摘要:

Chemical compounds representing seed treatments, soil-applied systemic insecticides, contact and systemic corrective sprays were tested on the groundnut pest complex for three seasons in the South African Highveld Region. The efficacy of the compounds was evaluated by determining the effect of the compounds on plant population, leaf feeding injury, incidence of subterranean insects, pod damage, yield, grading quality and shelling percentage. Despite a favourable cost/benefit ratio achieved with all the compounds tested, none of the chemicals gave consistent results for all the parameters evaluated. Groundnut seed treatment with liquid-based compounds cannot be recommended on a commercial scale since these treatments caused testa damage, resulting in split seed.

ISSN:0257-1862    

DOI:10.1080/02571862.1995.10634326

出版商:Taylor&Francis Group    

年代:1995

数据来源: Taylor

摘要:

A Clovelly soil in Tala Valley (Natal) was fumigated with different concentrations of dazomet (300, 400, 500 kg ha−1) (granular formulation), and metham sodium (500, 750, 1000 L ha−1) (liquid formulation). Half the treatments were covered with plastic sheets during fumigation. After fumigation weed germination was rated and soil analysed for parasitic nematodes. The trial site was planted with‘Robinvale’lettuce seedlings. Dazomet was more effective than metham sodium in decreasing weed germination and efficacy of both chemicals was improved by covering the sites with plastic.Meloidogyne(root-knot nematode) andTrichodorus(stubby root nematode) were present prior to fumigation but their levels were reduced by dazomet. Nematode control by metham sodium was inconsistent and not improved by higher concentrations of fumigant. Nematode populations were counted again at harvest from both soil and root samples. These results were variable and could not be directly related to treatments. Dazomet significantly increased lettuce yields from 81 ha−1(control) to 44 t ha−1(500 kg ha−1dazomet). Fumigation with metham sodium and covering with plastic sheets did not significantly improve yields.

ISSN:0257-1862    

DOI:10.1080/02571862.1995.10634327

出版商:Taylor&Francis Group    

年代:1995

数据来源: Taylor

摘要:

Die negatiewe invloed van bewerking op organiese materiaal in gronde en 'n groot afname in die eksterne insette van S het die vraag laat ontstaan of die swawelstatus van Suid-Afrikaanse gronde voldoende is om volhoubare gewasproduksie te verseker. Bewerkte en naasliggende ekwivalente onversteurde bogronde (0–200 mm) is by 50 lokaliteite, verspreid in die somerreënvalgebied (25°–30°S en 24°–30°0), gemonster. Die lokaliteite is geselekteerom 'n groot variasie in klimaatstoestande, grondeienskappe en bewerkingsperiodeste verkry. Totale, anorganiese en mineraliseerbare S is bepaal en organiese S bereken as die verskil tussen totale en anorganiese S, en plantbeskikbare S as die som van anorganiese en mineraliseerbare S. Totale S het met tussen 4 en 70% afgeneem asgevolg van bewerking, met die onversteurde gronde as verwysing. Daarwas gem id- deld 40% meer anorganiese S in die bewerkte gronde as in die onversteurde gronde. Die afname in totale S word toegeskryf aan versneide mineralisasie van organiese S. In bewerkte gronde het daar gemiddeld 30% meer S gemineraliseer as in die onversteurde gronde. Dus bevat die bewerkte gronde meer plantbeskikbare S as die onversteurde gronde. Die verhoudings van C:S, N:S en C:N:S het afgeneem met bewerking. Organiese C, totale N, fynslik-plus-kleiinhoud en ariditeitsindeks het goed gekorreleer met die verskillende fraksies van S van beide die onversteurde en bewerkte gronde. Dit blykdat bewerking die organiese S reserwe mettertyd sókan uitput dat tekorte na 'n lang bewerkingstyd mag voorkom.

ISSN:0257-1862    

DOI:10.1080/02571862.1995.10634328

出版商:Taylor&Francis Group    

年代:1995

数据来源: Taylor

摘要:

A number of common soil extractants, mainly those used for soil P, were used to extract K from a range of widely differing soils which occur in the Western Cape; the objective being to evaluate the simultaneous determination of P and K availability. Soil samples were taken mainly from the upper horizons of 110 profiles representing the dominant soil forms occurring in this region. The soils varied from highly weathered, deep, well-drained acid Oxisols (Hutton form) to younger less developed duplex Alfisols (Swartland, Glenrosa and Kroonstad forms) and deep sandy Inceptisols (Fernwood form). The soils exhibited a wide range of values of clay content, CEC, pH and exchangeable K. Seven soil P extraction methods (Bray No. 1, Bray No. 2, citric acid 1%, Olsen, ISFEI (Na), Ambic and Mehlich No. 3) were compared with two K extraction methods, (0.5M NH4CI and M NH4OAc). All the methods gave K indices which were significantly correlated with one another (r>0.9). The extractants containing NH/were better correlated with one another than with the other extractants. Significant linear relationships were obtained with all the methods between extractable K and soil K-values determined using the NH4OAc method over a range of values from<10 mg kg−1to over 300 mg kg−1. Apart from the results of the Bray No. 1 and ISFEI methods, which exhibited lower extractability, all R2values were greater than 0.9. It appears that any of the methods used for extracting soil P are suitable for assessing the K status of the soils of this region.

ISSN:0257-1862    

DOI:10.1080/02571862.1995.10634329

出版商:Taylor&Francis Group    

年代:1995

数据来源: Taylor

摘要:

Wheat crops produced under dryland conditions in the winter rainfall belt of South Africa are often subjected to water stress. To study the effect of water stress on the spring wheat cultivars Nantes, Palmiet and SST 66, an experiment was conducted in a glasshouse at a 15°/10°C (day/night) temperature. Three intensities of water stress (0% PEG = unstressed; 15% PEG = low stress intensity and 22.5% PEG = high stress intensity) were imposed with polyethylene glycol (PEG) 6000 during the period of anthesis to milk stage in the three spring wheat cultivars. Water stress increased leaf diffusive resistance (LDR) and decreased the relative water content (RWC) of all three cultivars. Although plants were rehydrated after milk stage was reached, leaf senescence was hastened and the kernel-filling period shortened. These effects increased with increasing stress intensities. The low stress intensity (15% PEG) did not affect grain yield, but plants subjected to the high stress intensity (22.5% PEG) had significantly smaller kernels and a 37.5% lower grain yield. Although cultivars differed in their response to stress treatments for some parameters, these differences were too small and inconsistent to be recommended for use in breeding programmes for drought tolerant cultivars.

ISSN:0257-1862    

DOI:10.1080/02571862.1995.10634330

出版商:Taylor&Francis Group    

年代:1995

数据来源: Taylor

摘要:

Five new or locally unexploitedLrgenes were evaluated as sources of resistance to leaf rust (Puccinia recon- ditaRob. ex Desm. f. sp.tritici) of wheat (Triticum aestivumL.) in South Africa. The expression ofLr36, Lr41andLr42, as well as the provisionally named genes'Lr39and‘Lr40’, their reaction to different temperatures and inheritance in two South African wheat cultivars were determined.Lr36in line C78.10 was more effective at higher temperatures whereasLr39(line KS86WGRC02) andLr40(line KS89WGRC07) conferred lower infection types at 15°C than at 25°C. Except for more pronounced flecking at 15°C, temperature had no detectable effect on the expression ofLr41in line KS90WGRC10. An interaction between temperature and pathotype showed thatLr42in line KS91WGRC11 was less effective to certain pathotypes at lower temperatures. According to seedling infection types in the F2and BC2F1,Lr36, Lr39andLr40were inherited as partially dominant genes in Karee and Palmiet. With these backgrounds,Lr39andLr40produced similar infection types.Lr41was partially dominant in Karee, but similar, highly resistant infection types suggested complete dominance in Palmiet.Lr42was partially dominant to pathotype UVPrt13 in Palmiet, but recessive to UVPrt9 in Karee. The results obtained in this study provided information for the establishment of reliable selection criteria forLrgene management during wheat leaf rust resistance breeding.

ISSN:0257-1862    

DOI:10.1080/02571862.1995.10634331

出版商:Taylor&Francis Group    

年代:1995

数据来源: Taylor

摘要:

The inheritance of and relationships between diastatic power, seed texture, steep mass, malt mass, dry malt mass, rate of moisture uptake during malting and percentage moisture of malt were analysed by means of a factorial crossing design, which involved the crossing of three grain sorghum females with eight males, as well as by means of correlation and path coefficient analyses. Especially in the case of diastatic power, but also for the other characteristics, the observed components of variation indicated a lack of genetic variability and the necessity to increase the number of plots and seasons for such experiments. Malt mass was the characteristic most strongly related to diastatic power. Its use in a breeding programme is discussed.

ISSN:0257-1862    

DOI:10.1080/02571862.1995.10634332

出版商:Taylor&Francis Group    

年代:1995

数据来源: Taylor

摘要:

The tolerance to alachlor [α-chloro-2′,6′?diethyl-N-(metoxy- methyl) acetanilide] of three sunflower (Helianthus annuusL.) cultivars was evaluated in an aqueous medium in a glass- house. Alachlor (0.79 - 6.32 mg L−1) caused significant reductions in the root and shoot growth of sunflower seedlings exposed to the herbicide in nutrient solution. The roots of seed- lings exposed to alachlor became progressively shorter, thicker and darker in colour as the herbicide concentration increased. Differential cultivar tolerance was demonstrated.

ISSN:0257-1862    

DOI:10.1080/02571862.1995.10634333

出版商:Taylor&Francis Group    

年代:1995

数据来源: Taylor

ISSN:0257-1862    

DOI:10.1080/02571862.1995.10634334

出版商:Taylor&Francis Group    

年代:1995

数据来源: Taylor