Yield, its components and pest incidence in mixed intercropping of oats (Avena sativa) and field beans (Vicia faba)

Authors

• Juha Helenius Department of Agricultural and Forest Zoology, University of Helsinki, SF-00710 Helsinki, Finland
• Päivi Ronni Department of Agricultural and Forest Zoology, University of Helsinki, SF-00710 Helsinki, Finland

DOI: https://doi.org/10.23986/afsci.72348

Abstract

Seed yields, yield components, pest incidence and damage were examined in two field experiments of mixed intercropping of oats (Avena sativa) with field beans (Vicia faba) in Southern Finland in 1984—1985.The stand types were monocrops and replacement series of mixtures with 2/3 and 1/3 or 1/3 and 2/3 of oats and beans, respectively, on plots treated or not treated with insecticide. In the first season when the overall performance of the crops was poor and the numbers of the main pest Rhopalosiphum padi (Horn., Aphididae) on oats low, the Land Equivalent Ratio (LER) index indicated an intercropping advantage in the bean yield and a disadvantage in the oat yield, the insecticide treatment having no effect on the overall nor on the relative performance of the component crops. The site used during the second season was of high fertility, thus favouring oats over beans. The LERs indicated no advantage or disadvantage in mixed cropping for either oats or beans when R. padi was not controlled. Spraying against R. padi improved the performance of oats, the mixture with 1/3 oats showing an advantage over the monocrop. Simultaneously, there were signs (p = 0.08) of a reduction in the relative performance of the beans. The indicative results support the hypothesis of interspecific dynamics in compensatory yielding as an element of improved reliability in intercropping. The yield components most sensitive to the change in cropping pattern were the number of panicles per plant in oats and the seed weight in beans, both increasing in the mixtures. Compared to known responses to stand density in monocrops, the beans responded to the mixed cropping in a more specific way than the oats. Mixed cropping increased the numbers of aphids in oats. There were signs of a reduced incidence, but not of a reduced average colony size, of Aphis fabae, and of a reduced rate of notching by Sitona spp. weevils on beans in mixed cropping. The results for damage by the frit fly (Oscinella frit) were inconclusive.