Produtividade e qualidade de raízes de mandioca, CV. Aciolina, sob diferentes doses de potássio e épocas de avaliação na savana de Roraima

Abstract

The objective of this study was to evaluate the productivity and quality of cassava cv. Aciolina under different levels of potassium and evaluation times in the savannah of Roraima. At the experiment was used a randomized block design with a split plot design with four replications. The five levels of potassium were randomized in plots (0; 30; 60; 120 and 240 kg ha-1 K2O) applied at planting and cover for 30 and 60 days after planting (DAP), and five-year assessment (150; 210; 270; 360 and 420 DAP) , the subplots. The experimental plot consisted of nine single rows of cassava with 6,4 m long containing eleven plants (99 plants per plot), where 4.8 m in the middle of the central rows corresponded to floor area (23.04 m2). The planting was done in single rows, according to the spacing of 0.8 x 0.8 m, totalizing 15,625 plants per hectare. Crops, as established seasons were performed manually, removing three entire plants of floor area per plot, the following variables were evaluated: plant height, shoot productivity (kg ha-1), number of roots, root diameter (cm), root productivity (kg ha- 1), harvest index (IC), HCN content in leaves, stem, root and pulp of the root cortex. Some variables were analyzed only at 360 DAP, number of commercial roots productivity for commercial roots (kg ha- 1), starch and dry matter productivity and flour. Productivity components of cassava plant height, productivity of shoot, root diameter and root productivity showed positive linear behavior, both due to harvest time, as a function of K2O levels, not being observed physiological rest period cv. Aciolina under the conditions of this study. For the number of storage roots, roots number of commercial, business productivity and productivity of root starch, the behavior is linear in terms of K2O levels. The highest harvest index, 71.5% is obtained with 173,1 kg ha- 1 K2O at 420 DAP. The highest root productivity was 78,000 kg ha- 1 and starch was 14,096 kg ha- 1, both obtained with the highest dose of K2O applied (240 kg ha- 1 of K2O), at 420 DAP. The starch content, dry matter content and flour productivity showed a quadratic behavior as a function of K2O levels, obtaining the highest percentages in doses of 150 kg ha-1, 147 kg ha- 1 and 203 kg ha- 1 K2O, respectively. The concentration of HCN in the cortex of the root and the sheet increases with increased doses of K2O. From 235 HCN content decreases with age harvest. The HCN content in the stem and the root HCN showed quadratic behavior as a function of K2O levels, and linear negative with respect to the evaluation times. The HCN content ranging from parts of the plant, and the highest concentrations found in the smaller leaves and the root.