Adubação com macro e micronutrientes ajustada à demanda nutricional da violeta africana

• Autor(a) principal: Santos, Glaucio Leboso Alemparte Abrantes dos
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5464
• topic: Conteúdos; Requerimento de nutrientes; Contents; Nutrient requirements; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

The African violet (Saintpaulia ionantha Wendl) is a very appreciated ornamental species. Nevertheless, because fertilization and nutrition of that species are based only on the experience of producers and fertilizer manufacturers, treatment indications are controversial, and N-P-K chemical formulations for other cultures are prescribed. It also happens that no information can be found about micronutrient fertilization. Currently, though, the manufacturer B&G Flores is launching, still in its experimental phase, a formulation specific for those plants. Therefore, the aim of this work was to develop a mineral macro- and micronutrient formulation which fits the nutritional demands of African violet, for which an experiment was conducted for dry matter production, demonstrating contents of both macro- and micro nutrients, in three varieties of African violet (Blue Az; Pink Rs, and Red Vr), with two fertilizations along the experiment period (eight different harvesting times, allowing for a three-week interval each). This way, a factor was found of 3x2x8, resulting in 48 treatments. Both fertilizations consisted of: ¼ of the recommended dose by application of fertilizer B&G Violet [0.75 g/L and 100 mL/EU (Experimental Unity), a total of 62.5 mg/dm3/application] and the manufacturer s prescribed fertilizing dose per application (3 g/L and 100 mL/EU, resulting in 250 mg/dm3/application). The Experimental Unity (EU) consisted of three pots, each holding one plant. Treatments were organized in random blocks, with four replications, applied every 10 and 11 days, while every 21 days the EU s under treatment were collected. At the purchase of seedlings, a first harvest was performed, corresponding to time 0d. Both fertilizing and irrigation were applied onto the plastic collector plates which remained under the EU s. At harvesting, the plants were withdrawn from the pots, washed and divided by vegetal organs (root, meristematic region, leaf and flower). The collected vegetal organs were dried in forced air circulation oven at 70oC up to constant weight for dry matter achievement, followed by milling, and further nitric-perchloric digestion aiming at the macro- and micronutrient determination. Contents of P, K, Ca, Mg, S, Fe, Zn, Mn, B, Cu and Mo were assessed by means of optical emission spectrometry in inductively coupled plasma (ICP-OES), and N content was determined by means of Kjeldahl method. Rising from nutrient content (TNu), and from each vegetal organ production of dry matter (CNu= TNuxMSo) as well as from their addition, the total content of plant nutrient (CNuTotal=CNu Raiz + CNu Meristem + CNu Leaf + CNu Inflorescence). Dry matter production regressions were adjusted as well as the nutrient contents according to time, so as to determine both proportion and demand of nutrients during the African violet growth period. On performing the division of nutritional demand (Dnu= nutritional demand generated by the regression adjusted models) by the nutrient recovery rate by plant (RRNu = DNu / QNu; QNu = amount of nutrient added via fertilization plus substrate nutritional supply), the plant nutrient demand (RNu = DNu / RRNu) was found. For contents, contrasts were performed among the varieties of plant: Az x Rs + Vr and Rs vs Vr. Within each variety, the following contrast was performed: dose 62.5 vs 250 mg/dm3/application of B&G Violeta fertilizer. By means of those contrasts, it was found that Rs produced more dry matter per plant than Vr, while Az produced less dry matter per plant than Rs and Vr. That scenery was repeated for N, P, S, K, Ca, Mg, B, Mo and Fe contents. The 62.5 mg/dm3/application dose resulted in higher dry matter content per plant than the 250mg/dm3/application dose in Az and Rs (also true for the Vr variety, but not significantly), making it evident that a lower dose was adequate on providing for plant growth, while the 250 mg/dm3/application dose was excessive. Taking into account only the demand curves of the Pink variety, at the 62.5 mg/dm3/application dose, to estimate the proportions among the nutrients in the nutritional fertilizing supplement, a formula was estimated for balancing the nutritional fertilizer supply for African violet in the following proportions: 10% of N; 4.82% of P; 4.41% of S; 18.02% of K; 15.32% of Ca; 16.79% of Mg; 0.082% of B; 0.002% of Mo; 0.589% of Zn; 3.979% de Fe; 2.021% de Mn, e 0.047% de Cu.