Yield advantage and competition in intercropped oats (Avena sativa L.) and faba bean (Vicia faba L.): Application of the hyperbolic yield-density model

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Abstract Both monocrops and intercrops of oats (Avena sativa L.) and faba bean (Vicia faba L.) were cultivated over a range of sowing densities in a field experiment of randomized complete blocks design. The hyperbolic yield-density model was applied to phytomass and seed yield. Predictions and parameters of the model were used to quantify intra- and interspecific competition, and to evaluate yield potential of the mixtures. The model accounted for 93% and 85% of the variation in phytomass and in seed yield, respectively. In both species intraspecific competition was more severe than interspecific competition. Oats was relatively the stronger of the two competitors, e.g. substitution rates were 0.33 plants of oats for a plant of bean with respect to oat seed yield, and 0.72 plants of bean for a plant of oats with respect to bean seed yield. Oats had a greater yield potential than bean. The mixture sown in densities of 400 oats/m2 and 40 beans/m2 out-yielded the most productive monoculture with respect to seed yield. Land equivalent ratios (LER) of this mixture, 1.05 for phytomass and 1.06 for seed yield, indicated yield advantage. The greatest LER obtained for seed yield was 1.10. The predicted yield curves demonstrated that the maximum (asymptotic) combined yields, 13 t/ha of phytomass and 6 t/ha of seeds might be obtained by planting bean and oats in 1:1 ratio. Land equivalent ratios of this mixture were 1.23 for phytomass and 1.31 for seed yield. Both the actual results and the model predictions suggest potential of intercropped oats and faba bean.