Abstract
Levels of weed infestation can be inferred from climate information since every species requires specific conditions for its germination process. This study aimed to evaluate weed species and their emergence flow in hilly areas, when subjected to different environmental conditions of temperature and luminosity. Two experiments were carried out in a completely randomized design with four replications. In the first experiment, treatments used plastic films (no film; film just on top; partially closed film; and fully closed film), whereas the second experiment used black polyethylene covers (0; 35; 50; and 80%). Weed emergence in the area was monitored daily, until the establishment of the emergence flow. Soil temperature, solar radiation interception and soil moisture were also monitored. For the analysis of species subjected to every type and level of covers, phytosociological parameters and the emergence speed index were calculated. Data were submitted to analysis of covariance and, when they were significant, the Tukey test (p ≤ 0.05) was applied. A hierarchical cluster analysis was performed to relate factors and experimental levels to distribution intervals of climate covariates. Increase of 8.5°C in soil temperature favors the emergence of crabgrass, while reducing the emergence of alexander grass, morning glory, beggartick and sida. The main species that adapted to decrease in temperature and solar radiation are sida, alexander grass and crab grass. Besides, decrease in radiation increases the number of magnoliopsida species and enables all species to establish faster.
Highlights
Since weed emergence takes place in different periods in agricultural areas, loss of control and consequent loss of productivity due to competition can happen
Knowledge of issues related to the emergence flow, causes of dormancy and environmental factors involved in weed germination helps to choose management practices (WERLE et al, 2014a)
Water influences weed germination since it is part of molecular structures, such as proteins and nucleic acids, besides lipids and carbohydrates; as a result, water is responsible for restrictions on the species growth and development (TAIZ et al, 2017)
Summary
Since weed emergence takes place in different periods in agricultural areas, loss of control and consequent loss of productivity due to competition can happen. Many weeds reach their reproductive stages, renew their seedbanks and, as a result, ensure their permanence in a certain area (WERLE et al, 2014a). The seedbank and vegetative propagules in the soil constitute the main sources of weed regeneration in agricultural areas which usually have high amount of seeds from several species. Knowledge of issues related to the emergence flow, causes of dormancy and environmental factors involved in weed germination helps to choose management practices (WERLE et al, 2014a). Germination of weed seeds is regulated by the interaction between their physiological condition and environmental ones (MONDO et al, 2010). Water influences weed germination since it is part of molecular structures, such as proteins and nucleic acids, besides lipids and carbohydrates; as a result, water is responsible for restrictions on the species growth and development (TAIZ et al, 2017)
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