CT-measured macropores as affected by agroforestry and grass buffers for grazed pasture systems

Abstract

Agroforestry and grass buffers have been proposed for improving water quality in watersheds. Buffer vegetation influences soil porosity, essential for water, gas and nutrient transport in soils. The objective of the study was to compare differences in CT-measured macropore ([greater than] 1000-[micro] m diam.) and coarse mesopore (200- to 1000-[micro] m diam.) parameters within agroforestry (AgB) and grass buffer (GB) systems associated with rotationally grazed (RG) and continuously grazed (CG) pasture systems, and to examine relationships between CT-measured pore parameters and saturated hydraulic conductivity (K[subscript]sat). Soils at the site were Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalf). Six replicate intact soil cores, 76.2 mm diam. by 76.2 mm long, were collected using a core sampler from the four treatments at five soil depths (0-50 cm at 10-cm intervals). Image-J software was used to analyze the five equally spaced images from each core. CT-measured soil macroporosity ([greater than] 1000 [micro] m diam.) was 13 times higher (0.053 m3m3) for the buffer treatments compared to the pasture treatments (0.004 m3m3) for the surface 0-10 cm soil depth. Buffer treatments had greater macroporosity (0.020 m3m3) compared to pasture (0.0045 m3m3) treatments. The K[subscript sat] values for buffer treatments were five times higher and bulk density was 5.6 [percent] lower compared to pasture treatments. CT-measured pore parameters (except macropore circularity) were positively correlated with K[subscript sat]. This study illustrates the benefits of agroforestry and grass buffers for maintaining soil pore parameters critical for soil water and nutrient transport.