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 (June 26, 2007) Includes bibliographical references.

Made available in DSpace on 2016-02-05T18:29:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-05-25. Added 1 bitstream(s) on 2016-02-05T18:33:16Z : No. of bitstreams: 1 000858322.pdf: 3070079 bytes, checksum: 53241947c37a83bc0428cc20b15a2271 (MD5) / A vitivinicultura é uma das principais atividades econômicas do Vale do Submédio São Francisco, responsável pela produção de vinhos e sucos. Diante do exposto foi realizado um experimento na Embrapa Semiárido, em Petrolina-PE, para a obtenção de informações sobre a prática da fertirrigação nitrogenada e potássica em videiras de vinho. No Campo Experimental de Bebedouro, a videira (Vitis vinifera L.) cultivar Syrah, uma das mais utilizadas na região, foi enxertada sobre o porta-enxerto 1103 Paulsen, e plantada em 30 de abril de 2009, no espaçamento de 1 m entre plantas e 3 m entre fileiras em um Argissolo Vermelho Amarelo. O sistema de condução foi feita em espaldeira com três fios, e o sistema de irrigação foi o de gotejamento, com emissores com vazão de 4,5 L h-1 espaçados em 0,5 m. Três ciclos de produção foram avaliados: de 17 de junho a 8 de outubro de 2013, de 7 de fevereiro de a 9 de junho 2014, e de 6 de agosto a 25 de novembro de 2014. Os tratamentos foram constituídos de cinco doses de nitrogênio (0, 15, 30, 60 e 120 kg ha-1) e cinco doses de potássio (0, 15, 30, 60 e 120 kg ha-1) aplicados via fertirrigação. A concentração de NO3- e K+ na solução do solo foi monitorada por meio de extratores de cápsulas porosas. A análise nutricional das plantas foi monitorada por meio da seiva do pecíolo das plantas e análise foliar. A avaliação da produtividade das plantas foi realizada por meio da produção total dos cachos, peso médio dos cachos e número de cachos por planta. A cada ciclo de produção, as uvas foram analisadas quanto a presença de compostos fenólicos, ácidos orgânicos e nutrientes. Os resultados foram submetidos à análise de variância (teste F)... / Viticulture is one of the main economic activity in the Lower-Middle São Francisco Valley, where wines and juices have been produced. Therefore, an experiment was carried out at Embrapa Tropical Semi-Arid, in Petrolina, State of Pernambuco, Brazil, to obtain information on the use of nitrogen and potassium fertigation in wine vines. The grapevine (Vitis vinifera L.) cv. Syrah is one of the main varieties cropped in the region. It was grafted onto the rootstock 1103 Paulsen, and plaanted in April 30, 2009, in a grid spacing of 1 m between plants and 3 m between rows in an Acrisol (Argissolo Vermelho Amarelo as in the Brazilian Soil Classification System). The trellis system used was cordon with three wires and the irrigation system was the drip with emitters of 4.5 L h-1 flow rate spaced at 0.5 m. Three growing seasons were evaluated: from June 17 to October 8, 2013, to February 7 to June 9, 2014, and August 6 to November 25, 2014. The treatments were five doses of nitrogen (0, 15, 30, 60 and 120 kg ha-1) and five doses of potassium (0, 15, 30, 60 and 120 kg ha-1) applied by the drip irrigation system. The concentration of NO3- and K+ in the soil solution was monitored by porous cup extractors. Plant nutritional status was monitored by petiole sap and leaf analysis. The assessment of plant productivity was performed using the total cluster weight per plant, average weight of cluster, and number of cluster per plant. Phenolic compounds, organic acids and nutrient analysis were performed on grapes in each growing season. Data were subjected to analysis of variance (F test) at 1% (0.01 >p) and 5% (0.05>p) and then the regression analysis was performed. The fertilizer levels did not influence the concentration of nutrients in the soil. Soil pH was influenced by nitrogen fertilization, increasing its acidity with increasing levels of N. The porous ...

Made available in DSpace on 2015-05-14T16:53:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-07-29Bitstream added on 2015-05-14T16:58:46Z : No. of bitstreams: 1 000829355.pdf: 1747915 bytes, checksum: 3a67989759a0c9ca0512f5b5e76359a3 (MD5) / O ciclo do N no sistema solo-planta é bastante complexo, com diversas vias de entrada e saída. Alterações no manejo do solo e das espécies cultivadas podem afetar sua dinâmica, de modo que a avaliação integrada desses processos é essencial para o melhor entendimento do ciclo do N em sistemas de produção agrícola. Objetivou-se avaliar a dinâmica do N em sistemas de produção de soja rotacionada com plantas de cobertura, com enfoque na contribuição dos sistemas para o estoque de N no solo e nas principais perdas de N. O experimento foi conduzido em um Latossolo Vermelho, de textura argilosa, em Botucatu, SP. A área vem sendo cultivada há treze anos em semeadura direta e os atuais tratamentos são os mesmos desde 2006. No outono/inverno foram cultivados brachiaria ruziziensis (Brachiaria ruziziensis), sorgo granífero (Sorghum bicolor) e estas espécies em consórcio; na primavera foram cultivados, em sub-parcelas, crotalária (Crotalaria juncea), milheto (Pennisetum americanum) e sorgo forrageiro (Sorghum bicolor), antecedendo a cultura da soja (Glycine Max) no verão. Avaliou-se por dois anos a produtividade de grãos, matéria seca, acúmulo de N e relação C/N das plantas envolvidas no sistema, bem como o estoque de N no solo. Avaliaram-se ainda, por um ano, as entradas de N via sementes, deposições atmosféricas e pulverizações, e as saídas via lixiviação de NO3-, emissão de NH3 a partir da palhada e da parte aérea das plantas e emissão de N2O a partir do solo. De modo geral, as perdas de N nas formas de NO3-, NH3 e N2O variaram, respectivamente, de 11,2 a 24,2, 10,6 a 19,0 e 1,2 a 9,7 kg ha-1 ano-1, sendo os maiores valores observados nos sistemas com brachiaria no inverno ou crotalária na primavera. Tais perdas parecem ser decorrentes do maior acúmulo de N nestas culturas. No caso da ... / Nitrogen cycling in the soil-plant system is quite complex, with diverse paths of input and output, and changes in soil and/or crop management can modify its dynamics affecting the N gain/losses balance. The integrated evaluation of these processes is essential for a better understanding of the N cycling in agricultural production systems. Our study aimed to evaluate N dynamics in soybean cropping systems in rotation with cover crops, with a focus on how the systems affect soil N storage and the major N losses from the soil-plant system. The experiment was carried out in a clay Rhodic Ferralsol, in Botucatu, São Paulo, Brazil. The experimental area has been cropped under no till for thirteen years, and the current treatments have been conducted since 2006. Congo grass (Brachiaria ruziziensis), grain sorghum (Sorghum bicolor) and a mix of both were cropped during fall/winter. In the spring, pear millet (Pennisetum glaucum), forage sorghum (Sorghum bicolor) and Sunn hemp (Crotalaria juncea) were cropped in sub-plots. Soybean (Glycine max) was cropped as summer crop. We assessed for two years the grain yield, dry matter, N accumulation and C/N ratio of the cropped species, as well as the soil N storage. We also quantified, for one year, N inputs via seeds, atmospheric deposition and pesticide spraying and N via NO3- leaching, NH3 emission from straw and above part of the plants and N2O emission from soil. Generally speaking, losses of N as NO3-, NH3 and N2O ranged, respectively, from 11.2 to 24.2, 19.0 to 10.6 and 1.2 to 9.7 kg ha-1 year-1, being the highest values observed in systems with Congo grass cropped in the fall/winter and Sunn hemp cropped in the spring season. These losses seem to have occurred due the highest N accumulation by these species. In the case of Sunn hemp, the largest contribution of N, even if it results in major losses, proved to be crucial for the positive balance of N in the ...

Orientador: Ciro Antonio Rosolem / Banca: Roberto Lyra Villas Bôas / Banca: Heitor Cantarella / Banca: Monica Sarolli Silva Mendonça Costa / Banca: Waldo Alejandro Ruben Lara Cabezas / Resumo: O ciclo do N no sistema solo-planta é bastante complexo, com diversas vias de entrada e saída. Alterações no manejo do solo e das espécies cultivadas podem afetar sua dinâmica, de modo que a avaliação integrada desses processos é essencial para o melhor entendimento do ciclo do N em sistemas de produção agrícola. Objetivou-se avaliar a dinâmica do N em sistemas de produção de soja rotacionada com plantas de cobertura, com enfoque na contribuição dos sistemas para o estoque de N no solo e nas principais perdas de N. O experimento foi conduzido em um Latossolo Vermelho, de textura argilosa, em Botucatu, SP. A área vem sendo cultivada há treze anos em semeadura direta e os atuais tratamentos são os mesmos desde 2006. No outono/inverno foram cultivados brachiaria ruziziensis (Brachiaria ruziziensis), sorgo granífero (Sorghum bicolor) e estas espécies em consórcio; na primavera foram cultivados, em sub-parcelas, crotalária (Crotalaria juncea), milheto (Pennisetum americanum) e sorgo forrageiro (Sorghum bicolor), antecedendo a cultura da soja (Glycine Max) no verão. Avaliou-se por dois anos a produtividade de grãos, matéria seca, acúmulo de N e relação C/N das plantas envolvidas no sistema, bem como o estoque de N no solo. Avaliaram-se ainda, por um ano, as entradas de N via sementes, deposições atmosféricas e pulverizações, e as saídas via lixiviação de NO3-, emissão de NH3 a partir da palhada e da parte aérea das plantas e emissão de N2O a partir do solo. De modo geral, as perdas de N nas formas de NO3-, NH3 e N2O variaram, respectivamente, de 11,2 a 24,2, 10,6 a 19,0 e 1,2 a 9,7 kg ha-1 ano-1, sendo os maiores valores observados nos sistemas com brachiaria no inverno ou crotalária na primavera. Tais perdas parecem ser decorrentes do maior acúmulo de N nestas culturas. No caso da ... / Abstract: Nitrogen cycling in the soil-plant system is quite complex, with diverse paths of input and output, and changes in soil and/or crop management can modify its dynamics affecting the N gain/losses balance. The integrated evaluation of these processes is essential for a better understanding of the N cycling in agricultural production systems. Our study aimed to evaluate N dynamics in soybean cropping systems in rotation with cover crops, with a focus on how the systems affect soil N storage and the major N losses from the soil-plant system. The experiment was carried out in a clay Rhodic Ferralsol, in Botucatu, São Paulo, Brazil. The experimental area has been cropped under no till for thirteen years, and the current treatments have been conducted since 2006. Congo grass (Brachiaria ruziziensis), grain sorghum (Sorghum bicolor) and a mix of both were cropped during fall/winter. In the spring, pear millet (Pennisetum glaucum), forage sorghum (Sorghum bicolor) and Sunn hemp (Crotalaria juncea) were cropped in sub-plots. Soybean (Glycine max) was cropped as summer crop. We assessed for two years the grain yield, dry matter, N accumulation and C/N ratio of the cropped species, as well as the soil N storage. We also quantified, for one year, N inputs via seeds, atmospheric deposition and pesticide spraying and N via NO3- leaching, NH3 emission from straw and above part of the plants and N2O emission from soil. Generally speaking, losses of N as NO3-, NH3 and N2O ranged, respectively, from 11.2 to 24.2, 19.0 to 10.6 and 1.2 to 9.7 kg ha-1 year-1, being the highest values observed in systems with Congo grass cropped in the fall/winter and Sunn hemp cropped in the spring season. These losses seem to have occurred due the highest N accumulation by these species. In the case of Sunn hemp, the largest contribution of N, even if it results in major losses, proved to be crucial for the positive balance of N in the ... / Doutor

Orientador: Luís Henrique Bassoi / Coorientador: Davi José Silva / Banca: Luís Reynaldo Ferracciú Alleoni / Banca: Roberto Lyra Vilas Boas / Banca: Antonio Odair Santos / Banca:Helio Grassi Filho / Resumo: A vitivinicultura é uma das principais atividades econômicas do Vale do Submédio São Francisco, responsável pela produção de vinhos e sucos. Diante do exposto foi realizado um experimento na Embrapa Semiárido, em Petrolina-PE, para a obtenção de informações sobre a prática da fertirrigação nitrogenada e potássica em videiras de vinho. No Campo Experimental de Bebedouro, a videira (Vitis vinifera L.) cultivar Syrah, uma das mais utilizadas na região, foi enxertada sobre o porta-enxerto 1103 Paulsen, e plantada em 30 de abril de 2009, no espaçamento de 1 m entre plantas e 3 m entre fileiras em um Argissolo Vermelho Amarelo. O sistema de condução foi feita em espaldeira com três fios, e o sistema de irrigação foi o de gotejamento, com emissores com vazão de 4,5 L h-1 espaçados em 0,5 m. Três ciclos de produção foram avaliados: de 17 de junho a 8 de outubro de 2013, de 7 de fevereiro de a 9 de junho 2014, e de 6 de agosto a 25 de novembro de 2014. Os tratamentos foram constituídos de cinco doses de nitrogênio (0, 15, 30, 60 e 120 kg ha-1) e cinco doses de potássio (0, 15, 30, 60 e 120 kg ha-1) aplicados via fertirrigação. A concentração de NO3- e K+ na solução do solo foi monitorada por meio de extratores de cápsulas porosas. A análise nutricional das plantas foi monitorada por meio da seiva do pecíolo das plantas e análise foliar. A avaliação da produtividade das plantas foi realizada por meio da produção total dos cachos, peso médio dos cachos e número de cachos por planta. A cada ciclo de produção, as uvas foram analisadas quanto a presença de compostos fenólicos, ácidos orgânicos e nutrientes. Os resultados foram submetidos à análise de variância (teste F)... / Abstract: Viticulture is one of the main economic activity in the Lower-Middle São Francisco Valley, where wines and juices have been produced. Therefore, an experiment was carried out at Embrapa Tropical Semi-Arid, in Petrolina, State of Pernambuco, Brazil, to obtain information on the use of nitrogen and potassium fertigation in wine vines. The grapevine (Vitis vinifera L.) cv. Syrah is one of the main varieties cropped in the region. It was grafted onto the rootstock 1103 Paulsen, and plaanted in April 30, 2009, in a grid spacing of 1 m between plants and 3 m between rows in an Acrisol (Argissolo Vermelho Amarelo as in the Brazilian Soil Classification System). The trellis system used was cordon with three wires and the irrigation system was the drip with emitters of 4.5 L h-1 flow rate spaced at 0.5 m. Three growing seasons were evaluated: from June 17 to October 8, 2013, to February 7 to June 9, 2014, and August 6 to November 25, 2014. The treatments were five doses of nitrogen (0, 15, 30, 60 and 120 kg ha-1) and five doses of potassium (0, 15, 30, 60 and 120 kg ha-1) applied by the drip irrigation system. The concentration of NO3- and K+ in the soil solution was monitored by porous cup extractors. Plant nutritional status was monitored by petiole sap and leaf analysis. The assessment of plant productivity was performed using the total cluster weight per plant, average weight of cluster, and number of cluster per plant. Phenolic compounds, organic acids and nutrient analysis were performed on grapes in each growing season. Data were subjected to analysis of variance (F test) at 1% (0.01 >p) and 5% (0.05>p) and then the regression analysis was performed. The fertilizer levels did not influence the concentration of nutrients in the soil. Soil pH was influenced by nitrogen fertilization, increasing its acidity with increasing levels of N. The porous ... / Doutor

>Magister Scientiae - MSc / The heterogeneous photocatalytic oxidation of dinitrogen to nitrate, NO3 and/or nitrite, no2 using peroxy species of titanium (IV) in aqueous suspensions has been investigated. The photocatalysts used were titanium peroxide and Degussa p25 TiO2 pretreated with H2O2. These photocatalysts were investigated by SEM and FTIR spectroscopy.

There is consensus that high CO2 results in enhanced growth and yield for most crop plants. However, most of these studies were carried out in the presence of adequate nutrients, which is also the case in agricultural systems (managed ecosystems). About 20% of the earth’s land mass have sufficiently low levels of nutrients to cause some kind of stress to plants. On the other hand, elevated [CO2] decreases foliar nutrient elements in plants and as a result partitioning of certain nutrient elements in plants is altered. Little data is available on the partitioning of most nutrient elements in plants, and this will definitely impact on growth and yield. To investigate this, wheat (Triticum aestivum L. c.v. Gamtoos) was grown in controlled environment cabinets at 360 and 700 µmol mol -1 CO2. The full Long-Ashton nutrient solution comprising of three-nitrogen concentrations ([N]) viz. (4,6 and 12 mM) was used to water plants everyday. The measurement of net assimilation rate (NAR), stomatal conductance (gs), transpiration rate (E), water use efficiency (WUE), foliar [N], nitrogen use efficiency (NUE) and growth parameters (total plant biomass (TPB), total plant height (TPH), leaf area (LA), shoot and root dry weight) were made 7 days after germination (7 DAG) till the onset of flowering. The increase in nitrogen supply in the order of 4, 6 and 12mM resulted in an increase in NAR, g_s_ , WUE and a decline in E under elevated [CO2]. Under elevated [CO2] NAR was observed to increase during the first two weeks reaching its maximum at 14 DAG, thereafter followed by a decline reaching its maximum at 28 DAG. This was later followed by an increase at 35 DAG onwards. Under elevated [CO2], NAR was increased significantly between the nitrogen regimes during the first (7-14 DAG) and the last two (35-42 DAG) weeks. The response of assimilation as a function of internal [CO2] (Ci), showed a decrease with age at ages 14, 28 and 35 DAG. This negatively affected the initial slope and the CO2 saturated photosynthetic rates under all treatments. This suggest that acclimation may have been as a result of both stomatal and biochemical limitations. All the photosynthetic pigment levels (chl_a_, chl_b_, chl_(a+b)_, and C_(x+c)_ ) increased with an increase in nitrogen supply from 4 to 6mM [N]. A 12mM [N] resulted in a significant decline in the photosynthetic pigment levels compared to a 6mM [N]. Chla remained higher than chlb under all treatments. Also, NAR was seen to increase and decrease concomitantly with the photosynthetic pigment levels. Foliar [N] was seen to decrease with an increase in nitrogen supply from 4 to 6 mM [N] under elevated [CO2] and the effects were adverse under the 4mM [N]. Under the 6mM N regime foliar [N] was positively correlated to NAR for elevated [CO2] grown plants. Similarly, E was positively correlated to foliar [N] under the same conditions. Elevated CO2 and increase in nitrogen supply had a pronounced effect on total plant height (TPH), total plant biomass (TPB), leaf area (LA), shoot and root dry weight and nitrogen use efficiency (NUE). The effects were more pronounced under a 6mM [N] as a result of high NUE. However, under 12mM [N] growth was not as expected as a result of lower NUE. Under all treatments shoot dry weight (SDW) was positively correlated to NUE. Anatomical studies revealed that total leaf and midrib thickness was significantly increased with an increase in nitrogen supply under elevated CO2 to support the larger leaf areas. There were no significant changes in the chloroplast ultrastructure as a result of the increase in nitrogen supply and CO2 enrichment. Starch grain surface area was seen to decline with an increase in nitrogen under both ambient and elevated CO2. Elevated CO2 and increase in nitrogen supply significantly increased total grain dry weight per plant by 47 and 46% respectively under 6 and 12mM [N]. In contrast, the increase was by about 21, 61 and 67% respectively under 4, 6 and 12mM [N] between the CO2 regimes.

Thesis (MScAgric)--University of Stellenbosch, 2000 / ENGLISH ABSTRACT: Approximately 7000 ha of potatoes are cultivated under irrigation. The greatest part of the planting is entered under the South African Certification Scheme as seed potatoes, representing between 35 and 40 % of seed production in South Africa. The production of high-quality tubers is, therefore, in the interest of the entire country. Some production factors in the area, however, have a very negative influence on quality with a resultant increase in input costs. These factors include mainly low clay content of the soil «5 %), low organic matter content (% C = 0,2 to 0,4 %), a low pH value as well as a high level of chlorides (400 mg.kg") in the irrigation water. Nitrogen conversion as well as uptake can be influenced by these factors. There may also be negative influences on the environment if leaching of nitrates to subterranean water sources is involved, which can pose a threat to sensitive protected areas. Leaching of various nutritional elements occurs as a result of the low clay content of the soils. Over-irrigation or intense thundershowers could lead to the leaching of nearly all of the fertilisers from these soils. Various management aids are therefore needed to facilitate the decision-making process for corrective steps. Soil, leaf or total-plant analyses are possible, but it is a time-consuming process and the results could become available too late to be of any use. Consequently, the development of methods to determine the nutritional element status of plants on the land and the establishment of norms are both essential. A method which has been tried on a wide scale with varying results is the use of the nitrate content of the petiole, which is determined by means of a reflectoquant and nitrate strips. To evaluate the sensitivity of the method two sites in the Sandveld have been selected. A trial planting has been established at Wadrift and information was also obtained from a leaching trial at Sandberg. The cultivars Up-to-Date and Hertha were established in four nitrogen treatments (100, 200, 300 and 400 kg N.ha-1 ), and repeated over two seasons. At Sandberg irrigation was applied at three application levels and three fertigation divisions for one season. Drip irrigation was applied in both cases to enable the accurate distribution of water and fertilisers during the planting season. Petiole samples were taken weekly or every second week in all the trials. The first mature leaf was sampled (about 20 to 30 leaves per plot). During the initial planting at Wadrift nitrate N in petiole sap (measured by means of nitrate strips and a reflectoquant) was compared to nitrate N of dried petioles measured with an auto-analyser. In all test cases a good correlation was found. The readings from the auto-analyser were about 14.5 times higher than the readings from the petiole sap as a result of moisture loss during the drying process. A better correlation was obtained during the second season when the petiole sap was used for strips as well as the auto-analyser. The petiole nitrate content was increased by high N application rates and the 400 kg N.ha-1 treatment showed significant differences from the other N treatments. A substantially higher yield was obtained during the last season. Varying results were obtained regarding specific gravity for cultivars and nitrogen treatments. At Sandberg (1998) over-irrigation lowered the nitrate content of the petiole sap significantly. It was found that the optimum irrigation level and frequency, is two fertigations a week and kept at field water capacity. From the trial it was clear that the use of nitrogen strips in combination with the reflectoquant gave a good indication of the nitrate-N content of the petiole sap. It is, however, difficult to lay down a norm or critical range, as conditions during the growth period on sandy soil as well as the growth stage have a significant influence on the nitrate-No If yield is the only objective the 400 kg N.ha-1 curve can probably be used as an optimum nitrate-N norm for the particular cultivars. It is also not clear whether the nitrate N content of the petiole sap gives a good reflection of growth and yield potential. / AFRIKAANSE OPSOMMING: In die Sandveld word bykans 7000ha aartappels onder besproeiing verbou. Die grootste deel van die aanplanting word as saadaartappels onder die Suid-Afrikaanse sertifiseringskema ingeskryf en verteenwoordig tussen 35 en 40% van Suid Afrika se saadproduksie. Die produksie van hoë kwaliteit knolle is dus van landsbelang. Somminge produksiefaktore van die area het egter 'n uiters negatiewe invloed op kwaliteit en het 'n meegaande verhoging van insetkostes tot gevolg. Faktore wat veral hieronder tel is die grond se lae klei inhoud «5%), lae organiese materiaal inhoud (%C = 0.2 tot 0.4%), lae pH asook hoë chloriede (400mg.kg-1 ) in die besproeiingswater. Hierdie faktore kan 'n invloed op die omsetting van stikstof en die opname daarvan hê. Daarmee saam kan dit 'n negatiewe effek op die omgewing hê indien loging van nitrate na ondergrondse waterbronne plaasvind wat sensitiewe bewaarareas kan bedreig. Weens die lae klei-inhoud van die gronde vind loging van verskeie voedingselemente plaas. Oorbesproeiing of hewige reënbuie kan tot gevolg hê dat bykans alle bemestingstowwe uit hierdie grond geloog word. Bestuurshulpmiddels is dus nodig om die besluitnemingsproses vir korrektiewe stappe te vergemaklik. Grond-, blaar- of hele plantontledings is moontlik maar is tydrowend en resultate daarvan kan soms te laat beskikbaar wees. Die ontwikkeling van metodes om die voedingselement inhoud van plante op die land te bepaal en die daarstelling van normes is dus noodsaaklik. 'n Metode wat reeds wyd deur ander navorsers met wisselende resultate beproef is, is die gebruik van nitraat inhoud van die petiool wat met 'n reflektoquant en nitraat strokies bepaal is. Om die sensitiwiteit van die metode te evalueer is twee proefpersele in die Sandveld gebruik. 'n Proef is by Wadrift geplant terwyl data ook van 'n logingsproef te Sandberg verkry is. By Wadrift is die kultivars Up-to-Date en Hertha by 4 N-behandelings (100, 200,300 en 400 kg N.ha-1) en vier herhalings vir twee seisoene aangeplant. By Sandberg is besproeiings teen drie toedingspeile met 3 sproeibemestingsverdelings vir een seisoen gedoen. In alle gevalle is van drupbesproeiing gebruik gemaak om akkurate plasing van water en bemestingstowwe oor die plantseisoen moontlik te maak. Petiool monsters is weekliks of tweeweekliks van alle behandelings geneem. Die eerste volwasse blaar is gemonster en daar is tussen 20 en 30 blare per perseel geneem. Tydens die eerste planting te Wadrift is nitraat-N in petioolsap, gemeet met nitraatstrokies en reflektoquant, vergelyk met nitraat-N van gedroogde petiole, gemeet met In outo-analiseerder. Hierdie waardes was goed gekorreleerd vir alle gevalle wat getoets is. Die outo-analiseerder se lesing was ±14.5 keer hoër as die petioolsap lesings weens die vog wat tydens droging verwyder is. Tydens die tweede seisoen is In beter korrelasie verkry waar petioolsap vir strokies asook vir die outo-analiseerder gebruik is. Petiool nitraat is deur hoë Ntoedieningspeile verhoog en die 400 kg N.ha-I behandeling het betekenisvol van die ander N-behandelings verskil en die laaste seisoen ook In betekenisvol hoër opbrengs gelewer. Wisselende resultate is t.o.v. soortlike gewig vir kultivars en stikstofbehandelings verkry. By Sandberg (1998) is gevind dat oorbesproeiing In betekenisvolle verlagende effek op die nitraat-N inhoud in die petioolsap het. Daar is getoon dat die optimum besproeiingspeil en frekwensie, veldwaterkapasiteit met twee sproeibemestings per week is. Uit die ondersoek is dit duidelik dat die nitraatstrokies in kombinasie met die reflektoquant In uiters bruikbare aanduiding van die nitraat-N in die petioolsap gee. Dit is egter moeilik om In norm of kritiese nitraat-N grens aan te dui, aangesien toestande tydens die groeiperiode op sandgrond en die groeistadium In beduidende effek op die nitraat-N het. Indien opbrengs as enigste doelwit gestel word, mag die 400 kg N.ha-I kurwe moontlik as aanduiding van 'n optimum nitraat-N norm vir die betrokke kultivars dien. Daar bestaan ook onduidelikheid of nitraat-N in die petioolsap wel In goeie refleksie van groei en opbrengspotensiaal is.

Dissertation (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Pine sawdust-shavings (Pinus spp.) is at present a very popular soilless substrate in South African greenhouses. Growers use fresh pine sawdust-shavings as a substrate, which is biologically highly unstable. The greenhouse industry is looking at alternative organic substrates such as coco peat, which already went through a decomposition process and is more stable. A biological inactive substrate such as sand was included to compare microorganism activity with organic substrates. The main objective of this study was to compare the growth, yield and quality of hydroponically grown tomatoes in response to different growth mediums in combination with nitrogen source, irrigation frequency, period of substrate use and liming. In general the drainage water pH declined with an increase in NlLt+-N in the nutrient solution. Low pH values in the drainage water, especially when coco peat was used, had a detrimental effect on marketable yield. The drainage water pH of pine sawdustshavings increased during the growing season when 100 % N03--N was used. Due to the higher cation exchange capacity of coco peat, the drainage water electrical conductivity tends to increase more rapidly than with pine sawdust-shavings, during conditions with high temperatures and when insufficient irrigation volumes per irrigation cycle is applied. As expected the drainage water N03--N content decreased as the NlLt+-N content increased in the nutrient solution. Pine sawdust-shavings recorded a much lower N03--N and NlLt+-N content than sand and coco peat and thus supports the hypothesis that microbiological activity is higher in pine sawdustshavings, especially in the second season of substrate use. Coco peat produced the highest number of marketable fruit and yield per plant, followed by pine sawdustshavings and sand in the first season of substrate use. The number of marketable fruit and yield decreased with an increase in NlLt+-N content in the nutrient solution during production in warmer, summer conditions. Contrary to these fmdings, production in cooler, winter conditions recorded high yields when only N03--N or 80% N03--N : 20% NRt +-N was applied. The unmarketable yield increased with an increase in NlLt+-N in the nutrient solution. Visual evaluations showed that blossom-end rot (BER) was the main contributor to unmarketable yield. Increasing levels ofN03--N as nitrogen source in the nutrient solution, reduced weight loss and increased the loss of fruit firmness of tomatoes during storage. Increasing levels of N03 --N also increased fruit pH and reduced total titratable acidity. Coco peat produced fruit with a higher pH than pine sawdust-shavings. An increase in irrigation frequency affected fruit firmness negatively when coco peat was used as substrate. Different irrigation and fertigation practices are needed for different growth mediums and management needs to be adapted according to the growing season (winter vs. summer). / AFRIKAANSE OPSOMMING: 'n Mengsel van dennesaagsels en -skaafsels (Pinus spp.) word tans deur Suid- Afrikaanse kweekbuisprodusente gebruik as grondlose groeimedium. Hierdie groeimedium word nie vooraf gekomposteer nie en is dus biologies onstabiel. Die kweekbuisindustrie ondersoek tans die gebruik van alternatiewe, gekomposteerde en stabiele organiese groeimediums soos kokosveen. 'n Biologies onaktiewe groeimedium soos sand is ook ingesluit om met organiese groeimediums te kan vergelyk. Die hoof doelwit van die studie was om plantontwikkeling, opbrengs en kwaliteit van hidroponies geproduseerde tamaties te evalueer in verskillende groeimediums en in kombinasie met stikstofbron-verhouding, periode van groeimedium gebruik, besproeiingsfrekwensie en bekalking. Oor die algemeen het die pH in die dreinaat gedurende die groeiseisoen toegeneem soos die NH/-N inhoud verhoog het in die voedingsoplossing. Lae pH waardes in die dreinaat, veral waar kokosveen gebruik was, het 'n nadelige effek op bemarkbare opbrengs gehad. Die pH in die dreinaat van dennesaagsels en -skaafsels het gedurende die groeiseisoen toegeneem met die gebruik van 100% NO)--N in die voedingsoplossing. Die elektriese geleiding in die dreinaat van kokosveen neem vinniger toe gedurende toestande waarin hoë temperature en onder besproeiing voorkom, as in dreinaat van dennesaagsels en -skaafsels. Die NO)--N inhoud in die dreinaat het soos verwag afgeneem soos die NRt+-N inhoud in die voedingsoplossing toegeneem het. 'n Baie laer NO)--N en NRt+-N inhoud is by dennesaagsels en -skaafsels aangeteken wat dus die hipotese ondersteun dat mikrobiologiese aktiwiteit, veral in die tweede seisoen van gebruik, hoër is in dennesaagsels en -skaafsels as in sand en kokosveen. Kokosveen het die hoogste aantal bemarkbare vrugte en massa per plant geproduseer, gevolg deur dennesaagsels en -skaafsels en sand. Die aantal bemarkbare vrugte en opbrengs het verlaag met 'n verhoging in NRt+-N in die voedingsoplossing gedurende warm, somer toestande. In teenstelling met vorige resultate is gevind dat 100% NO)-- N of 80% NO)--N : 20% NRt+-N hoë opbrengste gelewer het gedurende koeler, winter toestande. Die onbemarkbare opbrengs het verhoog met hoër NRt+-N vlakke. Visuele waarnemings het aangedui dat blom-end verrotting die grootste bydrae tot onbemarkbare opbrengs gelewer het. 'n Verhoging in NO)--N vlakke het massaverlies beperk en die verlies in fermheid verhoog gedurende opberging. Hoër NO)--N vlakke het ook die pH van vrugte verhoog en die totale titreerbare suur verlaag. Kokosveen het vrugte met 'n hoër pH as dennesaagsels en -skaafsels geproduseer. 'n Toename in besproeiingsfrekwensie het vrug fermheid negatief beïnvloed wanneer kokosveen as groeimedium gebruik was. Verskillende besproeiings- en voedingspraktyke word benodig vir verskillende groeimediums en bestuur van die groeimediums moet aangepas word by klimaatstoestande gedurende die spesifieke produksieseisoen.

Orientador: Juliano Carlos Calonego / Banca: Cristiano Malhalhães Pariz / Banca: Carlos Alexandre Costa Crusciol / Resumo: Como opção para produção de silagem, o consórcio do milho com o capim-marandu e o feijão-guandu pode aumentar a quantidade de silagem produzida, sendo essa de melhor qualidade. O consórcio entre gramíneas e leguminosas pode ser uma estratégia interessante para aumentar os estoques de C e N e a quantidade forragem pelas pastagens cultivadas em sucessão, que resultarão em palhada para cobertura do solo no Sistema Plantio Direto (SPD). Em sucessão aos consórcios de verão, a aveia se torna uma opção importante, principalmente pela possiblidade de sobressemeadura, o que torna viável o seu cultivo por produtores que não tem acesso à semeadoras específicas para sementes miúdas. Objetivou-se com esse trabalho avaliar a produção de fitomassa aérea das espécies cultivadas, em função da presença ou não do feijão-guandu em consórcio com milho e capim marandú no verão para produção de silagem, e também em função das modalidades de semeadura da aveia-preta no outono-inverno para produção de pasto e palha, em SPD, com integração Lavoura-Pecuária (iLP), visando a terminação de cordeiros em semi-confinamento. Além disso, verificar se as emissões de gases de efeito estufa (GEE) por esses cultivos são compensados por aumentos no aporte de C no solo. A presente pesquisa foi realizada, na Fazenda Experimental Lageado, pertencente à Faculdade de Ciências Agronômicas - UNESP, localizada no município de Botucatu (SP), e foi conduzido nos anos agrícolas 2013/2014 e 2014/2015. O delineamento experimen... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Optionally for silage production, the intercrop of corn with the marandugrass and pigeon pea can increase the amount of produced silage, and this best quality. The consortium of grasses and legumes can be an interesting strategy to increase the stocks of C and N and the amount forage for pastures grown in succession, which will result in straw for mulching in no-tillage system. In succession to summer intercrop, oats becomes an important option, especially the possibility of overseeded, making it possible its cultivation by farmers who do not have access to specific seeders for small seeds. The objective of this study was to evaluate the air biomass production of cultivated species, depending on the presence or absence of pigeon pea intercropped with corn and pasture in the summer for silage, and also depending on the seeding arrangements for aveia- yellow in autumn-winter pasture production and straw in SPD with Crop-Livestock integration, aimed at terminating lambs in semi-confinement. Also, check if emissions of greenhouse gases (GHG) by these crops are offset by increases in the C input to soil.This survey was conducted in the Experimental Farm Lageado, belonging to the Faculty of Agricultural Sciences - UNESP, located in Botucatu (SP), and was conducted in the agricultural year 2014/2015. The experimental design is a randomized block in a split plot with two factors (A and B) and 4 repetitions, Factor A is allocated in the main plot and consists of two summer treatments,... (Complete abstract click electronic access below) / Mestre