Influence of grass and agroforestry buffer strips on soil hydraulic properties for an Albaqualf

Agroforestry production systems have been introduced in temperate regions to improve water quality and diversify farm income. Agroforestry and grass-legume buffer effects on soil hydraulic properties for a Putnam soil (fine, smectitic, mesic Vertic Albaqualf) were evaluated in a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] watershed in northeastern Missouri. The no-till management watershed was established in 1991 with agroforestry buffers implemented in 1997. Agroforestry buffers, 4.5 m wide and 36.5 m apart, consist of redtop (Agrostis gigantea Roth), brome (Bromus spp.), and birdsfoot trefoil (Lotus corniculatus L.) with pin oak (Quercus palustris Muenchh.), swamp white oak (Q. bicolor Willd.), and bur oak (Q. macrocarpa Michx.) trees. Soil cores (7.6 cm in diam. by 7.6 cm long) were collected from the treatments from four 10-cm depth increments to determine saturated hydraulic conductivity (K(sat)), soil water retention, pore-size distributions, and bulk density. Bulk density was 2.3% lower (P < 0.05) within the grass and agroforestry buffers compared with the row crop areas. Total porosity and coarse mesoporosity (60- to 1000-micrometer diam.) were 3 and 33% higher (P < 0.05), respectively, for the grass and agroforestry buffer treatments than the row crop treatment. The K(sat) was three and 14 times higher (P < 0.05) in the grass and agroforestry buffer treatments compared with the row crop treatment. Results show that the grass and agroforestry buffer treatments increased potential water storage by 0.90 cm and 1.1 cm per 30-cm depth compared with the row crop treatment. Although the claypan horizon will dominate the surface hydrology, buffers may provide some benefit by reducing runoff from row crop management.