Some carabids , increased in abundance during the reproductive stages of weeds and showed low or no preference for A. gemmatalis larvae . Such behavior might suggest that those carabid species prefer to feed on weed seeds. By contrast, the populations of A. basistriata, C. granulatum, G. brasiliensis, O. nodicornis, and Scarites spp. decreased during the reproductive period of weeds and/or demonstrated high predation of A. gemmatalis larvae ; such findings suggest that those carabid species had a low preference for weed seeds. Finally, it should be emphasized that all weed species observed in the present study were only found in the edge of all five sites; however these weeds are commonly found in the interior of most Brazilian agricultural fields. Here, the weeds did not penetrate the studied fields/orchards because they were controlled by herbicides in the crop fields while the presence of spontaneous vegetation covering the soil surface of the orchards prevented the development of these plants. A decrease in crop yield or quality resulting from the interactions between weeds and crops forms the basis of modern weed science.
However, competition is one of the most debated issues in ecology . These unwanted plants are often more aggressive than existing or desired forage species and compete for light, water, and nutrients. Nimblewill is an important weed in pastures and hayfields . It is a native warmseason or C4 perennial grass that thrives in lightly shaded areas and easily invades lawns, waste areas, and other disturbed sites . In unmowed areas, nimblewill can grow to 20 – 60 cm in height; however, it is more aggressive in shaded areas with a moist, rich soil. Nimblewill spreads by seeds and has slender culms that fall to the ground and root at nodes; however, the plants do not have true rhizomes or stolons . Nimblewill is difficult to control with herbicides and poses a serious problem in pastures. The species is unpalatable to horses; thus, its presence decreases the grazing quality of bluegrass and other grass pastures. Therefore, every effort should be made to prevent the establishment of these weed grasses. However, selective control measures are often difficult. Selection of adapted turfgrass species and cultivars and the use of cultural practices are important in minimizing weed grass encroachment and competition. For the efficient management of this weed,vertical grow system it is necessary to investigate the factors contributing to its growth. Knowledge of weed biology is essential for establishing weed control strategies, and it is important to recognize the natural growth and developmental strategies of major weeds known to infest crop fields .
Weed biology is the study of plant attributes such as morphology, seed dormancy and germination, growth physiology, competitive ability, and reproductive biology.Plant growth analysis is an explanatory, holistic, and integrative approach to interpreting plant form and function. Various parameters can be used to compare species growth, including leaf area, height, branch number, and dry weight. These comparisons provide an indication of the relative size, productivity, and photosynthetic capacity of a species that may influence its competitive ability . Calculated parameters such as specific leaf area, leaf weight ratio, and leaf area ratio provide estimates of the photosynthetic area per unit of biomass. The proportion of biomass allocated to the leaves and an index of plant leafiness may reflect the ability of a species to obtain resources and compete with other plants .
A successful weed management strategy is one that is based on biology, including information on environmental factures and their effects on plant properties because plant growth requirements, characteristics, and competitive ability affect a species’ ability to survive and spread. Thus, understanding the growth and development of a species may help explain the recent success of that species. Investigating the mechanisms related to weed seedling growth rates is also important when considering weed management strategies that include the use of herbicides or cultural control measures. The main goal of this research was to evaluate the growth of Nimblewill , which poses an emerging threat to the growth of forage grass. Initially, a seedling depends on the reserves contained in its seeds and growth is slow. Following development of the root system and emergence of the leaves, rapid growth occurs due to the removal of water and nutrients from the substrate for the photosynthetic activity of the plant . Therefore, it appears that perennials invest more in biomass allocation than annuals, even at the beginning of their growth cycle.