THE EFFECT OF TYRE SOIL CONTACT PRESSURE AND ZERO TRAFFIC ON SOIL AND CROP RESPONSES WHEN GROWING WINTER-WHEAT

Winter wheat was grown for 4 years on a clay soil subjected to three levels of tyre/soil contact pressure, in conjunction with direct drilling and shallow tine cultivation. Zero, low and conventional tyre related stresses were applied to the soil in the course of normal cultural operations and measurements were made of soil, crop and machinery responses. Under zero traffic, a deep friable tilth was retained from one season to the next. Cone resistance and soil density generally increased with tyre contact pressure, but the greatest difference was between soil stressed by tyres compared with that which remained traffic free. Porosity was reduced by conventional traffic but saturated hydraulic conductivity at and below 0·5 m depth was unaffected by treatment. There was no conclusive evidence to suggest a difference in yield related to the traffic treatments but total yield from the zero traffic plots was lower than from the other treatments because of manganese deficiency. Compared with zero traffic, conventional and low ground pressure systems increased shallow tine cultivator draught by 60% and the energy for cultivations and drilling by up to 250%. Standard traction tyres were effective for low ground pressure operation, but safety during road use needs consideration. Zero traffic improved soil conditions and a cost effective means of achieving such a system should be explored. © 1997 Elsevier Science Ltd. All rights reserved.