Browsing by Author "Spammer, Zander"

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    The financial and managerial implications of herbicide resistance of annual ryegrass in the Central Swartland
    (Stellenbosch : Stellenbosch University, 2018-03) Spammer, Zander; Hoffmann, Willem H.; Stellenbosch University. Faculty of Economic and Management Sciences. Agricultural Economics.
    ENGLISH SUMMARY : Food security is under increased pressure due to the demands set by a growing global population. Farming, the sector primarily responsible for food security, experiences this growing pressure directly. Because arable land is fixed in absolute terms, production levels of available arable land need to increase by optimising yields. To achieve optimal crop yields the yield reducing factors have to be identified and managed to limit impact on production. Amongst the various yield limiting factors, one of the most important are weeds. This study focuses on winter cereal farming in the Central Swartland area of the Western Cape Province. In this area annual ryegrass has the most significant negative effect on production. This resulted in farmers becoming heavily reliant on the use of herbicides to effectively control ryegrass. This reliance on herbicides together with mal practises regarding the application of herbicides caused ryegrass to develop herbicide resistance. Herbicide resistance can lead to an increase in the cost of weed control, a decrease in potential income, a reduction in the number of possible crops that can be produced and a decrease in the value of the land. There are various methods to manage and prevent herbicide resistance which are discussed in this study, but the primary conclusion is that various methods of control such as chemical, physical and biological control have to be integrated into a producer’s complete weed management program. The detrimental effect of herbicide resistant ryegrass on the profitability of a winter cereal farm in the Central Swartland are researched on a per hectare basis in this study and forms the central focus of this study. A well-known simulation model, the Resistance Integrated Management model (RIM model), is used to simulate three different scenarios. A multi group discussion was held to verify and validate the parameters and assumptions needed to use this model in the Central Swartland. The three scenarios simulated in this study were: no resistance; known resistance (glyphosate and paraquat) and an unknown resistance (trifluralin). In both scenarios where resistance was simulated, a worst-case scenario was assumed, in other words zero percentage control. The gross margin per hectare for wheat monoculture (wheat-wheat-wheat-wheat) decrease from R2 488/ha to R329/ha after the effects of the resistance. With exception of the wheat and medic rotation, the known resistance decreased the gross margin by a minimum of 15% over a ten year period for all the other crop rotations. The unknown resistance decreased some of the crop rotations’ gross margins detrimentally, the wheat monoculture system decreased by 86% and the wheat-wheat-wheat-canola and wheat-wheat-wheat-legumes by 67% and 66% respectively. The wheat and canola rotation system were found to be the most profitable in both the no resistance and the known resistance scenarios. The wheat and medics rotation system achieved the highest level of control in all three scenarios as well as achieving the highest gross margin per hectare in the unknown resistance scenario.