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 Valle y in British Columbia, Canada are located in an area subject to about 1200 mm of rainfall annually. These soils were under intensive conventional till age practices for years, which contributed to their poor infiltrability, lo w organic matter, and overall poor structure. Development of tillage practi ces that incorporate winter cover crops and reduce traffic in spring is req uired to reduce local soil degradation problems. The objective of this stud y 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 aestiv um 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 lo am Humic Gleysol (Mollic Gleysol in FAO soil classification), Average aerat ion porosity was 0.15 m(3) m(-3) on NST and 0.22 m(3) m(-3) on ST, while bu lk density was 1.22 Mg m(-3) on NST and 1.07 Mg m(-3) 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 500-1 000 kPa in NST than in ST, but never reached value of 2500 kPa considered l imiting 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 dep th 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 significant change s of aggregate stability relative to ST. This experiment showed that limiti ng tillage operations to the fall did not adversely affect soil physical co nditions for plant growth in a humid maritime climate. (C) 2000 Elsevier Sc ience B.V. All rights reserved.