摘要:

The competitive effects of intercropped beans (maturation period: three months) on the growth, tiller development and yield of plant sugar-cane (maturation period: 18 months) in the subhumid coast-hinterland of Natal were investigated over two seasons. In the first season rainfall was exceptionally low and intercropping reduced tiller emergence, leaf area and dry matter production in the sugar-cane. Lower soil and leaf water potentials were measured in the intercropped treatments. Beans appeared to be the stronger competitor and produced yields of up to 940 kg ha−1. Second season rainfall was favourable and tiller emergence was more prolific in the intercropping treatments. This combined with a higher degree of tiller mortality in the monoculture in the preceding autumn and winter, compensated for reduced dry matter production in the intercropped treatments in the first summer. As a result there was no difference between treatments in the final yield of cane and sucrose. Availability of soil moisture was the major factor affecting plant response to intercropping.S. Air. J. Plant Soil1985, 2: 59–66

ISSN:0257-1862    

DOI:10.1080/02571862.1985.10634138

出版商:Taylor&Francis Group    

年代:1985

数据来源: Taylor

摘要:

Results of field studies conducted on highly weathered Natal soils in which the performance of white clover (Trifolium repenscv. Regal ladino) was examined under a range of lime and P treatments applied in factorial combination, are presented. Despite adverse moisture conditions over the three seasons during which the studies were in progress, highly significant yield responses to lime and P were noted. Up to 460 kg P ha−1were required in order to obtain a levelling-off of dry matter response to P. This large P requirement was consistent with information obtained from P sorption isotherms indicating extremely high P fixation in the soils under study. A noteworthy feature of P response data was a suggestion of increased P requirement under conditions of low rainfall. Yield responses to lime were commensurate with the elimination of exchangeable Al.S. A f r. J. Plant Soil1985, 2: 67–71

ISSN:0257-1862    

DOI:10.1080/02571862.1985.10634139

出版商:Taylor&Francis Group    

年代:1985

数据来源: Taylor

摘要:

The variability of the soluble salt content and the textural composition of the soil were investigated in a 28-ha sub-catchment of the Ecca River, a tributary of the Great Fish River. The frequency distribution of the soluble salts in the 0–300 mm depth layer, is log-normal, with the untransformed data having a coefficient of variation (CV) of 60%. The silt plus clay content of the soils also follows a lognormal distribution and has a CV that ranges between 32% (left slope) and 41% (right slope). No spatial structure is evident in the properties of the soil samples collected in the traverses parallel to the river. However, on both sides of the river channel, the mean salt content of the top-slope positions is higher than that of the foot-slope positions. A Student'sttest shows that some of these differences are statistically significant. On the left slope no differences can be detected in the silt plus clay content of the various slope positions, but on the right slope the percentage of fine material at the foot-slope is significantly higher than at the top-slope. Indications are that these trends in the spatial structure of the two soil properties might be related not only to the type of, but also to the dip of the geological strata.S. Air. J. Plant Soil1985, 2: 72–78

ISSN:0257-1862    

DOI:10.1080/02571862.1985.10634140

出版商:Taylor&Francis Group    

年代:1985

数据来源: Taylor

摘要:

Soils, collected from the south-eastern Transvaal, Natal north coast and the more arid areas of the Natal interior, were examined using physical, chemical and mineralogical methods. Most of the soils were associated with particular management problems such as poor internal drainage, high bulk density or clay dispersion. The results of the investigation confirm that there is a relationship between clay mineralogical composition and physical behaviour. Poorly drained soils tended to be dominated by smectite minerals, while dispersive and compact soils had a mixed clay mineralogical composition of smectite, mica and kaolinite. Problem-free soils were generally kaolinitic. The presence of iron oxides, as indicated by colour, had an ameliorative effect on the physical properties, tending to reduce swelling, dispersion and compaction. Properties such as modulus of rupture, coefficient of linear extensibility and Atterberg limits, successfully discriminated between soils associated with different management problems.S. Afr. J. Plant Soil1985, 2: 79–84

ISSN:0257-1862    

DOI:10.1080/02571862.1985.10634141

出版商:Taylor&Francis Group    

年代:1985

数据来源: Taylor

摘要:

Van die ses plantdoders wat geëvalueer is, het slegs oksifluorfen bevredigende siesoenlange beheer van onkruide in aanplantings van knoffel (Allium sativumL.) verskaf. Oksadiason, chloroksuron, nitrofen, metabenstiasuron, ioksinil en oksifluorfen het min of geen fitotoksiese simptome op knoffel teen aanbevole dosisse vir uie vertoon nie. Oksifluorfen, as 'n na-opkomsbehandeling toegedien, het swaar skroeisimptome veroorsaak wat binne 14 dae na toediening verdwyn het. Nie een van die behandelings het opbrengs, bolgrootte en stamdeursnit nadelig beïnvloed nie.S.-Afr. Tydskr. Plant Grond1985, 2: 85–88

ISSN:0257-1862    

DOI:10.1080/02571862.1985.10634142

出版商:Taylor&Francis Group    

年代:1985

数据来源: Taylor

摘要:

Working relationships between mean minimum temperatures and environmental factors by means of regression techniques were established and used to estimate temperatures at gridpoints. These estimated temperatures were then used with a computer package program to map the isotherms on a mesoscale. An example is presented. The environmental factors which were found to have a significant bearing on the minimum temperature in this specific case were elevation, latitude, longitude, distance from the sea and topographic features of the local terrain. An index was defined to describe the relevant local terrain properties.S. Afr. J. Plant Soil1985, 2: 89–92

ISSN:0257-1862    

DOI:10.1080/02571862.1985.10634143

出版商:Taylor&Francis Group    

年代:1985

数据来源: Taylor

摘要:

Die groei van verskillende peulplantspesies is op twee suur bogronde by 'n baie lae vlak van Ca-voorsiening, as hidroksied en sulfaat, in 'n glashuis ondersoek. Die hidroksiedbehandelings, wat met 'n mate van pH-styging gepaard gegaan het, het die beste resultate gelewer. Dit dui daarop dat groeiversteuring met onvoldoende neutralisering verband gehou het. Daar was groot verskille in die groeiprestasie van verskillende spesies met dieselfde vorm van Ca-voorsiening, en moontlike voedingsversteurings word aan die hand van volledige plantontledingsdata bespreek. Waar groei swak was, het verlaagde Mo- en Ca-opname prominent na vore getree, maar geen definitiewe patroon met betrekking tot enige‘metaaltoksisiteit’kon vasgestel word nie. Stikstofvoeding was nie na wense nie, wat dui op moontlike probleme met N2-binding by sekere behandelings. Dit was duidelik dat die spesies wat beter onder suurgrondtoestande presteer het, nie naastenby die produksievlak wat met neutralisering verkry is, bereik het nie.S.-Afr. Tydskr. Plant Grond1985, 2: 93–97

ISSN:0257-1862    

DOI:10.1080/02571862.1985.10634144

出版商:Taylor&Francis Group    

年代:1985

数据来源: Taylor

摘要:

Bromus diandrusseedlings were grown in sand culture under greenhouse conditions, using a two factor randomized block design. Two levels of sulphur nutrition (with and without) and three acid rain treatments were applied. The plants were harvested 45 days after the start of the simulated acid rain treatments, and analysed for sulphate and cations. Sulphur deficiency significantly reduced the growth of the plants but simulated acid rain did not. Sulphur deficient plants had significantly more magnesium in the shoots and less in the roots, suggesting redistribution of the magnesium. Root potassium content was significantly higher in sulphur deficient plants, and lower in those plants receiving acid rain of pH 2,5. The results suggest that acid rain is not a stress factor whereBromus diandrusis concerned.S. Afr. J. Plant Soil1985, 2: 98–100

ISSN:0257-1862    

DOI:10.1080/02571862.1985.10634145

出版商:Taylor&Francis Group    

年代:1985

数据来源: Taylor

摘要:

Sixty-seven maize cultivars were evaluated for tolerance to atrazine (4 p.p.m. v/v) in nutrient solution. Shoot dry masses (SDM) of only two cultivars, SAB149 and NPP x K64r, were reduced more than 40% and another 14 were reduced by more than 30%. CG4801, PNR432, SSM2043 and A280 were the most tolerant cultivars and showed no reduction in SDM with atrazine. Cultivars, reportedly injured in commercial maize production were not less tolerant than the other cultivars evaluated. The absence of phytotoxicity symptoms did not indicate tolerance. Cultivars TX14, A206 and SABI404 displayed very slight phytotoxic symptoms but had large reductions in SDM. In sand culture, the relative responses of 10 cultivars to atrazine (8 p.p.m. v/v) were compared under different temperature and nutrient conditions. HL1 and A477W were relatively more tolerant under the low temperature regime (20/10°C) than under the high temperature regime (30/20°C). The relative tolerances of CG4801, SSM2039 and SSM2045 remained the same at both temperature regimes. Relative tolerances of cultivars changed under good and poor nutrition. Only CG4801 was reasonably tolerant under both nutrient regimes. The relative tolerances of cultivars were not significantly different when atrazine was applied pre- or post-emergence. The results of this study do not explain the severe injury periodically reported from the field.S. Afr. J. Plant Soil1985, 2: 101–106

ISSN:0257-1862    

DOI:10.1080/02571862.1985.10634146

出版商:Taylor&Francis Group    

年代:1985

数据来源: Taylor

摘要:

Drying of herbage samples in the field using a microwave oven powered by a portable generator has saved time and eliminated the transporting of samples to other stations for handling. Microwave drying is compared to drying in conventional forced-air ovens and the influence of microwaves on chemical analysis of plant material is discussed.

ISSN:0257-1862    

DOI:10.1080/02571862.1985.10634147

出版商:Taylor&Francis Group    

年代:1985

数据来源: Taylor