Competition and yield advantage in barley-barley and barley-oats mixtures

Abstract

Competition and yield advantage in barley varietal mixtures and in barley-oats mixtures were investigated. The trials were based on replacement series, but in a few cases the overall density of the stand was varied on the basis of an addition series. Both models of competition, one based on the de Wit model and the other upon a linear regression model, agreed as to which component was the dominant and which was the subordinate in the mixture. The competition coefficients from regression analyses depicted competition between components better in a dense than in a sparse stand. The competitive ability of a genotype did not depend directly upon individual characters of the genotype, such as rate of initial development, earliness, culm height, tillering capacity or grain yield in monoculture (adaptation), A good combination of characters from the viewpoint of competition was provided by the barley cv. Arra with its rapid initial development and rapid culm growth (earliness), the variety being dominant irrespective of number of components in the mixture, stand density, level of nitrogen fertilization or growing season. This suggests that competitive relations and distribution of resources within a mixture are determined at an early stage in the growing period. In other cases the competitive ability of a genotype varied from one environment to another with the competitive relations between components being inconsistent. The dominance of an aggressor usually increased with increasing nitrogen fertilization especially when the total density of the stand was high. As a rule, competition affected all the components of yield with the kernel weight being least affected. The grain yield of varietal mixtures did not differ from the yield of the highest yielding component grown alone, i.e., mixtures did not over yield. The relative yield total of varietal mixtures was higher at low (RYT > 1) than at optimal densities (RYT =1). Also the relative yield total was higher under conditions where the nitrogen fertilization was not optimal. The results of a varietal trial repeated during three successive years indicated that the relative yield total of a given mixture varied from one growing season to another, fluctuating around unity. Thus highly adapted barley varieties appear to compete for the same resources, and the grain yield advantage of such mixtures is marginal. The results of the barley-oats mixture trials revealed that the mixture may over yield. The relative yield totals of barley-oats mixtures were usually equal to or greater than unity the latter suggesting that the mixtures of barley and oats may use resources more efficiently than monocultures, and some grain yield advantage could be achieved with such mixtures. The protein yield of the barley-oats mixtures did not differ from the yield of the highest yielding component grown alone. The ratio of actual and expected protein yield and the relative protein yield total were usually slightly greater than one. The grain yields of mixtures were not consistently more stable than monocultures as determined by the coefficient of variation.

Three-component barley mixtures: Ratio effects in replacement series

“…The grain yields of these three-way barley mixtures generally fell between the yields of the monocrops (Table 2) as has been reported for cereals in the literature (Wolfe 1985;Jokinen 1991a;Jedel et al 1998). Over all, only the 20:40:40, and 50:30:20 mixtures performed better than the weighted yields of the monocrops (Table 2).…”

“…However in most cases reported in the literature, the yields of intraspecific cereal mixtures are about the same as, or only slightly higher than, the weighted mean yields of the components (Jokinen 1991a;Jedel et al 1998). Lang et al (1975) had a twofold definition of yield stability.…”

“…Hordeum vulgare L., mélanges, cultivar, rendement, tolérance, stress Cultivar mixtures, multilines or bulk hybrids have been proposed as a means to use newly developed lines to increase within-crop heterogeneity and thereby give the crop a greater capacity to adjust to the many and varied biotic and abiotic stresses that occur during the life cycle, and ultimately lead to better yield stability and higher yields than pure-line monocrops (Jokinen 1991a). However in most cases reported in the literature, the yields of intraspecific cereal mixtures are about the same as, or only slightly higher than, the weighted mean yields of the components (Jokinen 1991a;Jedel et al 1998).…”

“…A replacement mixture is when plants of one component are replaced by plants of another component (total plant population is held constant) (Jokinen 1991a;Fukai and Trenbath 1993). Criticism of replacement series methodology have been made as it compares the performance of the components at an arbitrarily chosen plant density (Connolly 1986).…”

Yield, quality and stress tolerance of barley mixtures in central Alberta

“…In most previous studies, yields of mixtures have been neutral, i.e. about the same as, or slightly higher than, that of the weighted means of their components (Wolfe 1985;Jokinen 1991b). Neutral responses for barley mixtures were reported by Lang et al (1975), Valentine (1982), Harrabi et al (1986), Jokinen (1991a, c) and Mundt et al (1994).…”