Masters Degrees (Agronomy)

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Browsing Masters Degrees (Agronomy) by Subject "Barley -- Postharvest diseases and injuries"

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    Factors that have an influence on splitting of malting spring barley (Hordeum vulgare L.)
    (Stellenbosch : Stellenbosch University, 2020-03) Carstens, Louis Wilhelm; Pieterse, P. J.; Kotze, Theunis Nicolaas; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.
    ENGLISH ABSTRACT: In South Africa barley (Hordeum vulgare L.) is the second most produced small grain crop, where most of the barley is used by the beer-brewery industry for malting purposes. The Southern Cape (dryland) and Northern Cape (irrigation) is South Africa’s two main barley production areas. The term “splitting” refers to when the grain is cracked open through the pericarp, aleurone or testa, exposing the starchy endosperm. Split grain can result in non-uniform malt, the formation of foam in steep tanks or possible fungal growth, which is not suitable for the brewing process. This was recently detected in barley produced in the Northern Cape and consequently threatens the beer-brewing industry of South Africa. Some studies suggest that splitting is caused by abnormal climatic conditions or high nitrogen (N) application during the later stages of crop development. However, there is a lack of information regarding the causes of the splitting of barley under South African conditions. Therefore, the aim of this study was to identify such factors by investigating the influence of temperature, water stress, different light intensity conditions, and the rate of nitrogen application on a low-risk (Cristalia) and a high-risk (Overture) cultivar for splitting during different growth stages. Pot trials were conducted in a glasshouse at the Welgevallen Experimental Farm in Stellenbosch. For the temperature experiment, temperatures were lowered by 10°C at grain filling; maintaining 15°C/5°C for a week and then transferred back to normal growing conditions. The nitrogen experiment involved a total of 100 kg N ha-1 (low N), 150 kg N ha-1 (control) and 200 kg N ha-1 (high N) divided into increments and applied at planting, six weeks after planting and grain filling respectively. The shade experiment entailed no shading (control), 40% and 60% shade introduced at the end of tillering and removed at early milk development. For the water experiment, normal daily irrigation was applied until stem elongation after which low, medium and high water stress treatments were introduced. The effect of the treatments on vegetative and reproductive growth parameters and grain quality was determined. Low temperature during grain filling and high rate of nitrogen fertiliser resulted in an increase in splits. Different shade levels and water stress had minor effects on splitting. Therefore, a follow-up trial was conducted the next year where the combined influence of temperature and nitrogen on splitting was tested. It involved low-temperature conditions for three hours during grain filling. Nitrogen rates only differed at grain filling (0, 30, 40, 50 and 60 kg N ha-1) with a standard nitrogen rate applied at planting and six weeks after planting respectively. It was found that only nitrogen had a significant (p < 0.05) effect on splitting, as rates above 40 kg N ha-1 during grain filling resulted in an increase in split grain. The results of this study will aid in finding methods to prevent splitting of barley in the future.