Factors Influencing Wheat Yield and Variability: Evidence from Manitoba, Canada

By Carew, Richard; Smith, Elwin G. et al. | Journal of Agricultural and Applied Economics, December 2009 | Go to article overview

Factors Influencing Wheat Yield and Variability: Evidence from Manitoba, Canada


Carew, Richard, Smith, Elwin G., Grant, Cynthia, Journal of Agricultural and Applied Economics


Production functions to explain regional wheat yields have not been studied extensively in the Canadian prairies. The objective of this study is to employ a Just-Pope production function to examine the relationship between fertilizer inputs, soil quality, biodiversity indicators, cultivars qualifying for Plant Breeders' Rights (PBR), and climatic conditions on the mean and variance of spring wheat yields. Using regional-level wheat data from Manitoba, Canada, model results show nitrogen fertilizer, temporal diversity, and PBR wheat cultivars are associated with increased yield variance. Mean wheat yield is reduced by the proportion of land in wheat, the interaction of growing temperature and precipitation, and spatial diversity. By contrast, higher soil quality and PBR wheat cultivars increase mean yield. The wheat yield increases attributed to PBR range from 37.2 (1.4%) to 54.5 kg/ha (2.0%). Plant Breeders' Rights may have enhanced royalties from increased certified seed sales, but the benefits in terms of higher wheat yield or lower yield variability are limited. Future research is required to understand the interactive effects of fertilization practices, genetic diversity, and environmental conditions on regional wheat yield stability.

Key Words: climate, fertilizer, Manitoba, Plant Breeders' Rights, production risk, wheat, yield

JEL Classifications: O18, Q16

The wheat economy in Manitoba has undergone structural changes with wheat yields failing to keep pace with other competing crops, such as the oilseed canola (Statistics Canada, 2007). However, understanding of the environmental variables that affect regional wheat yield is limited and estimation of yield functions to identify wheat yield variability have received little attention in Canada. Substantive progress has been made over the years to gain a better understanding of nitrogen effects and application dates on spring wheat yield under field experimental conditions (Holzapfel et al., 2007; Subedi, Ma, and Xue, 2007; Tiessen et al., 2005). However, the manner in which nitrogen fertilizer, cultivar characteristicS) ^ environmental conditions affect regional wheat yields has received little attention, since regional wheat yield and input ¿ata ^6 not readily available for the northern Qreat plains m Cana(Ja Qne rf ^ fcw studies to look at wheat yield response to nitrogen fertilizer in this region found nitrogen to have a variance-increasing effect on yield (Smith, McKenzie, and Grant, 2003).

Much of yield increase for spring wheat yield over the last five decades has been attributed to a combination of management, genetic changes, and climatic conditions (McCaig and DePauw, 1995). Wheat advancements have also included improvements in protein levels, days to maturity, straw strength, and maintenance of resistance to major diseases and pests (Graf, 2005). While there are eight registered classes of western Canadian wheat, the Canadian Western Red Spring (CWRS) wheat class, recognized for its breadmaking qualities, represents the largest field crop grown in western Canada, comprising roughly 70% of the prairie wheat area (DePauw, Thomas, and Townley-Smith, 1986). The dominant CWRS wheat cultivar planted in Manitoba is "AC Barrie," accounting for over half of the total Manitoba CWRS wheat area from 1999 to 2002; however, it is now losing its dominance (Canadian Wheat Board, 2007). Wheat growers are adopting newer cultivars with improved traits, and reducing the high concentration of a few cultivars, potentially lowering yield variability, strengthening biodiversity, and avoiding the adverse effects of weather and pest conditions. Wheat producers on the Canadian Prairies tend to select cultivars based more on agronomic considerations (e.g., improvements in yield, days to maturity, and lodging resistance) than on protein content and disease resistance (Walburger, Klein, and Folkins, 1999). Barkley and Porter (1996) found that Kansas wheat producers' cultivar choices are significantly related to production characteristics, such as yield stability, cultivar age, and end-use qualities. …

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