Thesis (MScAgric)--Stellenbosch University, 1990. | ENGLISH ABSTRACT: Wheat (Triticum aestivum) is grown in monoculture in much of the winter rainfall region of the Western Cape Province of South Africa. This has led to a dramatic increase in the incidence of take-all (caused by Gaeumannomyces graminis var. tritici). In a tillage experiment on the Langgewens research farm of the Department of Agricultural Development, a close correlation was found between disease incidence following cultivation with a chisel plough, a mouldboard plough or no tillage. Cultivation with a mouldboard plough, or no tillage resulted in a low disease incidence and higher yields. | AFRIKAANSE OPSOMMING: In 'n groot gedeelte van die Winterreënstreek van Wes-Kaapland word koring (Triticum aestivum) onder monokultuurtoestande verbou. Hierdie praktyk het tot gevolg gehad dat vrotpootjie (veroorsaak deur Gaeumannomyces graminis var. tritici) die afgelope paar jaar dramaties toegeneem het. In 'n bewerkingsproef op die Langgewens-proefplaas van die Departement Landbou-Ontwikkeling is daar 'n noue verwantskap aangetref tussen vrotpootjie-voorkoms en die plasing van die vorige jaar se vrotpootjie-geïnfekteerde wortelkrone en wortels deur bewerking. Bewerking met 'n scarifier het aanleiding gegee tot betekenisvol meer vrotpootjie as in gevalle waar beitelploeg-, skaarploeg-, of geen-bewerking gedoen is. Waar skaarploeg- of geen-bewerking onder monokultuurtoestande toegepas is, is 'n lae vrotpootjie-voorkoms, met gepaardgaande goeie opbrengste, waargeneem. | Masters

During 1980-86, the aphid species Sitobion avenae (Fabricius), Rhopalosiphum padi (L.), and Metopolophium dirhodum (Walker) were the most prevalent aphids on cereal crops grown in Hungary. Other species occurred in a relatively low frequency. S. avenae started to appear by mid-May on winter wheat (Triticum aestivum L.) and winter barley (Hordeum vulgare L.), and colonies, mainly present on the spikes, reached maximum during the second half of June. Winter wheat, winter and spring barley, and oats (Avena sativa L.) were equally important host plants for R. padi, which was dominant throughout the season. The first winged individuals started to appear by mid-May, reaching maximum during the second 10 days of June. M. dirhodum were often present on leaves of winter wheat, winter barley, oats, and maize (Zea mays L.), but not on rye (Secale cereale L.). R. padi had the greatest fluctuations in annual numbers. There was no barley yellow dwarf epidemic in 1985 due to the severe winter of 1984-85, followed by unfavorable conditions for aphid multiplication in the spring.

On the basis of the results of three-year field trials performed on pseudogley illimerized soil, the influence of some cultural pracitices on the yield of winter wheat grain was evaluated. All the three varieties studied negatively responded to a delayed sowing (at late sowing, the yield of the Kosutka variety was lower by up to 12.3 per cent). The amount of seed sown was not a significant factor of intensification. Both the Agra and Roxana varieties were able to offset the studied differential range of 3.0 million germinative grains per ha. The Kosutka variety reacted adversely to the decrease in the sowing rate. Nitrogen application rate on the higher level tested (120 kg per ha), divided into two batches, proved to be optimum in the given region when wheat was grown after silage maize as forecrop. The sequence of the surveyed factors with their effect on the grain yields was as follows: year, date of sowing, variety, nitro fertilization, sowing rate.

Basing on the results obtained and analysis of equations of multiple regression and their coefficients of correlation the author ascertained that the content of Cu in the upper leaf of winter wheat is conditioned not only by content of Cu in a definite soil extract but also by the hydrolytic acidity of the soil. The content of zinc in the tops of winter wheat is very strongly correlated with the amounts of this element determined in the 0.1 M or 1 M HCl extracts as well as the total exchangeable bases in soil. No significant effect of the investigated soil features on the content of manganese in winter wheat is found

Our experiments sought to assess the effects of Russian wheat aphid, Diuraphis noxia (Mordvilko), on spring and winter wheat (Triticum aestivum L.) at different plant growth stages. Four initial aphid densities of 0, 1, 2, and 4 aphids per plant were used to infest the seedling, tiller, and boot stages of spring wheat. The same aphid treatments were used to infest winter wheat before, after, and both before and after the vernalization process. Plants were harvested and the following vegetative and reproductive parameters were measured: root weight, stem weight, leaf weight, tiller number, head weight, seed number, and seed weight. Spring wheat infested during the tiller and boot stages was most susceptible to reductions in head weight, seed number, and seed weight. Winter wheat was most sensitive to Russian wheat aphid after the vernalization process. Root weight, head weight, seed number, and seed weight were all reduced when aphids were introduced after vernalization had occurred, especially at the highest initial aphid infestation level.