Components of surface soil structure under conventional and no-tillage in northwestern Canada

Improvement in soil quality to maintain high production and reduce negative environmental impacts is necessary for alternative crop production strategies to become socially acceptable and viable in the long-term. No-tillage (NT) management of the predominantly small grain region of western Canada has the potential to curb soil erosion and increase profitability. An understanding of the direct effects of NT on soil properties is necessary to evaluate its potential for sustained long-term productivity. We have compiled data collected from two sites in northern British Columbia to ascertain the long-term effects of conventional tillage (CT) and NT on soil components thought to be important in surface soil structural improvement. Soil water retention was greater under NT compared with CT without dramatically altering bulk density due to redistribution of pore size classes into more small pores and less large pores. Soil organic C was greater under NT than under CT nearest the soil surface. Water-stable aggregation improved under NT compared with CT, perhaps because more soil organic C was sequestered within macroaggregates under NT compared with CT that helped to stabilize these aggregates. Steady-state water infiltration was greater under NT than under CT as a result of soil structural improvements associated with surface residue accumulation and lack of soil disturbance. Barley (Hordeum vulgave L.) yield tended to be greater under NT than under CT in years of low rainfall as a result of improvements in soil water retention and transmission that may have provided a better environment for root development. Our data indicate that NT is a viable management strategy to improve soil quality in the cold, semiarid region of western Canada. This strategy could lead to high production, minimal negative environmental impacts, acid a socially-acceptable farming system. (C) 1999 Elsevier Science B.V. All rights reserved.