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Previous issue date: 1988-04-14 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / A nitrogen balance study was carried out in four commercial cultivars of sugarcane grown in pots containing 64 kg of soil, with the objective of quantifying possible contributions of the biological nitrogen fixation (BNF) to the plants. Vinasse was added in half the vessels and all treatments were repeated 10 times. The pots were kept in the field and fertilized with the equivalent of 80 kg of N / ha with 15N labeled urea fertilizer.
After 12 months of growth the plants accumulated between 10 and 24% of the total N of the soil + Fertilizer added. In the next nine months of growth, without any further addition of nitrogen fertilizer, the plants accumulated the equivalent of 8.5 to 19% of the original soil N + fertilizer. The cultivar CB 47-89 accumulated significantly more N than the other cultivars. This difference was greater in the absence of vinasse, and in this treatment the 15 N enrichment in the CB 47-89 cultivar was half that of the other cultivars, suggesting that there was a contribution of unlabelled N of the air to this cultivar via FBN . After 21 months of cultivation the N content of soil and roots was determined in 5 replicates. These analyzes revealed that planted pots lost between 7.5 and 12.5 g of soil N + fertilizer, but all accumulated more than this in plant tissues. In the case of cultivar CB 47-89, in the absence of vinasse, the plants removed approximately 10 g of N from the soil and fertilizer but accumulated about 35 g of N.
In a second experiment, sugarcane cultivars were planted in pots containing 100 kg of soil, using two sources of 15N - labeled organic matter and gypsum pellets - with the objective of quantifying the contribution of the biological fixation of Nitrogen at different stages of the culture, using the 15n isotopic dilution technique. Harvests were carried out at 4.8.12 and 16 months of plant growth. There was not a good development of the plants that was attributed to the problem of aeration of the soil due to strong capacity, and there were no significant differences in the enrichment of 15N of the cultivars, suggesting that FBN contribution of the same magnitude occurred. Organic matter proved to be a better supplier of 15N for the soil solution, as it allowed a more constant N-labeling of soil for long-term experiments than did gypsum pellets.
These data constitute the first direct evidence of very significant contributions of FBN associated to a sugarcane cultivar. / Um estudo com balan?o de nitrog?nio foi realizado em quatro cultivares comerciais de cana-de-a??car crescidos em vasos contendo 64 Kg de solo, com o objetivo de quantificar poss?veis contribui??es da fixa??o biol?gica de nitrog?nio (FBN) para as plantas. Vinha?a foi adicionada na metade dos vasos e todos os tratamentos foram repetidos 10 vezes. Os vasos foram mantidos no campo e adubados com o equivalente a 80 Kg de N/ha com fertilizante ur?ia marcada 15N.
Ap?s 12 meses de crescimento as plantas acumularam entre 10 e 24 % do N total do solo + Fertilizante adicionado . Nos nove meses de crescimento seguintes, sem qualquer nova adi??o de fertilizante nitrogenado, as plantas acumularam o equivalente a 8,5 at? 19% do N original do solo + fertilizante. O cultivar CB 47-89 acumulou significativamente mais N do que os demais cultivares. Esta diferen?a foi maior na aus?ncia de vinha?a e, neste tratamento, o enriquecimento de 15 N no cultivar CB 47-89 foi a metade do que o dos outros cultivares, sugerindo que houve uma contribui??o de N n?o marcado do ar para este cultivar via FBN. Decorridos 21 meses de cultivo o conte?do de N do solo e das ra?zes foi determinado em 5 repeti??es. Estas an?lises revelaram que os vasos plantados perderam entre 7,5 e 12,5 g de N do solo +fertilizante, mas todos acumularam mais do que isto nos tecidos das plantas. No caso do cultivar CB 47 - 89, na aus?ncia de vinha?a, as planta removeram aproximante 10 g de N do solo e do fertilizante mas acumularam cerca de 35 g de N.
Em um segundo experimento, cultivares de cana-de-a??car foram plantados em vasos contendo 100 Kg de solo, utilizando-se duas fontes fornecedoras de 15N - mat?ria org?nica marcada e peletes de gesso - com o objetivo de quantificar a contribui??o da fixa??o biol?gica de nitrog?nio em diferentes fases da cultura, atrav?s da t?cnica da dilui??o isot?pica de 15n. Foram realizadas colheitas aos 4.8,12 e 16 meses de crescimento das plantas. N?o houve um bom desenvolvimento das plantas que foi atribuido ao problema de aera??o do solo em fun??o de forte capacita??o, n?o ocorrendo diferen?as significativas no enriquecimento de 15N dos cultivares, sugerindo ter ocorrido contribui??o da FBN de mesma magnitude. A mat?ria org?nica mostrou-se um melhor fornecedor de 15N para a solu??o do solo, pois permitiu uma marca??o do N do solo mais constante para experimentos de longa dura??o do que os peletes de gesso.
Estes dados constituem a primeira evid?ncia direta de contribui??es muito significativas da FBN associada a um cultivar de cana-de-a??car.
| Identifer | oai:union.ndltd.org:IBICT/oai:localhost:jspui/1632 |
| Date | 14 April 1988 |
| Creators | Lima, Eduardo |
| Contributors | Boddey, Robert Michael |
| Publisher | Universidade Federal Rural do Rio de Janeiro, Programa de P?s-Gradua??o em Agronomia e Ci?ncia do Solo, UFRRJ, Brasil, Instituto de Agronomia |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da UFRRJ, instname:Universidade Federal Rural do Rio de Janeiro, instacron:UFRRJ |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | FINEP |
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