South African Journal of Agricultural Science - latest Issue
Volume 9, Issue 3, 1966
Author B. CilliersSource: South African Journal of Agricultural Science 9 (1966)More Less
n Analise is op die Suid-Afrikaanse Friesras gedoen om vas te stel of die struktuur daarvan van so 'n aard is dat doeltreffende genetiese verbetering kan plaasvind. Monsters is geneem uit die registrasies van 1914/15, 1926/27, 1938/39, 1950/51 en 1962/63 waarop die volgende bepalings gedoen is: die teelstruktuur; die genetiese bydrae van belangrike kuddes, voorouers en ingevoerde diere; en 'n ontleding van die inteling, hoofsaaklik volgens die metodes van Robertson (1953) en Barker (1957). Die teelstruktuur neem tans nie die gewenste vorm aan nie. Die beskikbaarheid van ingevoerde diere bepaal die teelpatroon wat gevolg word deur telers. Verder is die inteling laag genoeg om as veilig beskou te word.
Author W. H. WesselsSource: South African Journal of Agricultural Science 9 (1966)More Less
Genetiese parameters en statistiek van vier vegetatiewe fases, wat nie aan direkte seleksie onderwerp was nie, en opbrengste van drie aanplantings wat maandeliks gemaak is, is bereken volgens die dialleelmetode van Jinks & Hayman (1953). Omgewingstoestande soos veroorsaak is deur die drie tye van plant binne dieselfde seisoen het nie slegs (a) die additiewe gene-effekte beinvloed nie, maar ook (b) die rigting van dominansie en (c) die aantal dominante gene, sowel as (d) die gene wat by die nie-allele genewisselwerking of epistase betrokke is.
Source: South African Journal of Agricultural Science 9, pp 525 –535 (1966)More Less
This investigation was undertalcen to study some aspects of the silicate-phosphate interrelationships in eight sandy soils of the Orange Free State Region. In a pot experiment the effect of silicate applications on plant yield and phosphorus uptake were investigated. The silicate additions significantly increased the plant yield and P uptake in certain soils. The increase in "" total available"" phosphorus in some soils when silicate and phosphate were added together, was explained on the basis of the formation of either alumino-silicates or alumino-phosphates. A laboratory experiment revealed that an increase in phosphate applications caused a similar increase in release of water-soluble silicate. The amounts of silicate released were smaIl. These results indicate the possible occurrence of isomorphous substitution of phosphate for silicate in these soils.
Author J. BotSource: South African Journal of Agricultural Science 9, pp 535 –538 (1966)More Less
The bollworm Heliothis armigeraRiibn., and the leaf cutter Prodenia Iitura F. can be reared on an aseptic artificial diet very similar to that previously descriptionbed by the author, for Plusia acuta Walker, Spodoptera exigua Rb., S. exempta Walk. and S. cilium Geun. The diet is made up of readily available food products and chemical substances including: wheatgerm, yeast, casein, cholesterol, choline, inositol, cysteine and ascorbic acid. Its preparation is simple. Insects reared on this artificial medium appear in general to be above average size and compare favourably in all respects with field collected material.
Invloed van katioonuitruilingskapasiteit en uitruilbare katione van kleisuspensies op die wortel- en stingelontwikkeling van mieliesaailinge.Source: South African Journal of Agricultural Science 9, pp 539 –546 (1966)More Less
Die invloed van kaolien en bentoniet op die wortel- en stingelontwikkeling van mieliesaailinge is bestudeer. Die uitwerking van verhoogde katioonuitruilingskapasiteite by gelyke ioonbesetting is in verskillende konsentrasies van kaolien- en bentonietsuspensies nagegaan. Om. die invloed van bindingsenergiee vir verskillende katione na te gaan, is die verhouding van geadsorbeerde K+: Ca2+ + Mg2+ op die klei gevarieer deur dit respektiewelik met een persent oplossings van KCl, CaCI2.2H.O en MgCI2.6H.O in ewewig te bring. 'n Verhoging in katioonuitruilingskapasiteit het geen betekenisvolle invloed op die wortel- en stingelontwikkeling gedurende die eerste drie dae gehad nie. In K + -bentoniet was. die wortelontwikkeling relatief beter as in Ca2 + - en Mg2 + -bentoniet, terwyl K + -kaolien die swakste wortelontwikkeling gegee het. Die uitwerking van die sames telling van die adsorpsiekompleks op die vroee groeistadium is dus nie net toe te skryf aan die gewysigde katioonverhoudings in die ewewigsoplossings nie, maar ook aan die bindingsenergie van die klei vir 'n bepaalde katioon. Op grond hiervan kan ook uit die resultate afgelei word dat bentoniet voorkeuradsorpsie vir kalsium vertoon.
Author P. S. PretoriusSource: South African Journal of Agricultural Science 9, pp 547 –560 (1966)More Less
Om die invloed van speenouderdom op groeitempo, bereiking van puberteit en wolproduksie te bepaal, is 32 Merino-ooilammers met geboorte, op 8, 16 en 24 weke gespeen. Die lammers wat met geboorte gespeen is, is op volroommelkpoeier grootgemaak. Die groeitempo van die lammers is slegs gedurende die eerste twee weke na speen gestrem. Speenouderdom het blykbaar geen invloed uitgeoefen op die ouderdom waarop puberteit bereik is nie. Die vaggewig, hoeveelheid skoon, droe wol en wolonsuiwerhede het geen nadelige invloed getoon toe die lammers op 'n gemiddelde ouderdom van 26 weke geskeer is nie. Wolveseldikte is ook nie nadelig belnvloed nie. Die vroegspeen van ooilammers kan blykbaar sonder nadelige gevolge in die praktyk toegepas word, mits aan die nodige voedingsvereistes voldoen word.
Source: South African Journal of Agricultural Science 9, pp 561 –576 (1966)More Less
The beta-carotene and true vitamin A content of four commercialJy available chicken rations in South Africa were chemically assayed in fresh samples and again after storage periods of two, five and ten weeks. Whereas lucerne meal and yellow maize meal are the main sources of betacarotene in a chicken ration, the beta-carotene value of these products incorporated by the different feed manufacturers in the rations, was also determined. Furthermore, the beta-carotene content ;of suncured and dehydrated lucerne meal .obtained from two of the largest lucerne co-operatives n South Africa was also determined. The average beta-carotene content in the fresh chicken mash samples amounted to 0649 milligrams (mg) per pound (lb) of which 202 per cent was lost during a storage period of five weeks at room temperature. The average beta-carotene content of the lucerne meal and yellow maize meal used by the feed manufacturers in compiling the rations amounted to 1143 mg and 059 mg per lb respectively. The suncured lucerne meal contained an average of 1964 mg beta-carotene per lb while the dehydrated product showed an average of almost 39 mg beta-carotene per lb. During six weeks storage at room temperature in burlap bags, a loss of 3737 per cent occurred in the beta-carotene content of suncured lucerne meal and a loss of 4956 per cent in the beta-carotene content of dehydrated lucerne meal. The deterioration of beta-carotene in the dehydrated lucerne meal was significantly faster during any given period of storage than in the suncured lucerne meal.
A hematological study of the Black Australorp in relation to certain economic characteristics. I. Blood glucose.Source: South African Journal of Agricultural Science 9, pp 577 –594 (1966)More Less
The blood glucose level of Black Australorp embryos increases from lO-day old to 21-day old at a rate of 224 mg/IOO ml of blood daily; and 21-day old embryos give lower glucose values than chicks of the same age. From 3 to 84 days of age blood glucose rises at a rate of 2 0 mg/l00 mI of blood per week in both sexes and adult values are reached at 84 days of age. Between 87 and 227 days of age and in the adult stage mean glucose levels are not correlated with age, however, a significant correlation existing between glucose level and age at sexual maturity. Non-laying and laying pullets do not differ in their glucose level. No significant correlation exists between glucose level and fertility, hatchability and rate of egg production. Body weight and glucose level are significantly and positively correlated in females, but not in males. The body weight of the progeny decreases with increasing glucose level of their dams. Fasting fowls have a lower blood glucose level than non-fasting birds. On the average, adult females have 221 mg glucose/l00 ml of blood more than males.
Author P. S. Knox-DaviesSource: South African Journal of Agricultural Science 9, pp 595 –600 (1966)More Less
A number of isolates of Macrophomina phaseoli (Maubl.) Ashby sporulated on filter paper treated with peanut meal-ether extract on a basal agar medium containing MgSO . 7H,O, KH,PO., glucose and peptone. High glucose concentrations favoured the formation of sclerotia, high peptone concentrations favoured pycnidium production. Sporulation also occurred when DL-asparagine replaced peptone in the medium and when a vegetable cooking oil replaced the peanut meal-ether extract. No sporulation occurred on mineral oil, ergosterol, l3-sitosterol or stigmasterol. Filter paper treated with vegetable oil on peptone or asparagine agar was a convenient medium for routine production of pycnospores.
Studies on zinc in selected Orange Free State soils. I. An assessment of the zinc status of selected surface soils.Source: South African Journal of Agricultural Science 9, pp 601 –616 (1966)More Less
Various extractiori procedures for the assessment of the plant available zinc status of surface soils were investigated. In order to obtain a suitable procedure which may be related to the plant avail able zinc, several factors affecting the results were examined. These included the ratio of soil to extractant, time of extraction an4 pH of extractant and for each the optimum conditions were selected. The modified procedures were then applied ,to 88 surface soil samples from the agronomically important areas of the Orange Free State. Neutral normal solutions of NH.OAc, KCl, MgCI. and CaCl. failed to extract detectable quantities of zinc from any of the soils, but slightly acidified solutions of these salts extracted extremely small amounts. Dithizone-ammonium acetate"" 01 N HCI and di-sodium ethylenediamine- tetra-acetic acid extractable zinc and total soil zinc vary in order of magnitude. There are, however, highly significant relationships (P = 0'01) between the total zinc and the extractable zinc values, and also between each pair of the three extractable zinc values. The total and extractable zinc contents of these soils are in most cases extremely low compared with accepted standards. Taking only the total zinc for all the soils investigated, it is evident that the cpntents vary between 55 and 256 ppm with a mean value of 112 ppm. Only eight soils have total zinc contents of more than 15 ppm. These results indicate conclusively that many Orange Free State soils are zinc deficient. Comparing the total and extractable zinc contents of the cultivated and the corresponding virgin soils it is evident that the values for the former are significantly lower (p = 0'05) than those of the latter.
Author A. D. P. BothaSource: South African Journal of Agricultural Science 9, pp 617 –628 (1966)More Less
Plantjies van die kruising Vamorr X Yellow Mammoth, Fh is op 'n ouderdom van ses weke in potte met swart kleigrond geplant. Die behandelings het vier peile van stikstof en drie peile van kalium ingesluit en is aangewend om die uitwerking van hierdie twee elemente op die ontwik' keling en samestelling van oonddroogtabak te bestudeer. Alhoewel geen betekenisvolle verskil in planthoogtes voorgekom het nie, het stikstofbemesting wei die totale plantgewig, wortelgewig, stronkdeursnee en blaargroottes laat toeneem. Die gevolg : was 'n verdunning van chemiese sames telling van die plant. Die groter opname van fosfor en kalium by die swaarder stikstoftoedienings word toegeskryf aan die groter absorpsie-oppervlakte van 'n sterker ontwikkelde wortelstelsel: Swaarder kaliumtoedienings het nie stikstof se nadelige effek op kwaliteit van die oonddroogtabak geelimineer nie, selfs nieteenstaande 'n hoer kaliumopname nie.
Author I. G. VenterSource: South African Journal of Agricultural Science 9, pp 629 –638 (1966)More Less
Solitary phase brown locust females were collected from each of four successive generations from each of five fixed sampling areas in the southern and south eastern parts of the outbreak region. Ovariole numbers of females varied from 53 to 74. Mean ovariole numbers of the different populations varied between 604 and 664. Some indication was found of a positive correlation between changes in plant conditions and fluctuations in mean ovariole numbers between successive generations from a given sampling area. The difference in mean ovariole numbers between contemporaneous populations from the different sampling areas, however, seems to have a heleditary basis. The possibility that two populations, as little as 10 miles apart, may differ from each other is strong evidence for the extremely sedentary behaviour of solitary brown locusts.
The histology of the foregut and mesenteron of the larva of the sugar cane borer Sesamia calamistis Hmpsn (Lepidoptera: Noctuidae).Author H. J. R. DurrSource: South African Journal of Agricultural Science 9, pp 639 –650 (1966)More Less
The foregut and mesenteron are clearly differentiated from each other. The pharyngeal intima bears numerous small teeth, and the foregut epithelium is syncytial. A blood sinus, together with enclosed tracheae, occurs in the oesophageal valve invagination. The anterior and posterior ring celis, which mark the boundaries of the fore- and hindgut respectively, have been positively identified. 'The anterior and posterior regions of the midgut differ as regards the distribution and size of the goblet cells, as well as in secretory activities of the midgut epithelium.
The effect of thinning and early harvesting on flowering and fruit set of "Flat White Boer" pumpkins.Author J. Strydom, E. & BreytenbachSource: South African Journal of Agricultural Science 9, pp 651 –660 (1966)More Less
A field study was made of the flowering and fruiting habit of a locally grown pumpkin (Cliclirbita maxima cv. Flat White Boer). Special attention was given to the effect of the early thinning of young fruits as well as the harvesting of full-grown, immature pumpkins, on fruit set and yield. About 80 per cent of the pistillate flowers and young fruits eventually abscised on unthinned plants while 20 per cent produced mature fruits. The removal of 25 and 41 per cent of the pistillate flowers and young fruits reduced the percentage natural abscission correspondingly, resulting also in a 20 per cent ultimate fruit production. The yield was not affected by thinning. The harvesting of fully developed immature pumpkins resulted in an increased fruit set and a higher yield than that of the unthinned control. A low fertilizer application produced a smaller number of pistillate flowers, a lower percentage of fruit set and a lower yield in all the treatments. The averagefruit weight was not affected by the lower level of nutrition. Two sexual phases could be observed on the main stems: an exclusive male stage up to approximately the fourteenth node, followed by a stage in which the male: female ratio was 3: 1. On the side shoots this ratio was about 4: 1. It was also found that mature fruits were produced only from pistillate flowers which developed during the five weeks period after the first pistillate flowers had been observed. It is proposed that intensive pumpkin fly control could be restricted to this period.
The value of multiple reading resazurin tests for estimating the bacterial count of milk in warm countries.Source: South African Journal of Agricultural Science 9, pp 661 –674 (1966)More Less
The estimation of the bacterial count of milk in warm countries by means of the single or multiple resazurin test was investigated in a series of 260 milk samples. The relationship between the bacterial count (z) and disc reading (x) was rendered approximately linear by the transformation y = VZ: The regression lines of y on Xl> X2 and x. were calculated for all possible combinations of the disc readings. The coefficients of correlation were found to range from - 0'71 to - 0'78. The relative value of a single reading test as compared to a multiple reading test was assessed by a study oflhe residual variance about the regression line. In general it was found that a double reading test was always significantly better than either of the single readings. The gain in accuracy is, however, of fairly limited practical importance. No significant improvement in the accuracy of the estimate could be effected by the addition of the 2-hour reading to the double reading test if the readings were taken after one and three hours.
Source: South African Journal of Agricultural Science 9, pp 675 –680 (1966)More Less
The reliability of the Igarashi-McCann assay for follicle stimulating hormone (FSH) was assessed in terms of its sensitivity, precision and specificity, Although the assay was found to be highly sensitive and reasonably precise the response parameter was not specific for FSH. Consequently, the technique cannot be recommended as an assay for FSH if the presence of other trophic hormones or thyroxine is suspected.