INFILTRATION AND SOIL PROPERTIES AS AFFECTED BY ANNUAL CROPPING IN THE NORTHERN GREAT-PLAINS

Fallow-wheat (Triticum aestivum L.) cropping systems may be responsibl e for declines in soil organic matter and degradation of soil physical properties. A change to annual cropping may improve or at least maint ain soil properties. Tillage and crop sequence effects on soil propert ies and water infiltration were tested after 9 yr of cropping on a Doo ley sandy loam (fine-loamy, mixed Typic Argiborolls) derived in glacia l till. Annual cropping tillage of fall sweep and spring disk (AWFST), and no tillage (AWNT) were compared with conventional tillage in whea t-fallow (FWCT) as the control. Statistical design was a randomized co mplete 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 carbo n (OC), pH, bulk density (BD), and particle size. Point resistance was measured in 0.02-m increments, Water infiltration into dry and wet so il was measured using a rainfall simulator, Maximum soil BD was 1.61 M g 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 M Pa on FWCT and 1.7 MPa on AWNT. Cumulative 3-h infiltration into dry s oil was 52 mm for FWCT and 69 mm for AWNT. Final infiltration rate int o 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 annua l 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, Grea ter amounts of OC on the annual crop treatments compared with the FWCT attest to the beneficial aspect of annual cropping in maintaining a l evel of soil quality that is greater than FWCT. From a soil conservati on perspective, no-tillage has an additional advantage because surface cover is maintained throughout the year, thereby reducing the potenti al for soil erosion.