The fate of weed seeds in the soil has been an area of much research in recent years. Most studies have focused on the seeds that successfully produce seedlings since these are the seeds that cause immediate problems for farmers. In most studies, annual emergence typically accounts for 1 to 30% of the weed seed in the soil. Thus, the majority of seeds found in the soil seed bank fail to produce seedlings in any given year. Now is the time to think about controlling summer annual weeds prior to seed set in cropping situations where possible. Preventing seed production is important for driving down the weed seed bank and reducing the need for weed control inputs (i.e. herbici Difference between marihuana vs cannabis vs weed seeds Cannabis vs Marihuana vs Weed Seeds Marihuana seeds (often spelt as marijuana seeds) are the main method of propagating the cannabis
Fate of weed seeds in the soil
The fate of weed seeds in the soil has been an area of much research in recent years. Most studies have focused on the seeds that successfully produce seedlings since these are the seeds that cause immediate problems for farmers. In most studies, annual emergence typically accounts for 1 to 30% of the weed seed in the soil. Thus, the majority of seeds found in the soil seed bank fail to produce seedlings in any given year. The fate of seeds that fail to germinate and emerge is poorly understood. While some of these seeds are simply dormant and will remain viable until the following year, others are lost due to decay or consumed by insects or small animals. This article will describe results of an experiment that monitored the fate of seeds for the first four years following introduction into the soil.
Methods: Seeds of velvetleaf, waterhemp, woolly cupgrass and giant foxtail were harvested from mature plants during the 1994 growing season. The seeds were cleaned and counted and then buried in the upper two inches of soil on October 21, 1994. Two thousand seeds were buried within a 3 sq ft frame to allow recovery during the course of the experiment. Weed emergence was determined by counting seedlings weekly during the growing season. Emerged seedlings were pulled by hand after counting. In the fall of each year one quarter of the soil within a frame was excavated and the remaining seeds were extracted and counted. Corn or soybeans were planted between the frames during the course of the experiment to simulate agronomic conditions.
Results: The emergence patterns of the four species were described in an earlier article (see emergence patterns). The fate of the seeds (emergence, loss or survival in soil) during the first four years after burial is shown in Figure 1. In the first year following burial waterhemp had the lowest emergence (5%) whereas greatest emergence was seen with woolly cupgrass (40%). Total emergence over the four years ranged from 300 seedlings (15% of seed) for waterhemp to 1020 seedlings (51%) for woolly cupgrass. More than three times as many seedlings emerged in the first year than in subsequent years for velvetleaf, woolly cupgrass and giant foxtail, whereas 140 waterhemp seedlings emerged in 1996 compared to only 100 in 1995.
Figure 1. Fate of seeds during the four years following burial in the upper two inches of soil. Two thousand seeds of each species were buried in the fall of 1994. The area in white represents the number of intact seeds present in the fall of each year, green represents the total number of seeds that produced seedlings during the four years, and the blue represents the total number of seeds lost. Buhler and Hartzler, 1999, USDA/ARS and ISU, Ames, IA.
Seeds of the two grass species were shorter lived than those of velvetleaf or waterhemp. At the end of the third year (1997) no grass seeds were recovered. Somewhat surprising is that waterhemp seed was more persistent than velvetleaf in this study. Velvetleaf has long been used as the example of a weed with long-lived seeds. In the fourth year of the study four times more waterhemp seedlings than velvetleaf emerged and four times more waterhemp seed than velvetleaf seed (240 vs 60) remained in the seed bank.
For all species except woolly cupgrass the majority of seeds were unaccounted for (the blue portion of the graph) in this experiment. Determining the fate of the ‘lost’ seeds is a difficult task. A seed basically is a storage organ of high energy compounds, thus they are a favorite food source of insects and other organisms. In natural settings more than 50% of seeds are consumed by animals. The importance of seed predation in agricultural fields is poorly understood, but recent studies have shown that predation can be a significant source of seed loss. Another important mechanism of seed loss likely is fatal germination. This occurs when a seed initiates germination but the seedling is killed before it becomes established. Fatal germination probably is more important with small-seeded weeds such as waterhemp and lambsquarters than with large-seeded weeds, but is poorly understood. A better understanding of the factors that influence seed losses might allow these processes to be manipulated in order to increase seed losses.
So what does this mean as far as managing weeds in Iowa. First, consider how the methods used in this experiment might influence the results. The seeds were buried in the upper two inches of soil, the zone most favorable for germination. Most long term studies investigating the persistence of seeds have buried the seeds at greater depths than used here in order to minimize germination. If the seeds were buried deeper one might expect less emergence and greater persistence since the seeds would be at a soil depth with less biological activity. If the seeds had been placed on the soil surface it is likely that there would be more predation, less emergence and shorter persistence.
The results indicate that the seed bank of giant foxtail and woolly cupgrass should be able to be depleted much quicker than that of the two broadleaves. Maintaining a high level of weed control for two years should greatly diminish populations of these weeds in future years and simplify weed management. Unfortunately, a single plant escaping control can produce more seed than was introduced to the soil in these experiments, thus the seed bank can be rapidly replenished any time weed control practices fail to provide complete control. Finally, over 50% of velvetleaf and waterhemp seed was lost in the first two years following burial. However, significant numbers of seed of these species remained four years after burial. This will make populations of these two species more stable over time than those of woolly cupgrass and giant foxtail.
Doug Buhler is a Research Agronomist at the National Soil Tilth Laboratory, USDA/ARS, Ames, IA.
Weed Seeds This Fall Means More Weeds Next Spring
Control annual weeds now in fallow areas to prevent seed set. Also, now is the time to start considering ways to manage perennials in small grain stubble.
Control weeds before seed set. Photo credit: Penn State Weed Science, D. Lingenfelter
Now is the time to think about controlling summer annual weeds prior to seed set in cropping situations where possible. Preventing seed production is important for driving down the weed seed bank and reducing the need for weed control inputs (i.e. herbicides). It is rather easy to prevent weed seed production following a cereal grain such as wheat, barley, or oats as well as some vegetable crops such as sweet corn or snap beans. Proper timing of the control practice is essential in preventing seed production. In general, below is a summary of estimated seed drop for various weed species:
- Giant foxtail: late August and peak seed rain usually occurs from late September through the month of October
- Yellow foxtail: early August and continues into late October
- Pigweed species: begin to produce mature seed by mid-August
- Lambsquarters and ragweed: generally, do not mature until the month of September
- Palmer amaranth or waterhemp: make sure to monitor them routinely over the next couple months and control any regrowth or new seedlings before they set seed. Palmer amaranth plants notoriously retain their seeds late into the summer and fall and thus seeds don’t necessarily fall to the ground upon maturity but are usually spread via the combine.
To prevent seed production, fields can be sprayed with an effective herbicide or mowed once or twice. Glyphosate is particularly effective at stopping grass growth and reproduction. The plant growth regulators (2,4-D and dicamba) would probably be a better choice for broadleaf weeds. With giant foxtail, even treating the field by mid-September can greatly reduce seed production. If seed heads are present, check suspect fields to determine how advanced flowering and seed rain are and time control practices accordingly. In alfalfa or pastures, if weeds are taller than the forage, consider running a brush-hog at a high setting to clip off the immature weed seed heads above the forage canopy. Taking the time to prevent seed production this year can make a big difference next year. About 80% of weeds next season come from weed seed this fall. For more information on weed emergence, weed seed set, and seedbank dynamics, refer to “A Practical Guide for Integrated Weed Management in Mid-Atlantic Grain Crops.”
In addition, many perennial broadleaves are evident in these same small grain stubble fields. The challenge with perennial weeds at this time of year is the fact they are still in the vegetative and reproductive phases. Therefore, most of the plant sugars are not being significantly transported to the roots and a herbicide application now will mostly only impact the top-growth. One consideration would be to mow those fields soon to prevent seed production and allow regrowth to occur. Then apply an effective systemic herbicide (ie, glyphosate, 2,4-D, dicamba) in late September or early October so the herbicide will be transported to the roots for more effective control.
Difference between marihuana vs cannabis vs weed seeds
Cannabis vs Marihuana vs Weed Seeds
Marihuana seeds (often spelt as marijuana seeds) are the main method of propagating the cannabis plant, although many private growers often distribute cuttings of prized strains. However many growers claim that they achieve the best results when growing from seed.
Marihuana seeds are produced when pollen from the male plants fertilises the female plants initiating the female plant to produce seeds. Marihuana seeds can then be planted and will themselves grow into mature cannabis plants allowing the reproductive cycle to repeat itself. The seeds will remain viable for a few years, and when stored in cool/dry conditions (such as a refrigerator) marihuana seeds will remain viable for many years though the germination rates will decrease over time.
In the 1980’s the Dutch cannabis industry took cannabis breeding and seed supply to new levels of professionalism and excellence. Dutch Passion were one of the first companies to begin expert cannabis breeding programs using qualified biologists and geneticists.
Only the best cannabis genetics from around the world were used in these specialised breeding programs. The result for companies such as Dutch Passion was the creation of marihuana seeds that gave new levels of quality and consistency in the final strains.
Marihuana seeds normally produce roughly equal numbers of male and female offspring. However Dutch Passion was able to stun the cannabis world in the 1990’s when they began selling feminised marihuana seed technology. These new feminised seeds gave rise to 95%+ female plants, this had been a dream of cannabis growers for many years but was widely believed to be technically impossible. Today, feminised marihuana seeds are now more popular than traditional seeds as they allow the grower to produce only the desired female plants.
The widespread availability of high quality marihuana seeds allowed an explosion of small- scale growing. Cannabis supply was no longer a battle between large foreign export gangs and government border control guards. Cannabis supply was domesticated and many small growers could produce their own personal supply simply by purchasing marihuana seeds of their favourite varieties which could be grown outside, in greenhouses or indoors under grow lights.
Growing your own cannabis had just become easy, convenient and highly satisfying. Just a small amount of knowledge was needed to get the best results. Cannabis is not difficult to grow, it has adapted to many different growing conditions and is not called ‘weed’ without reason. It can grow just about anywhere.
What Are Weed Seeds
Weed seeds is a street name for cannabis (or marijuana) seeds. They are natures method of allowing the cannabis plant to be spread around the environment and regrow.
Weeds seeds can be legally bought and sold in certain regions e.g. large sections of Europe but remain illegal in other areas. Over the last 2-3 decades many professional weed breeders have dedicated their expertise to breeding the best yielding and most potent weed varieties they can. The seeds from these prize strains can then be distributed to head shops and growers around the world.
One result of the trade in weed seeds has been the incredible enrichment in the genetic diversity of cannabis. Rare Cannabis indica genetics from in accessible Himalayan valleys have now found their way into back gardens and greenhouses all over the world.
Exceptional Cannabis sativa genetics from the deepest Thai jungles have made their way to growrooms and greenhouses in Canada and Scandinavia. Sometimes these strains retain their purebred characteristics, and other times the strains have been carefully and painstakingly crossbred with other varieties creating precious new weed strains.
Dutch Passion, as one of the very first companies to start selling weed seeds in the 1980’s, have played an important role in the preservation and diversification of cannabis.
Weed seeds of different varieties may have subtle differences in appearance, but they all perform the same job. The seeds will swell in moist conditions during germination and over the period of a few days a seedling will emerge complete with roots and a first pair of leaves. Weed seeds can be germinated and grown in soil or any number of modern alternatives such as coco fibre, clay pellets, glass wool etc. Growing great weed these days is not at all difficult. Good light levels are needed for respectable yields, along with a suitable growing medium with enough nutrients and water. But the first job for any potential grower is finding a seed supplier that has the experience and know-how to equip you with the best weed seeds that nature can provide. Dutch Passions advice is to get the best seeds you can, start with quality genetics from a trusted source.
Thanks to professional breeders, the choice of varieties has never been greater but the choice can sometimes seem confusing. The cheapest weed seed suppliers are rarely the best, but if you are looking for great quality at an affordable price then Dutch Passion recommend you take a look at their seed collection.
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