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item Franzluebbers, Alan

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2001
Publication Date: 8/1/2002
Citation: Franzluebbers, A.J. 2002. Water infiltration and soil structure related to organic matter and its stratification with depth. Soil & Tillage Research.

Interpretive Summary: Soil quality is a concept based on the premise that management can deteriorate, stabilize, or improve soil ecosystem functions. Getting water to infiltrate the soil, rather than allowing it to run off the surface, is an important ecosystem function controlled by biological and physical interactions to create a stable soil structure with enough large pores to rapidly transmit water. Soil that is continually disturbed with tillage often develops poor structure, leading to surface sealing of pores and crusting. Intensive rainfall in the southeastern USA contributes to this poor structure because of its high energy impact upon meeting the soil surface. Crop residues that are left on the soil surface in conservation tillage systems can relieve this high energy impact by absorbing the energy prior to reaching soil and by providing enough carbon resource for heterotrophic soil organisms to burrow and form more stable soil structure via biological gluing mechanisms. This study demonstrated that long-term n tillage management is vitally important to get more water into soil, which could lead to more efficient water use by crops.

Technical Abstract: Soil organic matter is a key attribute that impacts soil aggregation and water infiltration. Two soils (Typic Kanhapludults), one under long-term management of conventional tillage (CT) and one under no tillage (NT), were sampled to a depth of 12 cm. Soil cores (15-cm diam) were either left intact or sieved and repacked to differentiate between shortterm (sieving) and longterm (tillage management) effects of soil disturbance on water infiltration, penetration resistance, soil bulk density, macroaggregate stability, and soil organic C. The stratification ratio of soil organic C (i.e., of 0 to 3 cm depth divided by that of 6 to 12 cm depth) was highly 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 soil organic C, which are critical features that control water infiltration and subsequent water transmission and storage in soil. The stratification ratio of soil organic C could be used as a simple diagnostic tool to identify land management strategies that improve water infiltration.