Weed Occurrence in Sugarcane as Function of Variety and Ground Straw Management1

Abstract

-This study aims to verify the effect of crop varietal architecture and straw removal from planting rows in the occurrence of weeds in sugarcane and infer about the sustainability of the production system with no herbicide application. The experiment was established in 2011 in a randomized block design with split plots and four replications. Main plots were varieties IACSP95 5000 and SP91 1049. In the sub-plots there the straw removal was allocated (evenly scattered in the area, or concentrated in inter-rows). Assessments were conducted in 2012 and 2013 and the absolute levels of infestation, density, frequency and dominance of weed species were obtained. Areas were intra-characterized by the coefficients of Simpson and Shannon-Weiner and sustainability inferred by the SEP coefficient. Areas were grouped by the similarity coefficient of Jaccard. Other factors besides leaf architecture were more significant for level of infestation. Treatments with straw removal from planting rows were more infested than those with evenly scattered straw. In the second year of cultivation, those species most adapted to the system increased their importance value. Wild poinsettia was the dominant weed in all treatments, deserving attention from pre-planting on, to reducing its occurrence in the soil seed bank. Species diversity was higher where straw was evenly scattered due to the occurrence of species other than wild poinsettia. Sustainability was reduced from the first to the second year, indicating that only cultural practices are not enough, even with high shading provided by crop and straw production, demanding herbicides.Keywords: Saccharum spp., phytosociology, sustainability. RESUMO -Objetivou-se com o presente trabalho verificar o efeito da arquitetura varietal da cultura e da aplicação da prática de desaleiramento na ocorrência de plantas daninhas em áreas de cultivo de cana-de-açúcar, bem como inferir sobre a sustentabilidade do sistema produtivo sem aplicação de herbicidas. O experimento foi implantado em 2011 em delineamento experimental de blocos casualizados com parcelas subdivididas, com quatro repetições. As parcelas foram compostas pelas variedades IACSP95 5000 e SP91 1049. Nas subparcelas, alocou-se o manejo do palhiço (desaleirado ou não desaleirado). As avaliações foram realizadas nos anos de 2012 e 2013, sendo obtidos os níveis absolutos de infestação, a densidade, a frequência e a dominância das espécies de plantas daninhas. As áreas foram intra-caracterizadas pelos coeficientes de Simpson e Shannon

Weed Diversity in Corn with Different Plant Arrangement Patterns Grown Alone and Intercropped with Palisade Grass

“…Figure 3 shows the Simpson (D) and Shannon-Weiner (H') diversity coefficients, as well as the Shannon sustainability coefficients (SEP). The D coefficient quantifies the probability that two randomly collected individuals belong to the same species, i.e., it is mainly influenced by the occurrence of species with an abundant number of individuals (Concenço et al, 2016). On the other hand, Shannon-Weiner coefficient (H') is quantified by sporadically occurring individuals, i.e., it is influenced by the occurrence of rare species; treatments T3 and T8 presented changes in the weed community.…”

Weeds in Soybean Crop After Annual Crops and Pasture

“…In Figure 3, the Simpson (D) and Shannon-Weiner (H') diversity coefficients are presented, as well as the Shannon sustainability coefficients (SEP). In simple terms, D Coefficient quantifies the probability of two individuals collected at random belonging to the same species; that is, the Simpson coefficient is mainly influenced by the occurrence of abundant species by the number of individuals (Concenço et al, 2016).…”

Weeds in a Sugar Cane Soil Cultivated with Crotalaria juncea

“…All the plants included in the tables were collected, taken to the CSAT Herbarium for subsequent identification of their taxonomic identity by consulting specialized bibliography (Castillo-Campos, 1978-2015, Flora del Bajío y de Regiones Adyacentes ("Flora of Bajío and Adjacent Regions") (Rzedowski y Rzedowski, 1991-2015, Flora del valle de México ("Flora of the Valley of Mexico"); Malezas de México ("Mexico Weeds") (Vibrans, 2012); the samples were dried in a forced circulation oven at 60°C and weighed (Sadzawka et al, 2007). The data recorded were systematized and analyzed using Microsoft® Office Excel 2007 software, and were applied to calculate the diversity indices: S, H' and E (Magurran, 1988), the following components of the importance value index (IVI) of weeds: Density (De), Frequency (Fr), Dominance (Do) and their relative values (rDe, rFr y rDo) (Gámez-López et al, 2011;Concenço et al, 2016) were also determined by using the formulae: The dry weight of all weeds was analyzed according to a randomized complete block design, with five treatments and four repetitions each. The analysis of the variance was performed using the Statistica 2003 software and a Tukey's multiple comparison test was applied.…”