Competitive ability in mixtures of small grain cereals

Morphological and physiological differences in competitive ability among sp ecies and genotypes can affect the growth, development, and subsequent comp osition and value of feedstuffs produced from small grain cereal mixtures. Our objective was determine the final grain yields of the components of mix tures and compare these yields with those expected based on the yields of t he monocrops. Three field studies were conducted to evaluate the productivi ty of barley (Hordeum vulgare L.), oat (A vena sativa L.), triticale (x Tri ticosecale rimpaui Wittm.), and rye (Secale cereale L.) grown as monocrops and mixtures. Seeding rates ranging from 250 seeds m(-2) to 750 seeds m(-2) were evaluated to determine their effect on competitive ability of genotyp es and species of small grains. Differences in competitive ability were fou nd. The semi-dwarf barley 'Kasota' was less competitive than the standard-h eight 'AC Lacombe' and 'Seebe'. 'Noble' barley was more competitive than 'A C Mustang' oat or 'Wapiti' triticale. 'Prima' winter rye was more competiti ve than 'Pika' winter triticale. Relative grain yields were generally not d ifferent than 1.0 g g(-1), but when significantly different they were usual ly higher than one, indicating that the yields of those mixtures were bette r than expected based on yields when the cultivars were grown as pure stand s. Seeding rates had little effect on competitive ability. The specific fac tors that lead to better than expected grain yields of mixtures and to good competitive ability of cultivars and species are difficult to predict and must be evaluated on a case-by-ease basis.