Gisele Silva de Aquino

Produtividade e índices biométricos e fisiológicos de cana‑de‑açúcar cultivada sob diferentes quantidades de palhada

The objective of this work was to evaluate the effect of different amounts of straw mulch on the biometric and physiological indices and on the yield of the sugarcane variety SP 801816, in the first crop cycle (plant cane). Five treatments - with 0, 25, 50, 75, and 100% straw mulch - were evaluated at 60, 180, 270, and 350 days after planting. The following biometric indices were determined: leaf area, number of leaves, fresh matter weight, and number of tillers. The physiological indices were: leaf area index (LAI), crop growth rate (CGR), and relative growth rate (RGR). A significant effect of straw mulch was observed on all variables. Treatments with 100, 75, and 50% straw provided the highest values for LAI, CGR, RGR, and number of tillers, and the treatments with 50 and 75% straw provided the highest yields. Keeping straw mulch at the soil surface had no effect detrimental to sugarcane development. Total removal or straw kept at 25% resulted in the lowest yields. Removal of 50% straw can be done without harming the crop.

Estaquia de resedá-nacional ( Physocalymma scaberrimum Pohl.) em diferentes substratos e concentrações de AIB

O resed a-nacional ( Physocalymma scaberrimum Pohl.) e uma especie nativa do Brasil que apresenta grande potencial para uso no paisagismo e em reflorestamento, alem da madeira ser empregada na marcenaria de luxo. O objetivo deste trabalho foi avaliar o efeito de diferentes substratos e concentracoes de acido indolbutirico (AIB) na estaquia de resed a-nacional. O delineamento experimental foi o inteiramente casualizado, com cinco repeticoes em arranjo fatorial 3 x 3, sendo os fatores: tipos de substratos (areia de granulacao media; casca de arroz carbonizada e vermiculita de granulacao media) e concentracoes de AIB (0; 1.000 e 2.000 mg L-1), em parcelas compostas por dez estacas. Apos 104 dias da instalacao do experimento, foram avaliadas as seguintes vari aveis: sobrevivencia das estacas; retencao foliar; porcentagem de estacas com calos nao enraizadas; estacas enraizadas; numero de raizes por estaca; comprimento de raizes por estaca e massa seca das raizes por estaca. Nao foram observadas diferencas quanto ao enraizamento em relacao a aplicacao de AIB, obtendo-se, em media, 23,5%. Entre os substratos, embora as estacas enraizadas em areia e casca de arroz carbonizada tenham apresentado maior retencao foliar, todos os substratos testados podem ser utilizados.

Mulching with Sugarcane Straw Reduces Weed Density in Sugarcane Field

Occurrence of weeds in sugarcane crop according to levels of straw over the soil was studied. Experiment was carried out during two annual cycles. Treatments were 0 % (no straw); 25, 50, 75 and 100% (i.e., 5, 10, 15 and 20 t/ha of straw, respectively); and straw burned over the soil. Floristic analysis of weed species was achieved. Percent area occupied by weeds was assessed visually and regression analysis between weeds and amount of straw mulch was performed. Floristic analysis characterized 19 weed species, from eight botanical families: Amaranthaceae, Asteraceae, Commelinaceae, Convolvulaceae, Euphorbiaceae, Poaceae, Portulacaceae and Solanaceae. Highest richness of species was observed for Asteraceae and Poaceae, with seven and four species, respectively. Higher frequency was found for Amaranthus hybridus, A. viridis and Physalis angulata (85% of samples) for first annual crop cycle; and A. hybridus, Bidens pilosa and Cenchrus echinatus predominated (83% of samples) in second cycle. A. hybridus was the most frequent species in both cycles. The highest density of weeds was observed in treatments with straw burned. Application of 75 and 100% straw showed highest suppression for low and high density of weeds, respectively. Increasing level of straw leads correspondent weed control. That information is vital to orientate decision which amount will deposit over the soil since in recent years the straw is also demanded for alternative sources of energy, as thermal or second generation bio-ethanol.