Soil and grapevine responses to irrigation with treated municipal and winery wastewaters

Hoogendijk, Karla (2019-04)

Thesis (MScAgric)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: In recent years, water scarcity and the ongoing drought have had serious implications for the agricultural industry in the Western Cape. The present study investigated the sustainability of two different types of wastewater for use as alternative irrigation water for grapevine production. The first objective was to assess the long-term effects of treated municipal wastewater irrigation on soils and grapevines in commercial vineyards in the Coastal region. The second objective was to investigate the use of in-field fractionally applied winery wastewater with raw water for grapevine irrigation under different climatic conditions. To assess the impact of treated municipal wastewater irrigation on soil and grapevines, a long-term trial was conducted in commercial vineyards in the Coastal region of the Western Cape. Cabernet Sauvignon and Sauvignon blanc grapevines were irrigated using treated municipal wastewater from the Potsdam wastewater treatment works for 11 years. Grapevines were either rainfed (RF), irrigated with treated municipal wastewater via a single dripper line (SLD) or received twice the volume of wastewater via a double dripper line (DLD). Irrigation using treated municipal wastewater increased soil pH and electrical conductivity (ECe). Furthermore, an accumulation of chloride (Cl-) was observed in the topsoil, probably due to the chlorine-disinfection process that is carried out as part of the treatment process at the wastewater treatment works. Appreciable amounts of sodium (Na+) and potassium (K+) also accumulated in the topsoil due to wastewater irrigation. However, this did not result in enhanced uptake by grapevines. The near-saturation hydraulic conductivity (Kns) at the surface of the soil decreased as the ECe in the topsoil increased, with the lowest Kns recorded for the DLD treatments. The irrigation reduced water constraints throughout the growing season compared to RF conditions, particularly in the case of Cabernet Sauvignon. Consequently, the SLD and DLD grapevines produced stronger vegetative growth and higher yields compared to RF. The present study indicated that, with proper management, grapevines can be irrigated successfully using treated municipal wastewater. Previous research has indicated that soil type and winter rainfall have a pronounced effect on salt accumulation where winery wastewater is used for irrigation. The present study investigated the short-term effects of irrigation using in-field fractionally applied winery wastewater with raw water on different soil types under different climates. Suitable experiment sites were identified in the Coastal, Breede River and Lower Olifants River wine production regions, due to their vast difference in climate. Within each region, two plots of differing soil textures were selected. One season of irrigation using fractionally applied winery wastewater with raw water did not have a pronounced effect on soil ECe or soil organic carbon content (SOC). Variable amounts of plant nutrients were supplied to grapevines via the irrigation water. High K+ concentrations in the wastewater resulted in an accumulation in the soil and a subsequent increase in extractable potassium percentage (EPP´). Under the prevailing conditions, irrigation using in-field fractionally applied winery wastewater did not have adverse effects on grapevine vegetative growth, yield or grape juice characteristics. However, further research is needed to assess the sustainability of this particular practice over the long-term.

AFRIKAANSE OPSOMMING: Die onlangse waterskaarste en voortdurende droogte in die Wes-Kaap hou ernstige gevolge in vir die provinsie se landbousektor. Die studie het die volhoubaarheid van twee tipes afvalwater vir gebruik as alternatiewe besproeiingswater vir wingerdproduksie ondersoek. Die eerste doel was om die langtermyn effekte van besproeiing met behandelde munisipale afvalwater op grond en wingerdstokke in kommersiële wingerde in die Kusstreek te evalueer. Die tweede doel was om die gebruik van in-veld fraksioneel toegdediende kelderafvalwater met vars water vir wingerdbesproeiing te ondersoek onder verskillende klimaatstoestande. ‘n Langtermyn proef was uitgevoer in kommersiële wingerde in die Kusstreek om die impak van besproeiing met behandelde munisipale afvalwater op grond en wingerdstokke te evalueer. Cabernet Sauvignon en Sauvignon blanc wingerdstokke was vir 11 jaar besproei met behanddelde munisipale afvalwater afkomstig van die Potsdam afvalwatersuiweringsaanleg. Wingerdstokke was óf droëland verbou (RF), besproei met behandelde munisipale afvalwater deur ‘n enkel drupperlyn (SLD) óf het twee keer die volume afvalwater ontvang deur ‘n dubbele drupperlyn (DLD). Besproeiing met behandelde munisipale afvalwater het die pH en elektriese geleiding (ECe) van die grond verhoog. ‘n Opeenhoping van chloried (Cl-) was in die bogrond opgelet. Dit was waarskynlik as gevolg van die chloor-ontsmettingsproses wat as deel van die behandelingsproses by die suiweringsaanleg uitgevoer is. Noemenswaardige hoeveelhede natrium (Na+) en kalium (K+) het ook in die bogrond akkumuleer as gevolg van die afvalwaterbesproeiing. Dit het egter nie verhoogde opname deur die wingerdstokke veroorsaak nie. Die naby-versadigings hidroliese geleiding (Kns) by die grondoppervlak het afgeneem met ‘n toename in die ECe van die bogrond. In vergelyking met die RF toestande het afvalwaterbesproeiing die waterspanning van wingerdstokke verminder, veral in die geval van Cabernet Sauvignon. Gevolglik het die SLD en DLD behandelings sterker vegetatiewe groei en hoër opbrengste weerspieël in vergelyking met die RF. Die resulte van hierdie studie het aangedui dat wingerdstokke, mits dit korrek bestuur word, suskesvol besproei kan word met behandelde munisipale afvalwater. Vorige navorsing het aangedui dat grondtipe en winterreënval ‘n merkbare effek het op soutakkumulasie waar kelderafvalwater gebruik word vir besproeiing. Hierdie studie het die korttermyn effekte van besproeiing met in-veld fraksioneel toegediende kelderafvalwater met vars water op verskillende grondtipes onder verskillende klimaatstoestande ondersoek. Op grond van klimaatsverskille is geskikte eksperimentele persele geïdentifiseer in die Kus-, Breederivier- en Benede Olifantsrivier wynproduksiestreke. Binne elke streek is twee persele met verskillende grondteksture gekies. Een seisoen van besproeiing met fraksioneel toegediende kelderafvalwater het nie ‘n noemenswaardige effek of grond ECe of organiese koolstof (SOC) gehad nie. Wisselende hoeveelhede plant voedingstowwe is aan wingerstokke verskaf deur die besproeiingswater. Hoë K+ konsentrasies in die afvalwater het ‘n akkumulasie van K+ in die grond veroorsaak en het ook die ekstraheerbare kalium persentasie (EPP´) van die grond verhoog. Onder die heersende toestande het besproeiing met in-veld fraksioneel toegediende kelderafvalwater nie negatiewe effekte op vegetatiewe groei, opbrengs of mos eienskappe gehad nie. Verdere navorsing is egter nodig om die volhoubaarheid van hierdie praktyk oor die langtermyn te evalueer.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105936
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