Field Evidence of a Negative Correlation between Saturated Hydraulic Conductivity and Soil Carbon in a Sandy Soil

Soil organic matter (SOM) is generally assumed to be positively correlated with saturated hydraulic conductivity (KS). However, recent studies of pedotransfer functions suggest a possible negative KS-SOM relationship that still needs independent verification. Our field KS study of sandy soils in a semiarid region provides such in situ evidence of a negative KS-SOM relationship, which is nonlinear and is strongest at the lowest levels of soil carbon (\u3c0.1%). A regression analysis also shows that soil carbon is an important factor for explaining KS in those soils. The likely reason for the observed negative KS-SOM relationship is a reduced wettability caused by SOM, which is believed to outweigh the impacts of any increase in KS caused by soil aggregation. The low SOM content and large particle size of sand may explain the limited effect of SOM on soil aggregation processes in the examined soils