Traffic-soil-plant (maize) relations

Twenty-five treatments consisting of three vehicle contact pressures, 62, 41 and 31 kPa (0.63, 0.42, 0.32 kg/cm²), four numbers of tractor passes (1, 5, 10, 15,) before and after seeding groups, and a control of zero traffic were used to study the effect of soil compaction on corn plant root growth and distribution in a Ste. Rodalie clay soil. The average dry bulk density values for 0–20 cm depths measured during the season varied from a minimum of 0.89 g/cm³ to a maximum of 1.12 g/cm³ depending on the severity of the treatment. Root distribution maps were obtained for all the treatments by field measurements coupled with root washing methods. An average root density of 5.7 mg/g of soil in an uncompacted control plot was reduced to less than 2 mg/g in a plot with 15 passes of 0.63 kg/cm² contact pressure. Soil penetration resistance values in various plots were compared, and a statistical model was obtained in terms of the traffic treatments, soil moisture content and depth. Yield reductions and penetration resistance were compared to root distrubution density results.