摘要:

SummaryThe effect ofMeloidogyne incognita(Kofoid&White) Chitwood, 1949, on the competitive relationship between tomato (Lycopersicon esculentumMill.) and black nightshade (Solanum nigrumL.) was investigated under glasshouse conditions. Two intraspecific competition treatments were set up for the crop and the weed, and five interspecific treatments where the emergence ofS. nigrumplants was progressively delayed in relation to tomato. Nematodes reproduced in all inoculated plants, their multiplication rates being much higher in tomato than inS. nigrumplants. Under nematode‐free conditions, intraspecific competition of tomato was more severe than the interspecific competition shown by the weedS. nigrum.Tomato was as tronger competition withS. nigrumthan the weed was with itself. However, when infested byM. incognita, both species displayed a similar competitive ability. Tomato yield losses increased with prolonged weed competition but were greater under nematode‐infested conditi

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb01640.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe effect of metham‐sodium onOrobanche aegyptiacaPers. was tested in the laboratory and in soil columns. The laboratory experiment was carried out onO. aegyptiacaseeds placed in Petri dishes and germinated with GR24, a synthetic strigol analogue. In soil columns, metham‐sodium was applied by application of the chemical through the irrigation water to three different soils and its dissipation determined in three soil layers by gas chromatography, by a lettuce bio‐assay to check the herbicide's phytotoxicity, and with a flax bioassay to check its effect onO. aegyptiaca.Results of the germination experiments showed an exponential decrease inO. aegyptiacagermination, parallel with the increase of metham‐sodium concentration, with an average effective concentration (EC50) of 18 mg L−1. In a soil column, methylisothiocyanate (MIT, the metham active product) rapidly disappeared from the upper soil level (0–10 cm) within 24 h. Seven days after application only traces of MIT remained in all soil layers in all soils, except for the sandy Rehovot soil that contained low concentrations in the lower soil layer (20–30 cm). Flax bioassay confirmed the chemical analysis, showing thatO. aegyptiacatubercles developed only on plants grown in the upper soil layer of al

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb01641.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryAtrazine carryover often limits growers to production of atrazine‐tolerant crops the year following application, and allows the increase of triazine‐tolerant weed species such asPanicum miliaceumL. (wild proso millet). Tiriazine‐resistantBrassica napusL. cv. ‘Triton’ (oilseed rape) was tested to characterize the nature of interspecific interference withP. miliaceum.In a greenhouse study, atrazine at 2.2 kg ha−1depressed oilseed rape fruit (siliqua) number and fruit dry weight, and delayed flowering, but did not significantly affect height or weight of shoots, Oilseed rape fruit weight was reduced at 200P. miliaceumplants m−2. fruit number and shoot weight were inhibited at 400 weeds m−2. and height was reduced and flowering delayed at 600 weeds m−2. Number and weight of fruits were reduced by one‐third after 8 weeks of interference as compared to oilseed rape grown with the weed for 4 weeks. Oilseed rape height was reduced by 29% and shoot weight by 55% by 600 weeds m−2and 2–2 kg ha−1atrazine, while fruit number and weight were reduced by 72%. Oilseed rape shoot weight was reduced by 74% by 600 weeds m−2for 12 weeks of interference, while fruit number and weight were reduced by 85% and 82%. respectively.In a field study, fluazifop reduced early seasonP. miliaceumcover by 72%, but did not increase oilseed rape cover. Mid‐seasonP. miliaceumshoot weight was decreased by 97% by fluazifop and oilseed rape shoot weight was increased by 34%.P. miliaceumcontrol increased oilseed rape biomass by 38% at 89 days, but biomass of oilseed rape sown at 11.2 kg ha−1with 2.2 kg atrazine ha−1was not decreased byP.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb01642.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe success of weed management based on ecological principles and weed biology will depend on a better understanding of the effect of environment on lift history strategies, growth, and competition of weeds; and crops, and particularly upon the ability to predict weed and crop phenology, This paper reviews the importance of phenotypic plasticity to weed and crop competition and other biological interactions. We also discuss the utility of phenological predictions in weed management and review current weed phenology models that are based on thermal time. By understanding the variables that drive plant phenotypic responses, new approaches and more long‐term solutions for weed problems can be develope

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb01643.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe vegetative growth response ofErodium cicutarium(L.) ĽHer. ex Ait. to various day:night temperature regimes was studied under controlled environment conditions. Dry matter production was greatest with day temperatures of 18 to 34^C combined with night temperatures of 12 to 18^C. A high night temperature of 24^C was very detrimental, reducing dry matter production to 15 to 25% of that attained at 12^C. The optimum mean daily temperature for growth ofE. cicutariumis predicted to be in the range 17 to 20^C. Little growth is predicted at mean daily temperatures below 5^C and above 30^C. Partitioning of biomass in leaves, stems and roots was markedly affected by day and night temperatures. Stem weight ratio was greatest at day temperatures of 18 to 34^C and night temperatures of 18 to 24^C. Maximum leaf weight ratio occurred at day and night temperatures of 10 to 18^C. Root biomass was little affected by day temperatures, but was greatest at a night temperature of 12^C, declining substantially as night temperature increased from 12 to 24^C. Results are discussed in terms of the potential forE. cicutariumto become an increasingly troublesome weed in crops of the Canadian prairies and in terms of possible management strategies for its control

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb01644.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummarySeed populations ofAvena sterilisssp.ludoviciana(Durieu) Nyman were monitored in a naturally occurring infestation throughout its life cycle. Considering the large weed population present (298panicles m−2), total seed production was relatively low: 3838 seeds m−2. Only 68% of these seeds were recovered from the soil surface and a further 3% were removed with wheat grain and straw during harvest operations. The numbers of seeds from the stubble between mid‐July and mid‐September were relatively low (10%). Ploughing the stubble in October buried most of the recently produced seed rain and resulted in a relatively uniform vertical distribution of the seedbank. Maximum seed persistence in the soil ranged from 27 to 43 months (depending on the experimental technique used to do the study). Seed decline followed an exponential pattern on a yearly basis, with the greatest decline taking place between October and April (57–90% in year 1 and 10–40% in year 2), Between May and September the buried seed populations remained practically constant. Seedbank depletion was primarily due to seedling production (25%) and ‘lethal’ germination (24%). Although the depth of burial had very little effect on seed survival, the mode of seed disappearance was closely related to their depth in the soil. Seed depletion through ‘lethal’ germination increased with increasing depth in the soil, whereas depletion through seedling emergence decreased wi

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb01645.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThis experiment investigated the effect of pre‐germination moist chilling of seeds (for 3 weeks at 2^C) of 10 common arable weeds on the subsequent growth and flowering of the plants. In only three of the species (Alopecurus myosuroidesHuds.,Veronica persicaPoir. andTrifolium dubiumSibth.) was flowering markedly increased by the seed chilling treatments. At 3 months, the mean number of flowers and seed heads per plant on the treated plants was greater than that on the controls by factors of 13.9, 2.02 and 1.74 respectively. Shoot lengths of the seed‐chilled plants were also significantly greater in all three species, though dry weights did not differ significantly from those of the controls. Thus, the plants showed morphological changes associated with reproduction but no significant alteration in total dry weight. The ecological implications of the data are discussed in relation to possible effects of climatic change on species which require seed vernalizat

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb01646.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe seed germination behaviour of four populations each ofDiplotaxis erucoides(L.) DC. andD. virgata(Cav.) DC, two weedy Brassicaceae species widely distributed in the Mediterranean region, was studied under controlled light, temperature and moisture conditions. Germination rates inD. virgatawere generally higher at alternating (25/15^C) and low (15^C) temperatures, whereas inD. erucoidesoptimal germination rates were achieved at higher temperatures (25^C). No correlation between seed weight and germination was found in either species. InD. virgata, the geographic origin of the seed had an important effect on germination percentage. Great germination variability was found among the populations and even among seeds belonging to the same population. In this species, the application of gibberellic acid stimulated germination, especially in the populations with higher dormancy levels. Dormancy was found in matureD. virgataseeds but not in those ofD. erucoides.In both species, germination percentages decreased after a certain period of storage at low temperatures. This period varied depending on the species and the population considered.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb01647.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe competitive abilities of eight winter crops were compared againstLolium rigidumGaud, (annual ryegrass), an important weed of southern Australia, as a potential strategy to suppress weeds and reduce dependence on herbicides. Two cultivars of each species were chosen to represent the range of competitive ability within each crop and grown in field experiments in 1992 and 1993. The order of decreasing competitive ability (with the ranges of percentage yield reduction fromL. rigidumat 300 plants m−2in parenthesis) was as follows: oats (Avena sativaL.), 2–14%; cereal rye (Secale cerealeL.), 14–20%; and triticale (×Triticosecale), 5–24%; followed by oilseed rape, (Brassica napusL.), 9–30%; spring wheat (Triticum aestivumL.), 22–40%; spring barley (Hordeum vulgareL.), 10–55%; and, lastly, field pea (Pisum sativumL.), 100%, and lupin (Lupinus angustifoliusL.), 100%. Differences in competitive ability of cultivars within each species were identified, but competition was strongly influenced by seasonal conditions. Competition for nutrients (N, P and K) and light was demonstrated.L. rigidumdry matter and seed production were negatively correlated with grain yield of the weedy crops. More competitive crops offer the potential to suppress grass weeds while maintaining acceptable grain yields. Ways of improving the competitive abilities of grain legume crops

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb01648.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Résumé: SummaryCe projet a permis ?évaluer des programmes de désherbage combinant ľapplication ?herbicides en bandes et les sarclages mécaniques comme méthode alternative àľutilisation intensive ?herbicides dans le maïs‐grain (Zea maysL.). Les résultats des travaux menés au Québec en 1991 et 1992 indiquent que ľapplication ?herbicides en bandes (atrazine à 1,0 kg m.a. ha−1+métolachlore à 1,9 kg m.a. ha−1en post‐levée précoce) sur le rang (40% de la surface totale cultivée) suivie par des sarclages mécaniques sélectifs sur toute la surface procurent des rendements de maïs‐grain équivalents a ceux obtenus là où les herbicides ont été appliqués sur toute la surface cultivée. Il est donc possible de réduire la quantité?herbicides utilisée dans le maïs‐grain sans diminuer son rendement. La répression mécanique des mauvaises herbes a été plus efficace en 1991, qui a été une année sèche comparée à 1992 qui a été froide et pluvieuse. Il ressort de cette étude qu'un traitement combinant une application ?herbicides en bandes et deux sarclages sélectifs sur toute la surface à 2 et 4 semaines après ľémergence du maïs‐grain procure à la fois un désherbage adéquat des adventices et un rendement optimum du maïe.Reduced use of herbicides in corn through herbicide‐banding combined with cultivationsThe efficacy of various weed management systems utilizing banded applications of herbicides and mechanical cultivations were investigated in order to find alternatives to intensive herbicide use in grain maize (Zea maysL.) production. In experiments conducted in Quebec in 1991 and in 1992, banded applications of atrazine (1.0 kg a.i. ha−1) and metolachlor (1.9 kg a.i. ha−1) on maize rows (40% of field area) combined with post‐emergence cultivations, achieved a similar grain yield to that obtained when herbicides were broadcast over the whole field. In this project, decreasing herbicide was not accompanied with decreasing maize yield. Mechanical weed control was more effective in 1991, a drier year than 1992 which was cool and rainy. A banded application of herbicides followed by cultivations at 2 and 4 weeks afte

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1995.tb01649.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY