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Mupambwa H.A.,University Of Fort Hare | Dube E.,Agricultural Research Council Small Grain Institute | Mnkeni P.N.S.,University Of Fort Hare
South African Journal of Science | Year: 2015

South Africa is increasingly reliant upon coal-fired power stations for electricity generation. Fly ash, a byproduct of coal combustion, contains a high total content of essential plant nutrients such as phosphorus, as well as heavy metals. If the plant nutrient bio-availability in fly ash could be improved, and the toxic element content reduced, fly ash could contribute significantly as a fertiliser source in South African agriculture. In this review, we summarise up-to-date information on the soil fertility and detoxification benefits of fly ash composting, and identify information gaps in this regard. We discuss scientific studies on the potential of fly ash based composts to supply plant nutrients and to contaminate the environment. We also explore the roles of earthworms and microorganisms in improving the decomposition process, and hence the fertiliser value of fly ash composts. Although much progress has been made, further research efforts are required to optimise microbial and earthworm activity in the decomposition process, which could further enhance nutrient supply benefits and reduce toxic elements at higher fly ash incorporation rates. © 2015. The Author(s).

De Villiers C.I.,Agricultural Research Council Small Grain Institute
South African Journal of Plant and Soil | Year: 2014

Fusarium head blight (FHB), mainly caused by Fusarium graminearum, is a serious disease of wheat, barley, oat and maize. Yield losses up to 40% have been reported and grain may contain mycotoxins that are harmful to humans and animals. In South Africa no wheat cultivars are resistant to FHB and no fungicides have been registered locally. Genetic resistance has the potential to provide cost-effective control, therefore Fusarium-resistant wheat germplasm from the Scab Resistant Screening Nursery (SRSN) obtained at the International Maize and Wheat Improvement Center (CIMMYT) was imported and screened for Type II FHB resistance in the glasshouse. SST 825 (susceptible control), Sumai 3 (resistant control) and 13 entries from the ninth SRSN were screened. An area under the disease progress curve was calculated for each entry. SST 825 and Sumai 3 showed the highest and lowest FHB severities, respectively. Two entries were similar to SST 825 in their response to FHB, whereas seven entries were moderately susceptible. Three entries were moderately resistant, one entry was resistant, and Sumai 3 was highly resistant. © 2014 © Southern African Plant and Soil Sciences Committee.

Terefe T.G.,Agricultural Research Council Small Grain Institute | Visser B.,University of the Free State | Pretorius Z.A.,University of the Free State
Crop Protection | Year: 2016

To determine phenotypic diversity of Puccinia graminis f. sp. tritici (Pgt), the cause of stem rust of wheat, samples of infected stems were collected during 2009-2013 from commercial wheat fields, experimental plots, and rust trap nurseries across major wheat growing regions of South Africa (SA). Pgt races were identified based on their avirulence/virulence profiles on seedlings of 20 standard and five supplemental differential lines. Nine Pgt races were identified from 521 isolates pathotyped. Predominant races were TTKSF (2SA88, South African race notation) with 39%-85% frequency and BPGSC + Sr27,Kiewiet,Satu (2SA105) with 10%-20% frequency. Race TTKSF is virulent on major resistance genes such as Sr5, Sr6, Sr9e, and Sr38 and is one of the variants of the highly virulent Ug99 race group originally detected in East Africa. Race TTKSP (2SA106), also a member of the Ug99 lineage, was detected in 2009 and 2010. A new race virulent on Sr31, PTKST (2SA107), was detected in 2009. Two new races, TTKSF + Sr9h (2SA88 + Sr9h) and BFBSC (2SA108), were identified in 2010. Race TTKSF + Sr9h is similar to TTKSF except for its virulence on Sr9h. Race BFBSC appears related to Pgt races characterized by avirulence for Sr5 and often attacking triticale. Simple sequence repeat (SSR) analysis indicated that race BFBSC forms part of the non-Ug99 group of South African Pgt races. Despite some similarity in avirulence/virulence phenotype with the non-Ug99 races, BFBSC represents a third distinct genetic lineage within this group. Genes Sr13, 14, 22, 25, 26, 29, 32, 33, 35, 36, 37, 39, 42, and 43 that are effective against the new and other Pgt races can be used in resistance breeding in SA. Races like PTKST and TTKSF + Sr9h were also reported in other Southern African countries suggesting that they probably spread to SA from neighbouring regions. The new races are additions to nearly 30 Pgt races identified since the early 1980s, and suggest continued variability of the Pgt population in SA. Therefore, surveys should be conducted regularly to timely detect and manage new races, and utilize the latter in screening and identification of effective sources of resistance. © 2016 Elsevier Ltd.

Dube E.,University Of Fort Hare | Dube E.,Agricultural Research Council Small Grain Institute | Chiduza C.,University Of Fort Hare | Muchaonyerwa P.,University of KwaZulu - Natal
South African Journal of Plant and Soil | Year: 2013

The effects of maize rotation with oat (Avena sativa cv. Sederberg) and grazing vetch (Vicia dasycarpa cv. Max) winter cover crops on nutrient availability, maize grain yield and maize grain nutrient concentration were investigated. Soil samples were collected from the 0-5 and 5-20 cm depths of experimental plots after four years of continuous maize-winter cover crop rotations. Winter cover crops caused small increases of extractable soil Cu, Mn, P and Zn, but not Ca and K, concentrations. A small dose of fertiliser applied to maize (60, 30, 40 and 1.5 kg ha-1 of N, P, K and Zn, respectively) also caused a significant increase in P and Zn, as well as mineral N, concentrations but only in the vetch-maize rotations. Stratification of Mn, K and Zn in the 0-5 cm soil depth occurred in all treatments. Vetch additionally increased maize grain yield, grain N concentration and soil acidity more than either oat or fallow. Non-fertilisation of maize reduced maize grain yield on oat and fallow-maize rotations more than it did on vetch-maize rotations. A combined application of vetch winter cover crops and small doses of fertiliser could significantly improve sustainability of low input maize-based conservation agriculture systems. Copyright © 2013 Combined Congress Continuing Committee.

Hatting J.L.,Agricultural Research Council Small Grain Institute | Brand J.,Rooibos Ltd. | Thiebaut N.M.,Agricultural Research Council Biometry Unit
African Entomology | Year: 2013

The clearwing moth, Monopetalotaxis candescens, is a major root-boring pest of cultivated 'rooibos', Aspalathus linearis, in South Africa. Neonates penetrate the tap root at the base of the stem within a few hours of hatching, presenting a brief window for control of an otherwise highly cryptic pest. Several systemic and contact/stomach insecticides as well as the entomopathogenic fungus, Nomuraea rileyi, were evaluated from 2005-2012 on 6-8-month-old plantations of A. linearis. A strategy based on prophylactic applications of a contact/stomach insecticide (active ingredient: Esfenvalerate) during early to midNovember resulted in > 97 % control. This level of control was realized following delivery of 10 ml aliquots of a 0.4 % concentration of the chemical to the stem-base of individual plants. Attempts at biological suppression of M. candescens with N. rileyi proved unsuccessful. Commercial-scale application of the chemical was possible through the development of an automated measured-dose applicator (vehicle-mounted) consisting of multiple nozzle-lines carried/directed individually by operators. The stem-directed application strategy developed here implies reduced chances of the chemical coming into contact with leaves (and twigs) to be harvested early in the following year, minimum environmental pollution and/or little to no impact on beneficial insects residing on the plant.

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