摘要:

Field trials were carried out to study the effect of irrigation, phosphorus and weed control methods on weeds and field pea during winter seasons of 1986–87 and 1987–68 at Haryana Agricultural University, Hisar, India. Different irrigation and phosphorus levels had very little or no effect on the population and dry weight. Different weed control methods resulted in significantly lower population and weight of weeds as compared to unweeded at all the observation stages. The grain yield of field pea was significantly increased by irrigation, phosphorus and weed control levels. Irrigation at flowering or flowering + pod formation stages and application of 40 or 80 kg P2O5/ha produced 20–40% higher grain yield to that of no irrigation and no phosphorus. Weed‐free conditions registered 81% and 105% higher yield than unweeded during 1987 and 1988, respectively. Hand‐weeded twice at 30 + 60 d.a.s. or pendimethaline at 1.0 kg/ha increased the yields by 40–50% over weedy check.

ISSN:0143-6147    

DOI:10.1080/09670879209371635

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Various weed control practices were evaluated during the 1985 (November planting) and 1986 (June planting) wet seasons in Ane‐i, Claveria, Misamis Oriental, to determine suitable weed control practices for cowpea(Vigna unguiculata(L.) Walp. IT82D‐889). Weed species associated with the crop varied with planting time.Borreria laevis(Lam.) Griseb. andDigitaria setigeraRoth ex R.&S. were the dominant weed species in the 1985 and 1986 wet seasons, respectively. Despite variations in weed species and population, hoe weeding plus hand weeding at 14 and 28 days after emergence (d.a.e.) significantly reduced weed weight and resulted in the highest grain yield, net return, marginal benefit‐cost ratio (MBCR) and dominated other weed control practices in terms of net return at a given cost of weed control.

ISSN:0143-6147    

DOI:10.1080/09670879209371636

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

One laboratory and two field experiments were conducted at the International Rice Research Institute (IRRI) to determine the effect of herbicides applied as seed treatments on crop safety and weed control in wet‐seeded rice(Oryza sativaL.). In the laboratory experiment all the herbicides tested, except butachlor‐2,4‐D, did not affect rice seed germination. Butachlor‐2,4‐D reduced root growth the most, while thiobencarb caused the greatest reduction in shoot growth. In the first field experiment all the seed treatments except bensulfuron reduced crop stand. The same herbicides poured directly onto flooded fields several days after sowing did not decrease plant stand significantly. Plant heights were reduced significantly by seed treatments with both butachlor formulations and pretilachlor + fenclorim. The best weed control was observed with pretilachlor + fenclorim applied either as a seed treatment or poured onto water. In the second field experiment, pretilachlor + fenclorim at 0.45 kg a.i./ha reduced crop stand and slightly stunted plant height when applied to the seed. Weed weights were generally less, and crop yields were increased, in the herbicide‐treated plots compared with the untreated plots, regardless of application method. Seed treatment with herbicides appears to be a promising technique for controlling weeds in wet‐seeded rice.

ISSN:0143-6147    

DOI:10.1080/09670879209371637

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A survey of weeds of the main arable areas of Botswana was made over three seasons from 1987 to 1990. A total of 326 species representing 49 families was recorded from 186 fields and one‐third of the commerical farms of Pandamatenga. The majority of crops were sorghum or sorghum and cowpeas inter‐cropped. Maize, millet and sole cowpeas were also represented. The majority of weeds were dicotyledonous (80%), 16% were grasses and 4% sedges. Most species were rare and only 10% were found in more than one‐fifth of fields. Fields generally had many species (average 20.5) at trace to frequent levels of infestation. Soil differences accounted for much of the variation in distribution. The clay soil at Pandamatenga had a different flora from that found on the sandy soils that prevail in most of the country. Fields in the Okavango Delta likely to flood during the dry season, supported species not found on the sands. Two parasitic weeds were recorded;Alectra vogeliiBenth. was common on cowpeas andStriga asiatica(L.) Kuntze was recorded at low levels, mainly on sorghum.

ISSN:0143-6147    

DOI:10.1080/09670879209371638

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A root growth bioassay with sorghum (Sorghum bicolorL. cv. CSH 5) and wheat (Triticum aestivumL. cv. Sonalika) was developed for detecting the concentration of pendimethalin and fluchloralin in soils. The reduction in root growth of pregerminated seeds after 48 h was concentration dependent in both the herbicides having the range from 0.01 to 10.0 ppm in 20 ml water added to 100 g soil. Residue activity of both pendimethalin and fluchloralin were detected for up to 80 days after application of 1.5 kg/ha pendimethalin and 2.25 kg/ha fluchloralin in the 0.5 cm soil layer during 2 years when these herbicides were applied to field crops of mint.

ISSN:0143-6147    

DOI:10.1080/09670879209371639

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Echinochloa glabrescensMunro ex Hook. f., a common weed in flooded fields, was highly competitive with rice (Oryza sativaL.) when its seedlings were transplanted with rice seedlings. Age of the transplantedE. glabrescensseedlings had little effect on its weight at harvest and rice grain yield at different infestation levels. Average rice yield reductions from transplanted E.glabrescensranged from 6% at the 5% infestation level to 73% at the 40% infestation level. Transplanting shock delayed vegetative growth of rice andE. glabrescensat early stages and influenced growth patterns until maturity. When all rice hills were infested, competition resulted in 11.9 and 12.8% reduction in height; 60.5 and 62.5% reduction in tiller number; 59.1 and 51.5% reduction in maximum leaf area index (LAI); 77 and 81% reduction in total dry weight; and 90 and 94% yield reduction of rice under transplanted and dibbled conditions, respectively. Panicle length and 100‐grain weight were not affected by competition.E. glabrescenswas less affected by competition than rice under both planting methods

ISSN:0143-6147    

DOI:10.1080/09670879209371640

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Water overflowing from plots 2h after applying butachlor at rates ranging from 0.3 to 1.0 kg ai/ha did not decrease weed control of treated plots and grain yield were significantly higher than those of untreated check plots. Yields in plots that received butachlor directly, or by overflowing into similar sized receiving plots did not differ significantly from those in plots treated with butachlor where no overflowing occurred. Doubling or tripling the size of the untreated plots that received butachlor from a treated plot resulted in poor weed control and lower grain yields. Similar results were obtained when butachlor was applied as an EC or as a granule to the treated plots. The weed control obtained in untreated plots receiving overflow water from butachlor‐treated plots resulted from considerable amounts of the applied herbicide remaining suspended in floodwater for 1h after overflowing (3h after application). The performance of pretilachlor‐fenclorim, bensulfuron, butachlor‐2,4‐D, piperophos‐2,4‐D, and thiobencarb with or without 2,4‐D was also not affected by water overflowing from herbicide‐treated fields 2h after soil application.

ISSN:0143-6147    

DOI:10.1080/09670879209371641

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Major banana and plantain production centres in Malawi were surveyed for diseases and soil‐borne pests in June 1990. Fusarium wilt, which is also known as Panama disease (caused byFusarlum oxysporumf. sp.cubense)caused considerable damage throughout the Karonga and Chitipa Districts of the Northern Region. The disease has been recognized in these areas since the early 1970s and probably was introduced into Malawi from southern Tanzania. The disease has eliminated the preferred banana cultivar, ‘Bluggoe’, in northern parts of the Karonga District, and at the time of the survey had begun damaging ‘Pisang awak’, the cultivar many producers have used to replace ‘Bluggoe’. Fusarium wilt was also found for the first time in the Thyolo and Mulanje Districts of the Southern region on ‘Bluggoe’. Black leaf streak (caused byMycosphaerella fijiensis) was observed in the Nkhata Bay and Karonga Districts; it is reported for the first time in Malawi. The disease has been in the respective areas for 4 and <2 years, but significant damage was observed only in portions of the Nkhata Bay District; ‘Dwarf Cavendish’, ‘Red’, ‘Green red’, and several different plantain cultivars were badly affected. Environmental conditions are conducive to an increased severity of the disease in the Karonga and Nkhata Bay Districts in the near future. Cordana leafspot (caused byCordana musae)and Sigatoka leafspot (caused byM. musicola)caused locally important, but less severe, damage in the country than did fusarium wilt and black leaf streak. Serious nematode infestations were observed only in the Southern Region whereRadopholus similiscaused rhizome necrosis and some toppling of ‘Dwarf Cavendish’ in the Thyolo District. The banana borer.Cosmopolites sordidusobserved at low levels in the Karonga District, is reported for the first time in Malawi. Other diseases, nematodes and insect pests that were observed during the survey were not causing significant damage at the time of the survey.

ISSN:0143-6147    

DOI:10.1080/09670879209371642

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Ten pearl millet genotypes (Pennisetum glaucum(L.) R. Br.) were tested for downy mildew (Sclerospora graminicola(Sacc.) Schroet.) reaction in the field at four locations in West Africa and in the greenhouse at Reading University, UK, using collections of the pathogen from the same areas. Some of the test entries showed different reactions at different locations and when inoculated with different isolates. It was found that different pathotypes of S.graminicolaexist in West Africa (ICRISAT, 1987). The pathotypes from Bawku Manga (Ghana) and Samaru (Nigeria) were more virulent than the ones from Kamboinse (Burkina Faso) and Bengou (Niger). The breeding line IKM/CVP 39/83/84/351 showed stable resistance over all locations and all isolates at Reading.

ISSN:0143-6147    

DOI:10.1080/09670879209371643

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Research work on wilt/root rot diseases of chickpea (Cicer arietinumL.) in Ethiopia is reviewed. The five important wilt/root rot diseases in Ethiopia are wilt, dry root rot, wet root rot, black root rot and collar rot, which are caused byFusarium oxysporumf. sp.ciceri, Rhizoctonia bataticola, R. solani, F. solaniandSclerotium rolfsiirespectively. Of these, dry root rot and wilt are the most important diseases. The diagnostic symptoms of each of these five diseases are described. Research on control measures has so far focused on cultural practices such as dates of sowing and depth of sowing, chemical control by chemical seed dressing and development of resistant varieties. Research topics on wilt and root rots that need attention to improve the productivity of chickpea in Ethiopia are highlighted.

ISSN:0143-6147    

DOI:10.1080/09670879209371644

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor