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Title: The performance of cereal species and cultivar mixtures
Author: Taylor, Brian Richard
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1977
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The performance of cereal mixtures and of genotypes within mixtures was examined in experiments carried out near Aberdeen from 1969 to 1971. Three field trials tested mixtures of barley cultivars having differences in maturity, plant height and leaf habit. In one trial different mixing ratios and nitrogen levels were used. In three other trials mixtures of barley and oats were grown, and the effects of different cultivars, densities, and sowing arrangements investigated. Two pot experiments, examined the effect of twelve fertility treatments on thirty-five combinations of four, barley cultivars in 1969, and two barley, one oats and one wheat cultivar in 1970. In the field trials the grain yields of barley cultivar mixtures were similar to the means of the components grown in pure stand. In the pot experiment with barley cultivars mixture means consistently exceeded pure stand means at each fertility level, although the overall increase was only 3%. Differences from mid-component yields did not appear to be related to ratio of mixing, but a slight increase in yield occurred as the number of components in the mixture increased. In experiments with mixtures of barley and oats, a combination of Midas barley and Karin oats gave consistently higher yields than the mean of the components and slightly higher yields than the better component. The performance of this mixture was maintained over different sowing patterns and seed rates, but where sowing was arranged to give an advantage to one component of the mixture at the expense of the other, mixture yields were less than where both components; were closely mixed. The increased yield of the Midas-Karin mixture was attributed to the greater tillering of Midas in mixture than in pure stand, brought about by less competition before heading, and to a higher weight per grain of Karin in mixture than in pure stand - a result of its greater height after heading and the favourable disposition of its panicles- and upper leaves in the canopy. Total light interception was measured in mixtures of cultivars and species. Though there were instances where mixtures intercepted more light during the growing season than pure stands, it was difficult to relate these to increased grain yields. Light interception measured in the Midas-Karin mixture from before ear-emergence showed that only one mixture in six consistently intercepted more light than the mean of the components. The interaction of mixtures with replicates or fertility treatments was used as an estimate of stability in all experiments. Where two trials with barley mixtures formed part of a larger series, stability was also estimated from the regression of mixture yield on location mean yield. In no case was the stability of yield greater for mixtures than for pure stand, though in the pot experiments there was some indication that four-component mixtures were the most stable. In general, mixtures reflected the pure stand stabilities of their components. Competitive ability was measured using the method of Williams (1962) in some experiments, and the method of de Wit in all experiments. Where the two methods were used together, they showed good agreement. Competitive ability among barley cultivars appeared to be most closely associated with plant height, tall cultivars yielding more in mixtures; than in pure stands and short cultivars less. Competitive ability was most often shown in an increased number of fertile tillers. Barley was a better competitor than oats in the 1970 pot experiment and in one of the field trials. Levels of foliar disease were generally low, though there was some evidence of a buffering effect in mixtures of genotypes differing in susceptibility to pathogens, and disease levels were, if anything, slightly lower in mixtures than pure stands. Lodging occurred in few trials and it appeared that some support was; given to weaker-strawed genotypes in mixtures by stronger-strawed ones. In one trial, where a barley cultivar susceptible to head loss was included, losses, were comparatively less in mixtures than in pure stands.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available