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Computation and interpretation of competition parameters in a mixed crop with winter rape



Computation and interpretation of competition parameters in a mixed crop with winter rape



Zeitschrift fuer Acker- und Pflanzenbau 150(1): 6-18



Different parameters of a simple model of competition are computed and interpreted using the experimental results of an extensive competition field experiment with 3 components: 2 inbred lines of winter rape and their F1. The model gives for the phenotypic value PX of plant X: PX = .gamma.X + .SIGMA.i(X) .delta.i(X) + .alpha.X,i(X) + eX, where competitive ability of the plant X = .gamma.X and the competitive influence of X = .delta.X. The summation index i(X) runs over the neighbors of plant X, eX denotes the environmental deviation and aX,i(X) measures that part of the competitive effects which cannot be interpreted by the independent, linear and additive .gamma.-effects and .delta.-effects. Under different simplifying assumptions the parameters .gamma. and .delta. can be estimated using only pure-stand values of the components. The .delta.-parameter measures the dependence of the components to density. The .alpha.-parameter gives that competition dependent part of the phenotypic value which cannot be combined and explained using only the corresponding pure-stand values and the competition model and parameter definition given above. All parameters .gamma., .delta. and .alpha. are computed numerically and discussed for 9 plant characters. With all 3 components the characters 1000 kernel weight, plant height and number of grains per pod are not dependent on density. The remaining characters grain yield per plant, number of pods per plant, number of grains per plant and number of branching of 1st, 2nd and 3rd order per plant are dependent on density. With regard to the .alpha.-parameters all characters can be roughly divided into 2 groups: group I: .alpha. = 0, and group II: .alpha. .noteq. 0. Because .alpha. = 0, the mixed-stand value can be combined and explained in a simple and clear manner (additivity, linearity, independence) using only the corresponding pure-stand values.

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