Will Weeds Be Eternal?
Latvian Council of Science funded Fundamental and Applied Research program project "Characterization and dynamics of seed-associated microbiome in weed soil seed-bank" provides new insights into the impact of microbiomes on the degradation of weed seeds, potentially offering solutions for weed control and sustainable soil management. Project manager Jevgenija Ņečajeva, a leading researcher at the Latvia University of Life Sciences and Technologies, notes that such research advances the agricultural sector and addresses problems associated with weed proliferation and seed persistence in the soil, which often cause troubles for farmers.
Weeds – A Farmer’s Headache
Weeds, these resilient invaders of gardens and fields, seem to appear out of nowhere. In reality, they lie hidden beneath the soil surface, where weed seeds can persist for years—a phenomenon known as the soil seed bank. Farmers may think weeds have been eradicated, but under favorable conditions, they reemerge the next year, competing with crops. This study delves into the viability of weed seeds - wild oats (Avena fatua) and barnyard grass (Echinochloa crus-galli) - and investigates the factors affecting their survival and germination. These two weed species are particularly problematic as they significantly reduce crop yields, reproduce quickly, spread through various means, and negatively impact harvests.
Microorganisms – A Hope to Eradicate Weeds
Project manager Jevgenija Ņečajeva highlights that a key factor influencing the viability of weed seeds is the microbial community in the soil. These microscopic organisms, primarily bacteria and fungi, can degrade seed coats and reduce seed viability. The study, conducted with partners from the Latvian Biomedical Research and Study Center, examined these microbial communities in both soil and seeds. "This study aimed to understand the interactions between weed seeds and soil microorganisms, providing valuable insights into the causes of weed seed degradation," Jevgenija explains. Researchers preserve these microorganisms in the Latvian Microorganism Culture Collection, storing them in liquid nitrogen at -196°C. Laboratory experiments were conducted to examine how specific microorganisms impact weed seed viability. "In this study, we explored the fundamental aspects that influence weed seeds to potentially develop a product containing microorganisms capable of destroying specific weed species' seeds. Additionally, it’s crucial to investigate how these microorganisms can be cultivated under laboratory conditions for use in product manufacturing," says project researcher Anete Borodušķe.
What Else Affects Weed Viability?
To understand what impacts the viability of these weed species, it was essential to investigate external environmental factors. Soil nutrients, particularly nitrates, play a significant role in seed germination but can also influence the survival of weed seeds in the soil. High nutrient levels can stimulate germination, while low levels may delay or prevent it. Temperature and moisture are critical environmental factors affecting seed germination and survival. Specific temperature and moisture conditions are necessary for seeds to germinate. Extreme temperatures and prolonged dry periods - or conversely, soil flooding - can reduce seed viability. The depth at which the seed is buried in the soil also plays a crucial role, as deeply buried seeds are often protected from environmental factors like temperature fluctuations and herbivory but are unable to germinate. When closer to the surface, they can sprout again.
Many weed seeds also exhibit dormancy, a physiological state that prevents germination. Dormancy can result from factors such as impermeable seed coats, the presence of germination-inhibiting substances, or specific morphology of the seeds. A key goal of this study was to examine the impact of burial depth on seed viability, allowing researchers to develop strategies for reducing seed banks and controlling weed populations. By studying dormancy and conditions favorable for germination, researchers aimed to develop methods to break dormancy and induce germination at specific times.
"This understanding of how different weed species react to environmental factors can help researchers develop strategies to control soil seed banks and reduce weed populations," explains Jevgenija.
What’s Next?
Jevgenija acknowledges: "The more we learn, the more new questions arise for further research." All data from this study have been published and are accessible to other researchers and potentially to companies interested in developing products. Speaking about the benefits for farmers, Jevgenija highlights that data on seeds stored in the soil for known periods can, using mathematical models, predict how long these seeds will remain viable and when their viability will diminish entirely.
During the study, various mathematical models were developed, showing how long specific weed seeds can persist in the soil. For instance, if some seeds remain viable for ten years, while this is unwelcome news for farmers, it enables them to plan accordingly.
For example, if there is a high risk of weeds sprouting in a particular field, farmers can avoid planting crops vulnerable to these weeds.
Project researcher Anete explains that within three years, it’s impossible to bring such a study to a final product. There are research groups focusing on fundamental questions like those explored in this study. "Our research provides the foundation for subsequent studies to develop specific products for weed eradication. This is the main benefit—when foundational questions are answered, the next researcher doesn’t have to start from scratch," explains Anete.
As the global population continues to grow, so do agricultural demands, necessitating the development of sustainable weed control practices. "By combining traditional and innovative approaches, we can reduce dependence on herbicides and their negative environmental impacts," says Jevgenija. "Weed problems must be addressed, and fostering collaboration between scientists and farmers, sharing knowledge and resources, is crucial to accelerating the development of innovative weed control solutions."
The project "Characterization and dynamics of seed-associated microbiome in weed soil seed-bank" (lzp-2020/1-0163) is implemented under the Fundamental and Applied Research program and funded by the Latvian Council of Science
