Silvio Douglas Ferreira

SULFENTRAZONE SELECTIVITY AND EFFICIENCY IN CASSAVA CROPS IN SANDY AND CLAYEY SOILS

Weeds have the potential to dramatically interfere in cassava cultivation, reducing its productive potential; however, there are few studies on the selective herbicides in this crop. Therefore, the objective was to evaluate in this work the selectivity and efficiency of sulfentrazone in cassava crops grown in sandy and clayey soils. Two experiments were carried out: The first one was carried out in sandy soil conditions in the conventional system; and the second one was carried out in clayey soil conditions in the no-tillage system. The experimental design was a randomized block with four replications. The treatments consisted in doses of 250, 500, 750 and 1,000 g ha-1 of sulfentrazone, and weeded and non-weeded controls. Sulfentrazone application in cassava crops has linearly reduced the production of roots in a proportion of 0.0153 and 0.0107 t ha-1 at each increment in grams of the active ingredient, respectively. It was concluded that sulfentrazone was not selective for cassava crops grown both in sandy and in clayey soil; however, it was highly effective in weed control in both soils.

Allelopathy of aqueous Pachyrhizus erosus L. extracts on Euphorbia heterophylla and Bidens pilosa

1. Manuscript received in Jan./2018 and accepted for publication in Mar./2018 (http://dx.doi.org/10.1590/1983-40632018v4851117). 2. Universidade Estadual do Oeste Paranaense, Marechal Cândido Rondon, PR, Brasil. E-mails: jaquelineabarbosa@hotmail.com, agrosilvio@outlook.com, adriana.salvalaggio@outlook.com, neumarcio.costa@unioeste.br, mmecher@bol.com.br. Allelopathy contributes to the sustainable management of weeds in growing areas, due to its ability to inhibit the development of weed species. This study aimed to evaluate the allelopathic effect of Pachyrhizus erosus extract on Euphorbia heterophylla and Bidens pilosa germination. The experiment was carried out in a completely randomized design, in a 2 x 2 x 4 factorial scheme, with four replications. The first factor corresponded to the plant portion (shoot and tuberous root), the second to the extract preparation method (water at room temperature and boiling) and the third to the extract concentrations (0 %, 25 %, 50 % and 100 %). Phytochemical analyses were performed to identify the presence of secondary metabolites. The variables germination percentage, germination rate index and dry biomass decreased with increasing aqueous extract concentrations for both E. heterophylla and B. pilosa. When applied a P. erosus crude shoot extract (boiling), decreases of 18 % and 92 % were observed in the E. heterophylla and B. pilosa germination, respectively, with a decrease of 91 % in the dry biomass of E. heterophylla seedlings. The tuberous root extract (boiling), on the other hand, reduced the germination percentages for E. heterophylla and B. pilosa in 18 % and 80 %, respectively. The phytochemical evaluation indicated the presence of flavonoids, coumarins and saponins in the shoot and tuberous root extracts, while tannins were only observed in the shoot extract. Thus, it can be concluded that P. erosus extracts display an allelopathic effect on the weed species evaluated.

Efeito da adubação nitrogenada e da sazonalidade na produtividade de Ocimum basilicum L.

The basil (Ocimum basilicum L.) currently is distributed to all continents and was introduced in Brazil with the arrival of Italian colonization. The main parts used for commercialization in Brazil are the fresh or dried leaves. This study aimed to evaluate the effect of doses of nitrogen fertilization for cultivation in spring and fall, the yield characteristics and the productivity of basil, Basil red in the greenhouse. The experimental design was a randomized block, in a factorial 2 x 6 with five replications, where the first factor constituent of five nitrogen doses and one control (0.0; 45.0; 90.0; 135.0; 180.0 and 225.0 kg ha-1 of nitrogen) and by the second, the growing seasons (Spring and Autumn). For the productive characteristics of the cultivar red Basil, it was found that the nitrogen rates between 90.0 to 135.0 kg ha-1 were better, bringing all tested productive characteristics, the spring crop. When observed growing in the autumn, was only fit for the crown projection, fresh weight of shoot and leaf area. When there was significant adjustment, the dose of approximately 110.0 kg ha-1 of nitrogen was that promoted further development of culture. Regarding the growing seasons in the spring we recommended the use of mineral nitrogen fertilization, but when this crop is performed autumn, nitrogen fertilization is not responsive.