摘要:

The persistence of alachlor (2-chloro-2′, 6′-diethyl-N-methoxymethylacetanilide) and metolachlor [2-chloro-6′-ethyl-N-(2-methoxy-1-methylethyl)acet-O-toluidide] in soil was determined over an 80-day period at temperatures ranging from 5 to 50°C. Soils were maintained at either 50 or 100% of field capacity. The herbicides were less persistent at high temperatures, but the greater the soil moisture content, the slower the overall degradation rate. The effect of temperature on the phytotoxicity of these two soil-applied herbicides was also determined. The phytotoxic effect of alachlor and metolachlor on beans (Phaseolus vulgarisL. cv. Kamberg) was greatest at 40°C. Beans were not injured at 30°C when treated with metolachlor at 1, 5 I ha−1and alachlor at 4 I ha−1. At higher dosage rates of 3 to 7, 5 I ha−1metolachlor and 8 to 20 I ha−1alachlor, beans showed evidence of injury. At temperatures of 35°C and 40°C, all the dosage rates had adverse effects on the beans.S. Afr. J. Plant Soil1986, 3: 95–98

ISSN:0257-1862    

DOI:10.1080/02571862.1986.10634200

出版商:Taylor&Francis Group    

年代:1986

数据来源: Taylor

摘要:

Vrugontledings op appels van bome op gedeeltelik versuipte gronde gedurende die vruggroei-periode het hoër Na- en B- en laer N- en Mg-peile getoon as appels van bome op droër gronde. Die vrugte van nat persele was fermer en het hoër suikerpeile gehad as diévanaf droër persele. Geen betekenisvolle verskille in omvang van interne verval gedurende koelopberging is gevind nie. Dit blyk dat grondvogbepalings die enigste betroubare metode is om versuipte toestande te identifiseer.S.-Afr. Tydskr. Plant Grond1986, 3: 99–102

ISSN:0257-1862    

DOI:10.1080/02571862.1986.10634201

出版商:Taylor&Francis Group    

年代:1986

数据来源: Taylor

摘要:

Kleimineralogiese data vir 12 grondvorms, wat algemeen in die Hoëveldstreek voorkom, is ondersoek. Die persentasie monsters waarin 'n bepaalde kleimineraal voorkom, is bereken. Daaruit is dit duidelik dat smektiet algemeen in gronde van die Arcadia-, Bonheim, en Rensburgvorms voorkom, maar minder algemeen in gronde van die Avalon-, Hutton-, Clovelly- en Westleighvorms. Tussen 30 en 318 monsters, uit geselekteerde boerderygebiede in die Hoëveldstreek, is gebruik om regressievergelykings vir die verband tussen katioonuitruilkapasiteit en klei-inhoud vir 19 grondvorms te bereken. Katioonuitruilkapasiteit, tesarne met klei-inhoud kan gebruik word om die waterhouvermoëvan grondvorms te bereken. Dit is opvallend dat die waterhouvermoëvan verskillende grondvorms met vergelykbare klei-inhoude, maar met 'n variërende katioonuitruilkapasiteit met tot meer as 50 persent kan verskil. Die korrelasie tussen katioonuitruilkapasiteit, kleiinhoud en waterhouvermoëis goed binne 'n grondvorm, maar varieer baie tussen grondvorms.S.-Afr. Tydskr. Plant Grond1986, 3: 103–109

ISSN:0257-1862    

DOI:10.1080/02571862.1986.10634202

出版商:Taylor&Francis Group    

年代:1986

数据来源: Taylor

摘要:

Three-year-old nectarine trees of the cultivar Independence grown in free-drainage lysimeters were exposed to a wet and a dry treatment, i.e. high soil moisture content throughout or progressive soil drying respectively. The canopy temperature of the trees was measured with an infrared thermometer at midday. Leaf diffusion resistance (RL) and plant water potential (WP) were determined at the same time. Environmental conditions had an overriding effect on canopy temeperature. Water stress index (SI) and canopy temperature difference between the dry and wet treatment (CTD dry-wet) were therefore calculated. Stepwise multiple linear regression analysis indicated close correlation between SI or CTD (dry-wet) and WP and it was established that the effect of environmental conditions on SI and CTD dry-wet was unimportant.S. Afr. J. Plant Soil1986, 3: 110–114

ISSN:0257-1862    

DOI:10.1080/02571862.1986.10634203

出版商:Taylor&Francis Group    

年代:1986

数据来源: Taylor

摘要:

Maize plants exposed to atrazine at temperatures ranging from 10°C to 30°C showed increased hydroxylation of atrazine to form the non-toxic hydroxy-atrazine metabolite as temperature increased to 25°C, above which hydroxylation decreased again. When exposed to 12 ppm atrazine, accumulation of atrazine occurred in roots and shoots of maize plants under all temperature-regimes. The results presented show that hydroxylation of atrazine does occur in roots and shoots of maize plants. Therefore, in the case of insufficient atrazine hydroxylation in the roots, with resulting accumulation, atrazine will be transported via the transpiration stream to the shoots where subsequent hydroxylation will take place.S. Afr. J. Plant Soil1986, 3: 115–118

ISSN:0257-1862    

DOI:10.1080/02571862.1986.10634204

出版商:Taylor&Francis Group    

年代:1986

数据来源: Taylor

摘要:

Die verwantskap tussen kegelpenetrasieweerstand en droëbrutodigtheid word deur die mate van sortering beïnvloed. By swak sortering word laer penetrasieweerstande as in die geval van matige sortering met spesifieke brutodigthede geassosieer. Waterinhoud waarby maksimum verdigting plaasvind, word deur klei-inhoud en die omvang van die verdigtingspoging beïnvloed. Kritiese waterinhoud verhoog met toename in klei-inhoud en verlaag met toename in die omvang van die verdigtingspoging. Monsters van sanderige grand van die Viljoenskroon- en Bothaville-omgewings het tot hoëbrutodigthede by die onderskeie kritiese waterinhoude verdig.S.-Afr. Tydskr. Plant Grond1986, 3: 119–122

ISSN:0257-1862    

DOI:10.1080/02571862.1986.10634205

出版商:Taylor&Francis Group    

年代:1986

数据来源: Taylor

摘要:

The necessity to subdivide the wheat producing soils of the Winter Rainfall Region for extension purposes, was considered. Use was made of correlations, interaction variance components and pattern analysis procedures to reflect on the possible existence of sub-environments with different but consistent cultivar requirements. Yield data available at present seem to indicate primarily unpredictable sources of environmental variation to contribute to observed genotype×environment interactions. The implications for wheat extension programs are considered.S. Afr. J. Plant Soil1986, 3: 123–129

ISSN:0257-1862    

DOI:10.1080/02571862.1986.10634206

出版商:Taylor&Francis Group    

年代:1986

数据来源: Taylor

摘要:

Die verdraagsaamheid van mieliesaailinge (Zea maysL. kv SSM2041) teenoor atrasien is in 'n glashuis ondersoek. Plante is in potte gekweek, in voedingsoplossings met tekorte aan sekere makro-elemente. Atrasien in die voedingsoplossings is periodiek bepaal met behulp van hoëdrukvloeistofchromatografie. Tekorte aan N, P, K, Ca en Mg, afsonderlik of in sekere kombinasies, het oor die algemeen groot verskille in groei by plante van kontrolebehandelings (0 mg dm−3atrasien) veroorsaak. Die meer groeikragtige plante was oor die algemeen minder verdraagsaam teenoor atrasien. Nogtans was daar by bepaalde atrasienpeile (6 en 12 mg dm−3) nie betekenisvolle verskille in groei tussen plante van verskillende voedingsoplossings nie. Dit blyk dat groeibeperkende vlakke van bogenoemde makro-elemente nie die verdraagsaamheid van mieliesaailinge teenoor atrasien betekenisvol beïnvloed nie. Daar was wel 'n neiging tot laer verdraagsaamheid by plante wat 'n tekort aan Mg ondervind het. Dit hou waarskynlik verband met die belangrikheid van Mg in die struktuur van chlorofilmolekule, en die feit dat atrasien fotosintese inhibeer. Atrasienbepalings het getoon dat slegs 20–40% van die oorspronklik toegediende atrasien na 28 dae in die voedingsoplossings teenwoordig was. Dit het goed verband gehou met droëmateriaalopbrengste van die besondere behandelings.S.-Afr. Tydskr. Plant Grond1986, 3: 130–134

ISSN:0257-1862    

DOI:10.1080/02571862.1986.10634207

出版商:Taylor&Francis Group    

年代:1986

数据来源: Taylor

摘要:

After the extraction of free sugars and water soluble polysaccharides the cell wall constituents of leaf, stem and inflorescence samples ofThemeda triandra(red grass) at two stages of growth were separated into fractions by a sequence of extraction procedures. Pectic substances were present as a minor component of the dry matter and consisted mainly of glucose and galacturonic acid. Cellulose was the major type of polysaccharide and contributed about one third of the dry matter. The total content of hemicellulose A and B, calculated as the sum of the component sugars and total uronic acid, accounted for one sixth to one quarter of the dry matter. Leaves and inflorescences contained more hemicellulose B than -A, while this proportion was reversed in the stems.S. Afr. J. Plant Soil1986, 3: 135–139

ISSN:0257-1862    

DOI:10.1080/02571862.1986.10634208

出版商:Taylor&Francis Group    

年代:1986

数据来源: Taylor

摘要:

Die oplosbaarheid, diffusie en loging van twee kalktipes is in 'n suiwer sandmedium bestudeer. Deur van sand gebruik te maak is die kompliserende effek van die uitruilfase van grond geëlimineer. Die uitwerking van byvoegings van KCl, NH4Cl, Na2EDTA, organiese materiaal en 'n H-versadigde hars op kalkoplosbaarheid en -beweging is nagegaan. In horisontale kolomme is die omvang van beweging a.g.v. diffusie oor tydperke van 5 en 9 maande by twee waterinhoude bepaal. Na 5 maande en by 'n waterinhoud ietwat hoër as veldkapasiteit, het meer as 99,5% van die Ca nog in die kalkband voorgekom. KCl het min uitwerking op Ca-verspreiding gehad; NH4Cl het ietwat beter gevaar en NH4Cl + 'n H-versadigde harsband op 100 mm vanaf die kalk het die beste gevaar, hoewel na 9 maande meer as 80% van die Ca steeds in die kalkband voorgekom het. In die geloogde kolomme is 8 behandelings by besproeiings van 600 mm en 1200 mm vergelyk. Loging met 1200 mm water het onderskeidelik 18, 1% en 9, 6% Ca vanuit die twee kalktipes verwyder, vergeleke met tot 46, 1% vir 'n NH4Cl-oplossing en tot 54, 8% vir 'n EDTA-oplossing. 'n Organiese materiaal byvoeging het min invloed op die uitloog van Ca gehad.S.-Afr. Tydskr. Plant Grond1986, 3: 140–146

ISSN:0257-1862    

DOI:10.1080/02571862.1986.10634209

出版商:Taylor&Francis Group    

年代:1986

数据来源: Taylor