Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.5/2528
Título: Influência da fertilizaçao azotada na produção, composição botânica e qualidade de pastagens na Ilha do Faial, Açores
Outros títulos: The influence of nitrogen fertilization on herbage accumulation, botanical composition and quality of pastures in Faial island, Azores
Autor: Rodrigues, Nuno Pedro Pinheiro da Silva Carreira
Orientador: Torres, Maria Odete Pereira
Palavras-chave: pasture
botanical composition
crude protein
dry matter accumulation
nitrogen fertilization
composição botânica
fertilização azotada
proteína bruta
matéria seca
Data de Defesa: 2010
Resumo: With the rising difficulties of every economical sector in the past few years, society saw and still sees itself forced to find better and less expensive ways of obtaining some essential goods and services. The increase of oil prices and of the demand of specific raw-materials by the emerging economies, mainly cereals, oleaginous plants and micronutrients, along with the energetic and environmental concerns, led the farmers and farming companies, to the inevitable need of arranging other alternatives within the production strategies. This tendency has the purpose of reducing the resort to the expensive concentrated fodder (principally due to the biodiesel and bioetanol industry), and synthesized fertilizers. In addition, the negative impact that some nutrients are known to have on human health, mainly N, began to arise environmental and agricultural goods quality, safeguard policies. With the contingences mentioned, a renewed interest in white clover (Trifolium repens L.), and other legumes, along with the performance of mixed swards receiving lower levels of N, is taking place. Legumes are known to establish symbiotic associations with Rhizobium, which in return allows the plant to benefit with atmospheric N fixed by the bacteria, meaning that the costs in fertilizers can be reduced. Thus, there are several reasons for finding and encouraging better ways of improving the nitrogen fertilizer use efficiency. A fertilizer trial was conducted for 5 months, in Faial Island, Azores, on a permanent pasture, mainly consisting of perennial ryegrass (Lolium perenne L.), cocksfoot (Dactylis glomerata L.), italian ryegrass (Lolium multiflorum Lam.), white clover and red clover (Trifolium pratensis L.). The pasture is established on a light, well drained soil, classified as an Andissol, with an organic matter content of 5,17% and pH-H2O of 6,2. At the time, available phosphate was low (20 mg P2O5 kg-1 dry soil), and the potassium content very high (>200 mg K2O kg-1 dry soil). The aim of the experiment was to evaluate the effect of a range of 7 nitrogen levels and the traditional fertilization, on the dry matter accumulation (DM at 60-65 ºC and 100-105 ºC, the last one only evaluated for treatments 0, 40, 80, 120 kg N ha-1 and traditional fertilization), botanical composition and some quality parameters, namely organic matter (OM) and crude protein (CP). Seven N levels were tested, N0, N1, N2, N3, N4, N5, N6, corresponding to 0, 20, 40, 60, 80, 100 and 120 kg N ha-1. The traditional fertilization consisted on the application of 480 kg ha-1 of synthesized compost, adding up 125 kg N ha-1, plus Ca, Mg and S. The effect of the treatments on the sward was evaluated in 5 consecutive cuts during the trial. The botanical composition was evaluated, resorting to sub-samples collected from the cut material, where grasses, legumes, other species and debris were manually separated, and dried at 60-65 ºC for 48 h, to assess their percentage on total DM, after each cut. The compostition of legumes in the sward according to the treatments 0, 20, 40, 60, 80, 100, 120 kg N ha-1 and traditional fertilization, corresponded to 2.66, 5.54, 4.45, 0.40, 5.24, 0.80, 2.68 and 4.31% respectively. The OM was evaluated in percentage on DM, and the CP in mass and percentage on DM. The increase of N levels resulted in an increase of DM accumulation, mainly due to the enhancement of grasses, and the depressing of the legumes proportion. The DM (at 100-105 ºC) accumulation of the treatments 0, 40, 80, 120 kg N ha-1 and traditional fertilization, corresponded to 1.85, 1.88, 2.02, 2.37 and 2.11% respectively. Also the CP increased with N treatments, but had no significant effect on the levels of OM. The proportion of CP in the DM according to the treatments 0, 40, 80, 120 kg N ha-1 and traditional fertilization, corresponded to 12.71, 13.99, 14.52, 14.86 and 14.23% respectively. The cutting season had a significant effect on the grasses and legumes proportion, DM accumulation, and quality parameters of the pasture. The traditional fertilization revealed not to be the most adequate one, whilst treatment N4, corresponding to the application of 80 kg N ha-1, seems the one more suitable for the farm exploration, since it resulted in high proportions of legumes (5,24%) and CP (14,52%), without reducing significantly the DM, compared with other treatments.
Descrição: Mestrado em Engenharia Agronómica - Instituto Superior de Agronomia
URI: http://hdl.handle.net/10400.5/2528
Aparece nas colecções:BISA - Dissertações de Mestrado / Master Thesis

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