Using diluted winery effluent for irrigation of Vitis Vinifera. Cv. Cabernet Saugvignon and the impact thereof on soil properties with special reference to selected grapevine responses.

Howell, Carolyn Louise (2016-03)

Thesis (PhD)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: Wine production is an important industry in the Western and the Northern Cape regions of South Africa. Wineries produce large volumes of poor quality wastewater, particularly during harvest. International requirements, as well as national legislation, are putting pressure on wine producers regarding the responsible management of winery wastewater, which may have a large-scale detrimental impact on the environment. Currently, the Department of Water and Sanitation is drafting new legislation aimed at wineries to allow beneficial crop irrigation as a General Authorisation. In this regard, a multidisciplinary research project to investigate the impact of diluted winery wastewater on soils, crop growth and product quality was initiated and funded by the Water Research Commission of South Africa. The project was also co-funded by Winetech and the Agricultural Research Council. The possible re-use of winery wastewater for vineyard irrigation was investigated in a Cabernet Sauvignon vineyard in a sandy soil near Rawsonville in the Breede River Valley. Wastewater obtained from a co-operative winery was diluted to levels of 100, 250, 500, 1000, 1500, 2000, 2500 and 3000 mg/L chemical oxygen demand (COD), using water obtained from the Holsloot River. The dilution was carried out individually for each concentration in 15 m3 tanks at the vineyard. Control grapevines were irrigated with river water. In addition to the field trial, a pot trial was also included to determine the effect of diluted winery wastewater on near-saturation hydraulic conductivity (K) of four different soils. In general, soil potassium and sodium increased with an increase in COD level of the diluted winery wastewater, i.e. a decrease in dilution of the wastewater. Although irrigation using diluted winery wastewater had almost no other effects, element accumulation particularly with respect to potassium and sodium, might be more prominent in soils with higher clay contents or in regions with low winter rainfall. After three years, near-saturation hydraulic conductivity of shale-derived soil, alluvial and aeolian sands decreased with a decrease in the level of wastewater dilution. This indicated that severe degradation in hydraulic properties can occur if diluted winery wastewater is used for irrigation, and might even be aggravated if undiluted winery wastewater is used. Irrigation of grapevines using diluted winery wastewater did not affect grapevine water status, vegetative growth, production or evapotranspiration, irrespective of the level of dilution. Results showed that irrigation of grapevines using diluted winery wastewater did not have detrimental effects on juice characteristics with regard to ripeness parameters and ion content. Wine sensorial characteristics were not affected by irrigation using diluted winery wastewater. The grapevines did not respond to level of COD per se. This indicated that sufficient aeration occurred between irrigations which allowed organic carbon breakdown. Although salinity and sodicity levels in the diluted winery wastewater were below the thresholds where growth and yield reductions are expected for grapevines, it should be monitored frequently. The low salinity and sodicity levels in the diluted winery wastewater could be a further explanation why the grapevines did not respond negatively to the wastewater irrigation. Based on the above-mentioned results, the following criteria should be considered for possible amendments to the General Authorisations for wineries when using diluted wastewater for vineyard irrigation: (i) COD must be diluted to 3000 mg/L or less, preferably to less than 2000 mg/L to avoid unpleasant odours in the vineyard during irrigations, (ii) electrical conductivity (ECiw) must be less than 0.75 dS/m, (iii) sodium adsorption ratio (SARiw) must be less than 5, (iv) the soil must have a low cation exchange capacity, (v) unrestricted internal drainage in the root zone, (vi) irrigation water must not percolate beyond the root depth, (vii) only micro-sprinklers should be used, (viii) irrigation must be applied in such a way that bunches are not wetted, (ix) at least 50% plant available water depletion should be allowed between irrigations to allow sufficient aeration for oxidation of organic material applied via the irrigation water and (x) irrigation frequency and volumes must be such that wine quality is not reduced.

AFRIKAANSE OPSOMMING: Die produksie van wyn is ʼn belangrike industrie in die Wes- en Noordkaap streke van Suid-Afrika. Kelders produseer groot volumes swak gehalte afvalwater, veral tydens oes. Aangesien kelderafvalwater ʼn grootskaalse nadelige impak op die omgewing kan hê, word daar hoë internasionale vereistes, sowel as druk deur nasionale wetgewing op wynprodusente geplaas om kelderafvalwater verantwoordelike te bestuur. Die Departement van Water en Sanitasie is tans besig om nuwe wetgewing te formuleer wat daarop gemik is om kelders deur middel van ʼn Algemene Magtiging toe te laat om voordelige gewasse te besproei met afvalwater. ʼn Multidissiplinêre navorsingsprojek om die impak van verdunde kelderafvalwater op gronde, gewas groei en produk gehalte te ondersoek is deur die Water Navorsing Kommissie van Suid-Afrika geïnisieer en befonds. Die projek is ook gedeeltelik deur Winetech en die Landbou Navorsingsraad befonds. Die moontlike hergebruik van kelderafvalwater vir wingerdbesproeiing is in ʼn Cabernet Sauvignon wingerd in ʼn sandgrond naby Rawsonville in die Breede Rivier Vallei ondersoek. Kelderafvalwater van ʼn koöperatiewe wynkelder was met onbehandelde rivierwater van die Holsloot Rivier verdun tot konsentrasies van 100, 250, 500, 1000, 1500, 2000, 2500 en 3000 mg/L chemiese suurstof aanvraag (chemical oxygen demand in Engels of COD in kort). Die verdunnings is afsonderlik vir elk van die konsentrasies in 15 m3 tenke by die wingerd gedoen. Kontrole wingerdstokke is met die rivierwater besproei. Benewens die veldproef is ʼn potproef ook ingesluit om die effek van verdunde kelderafvalwater op naby versadigde hidrouliese geleiding (K) van vier verskillende tekstuur gronde te bepaal. Oor die algemeen het die kalium- en natriuminhoud van die grond toegeneem met ʼn toename in COD van die verdunde afvalwater, m.a.w. ʼn afname in die verdunning van die afvalwater. Alhoewel besproeiing met verdunde kelderafvalwater byna geen ander effekte gehad het nie, mag element aansameling, veral met betrekking tot kalium en natrium, dalk meer prominent wees in gronde met hoër klei inhoude of in gebiede waar die winter reënval laag is. Na drie jaar het K van die skaliegrond, asook alluviale en eoliese sande afgeneem met ʼn afname in die vlak van afvalwaterverdunning. Dit het daarop gedui dat K drasties kan afneem indien verdunde kelderafvalwater vir besproeiing gebruik sou word, en dat hidroliese eienskappe drasties kan benadeel indien onverdunde kelderafvalwater gebruik word. Besproeiing van wingerdstokke met verdunde kelderafvalwater het nie die wingerd se waterstatus, vegetatiewe groei, produksie of evapotranspirasie beïnvloed nie, ongeag die vlak van verdunning. Besproeiing met verdunde kelderafvalwater het nie suikertoename, totale titreerbare suur en elemente in sap benadeel nie. Derhalwe is die element samestelling en sensoriese gehalte van wyn ook nie nadelig beïnvloed nie. Die wingerdstokke het nie gereageer op COD vlak per se nie. Dit het aangedui dat daar voldoende deurlugting tussen besproeiing toedienings was wat die afbreek van organiese koolstof toegelaat het. Alhoewel die brak- en natriumvlakke in die verdunde kelderafvalwater laer as die drumpelwaardes vir die groei en produksie afnames van wingerdstokke was, moet dit dikwels gemonitor word. Die lae brak- en natriumvlakke in die verdunde kelderafvalwater kan ʼn verdere rede wees vir die gebrek aan wingerdstokke se reaksie op die besproeiing met afvalwater. Op grond van die voorafgaande resultate, behoort die volgende kriteria in aanmerking geneem te word by moontlike aanpassings vir die Algemene Magtigings vir kelders wanneer verdunde afvalwater vir wingerdbesproeiing gebruik word: (i) COD moet tot 3000 mg/L of minder verdun word, verkieslik minder as 2000 mg/L om onaangename ruike in die wingerd tydens besproeiing te vermy, (ii) elektriese geleiding (ECiw) moet minder as 0.75 dS/m wees, (iii) natrium adsorpsie verhouding (NAViw) moet minder as 5 wees, (iv) die grond moet ʼn lae katioonuitruilkapasiteit hê, (v) interne dreinering in die wortelsone moet vrylik kan plaasvind, (vi) besproeiingswater moet nie verby die worteldiepte loog nie, (vii) slegs mikrospuite moet gebruik word, (viii) besproeiing moet op so ʼn manier toegedien word dat die trosse nie benat word nie, (ix) ‘n minimum van 50% plant beskikbare water onttrekking moet gehandhaaf word sodat voldoende deurlugting verkry word sodat oksidasie van organiese materiaal wat deur die besproeiingswater toegedien, kan plaasvind en (x) besproeiingfrekwensies en -volumes moet sodanig wees dat wyngehalte nie benadeel word nie.

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