Uso dos adubos de liberação lenta na produção de mudas e plantio de eucalipto

Abstract

Slow release fertilizers (SRF) are under development worldwide, with a high degree of technology employed, capable of releasing nutrients over time to the plant. The use of SRF in the forest sector, is still incipient due to the lack and low supply of fertilizers with compatible formulations for forest species. In this context, recently, a new slow release fertilizer technology has emerged, with compatible formulations for seedling production and forest plantation. Thus, the objective of this work was to test the quality and adequate doses of the formulated fertilizer encapsulated with elemental sulfur and coated by non-water soluble organic polymers, in the seedling production phase, in nursery, and in eucalyptus plantations. For seedling production, the experiment was conducted in 180 days, and was arranged in randomized isolated design, in a 2 x 5 factorial design, where the first factor represents two tested slow-release fertilizers, SRF1 (encapsulated with elemental sulfur and coated with non-water-soluble organic polymers) and SRF2 (coated with organic polymers composed of an alkyd resin). The second factor, represents five tested doses (0, 2, 4, 6, 8 kg m-3). Both fertilizers tested showed efficiency for use, due to the satisfactory growth, within the recommendations for seedling dispatch. However SRF2 showed superior growth of seedlings in relation to SRF1, being recommended the use of 4 kg m-3 of substrate for both fertilizers. To test the use of SRF in eucalyptus planting, two experiments were carried out, one in pot and one in field. For planting in pot, was conducted in 120 days, and the experiment was arranged in a randomized block design in a 6x3 factorial scheme, where the first factor corresponds to six doses of BF, (0, 50, 75, 100, 125% phosphorus) of ALL and 100% phosphorus of superphosphate simple (SPS). The second factor corresponds to three applications of CF (0, 1 and 2 parcels of KCl and NH4NH3, these applied at 30 and 60 days after planting, according to treatment). Phosphorus, potassium and nitrogen doses were based on the recommendation of fertilization in pots of 300, 100 and 100 mg dm-3, respectively. For field planting, the experiment was conducted in ten months, and was arranged in a complete randomized block design, in a 5 x 2 factorial design (five doses of BF (0, 18, 27 and 36 g of P2O5 plant-1

) applied via RSF and 27 g of P2O5 plant-1

, applied via simple superphosphate (SPS) and two applications of CF (0 and 80 g of formulated fertilizer 20:00:20, at eight months). For both, it was found higher growth of plants with its use, in detriment of the fertilizer commonly used in the activity for basic fertilization (super phosphates). For these experiments, the doses already recommended for pot planting and field planting were maintained (300 mg dm-3 and 27 g of P2O5 plant-1, applied via ALL, respectively), however, the need for top cover was reduced. Thus, the use of this technology of fertilizers increased the quality of eucalyptus seedlings, promoting higher growth in plantations.