One of the most important yet often overlooked weed control tactics is to lower the quantity of weed seeds present in the field, so limiting the potential weed populations during crop production and hence reducing the risk of weed infestation. This is accomplished by the careful management.
In agriculture, You can buy weed seeds from a collection of viable seed’s bank present on the soil surface and dispersed throughout the soil profile. Both young weed seeds that have recently shed their skins and older weed seeds that have remained in the soil from past years make up this population.
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Soil’s Weed Contains
The soil’s weed seed contains the tubers, bulbs, rhizomes, and other vegetative structures that some of our most problematic perennial weeds use to perpetuate themselves, as well as the seeds that they produce. Weed is defined in the following discussion as the sum of viable weed seeds and vegetative propagules that are present in the soil and so contribute to weed pressure in future crops and is defined as follows.
Agricultural soils can contain thousands of weed seeds and a dozen or more vegetative weed propagules per square foot, as well as thousands of weed seeds and vegetative weed propagules.
The seed serves as a physical record of past cropping system successes and failures, and knowledge of its contents (including its size and species composition) can assist producers in anticipating and mitigating the potential negative effects of the crop–weed competition on crop yield and quality.
Weed Management
To make future weed management easier, removing “deposits” to the weed seed (also known as seed rain) is the most effective strategy available. When weeds were not permitted to generate seeds over five years in Nebraska, the density of broadleaf and grass weed seed was decreased to 5 percent of their initial density. While weeds were not controlled until the sixth year, the seed bank density grew to 90% of its previous level by the seventh year (Burnside et al., 1986).
Weed seed banks are especially important in organic farming systems, which rely on cultivation as a primary form of weed management to maintain crop productivity. Weed seedlings are normally killed in a predetermined proportion of the total number of seedlings present during a cultivation pass.
Surviving Cultivation
Therefore, a high initial population will result in a high density of weeds surviving cultivation and competing with the crop. Consequently, successful cultivation-based weed management necessitates a low seed bank density or numerous cultivations passes to achieve adequate weed control.
Decreased efficacy of cultivation equipment while dealing with thick weed stands (for example, a “sod” of smooth crabgrass or other grass weed seedlings) can be caused by the presence of dense weed stands.
Cultivation Equipment
Cultivation efficacy (weed kill) can vary significantly depending on the equipment used, the soil conditions, the stage of the plant’s growth, and the operator’s experience. Eighty percent mortality would be considered pretty respectable, and it would represent a degree of weed control that is significantly lower than that achieved with the majority of herbicides.
As a result, in the absence of the “great hammer” of selective herbicides to eradicate large weed populations from standing crops, organic farmers must take effective techniques to reduce seed banks to remain profitable.
Viable Seeds
It takes time for the number of viable seeds remaining from a given year’s weed seed return to diminish due to germination (whether successful or fatal), predation, and degradation to be depleted. When a proportion of the original number remains, the percentage decreases in an essentially exponential fashion, comparable to the decay curve of a radioactive chemical element the time required for the number to reduce by 50% is approximately the same regardless of the initial amount.
It is important to note that the half-life of weed seeds varies greatly from species to species. For example, hairy galinoga and some annual grass weeds (such as foxtail species) have a half-life of one to several years, whereas curly dock and common lambs quarters seed have more than 50 years.
Longevity Of Weeds
The seed longevity of agricultural weeds has gained notoriety in recent years. A proportion of the population may be viable for several years or decades after being dispersed from the parent plant. However, most weed seeds germinate or die within a few weeks of being dispersed from the parent plant.
Many types of grass produce seeds that are only viable for a brief period. One such experiment was carried out in field research near Bozeman, Montana, where wild oat seeds were mixed into the top four inches of a wheat-fallow field, and nearly 80% of them died during the first winter . Nonetheless, it is vital to notice that post dispersal survival differs significantly among weed species.
One method to assess a field’s weed bank involves waiting and watching to see which weeds develop during the first growing season. However, knowing something about the seed bank content before the season begins can assist the farmer in preventing significant weed issues before they arise on their land. In 2004, Davis (2004) advised the following straightforward approach for scouting the seed bank:
Final Thought
A little time and effort spent knowing your seed bank will provide you with valuable knowledge about the kind of weeds to expect in a given growing season, the density of weeds, and the time of year when the majority of weed germination will occur.
You may germinate weeds indoors while you’re waiting to plant and get your seeds from i49. The months of March and April are ideal for sampling weed seed banks for annual summer weeds such as velvetleaf, foxtail, lambs quarters, and pigweed, which are common in the North Central region.
Take 20 soil samples in a ‘W’ pattern from the field you’re interested in using a soil probe or a garden trowel to a depth of 2″ using the tools listed above. Place the dirt in a pie dish and place it in a warm place (above 65 degrees Fahrenheit) while keeping it moist. Within one to two weeks, you should have a good sense of the kind of weeds that will be developing in your field when the soil begins to heat up.
