DRAINAGE AND TILLAGE EFFECTS ON A CROSBY-KOKOMO SOIL ASSOCIATION IN OHIO .4. SOIL PHYSICAL-PROPERTIES

Bulk density, soil structure, penetrometer resistance, and moisture re tention characteristics were examined for the Crosby-Kokomo Associatio n near Columbus, Ohio. The soils are classified as fine mixed, mesic, Aeric Ochraqualf and fine, mixed, mesic, Typic Argiaquoll, respectivel y. Effects of four tillage methods were studied with and without subsu rface drainage. Tillage methods were: no-till, raised beds, ridge till and moldboard plow. The tillage treatments were laid out according to a Randomized Block Design with three replicates on each drainage site . Soil samples obtained in August, 1987 to 50 cm depth in 10 cm increm ents, were analyzed for aggregate size distribution, and moisture rete ntion characteristics. In addition, surface (0-10 cm and 10-20 cm dept hs) core samples were obtained in July 1989 for measurement of soil bu lk. density, and moisture retention characteristics. Penetrometer resi stance and soil moisture content for the surface layers were also meas ured in July 1989. The mean weight diameter (MWD) was higher for undra ined than drained treatment, 2.94 mm vs. 2.49 mm, respectively. Neithe r drainage nor tillage treatments had a significant effect on soil bul k density measured about 8 weeks after sowing. Penetrometer resistance was lower, and surface soil moisture content was higher in the undrai ned compared with the drained treatment. Soil moisture retention at al l suctions and plant-available soil moisture reserves were more in und rained than drained soil. Differences in soil moisture retention among drainage treatments axe attributed more to organic matter induced dif ferences in pore size distribution than to total porosity. For these s oils in central Ohio, drainage had a more significant effect on soil p hysical properties than tillage operations performed in the fall and/o r spring.