Soil compaction in conservation tillage: Crop impacts

Soil compaction effects on maize (Zea mays L.) plant population, height, and yield were studied from 2002-2005 in a no-tillage/in-row tillage study on a Hublersburg silt loam soil (Typic Hapludult) in Pennsylvania. Soil was compacted annually with a three-axle truck with 10-Mg axle load mounted with road tires (700 kPa inflation pressure) or flotation tires (250 kPa). In another treatment, soil was only compacted with road tires in the first year without subsequent compaction. Remediation treatments were deep (40 cm) in-row tillage before or after compaction with road tires and shallow (10 cm in 2002-2003 and 22 cm in 2004-2005) in-row tillage after compaction. Significant yield reductions averaging 17% in 3 yr out of 4 were observed for annual compaction with road tires compared with control (no-tillage without compaction). Compaction with flotation tires reduced yield significantly in 1 yr only. Yield reductions due to compaction disappeared after 1 yr. Deep tillage after compaction increased yield (17%) in 1 yr only, whereas shallow tillage did not increase yields. Yield improvements due to deep tillage were lost if it was followed by heavy traffic. Deep tillage and no-tillage without compaction gave similar yields in the first 3 yr, but no-tillage had higher yield in 2005. In-row tillage substantially reduced residue cover. Our results suggest little need for in-row tillage to manage compaction in long-term no-tillage when axle loads are no more than 10 Mg and flotation tires are used to keep inflation pressures below 250 kPa.