Spatial Dynamics Analysis of Weeds and Their Impact on Yield and Yield Components of Lentils (Lens culinaris) During the Growing Season

Background and objectives: Lentil (Lens culinaris Med.) is one of the important and nutritious legumes cultivated in many countries around the world. This plant is significant in human and animal nutrition. One of the major challenges in lentil production is the presence of weeds, which can negatively affect its growth and performance. Weeds compete for water, light, and nutrients, leading to a significant reduction in lentil yield. Research has shown that increased weed density results in decreased biomass and establishment ability of plants during the growing season. Understanding the spatial dynamics of weeds and their distribution in fields can help farmers adopt more effective strategies for weed control and increase lentil yield. This study aimed to investigate the impacts of weeds on the yield and yield components of lentil throughout the growing season, as well as to analyze their spatial relationships.
Materials and Methods: This research was conducted during the 2017 growth season in a lentil field located at the Faculty of Agriculture and Natural Resources, Razi University, Kermanshah. In this study, weed infestation was classified into six categories: less than 10%, 10% to 20%, 20% to 30%, 30% to 40%, 40% to 50%, and more than 50%. Sampling was conducted at five different phonological stages from the six-leaf stage until just before harvest. The examined traits included weed density and dry biomass, as well as dry biomass of lentils throughout the growing season, along with seed number, seed weight, pod number, pod weight, and thousand-seed weight. To identify the most sensitive growth stages of lentils to weed presence, stepwise regression analysis was employed. Additionally, the distribution of weeds and lentils as well as their spatial correlation were analyzed using ArcMap software.
Results: The findings revealed that the most significant effects of weeds were noted during the initial sampling period (25 days after emergence, coinciding with plant establishment) and the fourth sampling period (60 days after germination, coinciding with pod formation and seed filling). Specifically, for each gram per square meter of dry weed biomass recorded in the first sampling stage, there was a corresponding decrease of 0.5 g in seed weight and 1.61 g in the dry biomass of lentils per square meter. In the fourth sampling stage, this relationship changed slightly, with a reduction of 0.1 g in seed weight and 0.42 g in lentil dry biomass for every gram per square meter of dry weed biomass. Additionally, the strongest spatial correlations between lentil characteristics and dry weed biomass were observed during both the first and fourth sampling stages. In the first sampling stage, the spatial correlations for weed dry biomass with pod number, pod weight, seed number, seed weight, and lentil dry biomass were -74.6%, -73.3%, -72.4%, -73.5%, and -74.5%, respectively. In the fourth sampling stage, these correlations were -75.3%, -78.0%, -71.9%, -73.3%, and -71.0%. This indicates high competition and adverse effects of weeds on lentil traits during these two growth stages.
Conclusion: The findings from this study underscore the importance of effective weed management during critical growth stages of lentils. Identifying sensitive growth stages relative to weed presence and utilizing spatial mapping for implementing location-based management strategies can lead to increased crop yield. Thus, adopting timely and location-based management strategies for identifying high-density areas at risk for weed control is essential and can assist farmers in making better decisions regarding weed management.