Assessment of competition and yield advantage in addition series of barley variety mixtures

Abstract

In an addition series experiment the competition between three barley varieties (Agneta, Arra and Porno) and the yield performance of mixtures were evaluated. Also two levels of nitrogen fertilization (50 and 100 kgN/ha) were applied. Two approaches (the replacement series and the linear regression equation) were used to analyse the competitive relationship based on grain yields in two-component mixtures. In three component mixtures the replacement series approach was applied. Both methods showed a similar dominance order of the varieties with Arra always being dominant and Agneta subordinate. The relationship between varieties was independent of the number of varieties in the mixture. Increase in available nitrogen strengthened the competitiveness of Arra especially in the dense, two-variety mixtures. Some mixtures over yielded but the differences were not statistically significant. The yield advantage based on relative yield total or on the ratio of actual and expected yield was greatest when the density and nitrogen fertilization were low and especially when one component in the mixture was a rather low yielding variety (Agneta). The land equivalent ratios (LER) (the reference pure culture yield was the maximum yield of each variety) were close to one, suggesting that under optimal growing conditions the yield advantage of barley varietal mixtures is marginal.