Impacts of long-term wheat straw management on soil hydraulic properties under no-tillage

摘要

Crop residues left on the soil surface conserve soil and water, but residue impacts on near-surface soil hydraulic properties have not been widely studied. Therefore, soil hydraulic properties were determined under uncropped no-tillage (NT) plots receiving three levels of wheat (Triticum aestivum) straw mulch (0, 8, and 16 Mg ha-1 year-1) application for 10 consecutive years on a Crosby silt loam (fine, mixed, active, mesic Aeric Epiaqualfs) in central Ohio, USA. Water infiltration rates, earthworm population, saturated hydraulic conductivity (Ksat), soil water retention (SWR), total porosity, and pore-size distribution were determined and unsaturated hydraulic conductivity was estimated from SWR and Ksat data. Mulching significantly impacted hydraulic properties in the 0- to 3-cm soil depth (P<0.01), but water infiltration rate was unaffected. Earthworm counts were 0 m-2 in the unmulched treatment, 158+or-52 m-2 (mean+or-SD) in treatments with 8 Mg ha-1 year-1 of straw, and 267+or-58 m-2 in those with 16 Mg ha-1 year-1 of straw. Mulched treatments had a Ksat 123 times greater and retained 40 to 60% more water between 0 and -1500 kPa than the unmulched treatment. Soil porosity increased by 28% under 8 Mg ha-1 year-1 of straw and by 44% under 16 Mg ha-1 year-1 in the 0- to 3-cm depth compared with the unmulched treatment. Pore volume of macro- and mesopores was greater in mulched treatments and that of fine mesopores was greater in the unmulched treatment in the 0- to 3-cm depth. Straw mulching appears to be a viable practice to improve near-surface hydraulic properties in long-term NT soils, although residues may not increase water infiltration rates..