Thesis (M.App.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 115-119). Also available in electronic format on the Internet.

Thesis (M.S.)--California Polytechnic State University, 2010. / Title from PDF title page; viewed on June 21, 2010. Major professor: Terry L. Vassey, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Agriculture, Specialization in Environmental Horticulture Science ." "June 2010." Includes bibliographical references (p. 56-58).

Inaug.-diss.--Göttingen. / Lebenslauf. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 111-114).

Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2008. / Stieglitz, Marc, Committee Member ; Guillas, Serge, Committee Member ; Fu, Rong, Committee Member ; Curry, Judith, Committee Member ; Dickinson, Robert, Committee Chair.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 145-154). Also available in electronic version.

Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 24, 2007) Includes bibliographical references.

Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The application of water and nutrients via a drip irrigation system influences the water distribution in the soil, soil characteristics and root distribution beneath the dripper. To determine the water distribution pattern beneath a dripper in sandy soil, EnviroSCAN (Sentek) capacitance probes were installed directly below the dripper and at distances of 20, 40 and 60 cm from the dripper. The continuous monitoring of the soil water content (SWC) beneath the dripper provided a good indication of how the water applied through the dripper is distributed in the soil. In this study a semi-impermeable layer in the soil was detected through observing water accumulation patterns in the SWC. Water accumulated above the layer and SWC values increased to far above the upper level of easily available soil water (EAWupper),while the lower soil layers remained drier. The measurements also show that the horizontal water movement is restricted to 20 cm from the dripper. Specific parameters, such as the lower level of easily available soil water (EAWlower),can be used to determine optimal irrigation management. Together with the water distribution study, the root distribution beneath a dripper was also investigated. A high concentration of roots in the area beneath the dripper was found, which corresponds with the area wetted by irrigation. In another study, three irrigationlfertigation methods where investigated to ascertain the influence on soil characteristics and root distribution. These were: micro irrigation (MI) (micro-spinner irrigation with broadcast granular fertilization), conventional drip fertigation (CDF) (daily drip irrigation with daily or weekly fertigation with a unbalanced nutrient solution, containing macronutrients only) and daily drip fertigation (DDF) (daily fertigation of a balanced nutrient solution, containing macro- and micronutrients). The study was conducted in two locations, viz. in the Western Cape Province, on sandy soil, and in the Eastern Cape Province, on silt loam soil. Micro Irrigation: A wide and even root distribution in the entire wetted volume was found on the sandy and silt loam soil. On the sandy soil, the soil pH(KC1)directly beneath the spinner was significantly lower than the pH(KC1)at positions further away from the spinner. Conventional Drip Fertigation: Root studies on sandy soil indicate a poor root development beneath the dripper, with a high concentration of roots in the area between the drippers. The poor root development directly beneath the dipper may be due to oxygen deficiency and/or acidification beneath the dripper. The soil pH(KC1)values show a significant lower pH(KC1)value directly beneath the dripper than further away. In comparison to the sandy soil, the roots developed well beneath a dripper in a silt loam soil. It appears as if soil acidity and/or oxygen deficiency was not a problem on this soil type. The rest of the root system was also well developed. This may be due to this soil's higher water holding capacity which creates a bigger wetted zone. Daily Drip Fertigation: In the sandy soil it seems that the roots developed in a continuous column beneath the dripper line, with little root development further than 20 cm from the dripper line. Where over-irrigation occurred, it caused a poor root development directly beneath the dripper. The root density in this treatment was much higher than in the other two treatments. The use of a balanced nutrient solution and pulse irrigation may be reasons for the better root development. In a silt loam soil a very high concentration of roots was found beneath the dripper and the rest of the root system was also well developed. As with the CDF treatment, it appears as if oxygen deficiency was not a problem on this soil type. / AFRIKAANSE OPSOMMING: Die toediening van water en voedingstowwe deur 'n drip-besproeiings stelsel beïnvloed die waterverspreiding in die grond sowel as die grondeienskappe en wortelverspreiding onder die dripper. Die waterverspreiding onder 'n dripper in 'n sandgrond is bepaal deur EnviroSCAN kapasitansie meetpenne direk onder die dripper en 20, 40 en 60 cm van 'n dripper af te installeer. Die aaneenlopende monitering van die grondwaterinhoud het 'n goeie indikasie van waterverspreiding in die grond gegee. Die horisontale waterbeweging is grootliks beperk tot 'n 20 cm radius vanaf die dripper en die waterbeweging was hoofsaaklik in 'n vertikale rigting. Die teenwoordigheid van 'n semi-deurlaatbare grondlaag in die grondprofiel is opgemerk deur water-akkumulasie in die profiel waar te neem. Wortelverspreiding onder die dripper is ook ondersoek en 'n hoë konsentrasie wortels is in die benatte sone gevind. In 'n verdere studie is drie besproeiings/sproeibemestings behandelings gebruik om die invloed van besproeiing/sproeibemesting op grondeienskappe en wortelverspreiding te ondersoek. Die drie behandelings was: mikro-besproeiing (mikro-besproeiing met korrelbemesting), konvensionele-drip-sproeibemesting (daaglikse drip-besproeiing met daaglikse of weeklikse sproeibemesting van 'n ongebalanseerde, voedingsoplossing wat alleenlik uit makro-elemente bestaan) en daaglikse-drip-sproeibemesting (daaglikse drip-besproeiing met daaglikse sproeibemesting van 'n gebalanseerde voedingsoplossing wat mikro- en makro-elemente bevat). Die studie is in twee areas gedoen, een in die Wes-Kaap, op 'n sandgrond, en die ander in die Oos-Kaap, op 'n slik-leemgrond. Mikro-besproeiing: Die wortelverspreidings studies op die sand- en slik-leemgrond wys op 'n wye en eweredige wortelontwikkeling in die totale benatte volume. Op die sand grond is gevind dat die grond pR(KCl)direk onder die sproeiertjie betekenisvol laer was as die pR(KCl)waardes verder weg van die sproeiertjie. Konvensionele-drip-sproeibemesting: Die wortelverspreiding in die sandgrond wys op geringe wortelontwikkeling direk onder die dripper met die hoogste konsentrasie wortels tussen die drippers. Grondversuring en/of suurstoftekorte onder die dripper kan die oorsaak wees van die swak wortelontwikkeling direk onder die dripper. Die grond pR(KCl)direk onder die dripper was betekenisvol laer as die pR(KCl)verder weg van die dripper. In vergelyking met die sandgrond, het die wortels in die slik-leemgrond goed ontwikkelonder die dripper. Dit wil voorkom of versuring en suurstoftekorte onder die dripper nie 'n probleem was in die slik-leemgrond nie. Die res van die wortelstelsel was ook goed ontwikkel. Dit mag wees weens die grond se hoë waterhoudingsvermoë wat 'n groot benatte area tot gevolg het. Daaglikse-drip-sproeibemesting: In die sand grond wil dit voorkom asof die wortels in 'n aaneenlopende kolom onder die dripperlyn ontwikkel met weinig wortelontwikkeling verder as 20 cm van die dripperlyn. Waar oorbesproeiing 'n probleem was, was daar weinig wortelontwikkeling in 'n klein area direk onder die dripper. Die wortel-digtheid in die behandeling was baie hoër as in die ander behandelings. Die gebruik van 'n gebalanseerde voedingsoplossing en puls-besproeiing mag dalk redes wees vir die beter wortelontwikkeling. In die slik-leemgrond is 'n hoë konsentrasie wortels onder die dripper gevind en die res van die wortelstelsel was ook goed ontwikkel. Soos in die konvensionele-drip-sproeibemesting behandeling wil dit voorkom of suurstoftekort en versuring onder die dripper nie 'n probleem was in die grond nie.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The export of Japanese plums from South Africa is challenging. Exporting late season plums require fruit to last as long as 8 weeks in cold-storage. Prolonged storage periods can cause some cultivars to develop a shrivelled appearance due to moisture loss. Moisture loss from perishable commodities manifests mainly as shrivelling due to a loss in the turgidity of the surface cells of the fruit, or weight loss. ‘African DelightTM’ (highly susceptible to shrivel), ‘Laetitia’ (shrivel susceptible), ‘Sapphire’ (shrivel susceptible) and ‘Songold’ (not shrivel susceptible) plums were investigated by means of fluorescent microscopy for cracks and openings in the fruit peel. Only ‘African DelightTM’ had open hairline cracks in its peel, and fruit with wider cracks were associated with higher water vapour permeabilities. Open lenticels were found in the peels of ‘African DelightTM’, ‘Laetitia’ and ‘Sapphire’ plums. For ‘Songold’ no peel cracking or open lenticels were observed. The fact that the cuticle of this cultivar is mostly intact may be the reason why it is not susceptible to postharvest shrivel manifestation. The water vapour permeance of the fruit peel determines how easily fruit lose moisture. In this study it was determined to what extent fruit, trees, orchards, harvest date and cultivar contribute to the total variation in plum peel water vapour permeability. The permeabilities of ‘African DelightTM’, ‘Laetitia’, and ‘Songold’ were determined weekly from 4 weeks before harvest until post optimum maturity. Fruit to fruit variation made the largest contribution towards the total variation (> 45%), followed by harvest date (> 20%) and orchard (> 15%) effects. The permeability across all cultivars increased two-fold as fruit became over mature. The contribution of cultivar differences to fruit peel permeability varied greatly between seasons (42% in 2013/2014 and 5% in 2014/2015). Differences between cultivars may include cuticle thickness and composition, micro cracks in the peel and/or open lenticels. Current handling protocols suggest that fruit should be cooled as soon as possible after harvest, but this is not always possible. ‘African DelightTM’ plums were exposed to various handling scenarios in order to determine the handling protocol with the least risk of moisture loss. The control consisted of packaging and cooling the fruit within 6 h of harvest. Fruit quality was comparable or even better than the control when the fruit were pre-cooled to 0 °C and 15 °C for up to 72 h. High vapour pressure deficits caused fruit to lose more moisture, especially when fruit were exposed to ambient temperatures for 48 h and 72 h. It is recommended that handling protocols for plums should be followed stringently in order to reduce mass loss and shrivel manifestation. Since other studies found that silicate (Si) has positive effects on fruit quality, we applied potassium silicate preharvest to ‘African DelightTM’ trees. However, we did not find significant differences between treatments regarding crack width or crack incidence in the fruit peel, shrivel, decay, internal browning, gel breakdown or aerated tissue levels. Currently preharvest potassium silicate applications are not recommended to improve plum quality. / AFRIKAANSE OPSOMMING: Die uitvoer van die Japanese pruime uit Suid-Afrika is 'n uitdaging, omrede daar verwag word dat laatseisoen kultivars tot 8 weke in koelopberging moet bly. Lang opbergingsperiodes veroorsaak dat sommige kultivars 'n verrimpelde voorkoms ontwikkel a.g.v. vogverlies. Vogverlies uit vars produkte manifesteer hoofsaaklik as verrimpeling a.g.v. 'n verlies in die turgiditeit van die selle in en onder die vrugskil, en as massaverlies. ‘African DelightTM’ (hoogs vatbaar vir verrimpeling), ‘Laetitia’ (vatbaar vir verrimpeling), ‘Sapphire’ (vatbaar vir verrimpeling) en ‘Songold’ (nie vatbaar vir verrimpeling) pruime is ondersoek deur middel van fluoressensie mikroskopie vir krake en openinge in die vrugskil. Slegs ‘African DelightTM’ het oop haarlyn krake in sy skil gehad en vrugte met wyer krake het ʼn hoër waterdamp deurlaatbaarheid gehad. Oop lentiselle is gevind in die skille van ‘African DelightTM’, ‘Laetitia’ en ‘Sapphire’ pruime. ‘Songold’ het geen krake of oop lentiselle getoon nie. Die feit dat ‘Songold’ se kutikula meestal ongeskonde was, mag die rede wees waarom hierdie kultivar nie vatbaar vir verrimpeling is nie. Die waterdamp deurlaatbaarheid van 'n vrugskil bepaal hoe maklik vrugte vog verloor. In hierdie studie is bepaal tot watter mate vrugte, bome, boorde, oesdatum en kultivar bydra tot die totale variasie in die pruimskil se waterdamp deurlaatbaarheid. Die deurlaatbaarheid van ‘African DelightTM’, ‘Laetitia’, en ‘Songold’ is weekliks bepaal vanaf 4 weke voor die verwagte oesdatum tot die vrugte oorryp was. Vrug tot vrug variasie het die grootste bydrae tot die totale variasie gemaak (> 45%), gevolg deur oesdatum (> 20%) en boord (> 15%). Die skildeurlaatbaarheid van al die kultivars het verdubbel in die tyd van net voor oes tot die vrugte oorryp was. Die kultivar se bydrae tot die deurlaatbaarheid van die vrugskil het baie gewissel tussen seisoene (42% in 2013/2014 en 5% in 2014/2015). Verskille in skil-deurlaatbaarheid tussen kultivars kan kutikula-dikte en -samestelling, mikro-krake in die skil en/of oop lentiselle insluit. Huidige hanteringsprotokolle stel voor dat vrugte so spoedig moontlik afgekoel word na oes, maar dit is nie altyd moontlik nie. In hierdie studie is 'African DelightTM' pruime is blootgestel aan verskeie hantering scenario's om die hanteringsprotokol met die laagste risiko vir vogverlies te bepaal. Die kontrole vrugte is gepak en onder geforseerde verkoeling geplaas binne 6 ure na oes. Vrugkwaliteit was vergelykbaar of selfs beter in vergelyking met die kontrole wanneer die vrugte voorverkoel is tot 0 °C en 15 °C vir tot 72 uur. Hoë dampdrukverskille het veroorsaak dat vrugte meer vog verloor, veral wanneer vrugte aan kamertemperatuur blootgestel was vir 48 h en 72 h na oes. Dit word aanbeveel dat hanteringsprotokolle vir pruime streng gevolg moet word om massaverlies en verrimpeling te beperk. Aangesien ander studies gevind het dat silikaat (Si) ‘n positiewe uitwerking op vrugkwaliteit het, het ons kaliumsilikaat vooroes aan ‘African DelightTM’ bome toegedien. Daar was egter geen beduidende verskille tussen behandelings met betrekking tot kraakbreedte of kraakvoorkoms in die vrugskil of t.o.v. gehalte eienskappe soos die voorkoms van verrimpeling, bederf, interne verbruining, gelverval of deurlugte weefsel nie. Tans word voor-oes kaliumsilikaat spuite nie aanbeveel om pruimkwaliteit te verbeter nie.

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