Effective Weed Management and the Global Carbon Cycle
At a time when there is growing awareness of the role of human-induced global climate change in relation to rising atmospheric levels of carbon dioxide, farmers and agriculturists are embracing the additional benefits of sustainable organic farming. We’re starting to talk about carbon sequestration.
The burning of fossil fuels is the most common cause of excess carbon dioxide in the air. A lesser-known contribution to annual carbon dioxide pollution is deforestation and net soil organic matter loss.
All living plants, including weeds, absorb carbon dioxide from the air and convert it into plant tissue. When plants die or drop leaves, some of this sequestered carbon is returned to the atmosphere as carbon dioxide during decay, while some remains in the soil as stabilized organic matter, from which additional carbon dioxide is produced carbon is released slowly.
Management systems that result in a net decrease in soil organic matter also led to a net release of carbon dioxide, whereas systems that result in a net increase in soil organic matter sequester carbon in the soil increase.
What is the relationship with weed management? First, bare fields almost always experience a net loss of organic matter and release carbon dioxide, whereas fields covered with crops and weeds absorb carbon dioxide. Tillage activities stimulate the oxidation of organic matter and the release of carbon dioxide to some extent. The less bare soil there is in crop rotation, and the less tillage is done to control weeds, the less carbon dioxide the farm adds to the air.
Weed management measures that increase plant cover and accumulate soil organic matter have a positive impact on the global carbon budget. Research shows that organic, sustainable farms with optimal weed management can make a net contribution to addressing the global climate crisis.
Cover crops are particularly effective at sequestering carbon. Rapidly growing summer annuals such as pearl millet, sorghum Sudan grass, fodder soybeans, and sun hemp can produce 2–4 tons of biomass per hectare over a 2–3 month growth cycle (Schonbeck, 2006). Clark, 2007).
Plant biomass is about 40-45 pounds (dry weight basis), so growing one acre of these cover crops removes 25-35 pounds of carbon (or 90-130 pounds of carbon dioxide) from the atmosphere per day.
Can be removed. This matches or exceeds the carbon uptake of the most aggressive weed-fixing forests, and of course cover crops are much easier to manage! You can also “pay” for the carbon dioxide released within days as a result of grooming. Bicultural of grass and legume cover crops to maturity (flowers/panicles) maximizes the humus formed when the cover crops are returned to the soil and provides the greatest net fixing potential.
The more different the crop system is from the native vegetation of the area, the lower the diversity of the crop community, and the less the year-round soil surface coverage, the greater the gaps provided for weeds and the more labor required. Becomes larger for successful weed control (Sullivan, 2003).
For example, in the eastern United States, where natural plant communities consist of broadleaf mixed forests, even the well-managed vegetable gardens have more weeds than mature orchards with grasses and perennial undergrowth. In the Midwest, pastures of perennial grasses and legumes or hayfields mixed with multiple types of forage are likely to have fewer weeds than corn and soybean rotations which is effective for weed management.
Permaculture is an alternative food production system aimed at mimicking the local natural plant communities and ecological processes, minimizing space for pesky weeds and growing all available niches with plants that are beneficial all year round (Mollison, 1988). Permaculture emphasizes the use of perennial food-producing plants such as: B. Fruits and nuts on trees and shrubs, desired annual vegetables mixed with perennials or grown in relatively small beds.
Agroforestry is the practice of integrating tree crops (fruits, nuts, timber, and wildlife habitat) with meadows or hayfields to simulate sub humid savannah ecosystems. Traditional vegetable garden systems in Mexico and other developing countries include trees, shrubs, grasses, vegetables, and herbs that provide variety for food, feed, and even medicine, and leave room for harmful weeds to grow.
Permaculture approaches may be impractical on farms with primary crops of annual vegetables that require a prepared nursery for establishment. However, the grower can close off some weed niches through preventive measures based on an ecological understanding of weed–crop interactions.
A diverse crop rotation tends to grow fewer weeds than continuous corn or other monoculture for weed management. Cover crops, mulches, high density crop planting, reduced or strip till, intercropping, and relay cropping all reduce the “window of opportunity” for troublesome weeds (Yandoc et al., 2004).
Two permaculture concepts that are relevant to annual cropping systems are multifunctional components (i.e., components that perform several functions at once), and the use of multiple tactics to accomplish a particular objective.
Cover crops that protect and restore soil, harbor desirable insects, and suppress weeds are an example of a multifunctional component. Cover crops, livestock grazing, and timely cultivation to tackle problem weed management.
Imported Weeds and Invasive Exotic Plant Species:
Many of the most problematic weeds in a region are weeds that are not native to that region or continent. that these exotic plant species grow more vigorously in their new habitats than in their original habitats where specific soil organisms, herbivorous insects, climate patterns, and/or competing vegetation constrain them; Kudzu (Pueraria thunbergiana)
However, a tiny (4- to 18-inch) perennial weed called purple nut sedge (Cyprus rotundas), which has invaded the southern United States, causes much greater losses to crops (even sugarcane and coffee trees), making it one of the worst crops in the world considered a weed (Holm et al., 1991).
Some of the most important agricultural weeds were intentionally brought into the United States from abroad to provide food and fodder. European settlers brought common lamb quarters (Chenopodium album) to the New World as an important source of early season vegetables that prevented scurvy and other deficiencies.
Lamb quarter has spread all over the world and is currently listed as the 10th worst agricultural weed in the world bad weeds) and quaggrass (Elytrigia repens, an important weed in vegetable crops in the northeastern United States) were imported into the country as forage.
Other serious invasive weeds were first planted as flowers and other ornamental plants and then spread from cultivated gardens to surrounding agricultural lands and natural ecosystems. Food, bedding plants, or other substances may be accidentally introduced as seed contamination.
Many exotic weeds have become “naturalized” over time, and are now part of a region’s agricultural weed flora that must be managed (not necessarily eradicated) to protect crop yields. However, some newly introduced plants growing in the absence of the natural enemies with which they evolved may spread unchecked, choking out native vegetation as well as invading pastures or cultivated fields.
Imported weeds that threaten natural ecosystems and/or rangeland over wide geographic areas are designated invasive exotic plant species or invasive exotic weeds, and often become the focus of regional or nationwide coordinated eradication efforts.
Examples include water hyacinth (Eichhornia crassipes) and purple loosestrife (Lythrum salicaria) in wetlands; Canada thistle (Cirsium arvense), musk thistle (Carduus nutans), spotted knapweed (Centaurea maculosa), and St. Johnswort (Hypercom perforatum) in rangeland; and autumn olive (Elaegnus umbellate) and tree-of-heaven (Ailanthus altissimus) in eastern deciduous woodlands.
Classical biological control—the introduction of herbivorous insects or microbial pathogens that are natural enemies of these weeds in their native lands—has been used with considerable success to combat some invasive exotic weeds.
The arrival of new invasive alien weeds on organic farms is an example that may justify efforts to eradicate the new invasion. Early detection combined with understanding weed biology is critical for successful intruder elimination.