Acúmulo de matéria seca por duas cultivares de girassol (Helianthus annuus L.), em função da idade e da adubaçao

Abstract

Com o objetivo de se estudar o acúmulo de matéria seca, em função da idade da planta e a produção de grãos do girassol, instalou-se um experimento, em condições de campo, no Centro Nacional de Pesquisa de Soja/EMBRAPA, em Londrina, PR. O solo utilizado foi o Latossolo Roxo eutrófico e o delineamento estatístico foi o inteiramente casualizado com quatro repetições. Foram aplicadas seis doses de adubo: 0-0-0; 1-1-1; 2-1-1-; 1-2-1; 2-2-1 e 2-0-0 (NPK), correspondendo a 0 = zero;1 = 45 kg/ha e 2 = 90 kg/ha (N, P(2)0(5) e K2O. Para o estudo do crescimento da planta foram escolhidas a melhor e pior dose. O espaçamento foi de 0,80 m entre linhas com cinco plantas por metro linear. A colheita de amostras foi efetuada de 14 em 14 dias, da emergência até a colheita. Nas condições em que o experimento foi conduzido pode concluir que: a) a produção de matéria seca não foi afetada por nenhuma dose de adubo; b) a produção de grãos foi maior quando não houve adubação NPK; c) a maior velocidade de crescimento da planta ocorreu, em média, aos 56 dias após a emergência; d) o acúmulo máximo de matéria seca foi aos 88 dias após a emergência.

Sunflower micronutrient uptake curves

“…The values obtained in this study show that they are in agreement with those obtained by Sfredo et al (1984) and Castro & Oliveira (2005), with exception to Fe in which the content presented was higher to those of the other authors. This is probably due to the fact that the place where the experiment was carried out has clay texture and is originated from basaltic material presenting in its genesis high iron content, which led to a higher absorption of this element by the sunflower plant.…”

“…In the diagnostic leaf, the concentration was 42.6 mg kg -1 , value considered adequate (Table 2) It is noticeable that there was an intense Zn translocation from the leaf, stem and capitulum to achenes formation and, in the same way as for Sfredo & Sarruge (1990), the highest accumulations occurred in the stem and achenes. In the achenes, such accumulation happened at 97 DAE (R. 9 ), with 4.85 mg plant -1 of Zn representing an exportation of 52% of all Zn absorbed by the plant, differing from that shown by Sfredo (1984) which obtained 30% of exportation by the achenes.…”

“…Therefore, the sampling for leaf diagnosis was carried out in the beginning of flowering as described by Blamey et al (1997). The results of micronutrients concentrations on sunflower leaf tissue obtained in the start of flowering (Table 2) in which it is possible to consider these limits sufficient to a good development of sunflower plants by Sfredo et al (1984) and Castro & Oliveira (2005).…”

“…The nutritional demand is variable with the sunflower development cycle. However, in a general way, for macronutrients as well as for micronutrients, it follows the accumulation rate of dry matter during the vegetative stage until the end of flowering (Gachon, 1972;Sfredo, 1984;Castro & Oliveira, 2005).…”

“…It is relevant to know how the uptake of nutrients occurs during the periods of the plant vegetative cycle (Sfredo et al, 1984). In relation to micronutrients, such data are even less known with the exception of boron (B), Ciênc.…”