Dinâmica fitossociológica e uso do tempo térmico na predição da emergência de plantas daninhas em sistemas agroecológico e convencional

Abstract

The long-term phytosociological survey of weeds provided reliable parameters regarding population diversity in agricultural systems, aiding in the assessment of the impact of management practices on species selection. Therefore, this study aimed to evaluate and monitor the dynamics of the weed community in agroecological and conventional cropping systems. Five areas under agroecological management and one area under conventional management were evaluated at the experimental station of Unioeste, in Entre Rios do Oeste, Paraná. In each area, 20 fixed and georeferenced sampling points were established. Weed emergence was monitored weekly until crop canopy closure. At each point, a 0.25m² metal frame was used to delimit the area for weed counting. Frequency (FRE), abundance (ABU), plant density (DEN), and the importance value index (IVI) were calculated. To determine thermal parameters, germination tests were conducted under nine temperature regimes. Based on the data, emergence prediction was calculated. A total of 46 weed species belonging to 15 families were identified, with Poaceae being the most significant. The highest weed species diversity was found in system E, with 36 species. Agroecological system areas with green cover (A, C, D, and E) showed a reduction in weed emergence compared to the area without cover (B). Prediction models were successfully developed for Gamochaeta coarctata, Conyza canadensis, and Bidens subalternans. However, the thermal model failed to accurately predict the emergence dynamics of weed species. This implies that the thermal time model is not effective in predicting weed emergence when there is high variability among collected data. This highlights the need to refine the approach and incorporate additional variables to improve model accuracy. The variability in emergence over the years is directly related to fluctuations in recorded temperatures during the periods. Additionally, the influence of the seed bank present in the areas may have also contributed to the variability in weed emergence.