Impacts of Long‐Term Wheat Straw Management on Soil Hydraulic Properties under No‐Tillage

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 L.) straw mulch (0, 8, and 16 Mg ha −1 yr −1 ) application for 10 consecutive yr on a Crosby silt loam (fine, mixed, active, mesic Aeric Epiaqualfs) in central Ohio. Water infiltration rates, earthworm population, saturated hydraulic conductivity ( K sat ), soil water retention (SWR), total porosity, and pore‐size distribution were determined and unsaturated hydraulic conductivity was estimated from SWR and K sat 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 ± 52 m −2 (mean ± SD) in treatments with 8 Mg ha −1 yr −1 of straw, and 267 ± 58 m −2 in those with 16 Mg ha −1 yr −1 of straw. Mulched treatments had a K sat 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 yr −1 of straw and by 44% under 16 Mg ha −1 yr −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.