SOIL-WATER UNDER CONVENTIONAL AND ALTERNATIVE CROPPING SYSTEMS IN CRYOBOREAL SUBHUMID CENTRAL ALBERTA

Soil water limits plant growth in the Canadian Prairie Provinces. Effi cient use of soil water is, therefore, paramount in crop production. T wo 2-yr field studies were conducted (i) to determine the effects of c rop selection and cropping practice on the temporal and spatial distri bution of soil water and (ii) to quantify water use and water-use effi ciencies (WUE) of alternative crop/cropping systems for a subhumid reg ion of Alberta. The first study was at the Ellerslie Research Station on an Orthic Black Chemozemic and the second at the University of Albe rta Breton Plots on an Orthic Gray Luvisol. At each site three annual crops/cropping systems [barley (Hordeum vulgare L.), barley intercropp ed with field pea (Pisum sativum L.), and faba bean (Vicia faba L.) ] and a perennial forage [creeping red fescue (Festuca rubra)] were grow n in 1987 and in 1988. At Ellerslie, tillage methods to grow annual cr ops were conventional and zero tillage. At Breton, the two tillage met hods used were: (i) conventional and (ii) deep tillage (to enrich the surface horizon with clay from the subsoil). The experimental design u sed was a split plot with four replications. Soil water was measured b y neutron attenuation. Evapotranspiration was calculated as the change in soil water to 0.80-m depth plus precipitation. Soil water changes were more closely associated with the kind of crop grown than with the method of tillage used. The barley/field pea intercrop exhibited a pa ttern of water use similar to barley. Greater water-use efficiency mea sured in the intercrop system was attributed to differences in canopy structure and plant biomass production. Faba bean and red fescue had l ower WUE than barley and the intercrop. The water requirement by faba bean was close to that of red fescue and related to leaf area developm ent. Small tillage effects on soil water were observed during 1988. So il water under zero tillage was greater than under conventional tillag e. Faba bean and red fescue are likely to succeed more in agro-ecologi cal regions such as Breton. Further studies are required to improve ou r understanding of the effects of these cropping systems on water reso urces when they are used in rotational-production systems.