Thesis (MSc Food Sc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Fresh produce irrigation water from Western Cape Rivers carries faecal coliforms (FC) (Escherichia coli) at concentrations which often exceed the suggested limit of 1 000 FC per 100 mL and presents a health risk to consumers. On-farm ultraviolet (UV) irradiation presents several advantages for water disinfection but is an uncommon practice in South Africa. The aim of this study was to investigate the use of UV irradiation for river water disinfection prior to irrigation. Escherichia coli (E. coli) strains were exposed to low-pressure (LP) UV (4 mJ.cm-2) and UV/Hydrogen peroxide (H2O2) (4 mJ.cm-2/20 mg.L-1) treatments in Sterile Saline Solution (SSS). Strain variation in reductions was observed and ranged from 1.58 to 3.68 and 1.34 to 3.60 log for the UV and UV/H2O2 treatments, respectively. The UV/H2O2 treatment (4 mJ.cm-2/20 mg.L-1) was more effective, compared to UV singly, against some of the E. coli strains. Selected strains showed increased sensitivity at higher UV doses (8, 10 and 13 mJ.cm-2) and H2O2 concentrations (100 and 200 mg.L-1 with 4 mJ.cm-2) but a 3 log target reduction was not always reached. For all UV and UV/H2O2 treatments maximum resistance was shown by an environmental strain. Reference strains should, therefore, not be used for the optimisation of UV based disinfection parameters. At 10 mJ.cm-2 an American Type Culture Collection (ATCC) reference strain and an environmental strain (ATCC 25922 and F11.2) were both significantly less inactivated in sterilised river water compared to SSS. Enhanced water quality allowed for improved inactivation of the ATCC strain. Also, the efficiency of LP UV (5, 7 and 10 mJ.cm-2) and medium-pressure (MP) UV (13, 17 and 24 mJ.cm-2) radiation was investigated using water from the Plankenburg River. Water was sampled and treated on three respective days (Trials 1 to 3). Physico-chemical and microbiological water quality was always poor. The FC concentration reached a maximum of 6.41 log cfu.100 mL-1 while UV transmission was always below 38%. For LP and MP UV irradiation increased doses resulted in increased disinfection but a 3 log reduction of FC was only attained when MP UV light was used in Trial 1. Disinfection efficiency was dependent on water quality and on the characteristics of the microbial population in the water. Since FC were never reduced to below 3 log cfu.100 mL-1, the water did not adhere to guidelines for produce irrigation. Photo-repair following irradiation was investigated in river water using MP UV doses of 13 and 24 mJ.cm-2 and 3.5 kLux reactivating light, initially. Ultraviolet transmission was close to 50% and total coliform (TC) reduction exceeded 3 log, even at 13 mJ.cm-2. However, TC were reactivated from below 1 000 cfu.100.mL-1 to 3.93 and 4.41 log cfu.100 mL-1 for the 13 and 24 mJ.cm-2 treatments, respectively. A higher MP dose (40 mJ.cm-2) and a different treatment regime (2 x 20 mJ.cm-2) inhibited photo-repair (compared to 13 and 24 mJ.cm-2) but TC were always recovered to a final concentration surpassing 3 log cfu.100 mL-1, even under lower light intensities (1.0 to 2.0 kLux). In the current study UV irradiation did not produce water of acceptable standards for produce irrigation, mainly as a result of extremely poor water quality. However, on farm-scale, UV efficiency could be enhanced by improving water quality before irradiation. Also, stronger lamps that deliver higher UV doses may result in adequate disinfection, irrespective of water quality. Higher UV doses and the use of combination treatments (such as UV/Chlorine and UV/Peracetic acid) should be further investigated also to determine its disinfection efficiency and possible capability to inhibit post-disinfection repair. / AFRIKAANSE OPSOMMING: Varsproduk besproeiingswater vanuit Wes-Kaapse riviere bevat fekale kolivorme (FK) (Escherichia coli) in konsentrasies wat dikwels die voorgestelde limiet van 1 000 FK per 100 mL oorskry en hou `n gesondheidsrisiko vir verbruikers in. Plaasvlak ultraviolet (UV) bestraling bied verskeie voordele met verwysing na water dekontaminering, maar word selde aangewend in Suid-Afrika. Die doel van hierdie studie was om die gebruik van UV bestraling vir die dekontaminering van rivierwater, voor besproeiing, te ondersoek. Escherichia coli (E. coli) isolate is blootgestel aan lae-druk (LD) UV (4 mJ.cm-2) en UV/Waterstofperoksied (H2O2) (4 mJ.cm-2/20 mg.L-1) behandelings in Steriele Sout Oplossing (SSO). Isolaat variasie in reduksies is waargeneem en het gewissel tussen 1.58 tot 3.68 en 1.34 tot 3.60 log vir die UV en UV/H2O2 behandelings, onderskeidelik. In vergelyking met UV bestraling alleen was die UV/H2O2 behandeling (4 mJ.cm-2/20 mg.L-1) meer effektief teen sommige E. coli isolate. Geselekteerde isolate was meer sensitief tot hoër UV dosisse (8, 10 en 13 mJ.cm-2) en H2O2 konsentrasies (100 en 200 mg.L-1 met 4 mJ.cm-2), maar `n 3 log teikenreduksie was nie altyd haalbaar nie. Vir alle UV en UV/H2O2 behandlinge was die meeste weerstand deur `n omgewingsisolaat gebied. Verwysingsisolate behoort daarom nie aangewend te word vir die optimisering van UV-gebaseerde behandelingsparameters nie. By 10 mJ.cm-2 was beide `n ATCC verwysingsisolaat en `n omgewingsisolaat (ATCC 25922 en F11.2) betekenisvol minder gedeaktiveer in rivierwater as in SSO. Verbeterde waterkwaliteit het verhoogde inaktivering van die ATCC isolaat toegelaat. Die doeltreffendheid van LD UV (5, 7 en 10 mJ.cm-2) en medium-druk (MD) UV (13, 17 en 24 mJ.cm-2) bestraling is ook ondersoek deur watermonsters vanuit die Plankenburg Rivier te gebruik. Watermonsters was getrek en behandel op drie verskillende dae (Proewe 1 tot 3). Fisies-chemiese en mikrobiologiese kwaliteit van die water was deurentyd swak. Die FK konsentrasie het `n maksimum van 6.41 log kve.100 mL-1 bereik terwyl UV transmissie altyd laer as 38% was. Vir beide LD en MD UV bestraling het verhoogde dosisse gelei tot verbeterde dekontaminering, maar `n 3 log reduksie is slegs bereik toe MD UV lig gebruik is in Proef 1. Die effektiwiteit van die behandelings was afhanklik van waterkwaliteit en die eienskappe van die mikrobiese populasie in die water. Aangesien FK nooit tot onder 3 log kve.100 mL-1 verminder is nie het die water nie voldoen aan riglyne vir varsproduk-besproeiing nie. Fotoherstel na bestraling was ondersoek in rivierwater deur aanvanklik gebruik te maak van MD UV dosisse van 13 en 24 mJ.cm-2 en 3.5 kLux heraktiverende lig. Ultraviolettransmissie het byna 50% bereik en reduksie van totale kolivorme (TK) het 3 log oorskry, selfs by 13 mJ.cm-2. Totale kolivorme was egter geheraktiveer van onder 1 000 kve.100.mL-1 tot 3.93 en 4.41 log kve.100 mL-1 vir die 13 en 24 mJ.cm-2 behandelings, onderskeidelik. In vergelyking met 13 en 24 mJ.cm-2 het `n hoër MD dosis (40 mJ.cm-2) en `n veranderde bestralingstegniek (2 x 20 mJ.cm-2) fotoherstel onderdruk, maar TK was in elke geval geheraktiveer tot `n finale konsentrasie hoër as 3 log kve.100 mL-1, selfs onder laer intensiteit lig (1.0 tot 2.0 kLux). In hierdie ondersoek het UV bestraling nie water van aanvaarbare standaarde vir varsproduk besproeiing gelewer nie, hoofsaaklik as gevolg van swak waterkwaliteit. Nietemin, op plaasvlak mag die effektiwiteit van UV bestraling verhoog word deur waterkwaliteit voor bestraling te verbeter. Die gebruik van sterker lampe, om hoër UV dosisse te produseer, mag verder bydra tot voldoende dekontaminasie, ongeag van waterkwaliteit. Hoër UV dosisse en die gebruik van kombinasie behandelinge (soos UV/Chloor en UV/Perasynsuur) moet ook verder ondersoek word om die dekontaminasie effektiwiteit, en vermoë daarvan om heraktivering na dekontaminering te onderdruk, vas te stel.

A zero inertia mathematical model as described by Strelkoff and Katopodes (1977b) was used to simulate irrigations in blocked-end or ponded sloping borders. The model is based on the assumption that inertia is negligible. A linearization method was then used to decrease the difficulty and expense of the solution. The resulting mathematical expressions were solved with a double sweep technique. Border irrigations were simulated, using the model, for selected intake families (soil infiltration characteristics), required depths of infiltration, discharge rates, lengths, times of application, slopes, and roughness values. The output from the model, including the depth of infiltration, the maximum depth of flow at the upper end of the border, the maximum depth of ponding at the downstream end and the application efficiency, was used to develop the design charts for ponded sloping irrigation borders. These were combined with the operational input parameters to provide the design charts for a given intake family, slope and roughness. Since the same input parameters apply, the design charts developed can be used for ponded or free outflow borders. In cases of free outflow borders, ponding is replaced by runoff. Ponding can improve application efficiency over free outflow borders, provided that ponding affects a significant length of the border. Where runoff can not be reused, ponding or end-blocking a border strip is recommended. The maximum potential application efficiencies, on ponded borders, with adequate irrigation and minimum deep percolation were determined, with respect to intake family, required depth of infiltration, slope, roughness and length of run. A sensitivity analyses to evaluate the effect of infiltration showed that it is better to underestimate than to overestimate infiltration. The effects of roughness and slope on irrigation efficiencies and depth of ponding were also studied. A comparison of the Soil Conservation Service method for extended length, with blocked-end borders, and the maximum application efficiencies computed showed the SCS method to be satisfactory, provided that there is runoff adequate to irrigate the length extended.

Field and laboratory experiments to determine the effect of the quality of irrigation water and the combination effects of the quality of water and chemical amendments (Gypsum and H ₂SO₄) on growth and yields of sudangrass, total soluble salt and ionic distribution and the infiltration rates of a Pima soil were conducted. Pima soil was classified as calcareous saline-sodic soil. A field experiment was conducted on the University of Arizona Experimental Farm at Safford, Arizona, for a period of five years. During the first three years, three qualities of water as supplied by well, river and city were used. During the last two years, these waters were coupled with two chemical amendments, gypsum and sulfuric acid. The experiment was a randomized split plot design with nine main plots and 27 subplots and three replications. The rates of the amendments were arbitrarily chosen 1 and 1.72 ton/acre of H ₂SO₄ and gypsum respectively. Four harvests were made over the two-year period and city water treatment gave the best growth and yield of sudangrass as compared to well and river water treatments. H ₂SO₄ and gypsum increased the yield significantly in comparison to the control in 1975. No significant effects of the chemical amendments on the growth and yield of sudangrass were obtained in 1976. Significant negative correlations between the EC and ESP of the first two feet of soil and yield of sudangrass were obtained. Soil analysis indicated that significant decrease in the pH and ESP of the soil resulted from H ₂SO₄ application with the three water treatments. Gypsum reduced pH and ESP significantly just with well water treatment. Due to the stratified texture of soil profile, ions and salts accumulated in the center of the sampled profile. Infiltration rates were higher for well water treatments than for city water treatments. H ₂SO₄ increased the infiltration rates significantly with all water treatments; gypsum increased infiltration only with well water treatment. Infiltration was further studied in the laboratory using soil columns. Two rates of acid and two rates of gypsum were used (1 or 5 and 1.72 or 8.6 ton/acre H ₂SO₄ and gypsum respectively). The higher rate of H ₂SO₄ gave the highest infiltration rate and the lowest infiltration rates were obtained with control with all water treatments. The low rate of H ₂SO₄ and the high rate of gypsum gave similar infiltration rates with the three water treatments. Gypsum treated soil columns required more water to be leached to a specific EC than H ₂SO₄ treated and control columns. More salt can be removed from the soil per unit volume of water with H ₂SO₄ treatment than gypsum or untreated soil. The poorest quality of irrigation water required the least time and amount of water needed to reach equilibrium between the solid and solution phases of soil. The EC of effluent was found to be an index to predict the presence of gypsum and lime in the soil under very low water penetration. Regression equations were developed to predict the time and depth of water required to leach one foot of Pima soil column to a specific EC with a given quality of water and a given type and rate of chemical amendments (H ₂SO₄ and gypsum). A regression equation was developed to estimate the EC of the saturation extract from that of 1:1 soil :water ratio for Pima soil.

In Mexico, wastewater recycling is an important alternative source of water, particularly in arid regions like the state of Sonora, Mexico. In El Valle del Yaqui, Sonora, Mexico, where 500 million m3 per year of wastewater is available for recycling in agriculture activities . The main objective of the three studies presented in this dissertation was to assess the microbial water quality of surface water, untreated wastewater, and treated wastewater for produce irrigation, as well as the impact of microbial water quality on vegetable contamination. The results suggest that the three sources of water meet Mexican and international guidelines for use in production of food crops.Despite wide differences in the concentration of bacterial indicators (Escherichia coli, Clostridium perfringens) and enteric pathogens (Cryptosporidium, Giardia, and enteroviruses) in the various types of water studied there was little impact on contamination of the produce studied (carrots, lettuce, tomatoes, and peppers) at harvest. Apparently, the time between the last irrigation event and harvesting was sufficient to allow for die-off of enteric organisms that may have contaminated the produce.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Surface water is found in very limited quantities in most of southwestern Utah. In order to compensate for a deficit of surface water it has been necessary to use underground water where it is possible and profitable to do so. The Milford pumping area in southwestern Utah is an area where expanded irrigated agriculture has been established by pumping of ground water. It is one of four major pumping areas in the state of Utah.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Authors' manuscript; no date on item. / Experiments were conducted in southern Arizona to study the effects of irrigating wheat (Triticum aestivum L.) with a mixture of pump water and wastewater and pump water alone on wheat growth, grain yield, grain quality, soil properties, and irrigation water quality. In small plot research, wheat irrigated with a mixture of pump water and wastewater produced taller plants, more heads per unit area, heavier seeds, higher grain yields, and higher straw yields than did wheat grown with only pump water. When large fields were compared, wheat grown with a mixture of pump water and wastewater had taller plants, more lodging, lower grain volume-weights, and higher grain yields than did wheat produced with pump water. The pH and exchangeable sodium of soil irrigated with pump water alone or a mixture of pump water and wastewater were similar. Electricalconductivity and nitrate-nitrogen were higher in soils irrigated with pump water than they were in soils irrigated with a mixture of pump water and wastewater. Extractable phosphorus was higher in soils irrigated with a mixture of pump water and wastewater than in soils irrigated with pump water. Total soluble salts and nitrate-nitrogen were higher in pump water than they were in the pump water and wastewater mixture; however, the pump water and wastewater mixture had a higher level of phosphorus than did pump water.