Traffic pattern and tillage system effects on corn root and shoot growth

Controlled wheel traffic is one way to manage compaction in no-till and ridge-till systems. This study was conducted from 1990 to 1992 at Kanawha, IA, on a Webster silty clay loam (fine-loamy, mixed, mesic Typic Haplaquoll) to examine the effect of a wheel traffic pattern on corn (Zea mays L.) root distribution, shoot growth, and yield in no-till, ridge-till, and chisel-plow tillage systems. The wheel traffic pattern was configured so that some rows would have wheel tracks on both sides, on one side, or on neither side. Bulk density, hydraulic conductivity, root length density, shoot dry weight, and yield were measured at several positions across the traffic pattern. In general, the effect of tillage systems was not significant averaged across positions. Position relative to the traffic pattern had some effect, however, on all measured parameters. Bulk density was greatest in trafficked interrows (1.36 Mg m(-3)) and least in untrafficked interrows (1.09 Mg m(-3)). Hydraulic conductivity near saturation was less in trafficked (39.4 mu m s(-1)) than in untrafficked (104.7 mu m s(-1)) interrows. Root length density in trafficked interrows was on average one-third of that in untrafficked interrows. Root length density in a particular interrow also was influenced by the traffic pattern in the adjacent interrows. In 2 of the 3 yr, yields of rows with a trafficked interrow on only one side were 7% less than those of rows without trafficked interrows on either side. The wheel traffic pattern, and not just the presence or absence of wheel traffic, affected corn root growth and yield.