PERIODIC PLOWING EFFECTS ON SOIL PROPERTIES IN A NO-TILL FARMING SYSTEM

Soils in no-tillage management are often plowed for crop rotation or to correct a pest or soil management problem. This study determined whether soil properties created by no-tillage were retained or reestablished after plowing and return to no-tillage. The study was conducted on a Capac loam (fine-loamy, mixed, mesic Aeric Ochraqualf) in East Lansing, MI. In 1986 and 1987, one each of three treatments in no-tillage since 1980 was plowed and subsequently returned to no-tillage (NTP86 and NTP87) and compared with conventional tillage (CT) and long-term no-tillage (NT). In all treatments, plowing, compared with NT, decreased bulk density by 0.17 to 0.28 Mg m(-3) increased total porosity from 0.03 to 0.10 m(3) m(-3), increased macroporosity by 0.05 to 0.13 m(3) m(-3), and decreased microporosity by 0.03 to 0.05 m(3) m(-3). Wheel traffic increased bulk density 0.14 to 0.18 Mg m(-3) in the plowed soils but only 0.04 Mg m(-3) in the NT soil. Soil surface P, K, and organic C (OC) were redistributed in the surface 200 mm by plowing, but plowing did not eliminate stratification of chemical properties in the surface 50 mm. The NTP87 treatment enhanced mineralization of N over both CT and NT by 9.8 to 18.4 g N m(-3) in the surface 50 mm in 1987. Residual effects were evident 1 yr after plowing. However, 4 to 5 yr after plowing, most soil properties had returned to levels of NT, although reestablishment of C and N in the surface remained lower than NT.