摘要:

SummaryA pot experiment was done in the glasshouse to study the competition betweenAvena sterilisssp.macrocarpaMo. and six wheat cultivars of different lengths of growth cycle. The competitiveness of wild oat was similar for all six wheat cultivars with respect to grain weight, straw weight, number of ears and total accumulation of nitrogen. The cultivar with the longest cycle was the most affected by wild oat competition as regards height, because a large part of its stem extension and some of the heading took place after the panicles of wild oat had expanded. Wild oat competition with wheat plants was greater than the competition among wheat plants themselves. The wild oat had a similar tolerance to all the wheat cultivars.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00808.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

RésuméDans une expérience de plein champ, où tous les facteurs déographiques et génétiques de concurrence étaient déterminés, des densités différentes d'une variété d'avoine de printemps (espèce considérée comme une graminée adventice) ont étéétablies dans une culture de blé de printemps. Sur la moitié des parcelles du dispositif expérimental, l'avoine a été détruite par une application de diclofopméthyl au stade 3 talles du blé. Les mauvaises herbes dicotylédones ont été désherbées soit à la même date que celle du traitement au diclofopméthyl (traitement précoce), soit deux semaines plus tard (traitement tardif). Les poids secs de la plants cultivée el des adventices ont été mesurés plusieurs fois au cours du cycle de la culture sur des échantillons. Toutes les densités de l'avoine de printemps ont réduit le rendement et certaines composantes du rendement du blé en fonction du traitement herbicide: les rendements du blé ont été moins diminués sur les parcelles traitées que sur les parcelles témoins, les mauvaises herbes dicotylédones ont été mieux détruites par le traitement précoce que par le traitement tardif au 2,4‐D. D'après les résultats oblenus, l'existence d'interactions herbicides est

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00809.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryField experiments were done during the rainy season of 1984–85 and 1985–86 at Harma, Qatar. A weed survey of barley fields was conducted with the primary purpose of identifying the weed vegetation present. The effects of time of hand‐weeding and of application of the herbicide metoxuron on the yield and yield components of barley were studied. Removing weeds at 15,30,45 and 60 days after sowing gave yields similar to that of the clean‐weeded check. Neither a critical period nor a threshold density below which no yield loss occurred were observed. Metoxuron (1,2 and 3 kg ha−1) gave good to excellent broad‐leaved and grass‐weed control. The use of this herbicide at the rate of 1 kg ha−1showed consi

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00810.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryA series of eleven field experiments over two seasons investigated the control ofGalium aparine(cleavers) with mecoprop and a proprietary mixture of ioxynil plus bromoxynil. Applications of mecoprop (2⋅4 kg a.e. ha−1) between December and March gave variable results but a mixture of ioxynil + bromoxynil (0⋅6 kg a.i. ha−1) and mecoprop improved control up to at least 90%, at most sites. Applications of mecoprop alone in April were most effective and frequently achieved more than 90% control. In May, when theG. aparineplants were very large, it was less successful. The reasons for the environmental effects on performance are discussed. Preliminary examination of the effect of soil temperature on mecoprop activity indicates that the reliability of control increases with increasing temperature (0–12°C). An average of 94% control was achieved when soil temperatures were greater than 6°C.La destruction deGalium aparine(Gaillet) dans les cereales d'hiver avec du mecoprop seul ou avec ioxynil plu

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00811.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryThe regenerative responses of rhizomes and tubers from two populations ofHelianthus tuberosusL. to burial and fragmentation were studied in field experiments. The regeneration of both populations varied with planting depth and stage of growth at which fragmentation occurred. Shoots of both populations emerged from rhizomes or tubers planted to depths of 30 cm. The percentage of tubers that regenerated was higher than that of rhizomes, particularly from deeper planting depths. The regeneration from rhizomes and tubers of a riverbank population was greater than that of a‘weedy’population. Rhizomes and tubers from both populations that had failed to produce shoots I year after planting were found to have decomposed completely. The significance of these results in relation to the distribution and control ofH. tuberosusis discus

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00812.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryFour tests were carried out in 1980 and 1981 to determine: (a) the economic threshold density ofAbutilon theophrastiMedicus (velvetleaf) in maize, and (b) seed production with varying densities of infestation, both in the presence and in the absence of maize. The infestation was artificially created, and the density of the weed ranged from 0 to 80 plants m−2. The economic threshold, calculated using the Cousens (1987) model, varied between 0⋅3 plants m−2and 2⋅4 plants m−2, depending on the variables considered. The presence of maize reduced the seed‐rain ofA. theophrastiby 50%. This seed‐rain reached its maximum level at 20–30 plants m−2in maize, and at 30–35 plants m−2in weed monoculture. However, with only 4–5 plants m−2in competition with maize,A. theophrastiproduced 8–10 thousand seeds m−2. The usefulness of threshold density in weed management is debatable when one considers the ecological characteristics of theA. theophrastiseed, and the great capacity of

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00813.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryTen‐year‐old birches (Betulaspp.) and 15‐year‐old aspens (Populus tremulaL.) in field were cut and treated by the 'selective cutter', which also wetted the mantle area of the stump. Twenty per cent glyphosate, applied at the rate of 0⋅38 ml per cm stump diameter and 10% imazapyr at 0⋅14 ml per cm stump diameter, effectively killed the stumps or prevented sprouting. The cutter worked

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00814.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummarySeeds ofPoa annuafrom original collections in Louisiana, Maryland and Wisconsin were grown together in Louisiana over a 3‐year period. The freshly harvested seeds and samples stored in moist soil at 30°C were tested for germination at a range of temperatures to compare dormancy and germination characteristics. Seeds of the Louisiana population were dormant over the germination temperature range of 5–25°C, and imbibed storage for 2 weeks did not break dormancy. Freshly harvested seeds of the Maryland population germinated well (78%) at 10°C. With 1 week of imbibed storage at 30°C, germination was good over the range from 5 to 15°C and near 50% at 20°C. Storage for 2 weeks had little further effect. Freshly harvested seeds of two Wisconsin populations germinated above 50% throughout the range of temperatures, and imbibed storage for 2 weeks at 30°C had no effect on germination. The variations in the dormancy of freshly harvested seeds and the varying responses of dormancy breaking from storing imbibed seeds at 30°C suggests that these populations have adapted to avoid high summer temperatures in Louisiana and Maryland but to grow as a summer annual i

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00815.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryFreshly harvested seeds ofPoa annuaL. collected in south Louisiana were stored in moist soil at seven temperatures between 5°C and 35°C. At monthly intervals, seed lots were removed and germinated at each of the seven temperatures. Seed were dormant for at least 1 month at all test temperatures. Seeds stored for 2 months at 30 and 35°C showed conditional dormancy; there was 100% germination at 10 or 15°C, and poorer germination at 5 or 20°C. Seeds started to lose viability after 2 months at 35°C and were dead after 7 months. In seeds stored at 10–30°C, there were increased percentages and a wider range of germination temperatures as storage time or storage temperatures increased. Seeds stored at 10°C remained dormant for 9 months, but by 12 months of storage the seeds germinated only at 5 or 10°C. Nearly all seeds stored at the same temperatures in air dry soil remained dormant for 6 months, regardless of storage temperature. These results differ from other reports of low temperatures breaking seed dormancy inPoa annuaL. and suggest an adaptation to subtropica

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00816.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

SummaryIn the Taï region of the Ivory Coast, mature forest is felled and burned and a crop of rice is grown; forest is then allowed to regenerate for 20 or more years before being cropped again. The top 10 cm of soil beneath a 21‐year‐old forest prior to felling contained 2000 viable seeds m−2of mainly woody species of previous successional stages no longer represented in the vegetation. Seedling emergence was greater in full sunlight than under leaf canopy, especially for herbaceous species of open habitats. Burning destroyed almost half of the seeds, but overall germination of those that survived was advanced by about 2 weeks. Germination of some common pioneer species was enhanced by the fire. Provided that burning took place and the rice was planted immediately, vegetation arising from the seed bank did not present a problem. The density never exceeded 70 seedlings m−2and little or no weeding was required. Species present at densities greater than 1 seedling 10 m−2were all recorded in the

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1988.tb00817.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY