kanhapludults), one under long-term management of conventional tillage (CT) and one under long-term management of no tillage (NT), were sampled to a depth of 12 cm. Soil cores (15 cm diameter) were either left intact or sieved and repacked to differentiate between short-term (sieving) and long-term (tillage management) effects of soil disturbance on water infiltration, penetration resistance, soil bulk density, macroaggregate stability, and soil organic carbon (SOC). Mean weekly water infiltration was not different between sieved and intact cores from long-term CT (22 cm h−1), but was significantly greater in intact (72 cm h−1) than in sieved (28 cm h−1) soil from long-term NT. The stratification ratio of SOC (i.e., of 0–3 cm depth divided by that of 6–12 cm depth) was predictive of water infiltration rate, irrespective of short- or long-term history of disturbance. Although tillage is used to increase soil porosity, it is a short-term solution that has negative consequences on surface soil structural stability, surface residue accumulation, and surface-SOC, which are critical features that control water infiltration and subsequent water transmission and storage in soil. The stratification ratio of SOC could be used as a simple diagnostic tool to identify land management strategies that improve soil water properties (e.g., infiltration, water-holding capacity, and plant-available water).