TRAFFIC PATTERN AND TILLAGE SYSTEM EFFECTS ON CORN ROOT AND SHOOT GROWTH

Controlled wheel traffic is one way to manage compaction in no-till an d ridge-till systems. This study was conducted from 1990 to 1992 at Ka nawha, IA, on a Webster silty clay loam (fine-loamy, mixed, mesic Typi c 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 side s, on one side, or on neither side. Bulk density, hydraulic conductivi ty, root length density, shoot dry weight, and yield were measured at several positions across the traffic pattern. In general, the effect o f tillage systems was not significant averaged across positions. Posit ion relative to the traffic pattern had some effect, however, on all m easured parameters. Bulk density was greatest in trafficked interrows (1.36 Mg m(-3)) and least in untrafficked interrows (1.09 Mg m(-3)). H ydraulic conductivity near saturation was less in trafficked (39.4 mu m s(-1)) than in untrafficked (104.7 mu m s(-1)) interrows. Root lengt h density in trafficked interrows was on average one-third of that in untrafficked interrows. Root length density in a particular interrow a lso was influenced by the traffic pattern in the adjacent interrows. I n 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 a bsence of wheel traffic, affected corn root growth and yield.