ARS | Publication request: OVERWINTER CHANGES IN AGGREGATE SIZE DISTRIBUTION OF A LOAM IN WEST CENTRAL MINNESOTA

Submitted to: Seasonally Frozen Soils Symposium
Publication Type: Proceedings
Publication Acceptance Date: June 12, 1997
Publication Date: N/A

Interpretive Summary: Soils that have been cultivated for many years will experience an improvement in soil structural properties when put into sod. These improvements allow water to move rapidly into and through the soil profile and reduces the possibility of soil erosion. The Conservation Reserve Program (CRP) is a program where cultivated soils were put into sod for ten years. This study was conducted to determine what effect tillage systems will have on water movement into the soil and on soil erosion after sod has been returned to crop production. Rainfall simulation trials were conducted on plots that had been sod for six years. Treatments applied ranged from moldboard plowing of the sod to chemically killing the sod and establishment of no-till crop production. Four years of intensive tillage resulted in much water runoff and soil erosion and was characteristic of the pre-sod condition. No-till crop production did not have any water runoff or soil erosion. These results show that beneficial soil properties related to water runoff and soil erosion developed during sod will rapidly disappear with tillage, but can be maintained with no-till crop production. These data can be used by conservation planners and producers for development of sustainable conservation management plans on lands that were in CRP.

Technical Abstract: Changes in surface structure and stability during winter in northerly climatic regions can result in a highly erodible soil condition. Soil aggregates can degrade to smaller aggregates by the combination of freezing and thawing and freeze drying, making the soil susceptible to wind erosion. A study was conducted near Morris, Minnesota, on a loam to determine changes in aggregate size over three winters as affected by tillage and crop rotations. Aggregate size distribution was determined by dry sieving in the fall after fall tillage and again in the spring prior to spring tillage. Overwinter processes influenced aggregate size, with the magnitude and direction of change influenced by soil moisture during the winter season. In two of the three years of this study, when the soil was initially moist prior to freezing in the fall but dried by sublimation during the winter, aggregates degraded to size fractions susceptible to wind erosion. In the third winter when surface soil moisture was recharged by snowfall, aggregate size increased from fall to spring on treatments with surface residue.