Biomass and buffer management practice effects on soil hydraulic properties compared to grain crops for claypan landscapes

Abstract

Biomass production systems as well as agroforestry and grass buffers have been found to improve soil hydraulic properties and water quality relative to row crop management for temperate regions. Objectives of this study were to assess the effects of biomass crops, agroforestry buffers, and grass buffers grown on claypan soils relative to a traditional corn (Zea mays L.)–soybean (Glycine max L.) rotation for hydraulic properties which included saturated hydraulic conductivity (Ksat), soil water retention, bulk density, and pore size distributions. Experiment was conducted in northeastern Missouri, USA. Buffers and biomass crops were established in 1997 and 2012, respectively. Grain crop production watersheds were established in 1991. Agroforestry buffers consisted of grasses and forbs with pin oak (Quercus palustris Muenchh.) trees. Redtop (Agrostis gigantea Roth), brome grass (Bromus spp.), and birdsfoot trefoil (Lotus Corniculatus L.) were planted in grass buffer areas. Biomass crops included switchgrass (Panicum Virgatum L.) and native grasses. Undistributed soil cores (7.6 cm diam. by 7.6 cm long) were taken by 10 cm depth increments with six replications from the surface to the 40 cm depth. Samples were measured and evaluated for bulk density, Ksat, water retention, and pore size distributions. Results illustrated that bulk density values were significantly lower (P < 0.01) for the buffer treatments and biomass crops compared to the row crop treatment averaged across depths. Significantly greater Ksat occurred for biomass crops and agroforestry buffers than row crops affected by soil depth, particularly at the soil surface 0–10 and 10–20 cm depths. Macropores (> 1000 µm effective diam.) and coarse mesopores (60–1000 µm effective diam.) were significantly higher for the biomass treatment than the other treatments for the first depth 0–10 cm. Although the claypan soil horizon dominates hydrology in northeastern Missouri, this study showed that biomass crops as well as agroforestry and grass buffer practices improve soil hydraulic properties relative to row crop management; they also have valuable economic and environmental benefits.