Effect of soil organic carbon on soil hydraulic properties

Abstract

The primary soil hydraulic properties that soil organic carbon affects are porosity, soil water retention, and hydraulic conductivity. This chapter discusses the effect of organic carbon or organic matter on these properties and explains the way these effects can be incorporated into pedotransfer functions (PTFs). The sensitivity of water retention to changes in organic carbon content decreases as the initial organic carbon content increases. A similar conclusion can be drawn from the equations presented for water retention of soils amended with the organic waste in soils in the United States, England, India, and Germany. In a study discussed in the chapter, the reduction of the effect of increasing organic carbon content on water content at −5 kPa with the increase in the original value of the organic carbon content was reported. Water retention of peat soils presents a limit case for the increase of organic carbon content in samples. Soil-survey databases contain data on soils in natural ecosystems and on agricultural soils showing similar responses of soil water retention to changes in organic carbon content. Modeling of the changes of organic carbon content in soils and related changes in ecosystem productivity attracts significant attention with regard to climate changes and management changes. Existing models lack the feedback effect of organic carbon content accumulation on water retention and saturated hydraulic conductivity. Results presented in the chapter can be used in those models to improve their predictive ability.