No description available.

Drip irrigation lines placed 15 cm (deep) and 5 cm (shallow) below soil surface were compared to furrow irrigation with zucchini squash as a summer crop and cabbage as a winter crop. Both crops were grown on the same drip lines in each treatment. Urea phosphate was injected in drip lines during growing season while the furrow-irrigated plots received preplant application of phosphorus. In squash, deep lines produced higher yields than did shallow. Deep-drip yields were comparable to those with furrow but used half the water and half the fertilizer. In cabbage, deep-drip yielded slightly higher than shallow-drip and furrow. In these studies, deep-drip was superior in applying water and fertilizer.

Application of water and fertilizer through buried drip lines shows promise for vegetable production in Arizona. Use of an acidic product is necessary if phosphorus is added through the system. Urea phosphate was shown to be a satisfactory product for injecting into buried drip lines for squash and cabbage.

As the shortage of fresh water becomes more and more critical, alternative sources are being sought. The reuse of wastewater has become a viable option, particularly for agriculture and landscaping. However, the possible presence of the enteric pathogens, especially viruses, in wastewater has created concern about potential health risks associated with this practice. If wastewater is used for irrigation it may contaminate vegetable crops which are commonly eaten raw. Also, it may contaminate grass used for golf courses, school yards, and playgrounds where more people may be exposed. Rotaviruses may be of particular concern since they are a cause of infantile diarrhea and gastroenteritis in adults and have been a cause of waterborne disease outbreaks. No information, however, is available about the dissemination and survival of rotaviruses on uncooked food and landscaped areas. This information is necessary in developing criteria for determining safe uses of wastewater for crop irrigation. A method was developed for recovery of rotavirus from the surface of vegetables. The simian rotavirus SA-11, adsorbed onto the vegetable surfaces and effects of various eluents, pH, and exposure time, was evaluated to optimize recovery. The maximum recovery of rotavirus occurred with a solution of 3% beef extract at pH 8.0 after 5 minutes of exposure. Survival of rotavirus SA-11 on lettuce, radishes, and carrots stored at 4°C and room temperature was evaluated. Rotavirus SA-11 was able to survive up to 30 days at refrigeration temperatures and up to 25 days at room temperatures. Rotavirus survived longest on lettuce. The survival of coliphage and enteric viruses on grass was studied during winter and summer outdoors. Coliphage, poliovirus, and rotavirus SA-11 survived on two types of grass during winter and summer from 8 to 40 hours. Human rotavirus survived longer than the other enteric viruses, however, coliphage was more sensitive to inactivation. The occurrence of rotaviruses and enteroviruses in the secondarily treated sewage (activated sludge) was evaluated over a one year period. Total coliforms, pH, and turbidity were also determined. Rotavirus concentrations peaked during Spring and Winter while concentrations of enteroviruses peaked during May, September, and December. No correlation was found between the concentrations of total coliforms, rotaviruses and enteroviruses.

Call number: LD2668 .T4 1985 D385 / Master of Science

Thesis (MScAgric)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Poor water management and poor water use efficiency (WUE) have been identified as one of the major problems experienced by vegetable growers in most of the developing countries, including South Africa. This poor management and poor utilization of water have led to a drastic decline in the quality and quantity of available water. In South Africa agriculture uses about 50% of available water. Increasing water demand for domestic, industrial and mining uses, may decrease agriculture's share to less than the current 50%, henceforth, better utilization of this resource is imperative. Selection of a good irrigation system can limit water loss considerably. Some irrigation systems have a potential to save more water than others do. Since irrigation systems affect the WUE of crops, care should be taken when selecting an irrigation system under conditions of limited water quantity. Ebb-and- Flood watering systems have been introduced for effective sub-irrigation and nutrient delivery within closed systems. Such a system was adapted in South Africa, to develop a vegetable production unit for use by families in rural communities, while saving substantial amounts of water. A need to further improve the WUE of this system was subsequently identified. Two studies were conducted at the experimental farm of the University of Stellenbosch (Department of Agronomy). The first trial was conducted under controlled conditions in a glasshouse, and the second under open field conditions. In the first trial, Beta vulgaris (Swiss chard) and Amaranthus spp. ('Imbuya') were grown in two root media; gravel and pumice. In addition, an 'Ebb-and-Flood' and a 'Constant level' system were used with nutrient solutions at two electrical (EC) conductivity levels 1.80 and 3.60 mS cm-I. The results of this (2x2x2x2) factorial experiment indicated that a combination of the 'Ebb-and-Flood' system with gravel as a root medium produced the best results at a low EC, when 'imbuya' was used. A high total WUE was found with 'imbuya', (7.35 g L-I) at EC 1.80 mS cmicompared to a relatively low WUE of 5. 90 g L-I when the 3.60 mS cm-I nutrient solution was used. In the second trial, 'Imbuya's' foliage dry mass, leaf area and WUE was evaluated under field conditions at the Stellenbosch University experimental farm, during the summer of2002. The experimental farm (33°55'S, 18°52'E) is situated in the cooler coastal wine grape-producing region of South Africa with a relatively high annual winter rainfall. This trial was conducted on an alluvial soil, with clay content of 25% and a pH of 5.9 (KC!). A closed 'Ebb-and-Flood' system was compared with two open field irrigation systems ('Drip' and 'Flood') using nutrient solutions at two electrical conductivity levels (1.80 and 3.60 mS cm-i) in all three cases. Foliage dry mass, leaf area as well as WUE was best with 'Drip' irrigation, when a nutrient solution with an electrical conductivity of 3.60 mS cm-i was used. In spite of the fact that additional ground water was available for the soil grown 'Drip' and 'Flood' treatments, the 'Ebb-and-Flood' system outperformed the 'Flood' treatment, especially when the nutrient solution with an EC of 3.6 mS cm-i was used. Insufficient root aeration in the flooded soil could have been a contributing factor. The fact that the 'Ebb-and-Flood' and 'Drip' systems gave the best results when the high EC solution was used to fertigate the plants, may indicate that the plants could have hardened due to the mild EC stress, better preparing them to adapt to the extreme heat that was experienced in the field. / AFRIKAANSE OPSOMMING: Swak: bestuur van water en 'n swak: water-gebruik-doeltreffendheid (WOD) is as een van die belangrikste probleme geïdentifiseer wat deur groente produsente in die meeste ontwikkelende lande, insluitend Suid-Afrika, ervaar word. Hierdie swak bestuur en benutting van water het daartoe bygedra dat 'n drastiese afname in die kwaliteit asook in die kwantiteit van beskikbare water ervaar word. In Suid-Afrika gebruik die landbou-sektor ongeveer 50% van die beskikbare water. Toenemende water behoeftes vir huisgebruik, industrieë en die mynbou mag hierdie 50% aandeel van die landbou sektor laat krimp. Beter benutting van hierdie skaars hulpbron is dus noodsaaklik. Die keuse van goeie besproeiingsisteme mag waterverliese merkbaar beperk aangesien sekere sisteme se water-besparingspotensiaal beter as ander is. Aangesien besproeiingstelsels die WOD van gewasse beïnvloed, is spesiale sorg nodig waar 'n besproeiingstelsel onder hierdie toestande van beperkte waterbronne gekies moet word. 'Ebb-en-Vloed' sisteme kan aangewend word om water en voedingselemente van onder in 'n wortelmedium te laat opstoot en in 'n geslote sisteem te laat terugdreineer. So 'n sisteem is in Suid-Afrika ontwikkel waarmee groente vir families in landelike gebiede geproduseer kan word terwyl water bespaar word. 'n Behoefte om die WOD van hierdie produksiesisteem verder te verbeter is egter geïdentifiseer. Twee ondersoeke is by die Universiteit van Stellenbosch se proefplaas (Departement Agronomie) gedoen. Die eerste proef is onder beheerde omgewingstoestande in 'n glashuis uitgevoer en die tweede onder veld toestande. In die eerste proef is Beta vulgaris (Snybeet) en Amaranthus spp. ('Imbuya') in twee tipes wortelmedia; gruis en puimsteen verbou. 'n 'Ebb-en-Vloed' asoook 'n 'Konstante vlak' besproeiingsisteem is gebruik terwyl voedingsoplossings ook by twee peile van elektriese geleiding (EC) teen 1.80 en 3.60 mS cm-I toegedien is. Die resultate van hierdie (2x2x2x2) fakroriaal eksperiment het aangetoon dat 'n kombinasie van die 'Ebb-en-Vloed' sisteem met gruis as 'n wortelmedium die beste resultate teen 'n lae EC lewer waar 'imbuya' gebruik is. Die WOD met 'imbuya' was hoog (7.35 g L-1) by 'n EC van 1.80 mS cm-I, vergeleke met 'n relatief lae WOD van 5. 90 g L-1 waar die 3.60 mS cm-I voedingsoplossing gebruik is. In die tweede proef is 'Imbuya' se droë blaarmassa, blaar oppervlakte en WOD onder veldtoestande op die Universiteit van Stellenbsoch se proefplaas in die somer van 2002 ge-evalueer. Die proefplaas (33°55'S, 18°52'E) is in die koeler kusstreke van die wyndruif produksiegebied in die winterreëngebied van Suid-Afrika geleë. Hierdie proef is op alluviale grond met 25% klei en 'n pH van 5.9 (KCi) uitgevoer. 'n Geslote 'Ebb-en-Vloed' sisteem is met twee veld-besproeiingsisteme vergelyk ('Drup' en 'Vloed') terwyl voedingsoplossings teen twee peile van elektriese geleiding (1.80 en 3.60 mS cm-I) in al drie gevalle gebruik is. Blaar droëmassa, blaaroppervlakte asook die WGD was die beste met 'Drup' besproeiing waar die EC van die voedingsoplossing 3.60 mS cm-I was. Ten spyte van die feit dat ekstra grondwater vir die 'Drup' and 'Vloed' behandelings beskikbaar was, het die 'Ebben- Vloed' stelsel beter as die 'Vloed' behandeling gedoen veral waar die voedingsoplossing se EC 3.6 mS cm-I was. Swak wortelbelugting was waarskynlik die rede waarom vloedbesproeiing swak produksie gelewer het. Die feit dat die 'Drup' en die 'Ebb-en-Vloed' behandelings in die veldproef die beste gedoen het waar die EC hoog was, mag moontlik met die gehardheid van die plante verband hou wat aan ekstreem warm en dor toestande blootgestel was.

Thesis (MSc Food Sc (Food Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Agriculture in the Western Cape is not only one of the most important economic sectors but also provides many job opportunities. Over the last few years the sustainability of this successful industry has become threatened by the faecal pollution of rivers used to irrigate produce that will be consumed raw or after minimal processing. This situation not only poses an enormous risk to the health of the consumer but also to farmers who stand to lose their export licenses. The purpose of this study was to determine the microbial types and loads in river water, irrigation water and on irrigated produce. A baseline study was done on four sites in two Western Cape rivers. These sites were chosen to allow for the sampling of river water, irrigation water and irrigated produce so as to determine whether a link between the use of contaminated irrigation water and the microbial population found on irrigated produce exists. The physico-chemical analyses used in the study consisted of: pH, alkalinity, water temperature, conductivity and chemical oxygen demand. The microbial monitoring included the aerobic colony counts (ACC) and the enumeration of the total coliforms, faecal coliforms, staphylococci, enterococci, and aerobic and anaerobic sporeformers present in the water samples. The presence or absence of the potential pathogens like E. coli, Listeria and Salmonella, was also determined. During the baseline study faecal coliform counts as high as 160 000 organisms.100 mL-1 were noted in the Plankenburg River, while counts as high as 460 000 organisms.100 mL-1 were found in the Mosselbank River. Apart from this, high numbers of staphylococci and intestinal enterococci were often found, while E. coli, Listeria and Salmonella were present in samples from both of these rivers. Based on the results of the baseline study on the two rivers it was decided to do a more intensive study on the microbial load of the river and irrigation water as well as irrigated produce from the Mosselbank site. Lettuce and cabbages from a commercial farmer’s fields were chosen as the irrigated produce. During the warmer summer months, ACC counts in the river samples peaked at 12 8000 000 cfu.mL-1, while faecal coliform counts of 1 600 000 organisms.100 mL-1 were found. The three potential pathogens (E. coli, Listeria and Salmonella) were present in all the river samples taken during this period. While the counts of indicator bacteria in the irrigation water was often lower, faecal coliform counts as high as 1 600 000 organisms.100 mL-1 and several other potential pathogens were found on the irrigated lettuce and cabbage. This could indicate a possible “build-up” of contamination on the produce with the repeated application of the tainted irrigation water. According to guidelines published by DWAF in 2008, water to be used for irrigation should not contain more than 4 000 organisms.100 mL-1 faecal coliforms if it is used for the irrigation of crops that are to be consumed raw or after a minimal processing step, as this would increase the health risk to the consumer. Guidelines published by the South African Department of Health are even stricter and state that raw vegetables and fruit should not contain more than 200 coliform organisms per gram, while E. coli and L. monocytogenes should be absent in one gram, and Salmonella spp. in 25 grams of the produce, respectively. From the data obtained during this study it was evident that the two rivers monitored regularly contained faecal indicators at levels much higher than those proposed in national and international guidelines for safe irrigation, making them unfit for the irrigation of MPF’s. It could be concluded that the rivers investigated during this study contained high levels of faecal contamination. Since some of the pathogens isolated from the river and irrigation water and the irrigated produce, it suggests a carry-over of microbial contamination from the river water to the irrigated produce. This was, however, only done using the traditional international methods and the presence of specific pathogens should in future be confirmed by means of molecular techniques. / AFRIKAANSE OPSOMMING: Landbou is nie net die een van die belangrikste ekonomiese sektore in die Wes-Kaap nie, maar verskaf ook vele werksgeleenthede. Oor die afgelope paar jaar word die volhoubaarheid van hierdie suksesvolle industrie egter bedreig deur die fekale kontaminasie van riviere wat gebruik word vir die besproeiing van voedsel wat rou of na ‘n minimale prosesserings stap ingeneem word. Hierdie situasie hou nie net ‘n groot gevaar vir die gesondheid van verbruikers in nie, maar ook vir boere wat hul uitvoerlisensies hierdeur kan verloor. Die doel van hierdie studie was om die ladings en tipes mikrobes in rivier water, besproeiingswater en op besproeide produkte vas te stel. ‘n Basiese studie van vier liggings in twee Wes-Kaapse riviere is gedoen. Hierdie liggings is só gekies dat dit moontlik was om die rivier water, besproeiingswater en die besproeide produkte te monitor, en daar sodoende vasgestel kon word of daar ‘n verhouding is tussen die gebruik van gekontamineerde besproeiingswater en die mikrobe populasie wat op die besproeide produkte aanwesig was. Die fisiko-chemiese analises wat gedurende die studie gedoen is, het pH, alkaliniteit, water temperatuur, geleidingsvermoë en die chemiese suurstof vereiste (COD) ingesluit. Die mikrobiese analises het die aërobe kolonie tellings (ACC) en die enumerasie van die totale kolivorme, fekale kolivorme, staphylococci, enterococci en die aërobe en anaërobe spoorvormers ingesluit. Daar is ook vir die aanwesigheid van potensiële patogene soos E. coli, Listeria en Salmonella getoets. Gedurende die basiese studie is fekale kolovorme tellings van so hoog as 160 000 organismes.100mL-1 in die Plankenburg Rivier aangeteken, terwyl tellings van so hoog as 460 000 organismes.100mL-1 in die Mosselbank Rivier gevind is. Hoë tellings stafielokokki en intestinale enterokokki is gereeld genoteer, terwyl E.coli, Listeria en Salmonella uit die waters van beide hierdie riviere geïsoleer is. Gebaseer op hierdie resultate is daar besluit om ‘n meer intensiewe studie van die rivier, besproeiingswater en die besproeide produkte van die Mosselbank Rivier te doen. Blaarslaai en kool van ‘n kommersiële boer se lande is vir hierdie doel gekies. Gedurende die warmer somer maande het die aërobe kolonie tellings in die rivier ‘n piek van 12 800 000 kve.mL-1 bereik, terwyl fekale kolivorme tellings van 1 600 000 organismes.100mL-1 genoteer is. Die drie potensiële patogene (E. coli, Listeria en Salmonella) was aanwesig in al die monsters wat gedurende hierdie tydperk van die rivierwater geneem is. Alhoewel die tellings indikator bakterieë in die besproeiingswater meestal laag was, is tellings fekale kolivorme van so hoog as 1 600 000 kve.100mL-1 en verskeie ander potensiële patogene op die besproeide blaarslaai en kool gevind. Dit kan dui op ‘n moontlike opbou van kontaminasie op die produkte met die herhaalde besproeiing met gekontamineerde besproeiingswater. Volgens die riglyne wat in 2008 deur DWAF gepubliseer is, mag water wat vir die besproeiing van minimaal geprosesseerdevoedsels gebruik word nie meer as 4 000 organismes.100mL-1 bevat nie, aangesien dit die gesondheid van die gebruiker in gevaar mag stel. Die riglyne van die Suid-Afrikaanse Departement van Gesondheid is selfs strenger en beveel aan dat rou vrugte en groente nie meer as 200 kolivorme en geen L. monocytogenes per gram, en geen Salmonella spp. in 25 g van die produk mag bevat nie. Vanuit die data wat tydens hierdie studie ingesamel is, is dit duidelik dat die twee riviere gereeld fekale indikators bevat het teen vlakke baie hoër as wat in die nasionale en internasionale riglyne aanbeveel word. Hierdie water is dus nie geskik vir die besproeiing van minimaal geprosesseerde produkte nie. Die afleiding kan gemaak word dat die riviere wat tydens hierdie studie gemonitor is, hoë vlakke van fekale kontaminasie bevat het. Aangesien sommige van die patogene vanuit beide die rivier- en besproeiingswater, en vanaf die besproeide produkte geïsoleer is, kan dit dui op ‘n moontlike oordrag van mikrobiese kontaminasie vanuit die rivierwater na die besproeide produkte. Tydens hierdie studie is daar egter net van die tradisionele internasionale metodes gebruik gemaak. Vir toekomstige navorsing word dit aanbeveel dat die aanwesigheid van die spesifieke patogene deur die gebruik van molekulêre metodes bevestig word.

Water pollution is a major threat to human population and dumping of pollutants into water body result in rapid deterioration of water quality and affect the ecological balance in the long run. The present study was undertaken to assess pollution load from river Borkena. In urban and suburban parts of Kombolcha, the use of industrial wastewater for irrigation purpose is a common practice. Local farmers in Borkena watershed use the wastewater to irrigate their agricultural fields for cultivation of vegetables. But they suffered from loss of productivity of leafy vegetables and skin injury because of their exposure to the wastewater during irrigation practices. That is why this study focused on assessing the amount of industrial waste load on river Borkena and its effects on communities in the watershed. The main aim of this study was: to assess the physico-chemical characteristics of River Borkena before and after industrial waste discharges mixed to it by the waste carrier small streams; and its environmental impact on the surrounding communities and vegetable farms. The methodology consisted: 1) Basic survey in order to assess the physical and chemical characteristics of the river water, and 2) a case study performed by focus group discussions with the community authorities and farmers in the study area who used the river water mainly for irrigation purposes. Sampling was conducted at 6 sites in the study area during low and high flow periods with an interval of three months for a period of one year in order to account for the seasonal hydrological cycle of the river water. Laboratory measurements of river water and leafy vegetables for metal concentration were also determined to investigate the effect of the use of the river water for growing vegetables and other personal cases. The findings of this dissertation showed metal concentrations in leafy vegetables and irrigation water are within the permissible limits of FAO/WHO standards and not significant for the time being, but is expected to be a challenge in the near future if not well addressed. The concentrations of metals in leafy vegetables will provide baseline data and it shows that, in the current situation consumption of leafy vegetables grown in the study area may not have health risks in the context of metal concentrations. To avoid the entrance of metals into the food chain, municipal or industrial wastes should not be drained into the river and farmlands without prior treatment. The continuous monitoring of the soil, vegetable plant and irrigation water quality are prerequisites for the prevention of potential river water. Laboratory measurements of river water and leafy vegetables for metal concentration were also determined to investigate the effect of the use of the river water for growing vegetables and other personal cases. The findings of this dissertation showed metal concentrations in leafy vegetables and irrigation water are within the permissible limits of FAO/WHO standards and not significant for the time being, but is expected to be a challenge in the near future if not well addressed. The concentrations of metals in leafy vegetables will provide baseline data and it shows that, in the current situation consumption of leafy vegetables grown in the study area may not have health risks in the context of metal concentrations. To avoid the entrance of metals into the food chain, municipal or industrial wastes should not be drained into the river and farmlands without prior treatment. The continuous monitoring of the soil, vegetable plant and irrigation water quality are prerequisites for the prevention of potential health hazards to human beings. Finally this study fills the gaps in information for concerned regional and federal governmental offices and may use it as an input to design regulations and policies which benefits the communities in the watershed. / Environmental Sciences / Ph. D. (Environmental Science)