Soil hydraulic properties influenced by agroforestry and grass buffers for grazed pasture systems

Agroforestry buffers have been introduced in temperate areas to improve water quality and diversify farm income. The objective of this study was to evaluate saturated hydraulic conductivity and water retention for soils managed under rotationally grazed (RG) pasture, continuously grazed (CG) pasture, grass, buffers (GB), and agroforestry buffers (AgB). Pasture and GB areas included red clover (Trifolium pretense L.) and lespedeza (Kummerowia stipulacea Maxim.) planted into fescue (Festuca arundinacea Schreb.) while AgB included Eastern cottonwood trees (Populus deltoids Bortr. ex Marsh.) planted into fescue. Water retention data were measured at -0.4, -1.0, -2.5, -5.0, -10, -20, and -30 kPa (-0.058, -0.145, -0.363 -0.725 -1.45, -2.90, -4.35 pounds per square inch [psi]) soil water pressures using 76 mm (3.00 in) diameter by 76 mm long cores from the 0 to 10 cm, 10 to 20 cm, 20 to 30 cm, and 30 to 40 cm (0 to 3.94 in, 3.94 to 7.87 in, 7.87 to 11.81 in, and 11.81 to 15.75 in) depths. Soil bulk density was 12.6% higher for the RG and CG treatments (1.41 and 1.45 g cm(-3) [88.02 and 90352 lb ft(-3)]) than the GB and AgB treatments (1.25 and 1.29 g cm(-3) [78.03 and 80.53 lb ft(-3)). Sod water content at high soil water potentials (0 and -0.4 kPa) was greater in the buffer treatments relative to the other treatments for the 0 to 10 call soil depth. Sod macroporosity (>1,000 mu m [>0.0394 in] diameter) was 5.7, 435, and 3.9 times higher, respectively, for the AgB, GB, and RG treatments compared to the CG treatment for the 0 to 10 cm soil depth. Buffer treatments had greater macroporosity (>1,00,0 Pm diameter), coarse (60 to 1,000 mu m [0.00236 to 0.0394 in] diameter) and fine mesoporosity (10 to 60 pin [0.000394 to 0.00236 in] diameter), but. lower microporosity (<10 mu m diameter) compared to RG and CG treatments. Saturated hydraulic conductivity values for GB and AgB treatments were 16.7 times higher (56.95 vs. 61.33 mm h(-1) [2.24 vs. 2.41 in hr(-1)]) compared with RG and CG (3.98 vs. 3.11 mm h(-1) [0.157 vs. 0.122 in hr(-1)]). This study illustrates that agroforestry and grass buffers maintained higher values for soil hydraulic properties compared to grazed pasture systems.