Infiltration and soil properties as affected by annual cropping in the northern great plains

Fallow-wheat (Triticum aestivum L.) cropping systems may be responsible for declines in soil organic matter and degradation of soil physical properties. A change to annual cropping may improve or at least maintain soil properties. Tillage and crop sequence effects on soil properties and water infiltration were tested after 9 yr of cropping on a Dooley sandy loam (fine-loamy, mixed Typic Argiborolls) derived in glacial till. Annual cropping tillage of fall sweep and spring disk (AWFST), and no tillage (AWNT) were compared with conventional tillage in wheat-fallow (FWCT) as the control. Statistical design was a randomized complete block with four replications. Soil samples were taken at 0.03-m increments to a depth of 0.3 m and were used to measure organic carbon (OC), pH, bulk density (BD), and particle size. Point resistance was measured in 0.02-m increments. Water infiltration into dry and wet soil was measured using a rainfall simulator. Maximum soil BD was 1.61 Mg m-3 on FWCT and 1.56 Mg m-3 on AWNT. Soil BD was not changed by one winter of freezing and thawing. Maximum point resistance was 2.2 MPa on FWCT and 1.7 MPa on AWNT. Cumulative 3-h infiltration into dry soil was 52 mm for FWCT and 69 mm for AWNT. Final infiltration rate into wet soil was 5 mm h-1 for FWCT and 6 mm h-1 for AWNT. There was a significant difference in the depth distribution of OC between annual crop and FWCT treatments. Mass of OC in the top 0.09 m of soil was 1.65 kg m-2 on annual crop treatments and 1.45 kg m-2 on FWCT. Greater amounts of OC on the annual crop treatments compared with the FWCT attest to the beneficial aspect of annual cropping in maintaining a level of soil quality that is greater than FWCT. From a soil conservation perspective, no-tillage has an additional advantage because surface cover is maintained throughout the year, thereby reducing the potential for soil erosion