摘要:

Summary:In a study of the weed flora of dryland crops in the Córdoba region (southern Spain) in 1983 and 1984, a total of 256 species from 41 families was identified in the 201 fields surveyed. The families with the highest numbers of species were Compositae, Gramineae, Leguminosae and Cruciferae. Therophytes represented 79% of the biological spectrum, with hemicryptophytes and geophytes more especially in the spring‐sown crops. At the early and late crop growth stages about 4% and 8%, respectively, of the fields had severe or very severe infestations. The seasonality of the crop had a marked influence on the weed flora, mainly due to the relationship of its phenological cycle with well defined climatic periods and to soil management practices. Cluster analysis clearly differentiated typically autumn‐spring and spring‐summer floras as well as a set of common s

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01718.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Résumé:L'évolution de la composition spécifique du stock semencier a été suivie pendant huit années sur quatre parcelles expérimentales différant par le type de travail du sol (profond ou superficiel) et de désherbage chimique (absent ou sélectif). Nos résultats montrent que la composition spécifique du stock n'est pas modifiée sur les parcelles désherbées et que seuls des change‐merits d'ordre quantitatif interviennent au sein de la communauté: certaines espèces, commeEuphorbia exiguaetAnagallis arvensis, augmentent ainsi leurs dominances dans le stock sans accroissement de leurs abondances. A l'opposé, sur les parcelles non désherbées, on observe des modifications qualitatives et quantitatives de la composition spécifique avec l'arrivée d'espèces ‘opportunistes’, commeThlaspi arvenseetSinapis arvensis, qui augmentent considérablement leurs abondances alors qu'elles étaient pratiquement absentes du stock en début de suivi. Le type de travail du sol nuance un peu ces phénomènes en permettant une meilleure homogénéisation sur la couche arable des

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01719.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary:Avena saliva cv. Amuri andA. fatuawere sprayed with diclofop methyl (1.0 kg a.i. ha−1) alone and in combination with 2,4‐D (1.1 kg a.i. ha−1), bentazone (1.0 kg a.i. ha−1), chlorsulfuron (15 g a.i. ha−1) or dicamba (0.3 kg a.i. ha−1). Effects of the herbicides on leaf extension rate during the first 8 to 10 days after spraying and subsequent growth (dry weight) after 57–75 days were determined by comparison with unsprayed plants. Diclofop‐methyl applied alone did not cause a decrease in leaf extension rate ofA. salivaorA. fatuauntil at least 4 days after spraying. All broadleaf weed herbicides in combination with diclofop‐methyl caused a decrease in leaf extension rate of both species within 2 days of spraying. Ten days after spraying, leaf extension rates for plants sprayed with a broadleaf weed herbicide plus diclofopmethyl (all combinations) were lower than for unsprayed plants but greater than for plants sprayed with diclofop‐methyl alone. With the exception ofA. fatuasprayed with bentazone, long‐term growth of plants sprayed with a broadleaf weed herbicide plus diclofop‐methyl (all combinations) was lower than for unsprayed plants but greater than for plants sprayed with diclofop‐methyl alone. Bentazone applied with diclofop‐methyl caused a substantial decrease in leaf extension rate ofA. fatuawithin 24 h of spraying but at harvest, dry weight of plants from this treatment was similar to or less than that for plants sprayed with diclofop‐methyl alone. Application of diclofop‐methyl with bentazone at a rate of 0.3 kg a.i. ha−1also caused a reduction in leaf extension rate ofA. fatuawithin one day of spraying. At this rate of bentazone, dry weight of plants at harvest was intermediate to that of unsprayed plants and those sprayed with diclofop‐methyl alone. It is proposed that decreased leaf expansion rate during the first few days afte spraying is the cause of broadleaf weed herb

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01720.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Résumé:Les effets de la densité et de la période de concurrence deSolanum nigrumL. ont été déterminés dans des cultures de tomate en semis direct, en relation avec les techniques de désherbage utilisées dans le Sud‐Est de la France. DesS. nigrumlevant après une application de diquat au stade 2–3 feuilles de la plante cultivée et éclaircies à de faibles densites (entre 0 et 12,8 plantes par m2) au stade 5–6 feuilles de la plante cultivée, ont entraîné des pertes significatives de rendement lorsqu'elles concurrençaient la culture jusqu'à la récolte. Les rendements de tomate ont subi de plus faibles réductions lorsque de telles densités étaient présentes jusqu'au début de la floraison. Les courbes de régression ‘rendement de la culture × densité de la mauvaise herbe’ ont été différentes selon les conditions climatiques de l'année affectant la date de semis et la croissance des plantes; une comparaison entre années a été faite d'après la relation l'rendement de la culture × rapport de biomasses adventice/plante cultivée. Des interactions significatives entre la densite de l'adventice et sa période de concurrence ont été constatées pour quelques variables de rendement (fruits verts) ou composantes du rendement (poids moyen d'un fruit rouge). Dans le cas d'un semis direct tardif et pour de faibles densités deS. nigrumen concurrence avec la culture, deux désherbages au stade 5–6 feuilles et debut floraison on

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01721.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary:The influence of the nonionic surfactant, Agral 90, on the activity of imazamethabenz in wild oats (Avena fatuaL.) was investigated in glasshouse and laboratory trials. Agral 90 significantly increased the efficacy of imazamethabenz against wild oats at a range of growth stages; a significant decrease in activity of both imazamethabenz alone or with Agral 90 was observed following application to plants possessing tillers. At 0.1 kg ha−1, the growth of tillers was significantly reduced by imazamethabenz plus Agral 90. The retention of imazamethabenz on wild oat foliage was significantly increased by Agral 90 incorporation; Agral 90 also facilitated retention of imazamethabenz on the tillers. The absorption and translocation of imazamethabenz were significantly enhanced by Agral 90; greater amounts of the labelled material were found in all regions of the plant except the tillers which existed at the time of applicatio

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01722.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary:The study was conducted on the weed flora of the main irrigated crops of the Guadalquivir Valley. The TWINSPAN (Two Way Indicator Species Analysis) method was applied for each crop separately to all the species present as well as to their degree of infestation. The results indicated that soil texture may markedly influence the flora, whereas the effects of pH and carbonate content were less important. The climatic differences found in the three areas studied were of little importance. The type of irrigation markedly influenced the flora, although it was always related to edaphic factors, especially texture and slope.In general, the weed flora found in the crops can be divided into two communities. One is characterized by species such asRidolfia segetum, Picris echioides, Phalaris brachystachys, Phalaris paradoxaandChrozophora tinctoriaand the second byCapsella bursa‐pastoris, Cyperus rotundus, Paspalum paspalodes, Digitaria sanguinalis, Sorghum halepenseandPortulaca oleracea. The first community comprises weeds in the higher altitudes, further away from the riverbed, with a soil of clayey texture, a high slope and irrigated with sprinklers. The second community comprises the flora of flat areas, with sandy soils, located in the middle and low river terraces and furrow irrigate

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01723.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary:Fluroxypyr‐MHE (methylheptyl ester) was added to four soils and incubated at 26 ± 1°C and approximately 0.1 MPa moisture. After initial rapid hydrolysis of the ester to fluroxypyr, fluroxypyr degraded with half‐lives of 12, 12, 23, and 7 days in Barnes loam, Catlin silt loam, Hanford sandy loam, and Mhoon clay soils, respectively. Two metabolites (4‐amino‐3,5‐dichloro‐6‐fluoro‐pyridin‐2‐ol and 4‐amino‐3, 5‐dichloro ‐ 6 ‐ fluoro ‐ 2 ‐methoxypyridine) were identified, with the pyridinol at its maximum concentration after 2 to 4 weeks of incubation, and the methoxypyridine after 8 weeks. Degradation rates of fluroxypyr and its pyridinol were not significantly altered by diurnally varying soil temperature (21°C to 32°C) or moisture, nor by the presence of growing grass. Methoxypyridine dissipation was more rapid under greenhouse conditions, suggesting that laboratory studies underestimated th

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1990.tb01724.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY