Detalhes bibliográficos
| Ano de defesa: |
2010 |
| Autor(a) principal: |
Fonseca, Leandro Andrade da |
| Orientador(a): |
Peil, Roberta Marins Nogueira |
| Banca de defesa: |
Não Informado pela instituição |
| Tipo de documento: |
Dissertação
|
| Tipo de acesso: |
Acesso aberto |
| Idioma: |
por |
| Instituição de defesa: |
Universidade Federal de Pelotas
|
| Programa de Pós-Graduação: |
Programa de Pós-Graduação em Sistemas de Produção Agrícola Familiar
|
| Departamento: |
Faculdade de Agronomia Eliseu Maciel
|
| País: |
BR
|
| Palavras-chave em Português: |
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| Palavras-chave em Inglês: |
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| Área do conhecimento CNPq: |
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| Link de acesso: |
http://guaiaca.ufpel.edu.br/handle/123456789/2416
|
Resumo: |
Lettuce presents a great ability of nitrate accumulation, especially in hydroponics in which the ion availability is high. Nonetheless, nitrate accumulation depends primarily on genotype and light intensity. The objective of this work was to evaluate daily and seasonal variation of nitrate contents, growth and yield of lettuce cultivars according to the crop season in NFT system. Three experiments were conducted in three crop-seasons: spring of 2008, autumn and winter of 2009, in Pelotas RS. Four cultivars (Green Garden, Red Garden, Great Lakes Iceberg and Vera Sunny lettuce types) and four harvest times (8:00 am, 2:00 pm, 6:00 pm and 11:00 pm) were studied. In spring-summer, the lowest average nitrate contents were found at 6:00 pm and 11:00 pm (2058 and 2244 mg kg-1) and in Great Lakes Iceberg leaves (1825 mg kg-1). However, in this crop season, this cultivar did not present an appropriate head formation. Red Garden cultivar showed lower total plant fresh mass and yield than the other cultivars (236.7 against 389.4 g plant-1 obtained as the average of the remained cultivars, and 2724.2 against 4480.9 g m-2 as average from the other cultivars, respectively). In autumn, the lowest average nitrate contents were observed at 8:00 am (1378 against 1620 mg kg-1 obtained as average of the other harvest times) and for Red Garden and Great Lakes Iceberg cultivars (1360 and 1448 mg kg-1). Great Lakes Iceberg presented leaf dry mass, total plant dry and fresh mass higher than all other cultivars, and leaf area greater than Green Garden and Vera Sunny cultivars. In winter, Green Garden and Red Garden presented similar nitrate 10 contents (mean of 2182 mg kg-1) and for both cultivars the lowest nitrate contents was observed at 8:00 am (1545 against the average of 2394 mg kg-1 of the other harvest times). Great Lakes Iceberg presented lower nitrate accumulation than Vera Sunny (1915 and 2679 mg kg-1, respectively) and the harvest at 2:00 pm lead to a lower content than at 6:00 pm (2054 and 2454 mg kg-1, respectively). Great Lakes Iceberg presented higher total fresh mass production and yield (472.0 g planta-1 and 5590.1 g m-2, respectively) than the other cultivars, and it did not differ of Green Garden (390.2 g planta-1 and 4580.6 g m-2, respectively). In general, we can conclude that the lowest average nitrate accumulation is obtained in autumn (1559 against 2526 and 2189 mg kg-1 obtained in spring and winter, respectively). Vera Sunny cultivar in average presents the highest nitrate accumulation independently on the crop-season and Great Lakes Iceberg is the lowest nitrate accumulation cultivar. Late afternoon is the most recommended period for harvest in early summer day and the period of early-morning is the most indicated for lettuce harvest in autumn. On the other hand, in winter cloudy days, the period from morning to early afternoon is the most indicated for lettuce harvest. In spring, we can recommend Vera Sunny cultivar due its adequate growth, yield and absence of bolting tendency although its higher nitrate contends and considering that they are found in the acceptable consumption range. In autumn as well as in winter Great Lakes Iceberg represents an interesting alternative, due to its highest growth and the best yield responses in association to its leaves lowest values of nitrate. In winter, Green Garden cultivar can ocupy part of the NFT system, due to its also low nitrate contents and proper growth and yield. |
