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Accueil du site → Doctorat → États-Unis → 1994 → Growth and competitive ability of wheat (Triticum aestivum), rigid ryegrass (Lolium rigidum), and cowcockle (Vaccaria hispanica) (under greenhouse and field conditions in Morocco)

Colorado State University (1994)

Growth and competitive ability of wheat (Triticum aestivum), rigid ryegrass (Lolium rigidum), and cowcockle (Vaccaria hispanica) (under greenhouse and field conditions in Morocco)

Tanji, Abbes

Titre : Growth and competitive ability of wheat (Triticum aestivum), rigid ryegrass (Lolium rigidum), and cowcockle (Vaccaria hispanica) (under greenhouse and field conditions in Morocco)

Auteur : Tanji, Abbes

Université de soutenance : Colorado State University

Grade : Doctor of Philosophy (PhD) 1994

Résumé
Addition series experiments were conducted under greenhouse and field conditions in Morocco to study the competitive ability of spring wheat (Triticum aestivum L. ’Nesma’) grown with rigid ryegrass (Lolium rigidum Gaudin) or cowcockle (Vaccaria hispanica (Miller) Rauschert). Wheat was the dominant competitor in all addition series experiments, and the inverse linear model showed that one wheat plant was as competitive as 11 to 19 rigid ryegrass plants in the greenhouse and field experiments, respectively. One wheat plant was as competitive as 3 to 24 cowcockle plants in the greenhouse and field experiments, respectively. Intraspecific competition was more effective than interspecific. At the low wheat density (100-130 plants m$\sp-2),$ high densities of each weed species reduced leaf, stem, head, grain dry weights of wheat. Weed control with herbicides is recommended at low wheat density. Interspecific competition of wheat with rigid ryegrass or cowcockle reduced leaf, stem, head, and shoot dry weights of each weed species more than intraspecific interference. Dry weight fractioning of each weed species into root, leaf, stem, and inflorescence was not useful for in depth study of the competitive ability of wheat. Shoot dry weight was found to be a good parameter to explain competition. Growth analyses of individual plants in the greenhouse and field using the Richards function showed that wheat had a greater leaf area, shoot, and root dry weight, absolute growth rate, than either rigid ryegrass or cowcockle, particularly during the first 40 days after emergence. Relative growth rate and net assimilation rate for each species was not related to competitive ability. Increasing wheat seeding from 120 to 240 plants m$\sp-2$ would help minimize weed competition and achieve an acceptable grain yield in semi-arid areas of Morocco. All of these studies were conducted in a situation where about 25% of seedlings had been transplanted and where wheat emerged prior to the weed. Additional investigations are needed to study the effect of time of emergence of weeds and wheat on competition.

Mots clés : Ecology, Agronomy, Morocco, Biological sciences, Botany

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