Doctoral Degrees (Viticulture and Oenology)

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Browsing Doctoral Degrees (Viticulture and Oenology) by browse.metadata.advisor "Avenant, Eunice"

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    Water footprint analysis to improve water use efficiency in table grape (Vitis vinifera L. cv. Crimson seedless) production. A South African case study
    (Stellenbosch : Stellenbosch University, 2018-03) Kangueehi, Grace Nandesora; Strever, A. E.; Avenant, Eunice; Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology.
    ENGLISH ABSTRACT: Water scarcity is a major impediment to agricultural production, warranting economically viable water use strategies globally. The aim of this study was to evaluate the effects of differing cultivation conditions as well as environmental effects on table grapes (Vitis vinifera L. cv. Crimson Seedless) in terms of plant growth, plant physiology, yield water use efficiency (WUEy) and irrigation water use efficiency (WUEirr) in the Hex River Valley of the Western Cape, South Africa. The experiment consisted of four commercial vineyard blocks with the following irrigation system/soil scenarios: (1) drip on sandy clay loam; (2) micro-sprinkler on sandy clay loam; (3) micro-sprinkler on loamy fine sand and (4) drip on sandy clay loam. No treatment was applied in this study, and standard viticulture management practices as recommended for the production of export quality Crimson Seedless table grapes were applied in each block by the specific farm. The blue water footprint along the production chain only was determined for three regions in South Africa (one winter & two summer rainfall areas). Data used for the water footprint analysis were obtained through interviews and questionnaires. FruitLook data were also validated against field measurements. The four selected blocks showed great variability in terms of their soil characteristics and vegetative growth responses. Block D had vigorous growth in both seasons and the highest yield during the 2013/14 season, with the best fruit quality in both seasons. In contrast, Block A had poor vegetative growth, lower yield, as well as poor fruit quality in both seasons. Blocks B and D had higher specific leaf area (SLA). Blocks A and B had a tendency towards thinner leaves, which could have been linked to the lower stem water potential (ΨS) measured in those blocks at the different phenological stages. Higher values of net carbon assimilation rate and stomatal conductance corresponded with larger berry size and higher yield. The two blocks that were irrigated with micro-sprinklers had higher irrigation volumes and evapotranspiration (ET). Furthermore, the two micro-sprinkler irrigated blocks had a tendency towards a higher WUEy in the 2014/15 season, due to the higher ET and yield measured in these blocks. The drip irrigated Block D had a higher WUEirr in both seasons, and also produced grapes of the best quality, which means a certain stress level can be applied even when grapevines are cultivated for table grape production, without forfeiting fruit quality. Thus, using a drip irrigation system and irrigation applications as applied for Block D and under similar conditions to that in this study, could reduce the volume of irrigation water used and contribute to saving water. The regional average blue water footprint (WF) over two seasons was 210.35 m3/ton, 392.19 m3/ton and 272.42 m3/ton for the Western Cape, Lower Orange River region and the Northern Province respectively. The regional average WUEy values for both seasons was 5.04 kg/m3, 3.00 kg/m3 and 3.68 kg/m3 for Western Cape, Lower Orange River and Northern Province regions, respectively. Water footprints provide useful information on the water use of a specific area and strategies to improve WUE can be developed based on this information. This information can aid in decision making as to which crop can be produced sustainably with better economic benefits to the production area. Thus, WF determination can be used as a tool to raise awareness, as well as determine crop efficiency, which can be used in debates and decision making regarding water allocations. FruitLook data validation also showed a potential to be used in irrigation management decisions that could contribute to improved WUE. grapevines in general and table grapes specifically, were desktop studies and did not include actual plant growth and physiological measurements. Additionally, most of the global data available do not make a distinction between the different grape types (table grapes, raisin & wine grapes). The plant based measurements in this study also contributes to the scientific knowledge and understanding of how the grapevine’s water use and performance is affected by different soil types and irrigation systems, through direct plant based measurements during critical phenological stages.