Resiliência de clones de eucalipto ao défice hídrico e nutricional

• Autor(a) principal: Rocha, Julenice Bonifácio de Oliveira
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1657
• topic: Eucalipto - Deficit hídrico; Eucalipto - Nutrição; Eucalipto - Clones; Eucalyptus - water deficit; Eucalyptus - Nutrition; Eucalyptus - Clones; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

Eucalyptus plantations have been expanding mainly in cerrado areas, as a result, among other factors, of the relatively low cost of these lands and favorable physical conditions of the soil. However, water and nutritional restrictions reduce forest production in these areas. Thus, a crucial question arises: what would the magnitude of growth recovery (resilience) be if water and nutritional limitations were solved? .Generally observed during the winter months, water limitation causes lower initial growth of the planting performed during this period. However, adequate nutritional and water status of the planting is necessary for the productive potential of the area to be attained. That explains why in most of these areas, characterized by highly weathered and deep soils, and consequently, poor in nutrients, fertility correction is needed before and, or immediately after planting. For plantings conducted during periods of drought, not all the nutrients are supplied immediately, due to the low humidity of the soil that hinders dissolution and transport of these nutrients up to the surface of the roots. Thus, it is questioned whether late planting and cover fertilization application would allow the maximum expression of the yielding capacity of the area. This work aimed to verify the resilience of young eucalyptus clone plantations under late fertilization and water restriction situations and to evaluate the possible mechanisms involved in growth recovery, and their rates after these restriction conditions are overcome. Thus, an experiment using three clones (GG100, I-144 and 1528) was carried out during 10 months in Taparuba, MG. Approximately 90-day-old seedlings were transplanted into 60 cm diameter and 90 cm high plastic recipients. Portions of a dystrophic Red Yellow Latosol with sandy clay loam texture were used. The surface of the recipients was covered with a plastic sheet and tape to prevent rain from falling in and allow treatment application. Immediately after planting, an amount of water sufficient to increase and maintain humidity next to field capacity was added to each recipient, during one month. After this period, the application of water was reduced in the water- stressed treatments, until the soil reached humidity near tension of 1.500 kPa; the treatments without water stress, initially, or throughout the experiment, were maintained at humidity close to tension 10 kPa. The treatments were constituted as follows: sDH - without fertilization delay and without water deficit; DH4 - without fertilization delay and with water deficit up to the fourth month after planting; At2 - with fertilization delay up to two months and without water deficit; At2DH4 - with fertilization delay up two months and with water deficit up to 4 months after planting; At4 - with fertilization delay up to 4 months and without water deficit; and At4DH4 - with fertilization delay and water deficit up to 4 months after planting. The experiment was arranged in a completely randomized design, in a factorial scheme 3 x 3 x 2, and four repetitions. Survival, plant height, stem diameter, leaf nutrient contents, liquid photosynthesis (A), stomata conductance (gs), transpiration (E), Ci/Ca, a chlorophyll, fluorescence, leaf water potential, and soluble sugar concentration were periodically evaluated. At the end of the experiment, nutrient content as well as leaf, stem, and root dry matter were evaluated. Water and/or nutritional deficits reduced the growth of the plants and an adequate supply of water and nutrients promoted growth recovery at magnitudes variable with the clone. The mechanisms related to tolerance and resilience to water stress were. The gs reduction, which minimizes water loss; increase in quantic yield values of regulated energy dissipation in photo-system II to dissipate the excess of luminous energy absorbed; and accumulation of sugars, which confers osmo-protection to the plants. After re-supplying adequate water and nutrient conditions to soil, a rapid increase of the photosynthesis rate and nutrient absorption by the plants was verified.