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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Evaluation of the risks and profitability for early planting dates and bolt reducing strategies for Quebec celery production

Dessureault, Darlene January 2003 (has links)
The risks and profitability associated with four early planting dates, and three different types of bolting risk reduction strategies, were evaluated for Quebec celery production. The four planting dates studied were April 17 th, April 24th, May 1st and May 8 th. The impacts on yield if plants were harvested after eleven week, twelve, thirteen, and fourteen weeks in the field were investigated. The three risk reduction strategies considered were plants grown from planting until June 2nd with no row covers, under floating row covers of spunbonded polyester (Agryl P17, Plastitech) and under floating row covers made of clear, perforated polyethylene (Plastitech). The results suggest that the floating row covers can help plants reach the required market standards sooner that if no row covers were used from the planting date investigated until June 2nd. At the earliest two planting dates, the results suggest that row covers may significantly suppress bolting and allow greater yields at earlier harvest dates. The results also suggest that row covers may provide an advantage at later planting dates, as they may allow for the plants to reach marketable standards sooner. The results also suggest that there is a 50 percent chance of encountering bolting rate of 30 percent or higher if transplanting plants on April 17th. The row covers reduced the probability that plants will bolt to close to zero at for all four planting dates. The most profitable strategy was determined to be planting on April 17th, growing the plants under row covers made of spunbonded polyester (Agryl P17, Plastitech) from planting until June 2nd and then harvesting after the plants had been in the field for thirteen weeks.
72

Predicting yield and development of muskmelon (Cucumis melo L.) under mulch and rowcover management

Jenni, Sylvie. January 1996 (has links)
Field experiments were undertaken to predict the yield of 'Earligold' muskmelon grown with plastic mulches, rowcovers and thermal water tubes. Mulches were either black, photoselective or clear. Rowcover systems included a clear perforated polyethylene, a polypropylene agrotextile, or unperforated polyethylenes (standard or infra-red treated) with a water-filled tube. In all tunnel types, the photoselective mulch had an intermediate effect between clear and black mulch on air and soil temperatures, chilling injury and days to flowering. Plants with a clear mulch and an infrared or standard unperforated tunnel with a thermal tube survived chilling temperatures between 1.6-5.8C for seven days, flowered first, had the heaviest biomass at anthesis and had the highest early yields. Plant dry weight from transplanting to anthesis was predicted from a multiple linear regression based on heat unit formulas using air (base temperature of 14C, maximum threshold of 40C) and soil temperatures (base temperature of 12C). The base temperature for predicting developmental time to anthesis of perfect flowers was 6.8C. In order to study fruit growth, a rapid and non-destructive method for estimating volume of ovaries was established. Fruit phenology was described as six classes for flower development and seven for fruit development. Flower abortion was studied in relation to each class. Plants displayed either one or two fruit growth cycles. The second cycle was triggered as the absolute growth rate of the first cycle fruits decreased. Developmental time of individual fruits was predicted from a heat unit formula with a base temperature of 15C when temperatures were recorded from a meteorological station. Another heat unit formula was proposed for air temperature at 7.5 cm. Fruit growth from the second cycle had a 60-degree day lag. Fruit volume proportion from blooming to maturity of first cycle fruits was described by a common Richards function. Although 65% of the plants produc
73

The effects of the level and timing of nitrogen fertilizer application on red pepper production in Québec /

Fava, Erica. January 1998 (has links)
The use of plastic mulches in producing red bell pepper (Capsicum annuum L.) is relatively new to Quebec and management techniques need to be further developed in terms of nitrogen (N) fertilization as well as insect and disease control. A research project was undertaken in the 1995 and 1996 growing seasons to compare peppers grown on black and on silver mulches, and fertigated using either the conventional method (weekly N-fertigated) or N-fertigated using diagnostic chlorophyll meter readings. Both fertigation treatments resulted in similar yields, although those fertilized according to the chlorophyll meter received 28 to 42 kg N/ha less than the weekly fertilized treatments. The chlorophyll meter was able to detect N deficiencies. Alate aphid populations were significantly reduced by mulches, especially by the silver mulch in both years. However, apterous aphid populations were increased by mulches, most markedly by the black mulch. No significant effect of mulch or N was found on tarnished plant bug or European corn borer populations, or on the percentage of fruit with sunscald or viral symptoms.
74

The impact of predevernalization and plasticulture treatments on bolting of celery (Apium graveolens L.) grown in Quebec /

Cote, John Christopher. January 2002 (has links)
Vernalized celery seedlings (Apium graveolens L. var. Florida 683) were predevernalized under different temperature and light regimes prior to field transplanting. At least 89% of predevernalized plants bolted during both 1999 and 2000 suggesting that the predevernalization treatments were not effective in counteracting the vernalizing stimulus. Predevernalization treatments had no long-term effect on growth and development. Non-vernalized celery seedlings were transplanted on clear polyethylene mulch, thermo-selective polyethylene mulch or no mulch in combination with clear perforated polyethylene mini tunnel, single or double layer of agrotextile mini tunnel or no mini tunnel. Very few plants bolted in 1999. Mulch increased fresh weight and number of celery leaves compared with controls. Plants grown on clear polyethylene mulch had significantly higher mortality rates than other treatments. Agrotextile mini tunnels reduced bolting to 0% in 2000. Mini tunnels, especially a single layer of agrotextile, increased fresh weight, plant height and stem diameter in 2000.
75

Effects of mulchmini-tunnel and thermal-water tube combinations on daily carbon dioxide concentration and early growth of muskmelons

Aziz, Fahrurrozi. January 2000 (has links)
Experiments were conducted in 1997, 1998 and 1999 to determine the effects of mulch/mini-tunnel and thermal-water tube combinations on daily carbon dioxide (CO2) concentration, air, soil temperatures and early growth of muskmelons (var. Earligold) during the vegetative phase. Treatments consisted of mulched plot covered with a clear perforated, a clear non-perforated or a non-perforated infrared polyethylene mini-tunnel with the absence or the presence of a thermal-water tube compared with control treatments. Additional treatments consisting of the ventilation non-perforated clear and infrared tunnels containing no tube were used in 1998 and 1999. The non-perforated tunnels significantly increased CO2 concentrations, air and soil temperatures compared with those of perforated tunnels and controls. Inclusion of a thermal-water tube reduced air temperature fluctuations in the tunnels. Ventilating the non-perforated tunnels significantly decreased CO2 concentrations and air temperatures. / During the first 10--15 days after transplanting, muskmelons grown in the non-perforated tunnels had higher relative growth rate (RGR), net assimilation rate (NAR), and dry weight than those of grown under perforated tunnels and in the control plots. However, during the later period, 11--16 days after transplanting to anthesis, the effects of mulch/mini-tunnels on the RGR, NAR and dry weight of muskmelons were inconsistent. Muskmelons grown in the mulch/tunnels had significantly higher RGR, but generally lower NAR, than those of grown without tunnel. The use of mulch/mini-tunnels significantly increased dry weight at anthesis in 1997, but not in 1998 and 1999. The presence of thermal-water tube in the tunnels and ventilating the non-perforated tunnels generally increased RGR, NAR, and dry weight of muskmelons. The use of mulch/mini-tunnels reduced time for muskmelon to reach anthesis by 9 to 11 days. / The leaves of muskmelons grown in mulch/mini-tunnels had significantly lower ratios of variable to maximum fluorescence (Fv/Fm) than control plants throughout the experiments, except at 10 and 20 days after transplanting in 1997. Leaves of muskmelons grown in non-perforated tunnels had significantly higher levels of chlorophyll than all other treatments during first 15 days after transplanting. However, chlorophyll values in these treatments decreased as muskmelons reached anthesis. The presence of a thermal-water tube in the mulch/mini-tunnels and ventilating the non-perforated tunnels generally increased both Fv/Fm ratios and chlorophyll levels of muskmelon leaves.
76

Effects of incorporating sugarcane trash and pineapple residue on soil and plant characteristics

Asghar, Mohammad January 1977 (has links)
Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1977. / Bibliography: leaves 254-273. / Microfiche. / xiv, 273 leaves ill
77

Control of pre- and postharvest factors to improve apple quality and storability /

Tahir, Ibrahim, January 2006 (has links) (PDF)
Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniv. / Härtill 7 uppsatser.
78

The effective reduction of methane emissions from landfills using a biocover approach

Fleiger, Jillian. Chanton, Jeffrey P. January 2006 (has links)
Thesis (M.S.)--Florida State University, 2006. / Advisor: Jeffrey Chanton, Florida State University, College of Arts and Sciences, Dept. of oceanography. Title and description from dissertation home page (viewed Sept. 26, 2006). Document formatted into pages; contains ix, 84 pages. Includes bibliographical references.
79

Studies towards understanding sunburn in apples

Makeredza, Brian 12 1900 (has links)
Thesis (MScAgric)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Research was carried out to increase the current knowledge on sunburn development and its control in apples. In addition to its chief causes, viz. high irradiance and high temperatures, water stress has long been thought to contribute to sunburn susceptibility. Certain fruit chemical and textural characteristics have also been suspected to increase sunburn, while it is not clear how factors such as crop load affect sunburn in relation to other fruit quality parameters. In red and blushed cultivars, sunburn could be underestimated due to masking by the red colour overlay. Half and total irrigation water were withheld for two weeks in ‘Cripps’ Pink’ apples while in a concomitant trial, mulching with vermicompost (plus a thin layer of woodchips), woodchips, plant compost and black geotextile were used to regulate plant water by reducing soil evaporative loss. Sunburn increased with an increase in moisture stress. Mulching had no effect on plant water status, but it generally enhanced plant photochemistry, reducing fruit surface temperature (FST) and sunburn. Chemical and textural characteristics of exposed, but non-burned ‘Cripps’ Pink’ apples were compared with that of fruit with induced and naturally occurring sunburn. Flesh firmness, total soluble solids (TSS), and titratable acidity (TA) of induced and naturally occurring sunburnt fruit did not differ from each other, but were significantly different from the non-burnt fruit. Based on this, we concluded that sunburn induces textural and compositional changes in sunburnt fruit rather than some fruit being predisposed to develop sunburn due to their texture and chemical composition. Differences in heat stress tolerance, flesh texture and chemical composition of sun exposed and shaded fruit sides seem to relate to their light exposure history. The effect of crop load on sunburn and fruit quality were assessed on a fruit cluster level in 2008-09 and on a whole tree basis in 2009-10 in ‘Cripps’ Pink’. In 2008-09, sunburn, red colour and the proportion of first grade fruit decreased with an increase in number of fruit per cluster. Crop load did not have an effect on sunburn and fruit colour in 2009-10 although the lowest thinning severity seemed to increase sunburn severity while the proportion of first grade fruit was highest for the highest thinning severity. Fruit number per cluster had no effect on fruit size, while at the whole tree level, fruit size decreased with increasing crop load. Flesh firmness, starch breakdown, TA and TSS were neither affected by the number of fruit per cluster nor the crop load of the tree as a whole. Green ‘Granny Smith’ and ‘Golden Delicious’, blushed ‘Royal Gala’, ‘Fuji’, ‘Braeburn’ and ‘Cripps’ Pink’, and full red ‘Topred’ were used to assess how red colour (anthocyanins) masks superficial sunburn browning and bleaching. The greater reduction in superficial sunburn, but not in sunburn necrosis in red and blushed compared to green cultivars with increasing red colour a month towards harvest seemed to confirm the effect of masking. / AFRIKAANSE OPSOMMING: Hierdie navorsing is verrig ter uitbreiding van die huidige kennis oor die ontwikkeling en beheer van sonbrand in appels. Addisioneel tot die hoof oorsake van sonbrand, naamlik hoë irradiasie en hoë temperatuur, word waterstres gesien as bydraend tot sonbrandsensitiwiteit. Daar word ook vermoed dat sekere chemiese en teksturele eienskappe van die vrug sonbrand kan verhoog terwyl daar nie duidelikheid is oor hoe faktore soos oeslading sonbrand relatief tot ander vrugkwaliteitparameters kan affekteer nie. Die omvang van sonbrand in rooi en bloskultivars kan dalk onderskat word vanweë maskering deur die oorliggende rooi pigmentasie. Besproeiing is vir twee weke gehalveer of gestop in ‘Cripps’ Pink’ appels. Sonbrand het toegeneem met ‘n toename in vogstres. ‘n Deklaag van vermikompos (plus ‘n dun laag houtstukkies), houtstukkies, plantkompos en ‘n swart geotekstiel is toegedien om die plant waterstatus te reguleer deur evaporasie vanuit die grond te beperk. Die deklae het geen effek op die plant waterstatus gehad nie, maar het wel die blaar fotochemie bevorder en terselftertyd die vrugoppervlaktemperatuur verlaag en sonbrand verminder. Die chemiese en tekturele eienskappe van sonligblootgestelde ‘Cripps’ Pink’ appels sonder sonbrand is vergelyk met vrugte met geïnduseerde sonbrand en vrugte met sonbrand wat natuurlik ontwikkel het. Vrugvleisfermheid, totale oplosbare vastestowwe (TOV) en titreerbare suur (TS) van vrugte met natuurlik en geïnduseerde sonbrand het nie onderling verskil nie, maar het wel betekesnisvol verskil van vrugte sonder sonbrand. Ons het gevolglik afgelei dat sonbrand teksturele en komposisionele veranderinge teweeg bring eerder as dat sekere vrugte gepredisponeer word om sonbrand te ontwikkel vanweë hul tekstuur en chemiese samestelling. Dit kom voor dat verskille in hittestres toleransie, tekstuur en chemiese samestelling tussen die sonligblootgestelde en skadu kante van appels verband hou met hul verskil in sonligblootstelling. Die effek van oeslading op sonbrand en vrugkwaliteit in ‘Cripps’ Pink’ is ge-evalueer op trosvlak in 2008-09 en op ‘n per boom basis in 2009-10. Sonbrand, rooi kleur en die proporsie eersteklas vrugte het afgeneem met ‘n toename in die aantal vrugte per tros. Op ‘n per boom basis is rooi kleur en sonbrand egter nie deur oeslading geaffekteer nie. Die laagste vlak van vruguitdunning het wel oënskynlik die graad van sonbrand verhoog terwyl die hoogste vlak van vruguitdunning tot ‘n toename in die proporsie eersteklas vrugte gelei het. Die aantal vrugte per tros het geen effek op vruggrootte gehad nie terwyl vruggrootte afgeneem het met oeslading op ‘n heelboombasis. Vrugvleisfermheid, styselafbraak, TOV en TS is nie deur aantal vrugte per tros of die oeslading per boom geaffekteer nie. Groen ‘Granny Smith’ en ‘Golden Delicious’, rooiblos ‘Royal Gala’, ‘Fuji’, ‘Braeburn’ en ‘Cripps’ Pink’, en volrooi ‘Topred’ is gebruik om die maskering van oppervlakkige sonbrandverbruining en –verbleiking deur rooi antosianien te bestudeer. Oppervlakkige sonbrand het minder toegeneem in die maand voor oes in die rooi- en bloskultivars as in die groen kultivars terwyl vrugkleur skynbaar nie die aanwesigheid van die meer sigbare sonbrandnekrose geaffekteer het nie. Maskering speel dus ‘n rol in die aanwesigheid van sigbare sonbrand.
80

Eficácia do herbicida amicarbazone em aplicação conjunta com a colheita de cana-de-açúcar no controle das principais plantas daninhas da cultura

Carbonari, Caio Antonio [UNESP] 05 February 2007 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:28:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-02-05Bitstream added on 2014-06-13T20:58:38Z : No. of bitstreams: 1 carbonari_ca_me_botfca.pdf: 2020066 bytes, checksum: 543976b2b8888c3c6c66975a6d66c2fb (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os herbicidas aplicados em pré-emergência em cana-crua tem como principais limitações a retenção parcial dos produtos na palha (mesmo após chuvas) e a dependência de chuvas após a aplicação para que o herbicida atinja o solo. Para minimizar estas limitações, foi desenvolvido um sistema de aplicação de herbicidas adaptado à colhedora de modo que as operações de colheita e aplicação do herbicida fossem feitas simultaneamente. A aplicação ocorre entre o sistema de coleta e o lançador de palha da colhedora, atingindo o solo e sendo coberto pela palhada. O objetivo deste trabalho foi avaliar a eficácia do herbicida amicarbazone, aplicado em operação conjunta com a colheita mecanizada da cana-de-açúcar, no controle das principais plantas daninhas da cultura em diferentes épocas de aplicação. Os experimentos foram conduzidos em áreas de cana-crua das Usina Ferrari, nos municípios de Porto Ferreira/SP e Santa Cruz das Palmeiras/SP e Usina Dedini, no município de Tambau/SP. Foram conduzidos cinco experimentos, em diferentes épocas, sendo realizadas aplicações nos dias 27 de junho, 31 de agosto, 03 de outubro, 20 de outubro e 23 de novembro, no ano de 2005. As parcelas experimentais foram constituídas de cinco linhas de cana-de-açúcar espaçadas em 1,5 m, com 8,0 e 11,0 m de comprimento (para a primeira e as demais épocas de aplicação, respectivamente), com 1 m de corredor frontal e 3 m de corredores laterais, com quatro repetições. As espécies Ipomoea grandifolia (Dammer) O Donell, Ipomoea quamoclit L., Ipomoea nil (L.) Roth., Merremia cissoides (Lam.) Hall.f., Euphorbia heterophylla L., Bidens pilosa L., Brachiaria decumbens Stapf, Panicum maximum Jacq e Digitaria spp foram semeadas nas parcelas para garantir as infestações e testar o desempenho do herbicida. Os tratamentos testados foram... / The application of pre-emergence herbicides in sugarcane harvested without burning the leaves is limited by the retention of the compounds by the mulch set up after the harvest and having 5 to 20 t of dry matter ha-1. To avoid this limitation, it was developed an application system set up with a magnetic speed sensor, a tank of 200L in capacity, an eletric pump coupled to a flow regulator and a boom, with two nozzles, wide enough to treat one row of the crop. This equipment mounted on the harvester allowed applying the herbicide over the soil surface before the sugarcane residues were deposited on the soil surface by the backside of the harvester. The objective of this study was to evaluate the efficacy of the amicarbazone applied by a sprayer mounted on a sugarcane harvester to control weeds. The herbicide was also conventionally sprayed over the soil (without mulch) and over the mulch (after the harvest) in five application timings (June 27, august 31, october 03 and 20 and november 23) and locations of São Paulo State - Brazil. Two treatments without the application of the herbicide (with or without the mulch) were also set up to referee the efficacy evaluations. Each plot corresponded to 5 lines of the crop lengthening 8-11 m. The experiments were set up with four replications. Ipomoea grandifolia, Ipomoea nil, Ipomoea quamoclit, Merremia cissoides, Euphorbia heterophylla, Bidens pilosa, Brachiaria decumbens, Panicum maximum and Digitaria spp were seeded in the plots to improve the precision of the efficacy evaluations. The herbicide amicarbazone was applied at the rate of 1050 g. ha-1. For P. maximum and Digitaria spp. when applied in the dry season (June 27 and august 31) highest efficacy levels were observed on the plots applied by the equipment set up in the harvester. The application of amicarbazone over... (Complete abstract, click electronic access below)

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