A Revised Analysis of Plant Competition Experiments

McGilchrist, C. A.; Trenbath, B. R.

doi:10.2307/2528603

Cited by 203 publications

(116 citation statements)

References 8 publications

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“…In the corrected diallel these correlations are considerably enhanced as was predicted by the competition diallel model. This has also been noticed by McGilchrist & Trenbath (1971). Another observation is that for many 2 x 2 comparisons in the corrected diallel the duoculture average exceeds 1.0, which implies the presence of negative interference.…”

Section: Resultssupporting

confidence: 65%

“…The diallel is formed by competing each strain with every other strain, including itself, and recording the performance of the primary (indicator) genotype in the presence of various associate competitors. However, with notable exceptions (McGilchrist & Trenbath, 1971) the analysis of such diallels has been largely empirical (Williams, 1962;McGilchrist, 1965;Norrington-Davies, 1967, 1968Breese & Hill, 1973;Mather & Caligari, 1983;Eggleston, 1985;de Miranda & Eggleston, 1987, 1988c with little regard for the biological determinants underlying the diallel. Hence, in this paper we present an analytical model for the competition diallel based on three linear biological parameters, representing both the exploitation (acquisition and utilization of a common resource) and interference (unique resources and mixture benefits) components of competition (Birch, 1957).…”

Section: Introductionmentioning

confidence: 99%

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The competition diallel and the exploitation and interference components of larval competition in Drosophila melanogaster

1991

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A logistic model of the competition diallel is presented based on two linear parameters for the exploitation component of competition, namely the acquisition rate (f) and utilization efficiency (u), and one linear parameter for the interference component of competition (i). This interference component encompasses all phenomena that are uniquely related to duocultures, such as resource partitioning, mutual stimulation, inhibition and complementation. The model uses yield-density regression coefficients (c-values), but could be adapted to suit other variates that account for both competitor density and relative frequency. In Drosophila larval competition most interference is negative and depresses the performance of duocultures with respect to monocultures, over and above that expected from shared exploitation of a common resource. Even in the closely controlled competitive conditions of these experiments this interference accounts for a considerable proportion of the total variation. The isolation of a general, and therefore predictable, interference component may prove useful in agriculture when assessing the relative importance of mixture effects to the yield potential of different crops.

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Section: Resultssupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

The competition diallel and the exploitation and interference components of larval competition in Drosophila melanogaster

1991

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“…One can also calculate indices of competitive relationships, such as relative crowding coefficient (de Wit 1960), coefficient of aggressivity (Mcgilchrist and Trenbath 1971) and competitive ratio (Wiley and Rao 1980). Of these, the competitive ratio is independent of any possible yield advantage of the mixture (Willey and Rao 1980).…”

Section: Characterization Of Yieldmentioning

confidence: 99%

Competition and yield advantage in barley-barley and barley-oats mixtures

Jokinen¹

1991

AFSci

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Competition and yield advantage in barley varietal mixtures and in barley-oats mixtures were investigated. The trials were based on replacement series, but in a few cases the overall density of the stand was varied on the basis of an addition series. Both models of competition, one based on the de Wit model and the other upon a linear regression model, agreed as to which component was the dominant and which was the subordinate in the mixture. The competition coefficients from regression analyses depicted competition between components better in a dense than in a sparse stand. The competitive ability of a genotype did not depend directly upon individual characters of the genotype, such as rate of initial development, earliness, culm height, tillering capacity or grain yield in monoculture (adaptation), A good combination of characters from the viewpoint of competition was provided by the barley cv. Arra with its rapid initial development and rapid culm growth (earliness), the variety being dominant irrespective of number of components in the mixture, stand density, level of nitrogen fertilization or growing season. This suggests that competitive relations and distribution of resources within a mixture are determined at an early stage in the growing period. In other cases the competitive ability of a genotype varied from one environment to another with the competitive relations between components being inconsistent. The dominance of an aggressor usually increased with increasing nitrogen fertilization especially when the total density of the stand was high. As a rule, competition affected all the components of yield with the kernel weight being least affected. The grain yield of varietal mixtures did not differ from the yield of the highest yielding component grown alone, i.e., mixtures did not over yield. The relative yield total of varietal mixtures was higher at low (RYT > 1) than at optimal densities (RYT =1). Also the relative yield total was higher under conditions where the nitrogen fertilization was not optimal. The results of a varietal trial repeated during three successive years indicated that the relative yield total of a given mixture varied from one growing season to another, fluctuating around unity. Thus highly adapted barley varieties appear to compete for the same resources, and the grain yield advantage of such mixtures is marginal. The results of the barley-oats mixture trials revealed that the mixture may over yield. The relative yield totals of barley-oats mixtures were usually equal to or greater than unity the latter suggesting that the mixtures of barley and oats may use resources more efficiently than monocultures, and some grain yield advantage could be achieved with such mixtures. The protein yield of the barley-oats mixtures did not differ from the yield of the highest yielding component grown alone. The ratio of actual and expected protein yield and the relative protein yield total were usually slightly greater than one. The grain yields of mixtures were not consistently more stable than monocultures as determined by the coefficient of variation.

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“…It is defined as the relative land area under sole crops that is required to produce the same yield achieved by intercropping (Vandermeer 1989). LER for a cereal-pea intercrop was calculated on the basis of the total harvested dry matter and as the sum of partial LER values for cereal (L C ) and pea (L P ) in accordance with De Wit and Van den Bergh (1965): The competitive relationship between the two components of intercrop was determined using the Aggressivity value (A) proposed by McGilchrist and Trenbath (1971) as follows:…”

Section: Calculation and Statisticsmentioning

confidence: 99%

Cereal-pea intercrops to improve sustainability in bioethanol production

Pellicanò

Romeo

Pristeri

et al. 2015

Agron. Sustain. Dev.

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The environmental performance of secondgeneration biofuels from lignocellulosic biomass, such as crop residues, is foreseen to be superior to that of first-generation biofuels such as maize bioethanol. Moreover, using a legume as an intercrop can reduce costly N fertilizers inputs and can increase the N content of the straw mixture. Therefore, we studied cereal-legume intercrops as a source of food grain and straw bioethanol. We grew field pea and four cultivars of durum wheat, triticale, oat, and barley. Crops were grown during 2 years as a sole crop, in additive intercrop with 100 % of the sole crop density for the cereal and 50 % of sole crop density for the legume, and in replacement intercrop with 50 % of the sole crop density for each crop. Tall cereal cultivars were preferred over shorter cereals for an extra production of straw. Results show that growth resources were used up to 23-26 % more efficiently in intercrop than in sole crop for grain and straw production. Tall cereal cultivars suppressed legume yields in intercrops, thus reducing potential intercrop advantages. Pea in intercrop increased straw mixture N by 54 % the first year and by 91 % the second year, versus cereal alone.

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A Revised Analysis of Plant Competition Experiments

Cited by 203 publications

References 8 publications

The competition diallel and the exploitation and interference components of larval competition in Drosophila melanogaster

The competition diallel and the exploitation and interference components of larval competition in Drosophila melanogaster

Competition and yield advantage in barley-barley and barley-oats mixtures

Cereal-pea intercrops to improve sustainability in bioethanol production

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