Erosion‐Induced Changes in the Properties of a Fragipan Soil

Accelerated erosion of fragipan soils results in a relatively fast decline in productivity, compared with soils without root‐restricting layers. This study was conducted to determine how the characteristics of fragipan soils change with an increase in degree of erosion, as indicated by a decrease in depth to fragipan. Samples were collected at 130 points from the A horizon at five sites on a Grenada silt loam (fine silty, mixed, thermic Glossic Fragiudalf) with depth to fragipan ranging from 15 to 112 cm. Laboratory analyses included a range of chemical and physical properties that influence soil productivity. The data were separated into eight groups on the basis of difference in depth to fragipan and analyzed by regression techniques. Several significant changes occurred as the depth to fragipan decreased. The amount of organic matter, extractable Mn, and silt decreased, whereas increases were observed in exchangeable Na, extractable Fe, percent sand, percent clay, modulus of rupture, color value, and chroma. A minimum of 82% of the variability in these parameters was explained by depth to fragipan. As the degree of erosion increases on fragipan soils several management problems, related to modification of the chemical and physical properties of the plow layer, can be expected. These include greater susceptibility to erosion, reduced seedling emergence and plant vigor, and less drought tolerance.