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

Soils in no-tillage management are often plowed for crop rotation or t o correct a pest or soil management problem. This study determined whe ther soil properties created by no-tillage were retained or reestablis hed after plowing and return to no-tillage. The study was conducted on a Capac loam (fine-loamy, mixed, mesic Aeric Ochraqualf) in East Lans ing, MI. In 1986 and 1987, one each of three treatments in no-tillage since 1980 was plowed and subsequently returned to no-tillage (NTP86 a nd 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 tr affic 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 plowi ng did not eliminate stratification of chemical properties in the surf ace 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. Resid ual effects were evident 1 yr after plowing. However, 4 to 5 yr after plowing, most soil properties had returned to levels of NT, although r eestablishment of C and N in the surface remained lower than NT.