Short-term responses of soil physical properties to corn tillage-planting systems in a humid maritime climate

The fertile, but naturally poorly drained soils of the western Fraser Valley in British Columbia, Canada are located in an area subject to about 1200 mm of rainfall annually. These soils were under intensive conventional tillage practices for years, which contributed to their poor in®ltrability, low organic matter, and overall poor structure. Development of tillage practices that incorporate winter cover crops and reduce traf®c in spring is required to reduce local soil degradation problems. The objective of this study was to determine short-term responses of soil physical properties to fall and spring tillage (ST) and fall and no spring tillage (NST) systems, both using spring barley (Hordeum vulgare L.) and winter wheat (Triticum aestivum L.) as winter cover crops. Field experiments were conducted for 3 years following seeding of the winter cover crops in fall 1992 on a silty clay loam Humic Gleysol (Mollic Gleysol in FAO soil classi®cation). Average aeration porosity was 0.15 m mÿ3 on NST and 0.22 m mÿ3 on ST, while bulk density was 1.22 Mg mÿ3 on NST and 1.07 Mg mÿ3 on ST at the 0±7.5 cm depth. Neither of these two soil properties should limit seedling and root growth. After ST, mechanical resistance was consistently greater for 500±1000 kPa in NST than in ST, but never reached value of 2500 kPa considered limiting for root growth. The NST system did not increase soil water content relative to ST, with soil water contents being similar at 10 and 40 cm depth in all years. In 2 out of 3 years NST soil was drier at the 20 cm depth than was ST soil. Three years of NST did not result in a signi®cant changes of aggregate stability relative to ST. This experiment showed that limiting tillage operations to the fall did not adversely affect soil physical conditions for plant growth in a humid maritime climate. # 2000 Elsevier Science B.V. All rights reserved.