TILLAGE-INDUCED SOIL CHANGES AND RELATED GRAIN YIELD IN A SEMI-ARID REGION

Abstract

Crop yields are affected by tillage-induced changes in soil chemical and physical parameters. This study was conducted to determine the tillage-induced soil changes and related grain yield and grain N concentration for two crop rotations in a semi-arid region. Soil physical and chemical properties were measured in winter wheat-barley-fallow and continuous wheat rotations under no-till (NT) and conventional till (CT). The field measurements were made in 1983 and 1984 on a Lethbridge loam and a Chin clay loam in a semi-arid region of Alberta. Soil moisture, temperature, bulk density and inorganic N were measured. The effects of tillage-induced soil changes on grain yield and grain N concentration were assessed. In 1983, at Lethbridge, tillage had no effect on grain yield. Grain yield was greater for NT than for CT crops in 1984, a year characterized by early summer drought. At Vauxhall, yield of NT crops was equal to or greater than that of CT crops except for barley in 1983, where volunteer winter wheat growth was a severe problem in the NT treatment. May soil temperatures (2-cm soil depth) for spring-seeded barley averaged 14.7 °C in the CT compared with 13.9 °C in the NT treatment. Inorganic N (0 to 30 cm) was not significantly affected by tillage in 1983, but in 1984 inorganic N was consistently greater in the CT than in the NT treatments at midseason and in the fall. The dominant effect on grain N concentration was an inverse relationship with grain yield. However, when grain yields were similar between tillage systems, greater inorganic N with the CT treatment was reflected in larger grain N concentrations for CT. Greater grain yield with NT than with CT at Lethbridge was associated with greater total soil water and improved seedbed moisture resulting in greater seed imbibition of water and plant emergence. At Vauxhall, tillage treatment did not significantly affect total soil water conservation, but greater grain yields with NT than with CT were attributed to improved plant emergence with NT. Conserving both seedbed moisture and total soil water by reducing tillage had beneficial effects on crop yield in this semi-arid region. Key words: No-till, conventional till, soil water, soil temperature, soil nitrogen