Competition Among Crop and Pasture Plants

Donald, CM

doi:10.1016/s0065-2113(08)60397-1

Cited by 651 publications

(411 citation statements)

References 101 publications

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“…The best understood mechanism, which influences the growth of plants irrespective of whether they grow in mixtures or pure stands, is competition for resources (de Wit 1960, Donald 1963, Harper 1977, Trenbath 1974, 1976, Tilman 1982, Vandermeer 1989. Plants compete for limited resources which are essential for plant growth and development (light, water, nutrients, oxygen and carbon dioxide).…”

Section: Definition Of Mixturesmentioning

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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Section: Definition Of Mixturesmentioning

confidence: 99%

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

Jokinen¹

1991

AFSci

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“…Consequently expression of cool-season growth by Manawa was greater where nitrogen was applied, boosting its competitive advantage over Ruanui. Effects of phosphorus on competition, although small, comply with Donald's (1963) concepts of interaction of competition for two or more factors. Thus where nitrogen was supplied without phosphorus, heightening the effects of phosphorus as a limiting factor, and where frequent cutting further increased the phosphorus effect, Ruanui, already suppressed by Manawa's ability to compete where nitrogen was applied, was further suppressed by its reduced capacity to compete for phosphorus (Table 9).…”

Section: Discussionmentioning

confidence: 65%

Competition among pasture plants

Harris¹

1973

New Zealand Journal of Agricultural Research

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Yield, plant numbers, and tiller numbers were measured Qn brQadcast swards Qf a mixture Qf 'Grasslands Manawa' and 'Grasslands Ruanui' ryegrass and Qn simulated swards Qf mQnQcultures and a mixture Qf the ryegrasses grown at cQntrasting levels Qf nitrQgen and phQsphQrus and under twO' cutting frequencies.Greatest yield resPQnses were to' applied nitrQgen, but this reSPQnse varied with seaSQn, and interacted with the Qther treatment effects. Overall, small yield increases were Qbtained by applying phQsphQrus, and greater yield was Qbtained with infrequent cutting. Response to' phQsphQrus was relatively greater under frequent cutting. During flowering, resPQnse to' nitrQgen was relatively greater where cutting was infrequent.Initially Manawa grew mQre than Ruanui, giving Manawa a cQmpetitive advantage in all treatments. Manawa dQminance was increased by applied nitrogen, and in broadcast swards this dQminance was greater with infrequent cutting. In simulated swards, lQW seeding density and sub-Qptimal availability Qf nitrogen and probably water, by reducing light cQmpetitiQn, restricted effects Qf cutting frequency Qn Manawa dQminance Qver Ruanui. In summer direct susceptibility Qf Manawa to' intensive defQliatiQn led to' dQminance Qf Ruanui in the frequent cutting treatment. Where nitrQgen applicatiQn and frequent cutting increased the effect Qf phosphQrus as a limiting factQr, cQmpetitiQn for phQsphQrus was indicated by further suppressiQn Qf the cultivar already suppressed by Qther effects.From widely different seeding densities tiller densities Qf brQadcast and simulated swards cQnverged, increases in tiller numbers per plant being greater and plant mQrtality less in simulated swards. Overall, applied nitrQgen and phQsphQrus and frequent cutting increased tiller numbers, but these effects varied with seaSQn and cultivar. ResPQnse Qf Ruanui to' nitrQgen was relatively greater than that of Manawa under frequent cutting. Greater yield reSPQnse to' phQsphQrus under frequent cutting was assQciated with larger tillers during [lowering. Frequent cutting caused mQst plant death and reduced survival Qf Manawa in summer, but Qther effects Qn plant survival invQlving all factQrs were indicated.The results allQw definitiQn Qf situations where mixing Qf Ruanui and Manawa may prQvide productiQn advantages. 399

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“…HODGSON et BLACKMAN (1955), pour Vicia faba, ne trouvent pas d'influence de la rectangularité ; DELVAUX (1967) n'observe non plus aucune diffé-rence, mais cela peut venir de ce qu'il s'adresse à des clones. En liaison avec l'effet de rectangularité, se manifeste une influence de l'orientation des lignes (DONALD, 1963).…”

Section: Influence De La Disposition Des Plantsunclassified

“…Une définition en a été donnée par un zoologiste (MILNE, 1961), après CLÉ-MENTS (1907), lors d'une intéressante confrontation entre les points de vue quelque peu divergents des physiologistes et agronomes, des généticiens et des écologistes (Symposium of the society of expérimental biology, 1961). DONALD (1963), dans une importante mise au point, a repris et modifié cette définition, que nous ferons nôtre : « Il y a concurrence entre deux ou plusieurs organismes lorsque chacun d'eux cherche à se procurer le montant nécessaire à ses besoins d'un facteur ou d'une chose qui sont fournis immédiatement en quantité inférieure aux exigences combinées de ces organismes. » Cette situation implique donc qu'il résulte un effet négatif au moins sur un des deux organismes A par rapport au cas où l'autre B n'intervient pas, l'effet sur B étant nul ou négatif.…”

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