Axle load and tillage effects on crop yield for two soils in central Ohio

A load of 5±20 Mg on a single axle cart is a common practice for spreading manure and harvesting grains in the US Corn Belt. Yet, effects of such a load used for a long time of 5±10 years on crop yield are not known for predominant soils of the region. Further, axle load effects on crop yield may depend on tillage methods. Thus, effects of axle load and tillage methods on corn (Zea mays L.) grain yield were studied for Wooster silt loam an Orthic Luvisol (at Wooster) and Crosby silt loam a Gleyic Luvisol (at South Charleston) in Ohio. Experiments were conducted for 11 consecutive growing seasons (1988 through 1998) at Wooster and 6 seasons (1991±1994, 1997±1998) at South Charleston. Three axle load treatments at Wooster consisted of: (1) regular machine traf®c (RMT), (2) 7.5 Mg axle load as guided or controlled traf®c (CT), and (3) 7.5 Mg axle load covering the entire plot (CEP). There were three tillage methods at Wooster: (1) no till (NT), (2) chisel plowing (CP), and (3) moldboard plowing (MP). Three axle load treatments at South Charleston were: (1) control, (2) 10 Mg axle load, and (3) 20 Mg axle load. Two tillage methods used at South Charleston were NT and MP. There were no signi®cant differences in soil bulk density and penetration resistance of Wooster silt loam soil measured after 11 seasons of harvest traf®c. Harvest traf®c treatments at Wooster signi®cantly affected corn grain yield only in 1988 and 1998, for 2 out of 11 seasons. In 1988, corn grain yield was reduced by 14% by 7.5 Mg axle load treatments. In 1998, the reduction in grain yield was 5% by the CT and 15% by the CEP axle load treatments. Mean corn grain yield for 11 years was 6.6 Mg haÿ1 for RMT, 6.3 Mg haÿ1 for 7.5 Mg axle load with CT (reduction of 5%), and 6.0 Mg haÿ1 for 7.5 Mg axle load with CEP (reduction of 9%). The mean grain yield reduction for the 11-year period for the CEP treatment was 10%. There were no consistent trends in grain yield from year to year with regard to tillage methods. The CP treatment out-yielded the other tillage treatments in 4 out of 11 years. Mean corn grain yield in CP was 7% more than that of NT and 13% more than that of MP. Neither axle load nor tillage treatment had any effect on corn grain yield at South Charleston, and mean corn grain yield was 7.5 Mg haÿ1 for control, 7.6 Mg haÿ1 for 10 Mg axle load, and 7.3 Mg haÿ1 for 20 Mg axle load. The mean corn grain yield was 7.0 Mg haÿ1 for NT and 7.8 Mg haÿ1 for MP treatment. # 2000 Elsevier Science B.V. All rights reserved.