Abstract
The research in intraspecific competition within an alfalfa stand and interspecific competition between alfalfa and weeds was begun on the Michigan State University farm in East Lansing in 1972. Alfalfa seeding densities of 50, 400 and 800 seeds/m2 were used to determine intraspecific competition. Interspecific competition between alfalfa and weeds occurred mainly in noncontrolled alfalfa stands at various levels of seeding densities. Plant competition was evaluated with importance values and with relative crowding coefficients. Both measurements were found to be suitable for this kind of study. Importance values primarily indicated the quantity relationships of different species. Relative crowding coefficients mainly characterized the competitive ability of a species in a mixed stand. The importance of alfalfa exceeded the importance of weeds in noncontrolled and herbicide controlled stands at the seeding rates of 14 and 7 kg/ha respectively. Relative crowding coefficients show the competitive ability of alfalfa with regard to weeds. In the case of intraspecific competition there was no change in the crowding coefficient of alfalfa in respect of weeds when the seeding rate of alfalfa was increased beyond 9 kg/ha. The crowding coefficient of weeds presented equal values under all treatments thereby indicating the variability and plasticity of weeds. The maximum yield level was obtained in all treatments with the alfalfa seeding rate of 9 kg/ha. The total biomass production per unit area was equal in the noncontrolled system at all seeding densities and in the herbicide controlled system at seeding rates of 9 kg/ha or more.
Highlights
IntroductionCompetition occurs between different species and among pure stands
Plants compete for light, moisture and nutrients
Cultivated plant community and plant competition described by importance values
Summary
Competition occurs between different species and among pure stands. Competition has been studied by way of mathematical models, laboratory and field experiments with single populations or limited mixtures and with influences from natural and seminatural populations growing in mixed communities with or without experimental manipulation. Me Intosh (1965) noted that each species has a genetic potential of response to the environment which determines if and how well it can grow on a given site. Its success is not solely dependent on site conditions, but is to a large degree controlled by interaction with other plants. The familiar measures of the competitive effect are reduction in size or reduction in reproductive capacity (plasticity) and reduction in number of plants (mortality). Cook (1965) has stated that intraspecific competition is mainly characterized by plastic response, while interspecific competition mainly results in mortality The familiar measures of the competitive effect are reduction in size or reduction in reproductive capacity (plasticity) and reduction in number of plants (mortality). Cook (1965) has stated that intraspecific competition is mainly characterized by plastic response, while interspecific competition mainly results in mortality
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