| The effect of water stress on the efficacy of diclofop-methyl and CGA 184′927+S on wild oat (Avena fatua) | Agenbag, G. A. | 1993 |
KeywordsAvena fatua, herbicide efficacy, water stress AbstractThe response of wild oat (Avena fatua) to diclofop-methyl and CGA 184′927+S under conditions of water stress was assessed in a pot experiment. Treatments with 0, 8, 16 and 24% polyethylene glycol (PEG 6000) were used to impose water stress. The water stress treatments were initiated when the plants reached the two-leaf stage and continued for seven days prior to and two days after the herbicides were applied. Leaf extension rate was the most sensitive plant parameter to water stress and was decreased by all water stress treatments. Stomatal diffusive resistance of wild oat. Leaves was increased significantly by the 16 and 24% PEG treatments. These water stress treatments caused a reduction in the response of wild oat to diclofopmethyl as illustrated by a continuation of the leaf extension rate during the first week after spraying. The survival and seedhead production of diclofop-methyl-sprayed plants were greatest at the highest water stress level (24% PEG). Water stress did not affect the efficacy of CGA 184′927+S on wild oat. The leaf expansion of plants sprayed with this herbicide stopped within four days after spraying and all plants died within 35 days, irrespective of the water stress level imposed. AuthorsAgenbag, G. A., de Villiers, O. T. and van Biljon, J. J. Year Published1993 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1993.10634658 This article contributed by:
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| Die invloed van grondbewerking op enkele grondeienskappe en die gevolglike ontwikkeling en opbrengs van koring in Suid-Kaapland | Agenbag, G. A. | 1988 |
KeywordsSoil properties, tillage, wheat, yield components AbstractVier 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−2 veroorsaak het, het dan ook oor jare die grootste bydrae (r 2 = 0,59 tot 0,90) gelewer tot die gemiddeld 61,7% hoër graanopbrengs wat met konvensionele in vergelyking tot geen-bewerking verkry is. AuthorsAgenbag, G. A. and Stander, J. J. Year Published1988 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1988.10634274 This article contributed by:
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| Growth, yield and grain protein content of wheat (Triticum aestivum L.) in response to nitrogen fertiliser rates, crop rotation and soil tillage | Agenbag, GA | 2012 |
Keywordscropping systems, fertiliser applications, soil properties, soil tillage, Triticum aestivum AbstractSoil tillage affects both the profitability and sustainability of cropping systems. Minimum- and no-tillage systems are promoted because research has shown that these systems may reduce production costs and improve biological sustainability when compared to conventional systems, in which mouldboard and disc ploughs are used. However, responses to different tillage systems may differ for different crops as well as different soil and climatic conditions. This long-term study, conducted under a Mediterranean-type climate, showed that no-tillage systems can be used successfully to produce spring-type wheat crops in sustainable crop rotation systems under rain-fed conditions in the Swartland wheat-producing area of the Western Cape province of South Africa. Higher wheat yields when wheat is grown in a crop rotation system compared to a monoculture system can be ascribed to improved soil organic carbon and nitrogen (N) contents, which result in more plant-available mineral N and hence more vigorous crop growth. Grain yields of wheat responded positively to increased N application rates and the results suggest that application rates of more than 100 kg ha−1 should be considered where minimum and no-tillage are practised. Higher N application rates resulted in higher grain protein and hence improved bread-making quality of the wheat. AuthorsAgenbag, GA Year Published2012 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2012.716457 This article contributed by:
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| The effect of temperature on the germination of six selected weed species | Agenbag, GA | 2004 |
Keywordsgermination, temperature, tetrazolium, winter weeds AbstractField-collected seeds were incubated in a germination cabinet at three temperature regimes and germination percentage was determined after incubation. Species such as Arctotheca calendula, Avena fatua, Bromus diandrus and Raphanus raphanistrum germinated best when subjected to a diurnal temperature regime of 12h/12h at 10/15 °C, which correlates with late autumn to early winter temperatures in the Western Cape. Among the germinated weed species, A. fatua germinated most with a cumulative value of 90% as compared to R. raphanistrum which germinated least with a cumulative value of 12%. AuthorsAgenbag, GA, Manoto, Martha M. and Ferreira, MI. Year Published2004 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2004.10635052 This article contributed by:
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| Invloed van tyd van ringelering op vruggrootte en rypwording van nektariens | Agenbag, Hannelie | 1990 |
KeywordsFruit size, girdling, nectarine, ripening, split pit AbstractVoldraende Sunlite nektarienbome is in vyf produksie gebiede op 5, 6, 7, 8 en 9 weke na volblom geringeleer in 'n poging om ringelering se effek op vrugkwaliteit vas te stel. Alle ringeleerbehandelings het skynbaar tot groter vrugte gelei, maar ringelering op 5 en 6 weke na volblom het die grootste invloed gehad. Hierdie groot vrugte het egter ook die hoogste voorkoms van gesplete pitte getoon. Ringelering het rypwording oor die algemeen met 'n week vervroeg. AuthorsAgenbag, Hannelie Year Published1990 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1990.10634569 This article contributed by:
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| A preliminary investigation of the potential for maize - legume intercropping in the semi-arid area of Sidamo region, Ethiopia. I. Maize response | Alemseged, Y. B. | 1996 |
KeywordsAnnual legumes, intercropping, maize, perennial legumes, semi-arid AbstractAn intercropping trial involving four legumes, three maize planting densities and two legume planting times was undertaken at Dembela Wacho in the Sidamo region of Ethiopia during the 1987 growing season. The objective was to explore the potential of intercropping maize (Zea mays) with legumes within the existing Borana cropping system. The legumes examined were cowpeas (Vigna unguiculata), lablab (Lablab purpureus), cassia (Cassia rotundifolia) and centro (Centrosema schottii). In an ‘average’ growing season for the area, maize grain yield decreased by about 30% when intercropped with both cowpeas and lablab. The effect of cassia and centro was not significant. Legume planting time showed a significant effect on maize grain yield only when the legumes were cowpeas and lablab. Maize grain yield increased by 43% and 36% for cowpeas and lablab respectively when planted 20 days after the maize was sown. Maize planting density had a significant effect on maize grain yield in that yield increased with increased plant population. However, the increase in grain yield was not proportional to the maize planting density. The dry matter yield followed the trend of the grain yield. These results showed that intercropping was more advantageous than sole cropping of maize. Delaying the planting time of cowpeas and lablab after that of maize is recommended, while cassia and centro could be planted together with maize. The best maize planting density under the given conditions was about 55 000 plants ha−1. AuthorsAlemseged, Y. B., King, G. W., Coppock, L. R. and Tothill, J. C. Year Published1996 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1996.10634387 This article contributed by:
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| A preliminary investigation of the potential for maize - legume intercropping in semi-arid area of Sidamo region, Ethiopia. II. Legume response | Alemseged, Y. B. | 1996 |
KeywordsAnnual legumes, intercropping, maize, perennial legumes, semi-arid AbstractAn intercropping trial of maize (Zea mays) with two dual-purpose and two forage legumes was undertaken at Dembela Wacho in the Sidamo region of Ethiopia during the 1987 growing season. The objective was to explore the potential of intercropping in order to improve food security, provide high-quality livestock feed and improve soil stability within the existing Borana cropping system. The legumes examined were two annual dual-purpose legumes, cowpeas (Vigna unguiculata) and lablab (Lablab purpureus), and two forage legumes, cassia (Cassia rotundifolia) and centro (Centrosema schottii). The other treatments imposed were four maize planting densities (0, 20, 35 and 50 thousand plants per hectare) and two legume planting times (at maize planting and 20 days later). Cowpeas produced 55% more grain than lablab. Maize planting density did not affect legume grain yield, but monoculture legume grain yield was about twice that of the intercropped ones. Monoculture cowpea grain yield was reduced by 44% when the planting time was delayed by 20 days while the reduction of lablab was only 12%. On the other hand, lablab grain yield was reduced by 56% due to delayed sowing in the intercrop situation. The dry matter yield of cowpeas and lablab was significantly higher than that of cassia and centro. Monoculture legume dry matter yield was significantly higher than the intercropped legume dry matter yield in all cases. The annual combined maize and legume grain and dry matter yields were higher than those in monoculture, thus showing yield advantages for intercropping. The perennial forage legumes did not appear to reduce maize yield when sown at the same time, suggesting that this practice could be a useful strategy in the last year of a cereal cropping cycle to prevent future soil erosion. AuthorsAlemseged, Y. B., King, G. W., Coppock, L. R. and Tothill, J. C. Year Published1996 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1996.10634388 This article contributed by:
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| Evaluation and identification of old and new macadamia cultivars and selections at Pietermaritzburg | Allan, P. | 2007 |
KeywordsKernel quality, M. integrifolia, M. tetraphylla, morphology, yield AbstractNewer and older cultivars and selections of macadamias have been evaluated at Pietermaritzburg over periods of from five to 35 years. In their sixth year, trees of some of the newer selections have produced good yields of over 10 kg per tree, which is as good as the precocious Beaumont (695) cultivar. Older trees have shown alternation of bearing with low averages, over the past three seasons', of 10 to 20 kg per tree on the marginal soils with close spacing. Kernel quality (kernel percent and % No.1 kernel) is generally better in the newer than the older selections. Selections ‘783’, ‘842’, ‘887’, and ‘Daddow’ have given best overall quality with hybrids ‘A 4’ and ‘A 16’ giving excellent quality but of very large kernels. All selections should produce better quality under warmer subtropical conditions. Tables of morphological characteristics of typical leaves and fruits are presented which enables the identification of the different selections available in South Africa. AuthorsAllan, P. Year Published2007 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2007.10634793 This article contributed by:
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| Progress and problems in rooting clonal Carica papaya cuttings | Allan, P. | 2007 |
KeywordsAir filled porosity, bacteria, bark, papaws, perlite AbstractCarica papaya (L) is one of the few fruit crops that is still propagated commercially by seed. In the cool subtropical Pietermaritzburg area, a female clone ‘Honey Gold’ has been vegetatively propagated, by rooting leafy cuttings, for over 40 years. Vigorous stock plants, strict sanitation, adequate bottom heat (30 °C), and even distribution and good control of intermittent mist to ensure leaf retention, are crucial for success. Suitable rooting media were either perlite or well composted, mature pine bark of varying air filled porosity (9–30%) and water holding capacity (58–82%). Bacterial infection can be a problem and this warrants further research. Up to 7595% rooting of small to medium-sized leafy cuttings can be achieved in six to ten weeks during summer, but slow and poor rooting (20% after 16 weeks) has occurred in certain bark media, possibly because of insufficient bottom heat, different physiological conditions in spring, or toxic compounds other than high levels of tannin. Well-rooted cuttings have given excellent production of uniform quality fruit that sells at premium prices in South Africa, where distortion ringspot virus is not a problem. AuthorsAllan, P. and Carlson, Colleen Year Published2007 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2007.10634776 This article contributed by:
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| Genetic relationships amongst macadamia varieties grown in South Africa as assessed by RAF markers | Allan, P. | 2005 |
KeywordsCultivars, DNA fingerprinting, genetic relationships, macadamia, RAF markers AbstractMacadamia is an important horticultural crop of South Africa, and the major cultivars grown have a wide range of attributes. These cultivars originated from diverse backgrounds, but the genetic relationships between them are unclear. Here we describe new insights into the genetic identity, relationships, and species composition of 38 varieties of macadamia representing the diversity currently available within the macadamia industry of South Africa. The varieties were surveyed with the DNA marker system, RAF (randomly amplified polymorphic DNA). Varieties ranged from pure Macadamia integrifolia, through hybrids of varying species proportions, to pure M. tetraphylla, and fall into at least seven major germplasm groups. Local hybrid selections were genetically distinct from those of other selection origins. The cultivar 791 was unusual, identified as a tri-species hybrid containing a significant proportion of the wild species M. ternifolia. It was also shown that 741 u is the true 741 cultivar and 741s is actually the cultivar 800. AuthorsAllan, P., Peace, C. P., Vithanage, V., Turnbull, C. N. and Carroll, B. J. Year Published2005 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2005.10634684 This article contributed by:
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