摘要:

Reciprocal differences in a diallel cross experiment with air-cured tobacco strains were found to be significant for certain characteristics, but relatively small compared to differences between strains in general combining ability. A factorial analysis designed to detect maternal effects in the same material failed to substantiate significance for these characteristics. A separate experiment with flue-cured tobacco strains involving genome transfer by backcrossing, gave no indication of a cytoplasmic contribution to variation in the characteristics measured.

ISSN:0257-1862    

DOI:10.1080/02571862.1988.10634267

出版商:Taylor&Francis Group    

年代:1988

数据来源: Taylor

摘要:

Die invloed van drie nitraat:ammoniumverhoudings by twee stikstofkonsentrasies op planteienskappe is met blomtyd en na fisiologiese volwassenheid vir suiwerlyne gemeet. 'n Kwartssandkultuur is as groeimedium in 'n glashuis gebruik. Toenemende NH4+-verhoudings het planthoogtes, blaaroppervlaktes en droëmateriaalproduksie van verskillende plantkomponente verminder. Die akkumulasie van totale N in die stamme tydens die graanvul- periode is verhoog deur hoër NH4+-verhoudings by albei N-konsentrasies. Die translokasieverlies van totale N uit die blare tydens die graanvulperiode was minder met toenemende NH4+-verhoudings by 100 en 400 mg N−1. Die 3:1 nitraat:ammoniumverhouding wat die hoogste translokasieverlies vanuit die blare gehad het, was egter 'n uitsondering op hierdie reël.

ISSN:0257-1862    

DOI:10.1080/02571862.1988.10634268

出版商:Taylor&Francis Group    

年代:1988

数据来源: Taylor

摘要:

Die invloed van ses nitraat:ammoniumverhoudings by 200 mg N l1in een proef en twee ander verhoudings by 50, 100 en 200 mg N l1in 'n tweede proef is op droëmateriaalproduksie en stikstofinhoud ondersoek. Die algehele beste behandeling was 'n 3:1 nitraat:ammoniumverhouding by 100 mg N l1. Hierdie behandeling was betekenisvol beter as 'n 3:1-verhouding by 200 mg N l1en 'n 1:0-verhouding by 100 of 200 mg N l1vir droëmassaproduksie en stikstofopname. Nitraat:ammoniumverhoudings van 2:3,3:2,1:4,4:1 en 3:1 by 200 mg N l1het betekenisvol hoër N% in die bogrondse plantdele bo 'n 1:0-verhouding by dieselfde N-konsentrasie gegee. Vyf basters het betekenisvol van mekaar verskil in hul vermoëom stikstof op te neem. Hierdie verskille het verskil vir die twee proewe.

ISSN:0257-1862    

DOI:10.1080/02571862.1988.10634269

出版商:Taylor&Francis Group    

年代:1988

数据来源: Taylor

摘要:

In a water culture experiment with wheat, the influence on growth and nutrient uptake of varying the P supply from 0,02 to 5 mmol H2PO4−dm−3and the NH4+:NO3−ratio from 0:15 to 12:3, with a Hoagland nutrient solution (No 2) as control, was studied. Poor growth due to low P supply was characterized by a higher root:top growth ratio than plants which received adequate P, indicating that under these conditions root development of wheat takes preference over top growth. Root P was also higher than top growth P with low P supply, indicating that wheat requires a certain level of P in the roots before P can be transported freely to the tops. It was postulated that NO3−reduced the detrimental effect on growth of high P supply by causing P to be. precipitated as Ca3(PO4)2in the roots, while with high P and N supply, more Ca2+is required for balanced nutrition. Increased NH4+supply increased the P demand with added P apparently reducing the antagonistic effect of NH4+on Ca2+uptake. This is especially important in highly leached acid soil where the Ca2+content tends to be low and fertilization early in the season should be carefully planned.

ISSN:0257-1862    

DOI:10.1080/02571862.1988.10634270

出版商:Taylor&Francis Group    

年代:1988

数据来源: Taylor

摘要:

Alachlor [2-chloro-N-(2,6 diethylphenyl)-N-(methoxymethyl) acetamide], metolachlor [2-chloro-N-(2-ethyl-6- methylphenyl)-N-(2-methoxy-1 -methylethyl) acetamide]and acetochlor [2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6- methyl-phenyl) acetamide], members of the chloroacetanilide herbicides, are used pre-emergence to control grasses and some broadleaf weeds. Two concentrations, i.e. 0,5 and 2 mg ai kg−1of the above herbicides did not inhibit germination of threePhaseolusbean taxa. Hypocotyl-epicotyl growth was reduced by increased herbicide concentrations between 0,5 and 2 mg ai kg−1and increased temperatures (18 to 25°C). Significantly higher phytotoxicity was observed at 25°C than at 18°C. The order of phytotoxicity was acetochlor>alachlor>metolachlor. Acetochlor (1,5 mg ai kg−1) at 25°C reducedPhaseolus vulgarisL. cv. Kamberg hypocotyl—epicotyl growth by 42%,Phaseolus vulgarisL. cv. Bonus by 16% andPhaseolus coccineusvar.albonanus(Large white kidney) by 17%. At 18°C, acetochlor (1,5 mg ai kg−1) reduced hypocotyl—epicotyl growth of Kamberg by 27%, Bonus by 24% and Kidney by 18%. Higher herbicide concentrations increased bean injury as assessed by dry mass production during hypocotyl-epicotyl growth.

ISSN:0257-1862    

DOI:10.1080/02571862.1988.10634271

出版商:Taylor&Francis Group    

年代:1988

数据来源: Taylor

摘要:

Field trials were conducted to determine the effect of time and rate of single and split applications of nitrogen on various malting parameters of barley. The effect of a single low nitrogen application of 50 kg Nha−1at sowing was compared with high nitrogen applications of 150 kg N ha−1given as split applications at different growth stages. The barley was malted in an automatic micro-malting system and the malt analysed for various quality parameters. A number of the high nitrogen applications significantly increased total nitrogen, soluble nitrogen, free amino-nitrogen, and alpha- and beta-amylase activity, whereas the fine-grind extract was not significantly affected. The growth stage at which supplementary nitrogen was applied significantly affected all malting parameters except the total nitrogen content. Highest values in general were found when split applications of nitrogen were done at five different growth stages until ear emergence.

ISSN:0257-1862    

DOI:10.1080/02571862.1988.10634272

出版商:Taylor&Francis Group    

年代:1988

数据来源: Taylor

摘要:

Due to the transformations which sludge undergoes after addition to soil, single measurements of P availability are of little value in soils which have recently received additions of sewage sludge. This study assessed six procedures on two soils—a clay of the Griffin form (Typic Haplorthox) and a sandy clay loam of the Clovelly form (Tropeptic Haplorthox). Five chemical tests based on laboratory incubation and chemical analyses were compared to a short-term bioassay procedure. Soil—sludge and soil—inorganic P mixtures (supplying 375, 751 and 1503 mg P kg−1soil) were incubated in the laboratory for up to 92 days, and available P assessed by extraction with Bray 1, Bray 2, Olsen, ISFEI and CaCl2solutions. The bioassay was based on the short-term uptake of P by P-deficient Italian ryegrass (Lolium multiflorumvar. Midmar) from soil—sludge or soil—inorganic P mixtures. Ryegrass cumulative P uptake and amounts of plant-available P extracted by the various reagents was regressed against amount of P applied for each soil x P—source x time combination. The ratio of the slopes of the (linear) regression lines for the two P sources was then used as a measure of the relative efficiency (E value) of sludge as a P fertilizer compared with inorganic P source. All the chemical tests greatly underestimated the effectiveness of sludge P as a source of fertilizer P. %E values derived by laboratory incubation and chemical extraction were approximately 50–70% initially for Bray, Olsen and ISFEI methods, and tended to remain constant or decrease with time. %E values from incubation and extraction with CaCl2were generally less than 10%. In contrast initial %E values from the bioassay were 44 and 64% for the Clovelly and Griffin soils respectively, and these values increased to 82 and 118% after 97 days of root—P source contact. Thus laboratory incubations of soil—sludge mixtures and extraction of various P forms cannot be reliably used as an indication of the P fertilizer value of the sludge.

ISSN:0257-1862    

DOI:10.1080/02571862.1988.10634273

出版商:Taylor&Francis Group    

年代:1988

数据来源: Taylor

摘要:

Vier verskillende bewerkingsbehandelings, wat Wissel in bewerkingsintensiteit van die intensiewe, konvensionele. skaar- en skottelbewerkingstelsel tot geen-bewerking, is oor 'n periode van 6 jaar vergelyk ten opsigte van die uitwerking op grondfaktore en die groei en opbrengs van koring. In hierdie proewe wat op 'n Escourt-döhne-grond in die maritieme-reëngebied van die Suid-Kaap-koringproduksiestreek uitgevoer is, het minder-intensiewe be- werkingstelsels die organiese C- en totale N-inhoud van die grond verhoog. Grondwaterinhoud met saaityd is ook verhoog. Penetrometerweerstande in veral die geen-bewerkingspersele was egter so hoog dat plantvestiging be- nadeel is deurdat saai-implemente nie behoorlik in die grond kon penetreer nie. Digter en meer egalige stande, wat meer are m−2veroorsaak het, het dan ook oor jare die grootste bydrae (r2= 0,59 tot 0,90) gelewer tot die gemiddeld 61,7% hoër graanopbrengs wat met konvensionele in vergelyking tot geen-bewerking verkry is.

ISSN:0257-1862    

DOI:10.1080/02571862.1988.10634274

出版商:Taylor&Francis Group    

年代:1988

数据来源: Taylor

摘要:

Drie-en-twintig plaaslik-geteelde pruimonderstamseleksies is met virusvrye, klonale Marianna, virusbesmette Marianna en perskesaailing vergelyk. In teenstelling met perskesaailing wat oorwegend Kakamas en Du Plessis is, word hierdie seleksies vegetatief vermeerder. Kumulatiewe opbrengs, stamomtrek en opbrengsdoeltreffendheid is as maatstawwe vir vergelyking gebruik. Siegs 16-4, 13-61 en 16-13 hou belofte in en is geselekteer vir verdere evaluasie teen variërende plantdigthede met verskillende bostamkultivars. Seleksie 16-4 is 'n groeikragtige onderstam met 'n hoër kumulatiewe opbrengs as Marianna en perskesaailing. Dit is ten opsigte van opbrengsdoeltreffendheid vergelykbaar met die kontroles. Die twee groeikragtige seleksies 13-61 en 16-13 se opbrengsdoeltreffendheid is net so goed soos diévan virusvrye Marianna en perskesaailing. Nie een van die verdwergende en semi-verdwergende onderstamme wat getoets is se prestasie was van so 'n aard dat hui vir verdere evaluasie geselekteer kan word nie.

ISSN:0257-1862    

DOI:10.1080/02571862.1988.10634275

出版商:Taylor&Francis Group    

年代:1988

数据来源: Taylor

摘要:

The object of this study was to investigate the interrelationship between yield, its components, base temperature and drought resistance of grain sorghum. Seven commercial cultivars and 27 F1progenies were compared in two separate randomized block trials. A total of 24 characteristics were evaluated and their association was determined by simple correlation and path coefficient techniques. The results suggested that simultaneous selection for more than one characteristic is possible. Drought resistance and base temperature were indicated to have an important bearing on grain yield and its components.

ISSN:0257-1862    

DOI:10.1080/02571862.1988.10634276

出版商:Taylor&Francis Group    

年代:1988

数据来源: Taylor