Efeito da densidade populacional de Canavalia ensiformis na fitorremediação de solo contaminado com sulfentrazone

RESUMO Existem poucas informações quanto à fitorremediação do herbicida sulfentrazone, reforçando assim a necessidade de pesquisas que visam oferecer alternativas seguras para sua utilização em sistemas que integram a sucessão/rotação de culturas, focando a sustentabilidade da produção agrícola, sem prejuízos ao sistema produtivo e ao ambiente. Com isso, objetivou-se neste trabalho avaliar a influência da densidade populacional de Canavalia ensiformis sobre a fitorremediação de solo contaminado com o herbicida sulfentrazone. O experimento constou de um fatorial 4 x 3, no delineamento inteiramente casualizado, com quatro repetições. O primeiro fator foi constituído pela combinação de quatro densidades populacionais da espécie fitorremediadora C. ensiformis (0; 10; 20 e 40 plantas m-2) e o segundo por três doses do herbicida sulfentrazone (0; 200 e 400 g ha-1). Aos 75 dias após a emergência, as plantas foram cortadas na altura do coleto. Nesse mesmo período, efetuou-se, no próprio vaso, a semeadura da espécie bioindicadora da presença do sulfentrazone, milheto (Pennisetum glaucum), na qual foram avaliadas a fitotoxicidade, a altura e a biomassa fresca e seca da parte aérea e da raiz. O cultivo prévio da espécie fitorremediadora C. ensiformis promoveu a remediação do solo contaminado com sulfentrazone. A densidade populacional mínima de C. ensiformis que possibilita o desenvolvimento do milheto é de 10 plantas m-2. Todavia, melhores resultados foram obtidos na densidade de 40 plantas m-2

Effects of tillage systems on physical properties of a cohesive yellow argisol in the northern state of Espírito Santo, Brazil

Tillage systems are a key element of the technology of crop production, both with a view to crop yield and from the perspective of soil conservation and sustainability of the production system. The aim of this paper was to evaluate the effects of five tillage systems on the physical properties of a cohesive Yellow Argisol. The experiment was installed in the field on January 21, 2011 and lasted 260 days, in an area previously used as pasture with Brachiaria grass without liming or fertilization, but irrigated by a low pressure spray system. The treatments, in five replications and in a randomized block design, consisted of: 1) disk plow (twice) + disk harrow + ridge-furrow tillage (raising a ridge along the planting row), 135 days after transplanting (DP + RID); 2) disk plow (twice) + disk harrow (DP no RID); 3) subsoiler (SB); 4) disk plow (twice) + disk harrow + scarification with three shanks along the plant row (DP + SPR); and 5) disk plow (twice) + disk harrow + scarification with three shanks in the total area (DP + STA). In all tillage systems, furrows were mechanically opened for the papaya plants. After the treatments, the mechanical resistance to penetration was determined, followed by soil moisture, mean weight diameter (MWD), geometric mean diameter (GMD), bulk density (BD), macroporosity (Ma), microporosity (Mi), and number of fruits per plant. There were differences in penetration resistance (PR) between treatments. The subsoiler was more effective to decrease RP to a distance of 0.35 m from the plants, perpendicular to the plant row. The scarifier resulted in a lower PR than DP or SB, even at the depth of 0.40 m, and it was more effective at greater distances perpendicular to the plant. All tillage systems induced a PR between 2.0 and 3.0 MPa at the depth with the highest concentration of papaya tree roots (0-0.25 m), improving the physical conditions to this depth. There was no statistical difference among the treatments for BD, Ma, Mi, MWD, and GMD at a depth of 0.20 m. The disk plow changed the physical properties of the soil most intensely to a depth of 0.20 m. The use of scarification, reduced tillage with a forest subsoiler, or ridge-furrow tillage did not improve the physical properties in the rhizosphere. Reduced tillage with a forest subsoiler resulted in a lower number of fruits per plant than all other treatments, which did not differ from each other