DEVELOPMENT OF A BARLEY YIELD EQUATION FOR CENTRAL ALBERTA. 2. EFFECTS OF SOIL MOISTURE STRESS

Abstract

An equation was derived relating barley yield to inputs of fertilizer nitrogen (NA) and phosphorus (PA), soil test values for nitrate nitrogen (NS) and extractable phosphorus (PS) and moisture stress (W). This model, fitted to pooled data of 17 site-years, explained about 57% of yield variation in an investigation conducted on Chernozemic and Luvisolic soils in central Alberta. To identify days of moisture stress, a daily soil moisture budget was calculated for each site. A moisture stress equation derived from data external to this study was used to estimate a site moisture stress index. The moisture stress equation indicated that barley yield was decreased significantly by stress occurring within three stages of crop development: planting–emergence, emergence–onset of tillering, and jointing–heading. Such an equation should be useful for estimating, at intervals from seeding to heading, what the final yield of barley is likely to be in central Alberta at the end of the season. A yield equation was derived which indicated that the marginal product with respect to PA was influenced by PS, whereas the marginal product with respect to NA was influenced by NS, PS and W. Because the optimal input of fertilizer N for barley production depends upon moisture stress for the growing crop, inputs of N could be adjusted according to stress conditions occurring during the period from seeding to the 4- or 5-leaf stage.