Dr W. K. J. Roepke als hoogleraar te Wageningen

Ohne Zusammenfassung     

Competitive growth of Echium plantagineum L. and Trifolium subterraneum L.

Echium plantagmeum is a widespread, persistent, and often dominant votunteer species in southern Australia. In pastures. it commonly grows with Trifolium subterraneion. This paper describes glasshouse studies investigating the effects of soil fertility. plant density. sward composition, defoliation frequency. and delayed estabilishment of t. subserraneum on the growth of E. pluntagineum and T. subterraneum when grown in pure swards and in mixtures. Generally. herbage production of swards was increased by the presence of E. plantagineum. the addition of nutrogen and phosphorus fertilizers, and increasing density, It was decreased by defoliation. E. pluntagineum plants generally produced more shoots and roots than did T. subterraneum. Both species responded. E. plantiagineum generally more than T. subterraneum. to added phosphorus and nitrogen fertilizers. Both species showed a non-linear reduction in plant size as plant density of the sward was increased. especially during early growth. E. plantagineum was, however. more plastic in its response to density than T. subterraneum. Defoliation reduced the plant weight of both species. more for E. plantagineum than for T. subterraneum. In mixtures. there was little competition between the two species during early growth. when swards were defoliated and when both species established at the same time. T. subserraneum was, howerver. sometimes suppressed during later growth if swards were undefoliated. if soil fertility was high. and if E. plantaginteum established before t. subserraneum. Such competition appeared to be between shoots rather than between roots. In the field. E. plantagineum is likely to be fovoured in undergrazed situations, where soil fertility is high and when false or early seasonal breaks allow it to establish earlier than t. subterruneum. Its high productivity under a wide range of pasture situations - especially in autumn and winter when pasture availability is ofter critically low and the fact that it is relatively nutritious and readily eated by stock suggest that it is a useful pasture species.     

豚草(Ambrosia artemisiifolia L.)

豚草又名艾叶破布草和豕草，学名：Ambrosia artemisiifolia L．英文俗名：Common ragweed，Bitterweed，Blackweed，Hay—fever Weed，属双子叶植物纲菊科豚草属。     

毒麦(Lolium temulentum L.)

毒麦学名：Lolium temulentum L．；英文俗名：Poison Ryegrass，Bearded Ryegrass，Darnel；属单子叶植物纲(Monocotyledoneae)莎草目(Cyperales)禾本科(Poaceae)黑麦草属(Lolium L．)。俗名黑麦子、迷糊、小尾巴麦子。     

Field emergence of Lamium amplexicaule L. and L. purpureum L. in relation to the annual seed dormancy cycle

Seedling emergence of Lamium amplexicaule L. and L. purpureum L. was monitored in field plots tilled at various times during the growing season, and the number of viable seeds in the soil was determined. In plots tilled in early spring, only seeds of L. amplexicaule, germinated, but seeds of both species germinated in the same plots in autumn without further disturbance. Additional seeds of L. amplexicaule, but not of L. purpureum, germinated the following spring. In plots tilled in late spring and summer, seeds of L. amplexicaule germinated in autumn and the following spring, whereas seeds of L. purpureum germinated only in autumn. The number of viable seeds in the top 13 mm layer of soil ranged from 189 to 1216 m^?2 for L. amplexicaule and from 131 to 854 for L. purpureum. These field results support those obtained in previous glasshouse-laboratory physiological studies on the annual dormancy cycle in the two Lamium species. Levée au champ de Lamium amplexicaule L. et L. purpureum L. par rapport au cycle annuel de la dormance des graines La levée de jeunes plants de Lamium amplexicaule L. et L. purpureum L. a été observée sur des parcelles cultivées à différentes époques de la saison de végétation et le nombre de graines viables au sol a été déterminé. Sur les parcelles cultivées en début de printemps, seules les graines de L. amplexicaule ont germé, mais des graines des deux espèces ont germé en automne sur les mêmes parcelles, sans cultivation ultérieure. Au printemps suivant, une nouvelle germination a été constatée chez L. amplexicaule mais pas chez L. purpureum. Sur les parcelles cultivées en fin de printemps et en été, des graines de L. amplexicaule ont germé en automne et aussi au printemps suivant, tandis que les graines de L. purpureum n'ont germé qu'en automne. Le nombre de graines viables dans les premiers 13 mm de la surface du sol allait de 189 à 1216 m^?2 pour L. amplexicaule et de 131 à 854 pour L. purpureum. Ces résultats sur le terrain confirment ceux obtenus dans des études physiologiques sur le cycle annuel de dormance chez les deux espèces de Lamium, menées préalablement en serre et au laboratoire. Ueber dus Auflaufen von Lamium amplexicaule L. und L. purpureum L. in Bezug auf den Jährlichen Zyklus der Samenruhe unter Feldbedingungen In Parzellen, die zu verschiedenen Zeitpunkten während der Vegetationsperiode einer Boden-bearbeitung unterworfen worden waren, wurde sowohl das Auflaufen der Keimlinge von Lamium amplexicaule L. und L. purpureum L. registriert, als auch die Anzahl lebenfähiger Samen festgestellt. Nach Bodenbearbeitung im frühen Frühling keimten nur Samen von L. amplexicaule; im Herbst keimten in denselben Parzellen jedoch Samen beider Arten, sofern der Boden nicht mehr bewegt worden war. Weitere Samen von L. amplexicaule, nicht aber von L. purpureum, keimten im folgenden Frühling. In Parzellen, die im späten Frühling und im Sommer bearbeitet worden waren, keimte L. amplexicaule im Herbst und im folgenden Frühling. Während L. purpureum nur im Herbst keimte. Die Anzahl lebensfähiger Samen m^?2 in den obersten 13 mm des Bodens bewegte sich zwischen 189 und 1216 für L. amplexicaule und zwischen 131 und 854 für L. purpureum. Diese Feldresultate bestätigen Ergebnisse von Gewüchshausstudien über den jährlichen Zyklus der Samenruhe der beiden Lamium-Arten.     

The nutritive value of Echium plantagineum L. and Trifolium subterraneum L.

Echium plantagineum is a widespread, persistent, highly productive and often dominant species in southern Australia. In pastures, it usually occurs with Trifolium subterraneum. which is commonly regarded as a valuable forage species. However, there is considerable controversy over the value of E. plantagineum as a pasture species. In this study, the nutritive value (dry matter content, in vitro digestibility, nitrogen content) of herbage of E. plantagineum and T. subterraneum generally was similar at any time during the year. It is concluded that E. plantagineum is a useful forage species because it is highly productive, is readily eaten by grazing stock and has a relatively high nutritive value.     

Growth and reproduction of Cyperus esculentus L. and Cyperus rotundus L.

The growth of both species (as characterized by their total dry weight, inflorescence dry weight, root and rhizome dry weight and number of shoots per pot) was similar, but they differed in the manner in which the dry weight was partitioned to reproductive structures. Each species partitioned less than 2% of its dry weight into floral formation. However, yellow nutsedge (Cyperus esculentus L.) partitioned only 28% of its dry weight to tubers, whereas purple nutsedge (C. rotundus L.) partitioned 50% of its dry weight to fewer and larger tubers. The allocation of dry weight to reproductive structures was related to changes in day-length. Yellow nutsedge tuber formation increased as day-length decreased from 14.5 to 12.5 h, while floral formation did not begin until the day-length dropped below 14 h. Purple nutsedge formed inflorescences earlier and production continued throughout the remainder of the study, but tuber formation was curvilinear and accelerated as the day-length decreased.     

Interference of Sinapis arvensis L. and Chenopodium album L. in spring rapeseed (Brassica napus L.)

Interference of Sinapis arvensis L. (wild mustard) and Chenopodium album L. (lamb's-quarters) in spring rapeseed (Brassica napus L.) was studied under field conditions in 1983 and 1984. Both weed species interfered with rapeseed early in the growing season, causing significant reductions in rapeseed dry weight by June of each year. Sinapis arvensis caused greater rapeseed grain yield reductions than did C. album. With weed densities of 20–80 plants m^?2, rapeseed grain yield reductions ranged from 19 to 77% with S. arvensis but only 20 to 25% with C. album. Rapeseed yield reductions caused by mixtures of both weed species ranged from being less than to being equal to the sum of reductions caused by each weed alone, depending on the weed density and year of study. Both weed species were prolific seed producers capable of returning large quantities of seed to the soil. With weed densities ranging from 10–80 plants m^?2, S. arvensis produced 5700–30 100 seeds m^?2 while C. album produced 3100–63 600 seeds m^?2.     

Factors affecting seed germination of Echium plantagineum L. and Trifolium subterraneum L.

Echium plantagineum L. is a widespread, persistent, and often dominant volunteer species in southern Australia. This paper describes laboratory and field experiments investigating seed germination in E. plantagineum and a commonly associated species, Trifolium subterraneum L. In the laboratory, E. plantagineum germination was favoured by relatively high temperatures, and the seed showed considerable innate and temperature-enforced dormancy. In the field, this dormancy appeared to prevent some germination in response to rainfalls immediately after seed formation, and permitted sporadic germination during summer and autumn in subsequent years. In 1972 and 1974, both species emerged well in autumn whilst E. plantagineum was favoured in summer and T. subterraneum was favoured in winter. No seedlings emerged in spring. Emergence appeared to be controlled primarily by moisture availability and temperature but also was affected by cultivation and removal of soil-surface litter. The results of these seed germination studies show that E. plantagineum is well adapted to persist in a Mediterranean-type climate, and will be favoured in years with early seasonal breaks. T. subterraneum is likely to be favoured with later breaks.