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define weed seed bank

Richter et al. (2002) have reviewed the use of models to evaluate the dynamics of herbicide resistance and to develop suitable anti-resistance strategies. Herbicide resistance is impacted by a high initial frequency of resistance alleles in a population, out-breeding, dominance of inheritance, a short persistence of the seed bank in the soil, and the lack of a fitness penalty for resistant versus susceptible biotypes of a weed species, along with agronomic factors having a positive influence on weed development. The occurrence of herbicide-resistant weeds in a field usually means the loss of an effective control measure. This is particularly serious if resistance develops in species for which there are few if any effective alternatives. As a rapid increase in the development of herbicides with new modes of action is not likely, and since economic and environmental conditions often will not support cultural control measures or alternative cropping systems, it is important to manage resistance wisely in order to avoid further loss of herbicides.

Weed populations are never constant, but are in a dynamic state of flux due to changes in climate, environmental conditions, tillage, husbandry methods, use of herbicides, and other means of control. Weeds that were at one time of minor importance, but not controlled by certain broad-spectrum herbicides, have increased to become major problems. Reduction in tillage has sometimes led to the increased occurrence of perennial weeds and annual grasses, particularly of those species that readily establish near the soil surface and have relatively short periods of dormancy. Many perennials have increased in importance under minimal cultivation (e.g., field bindweed and Canada thistle). The occurrence of herbicide-resistant weed biotypes is also a phenomenon of increasing concern. Some research results show that large changes in the seedbank can impact weed control efficacy. Winkle et al. (1981) and Buhler et al. (1992) found large increases in weed densities reduced weed control with herbicides and mechanical practices.

Increased weed seed germination results in an output to the seedbank. This can be achieved, e.g., by the application of the false- and stale-seedbed techniques, i.e., the anticipated soil seedbed preparation which allows stimulation of germination and emergence of weed seedlings that are subsequently destroyed before the actual crop seeding or crop emergence takes place ( Cloutier et al., 2007 ). In the false seedbed technique seedling destruction usually occurs by harrowing or similar mechanical tools whereas in the case of the stale seedbed technique it occurs by chemical herbicides or by thermal methods (flame weeding or soil steaming), to avoid any further soil disturbance. Weed seed losses can also occur when seed germination is not followed by seedling emergence, usually because the seed is placed too deep down the soil and has not enough reserves in its endosperm to sustain seedling growth until it reaches the soil surface and becomes autotroph. This phenomenon is referred to as “fatal germination” ( Fenner and Thompson, 2005 ).

Weeds Resistant to Nontriazine Classes of Herbicides

In terms of the linkage between weed seed rain and in-crop weed populations, Gallandt et al. (2010) found that by preventing weed seed rain they could reduce subsequent years' weed seedbanks compared with other autumn treatments between 45% and 93% and weed seedling densities by 23% to 90%. In Western Australia preventing the seed rain of annual ryegrass ( Lolium rigidum) reduced in-crop ryegrass emergence by 90% in 4 years ( Walsh et al., 2013 ). Another perspective is illustrated by a study by Rahman et al. (1998) whereby they tilled soil monthly for 4 years, achieving an exponential decline in the weed seed bank, represented by four weed species, both monocotyledons and dicotyledons ( Fig. 5.10 ).

Müller-Schärer et al. (2000) reviewed the progress made during 1994–1999 by 25 institutions within 16 European countries on biological weed control. These efforts were aimed at control of major weed species, including common lambsquarters, common groundsel, and species of pigweed, broomrape and bindweed in major crops, including corn and sugar beet. No practical control has yet been reached for any of the five target weeds, however, the authors concluded that potential solutions have been identified.

To illustrate the direct relationship between the weed seedbank and in-crop weeds, a study by Rahman et al. (1996) studying the number of emerged weeds vs. the number of viable weed seeds in the soil found a clear, almost one-to-one relationship ( Fig. 5.9 ). Clearly, the larger the weed seedbank, the larger the population of in-crop weeds.

Changes in weed species and populations also cause changes in plant diseases and insect pests since certain weeds serve as their hosts ( Bendixen et al., 1981 ; Manuel et al., 1982 ; Weidemann and TeBeese, 1990 ; Norris and Kogan, 2000) . Herbicide-resistant weed biotypes are present in our weed populations, although often at very low frequencies, even when herbicides are not used. Weed species have acquired built-in genetic adaptability to survive most control methods used against them. For example, dandelions usually develop a vertical growth habit when growing wild, but when growing in a frequently mowed lawn, more prostrate or flat-growing biotypes evolve. We should continually add to our weed control technology and keep tools available in order to address the adaptability of weeds to different control methods. For further information on the biological characteristics of weeds, including growth strategies, mimicry with crops, plasticity of weed growth, photosynthetic pathways, weed seed reservoir, and vegetative reproduction see Cousens and Mortimer (1995) and Buhler et al. (1998) .

Seed feminization is even more important, particularly for growers. Only female plants grow buds – male plants may have trace amounts of THC in their leaves, but they produce pollen, instead of THC-laden buds. Therefore, growers should focus primarily on growing female plants.

A marijuana seed bank is not just another grower, or a seed repository. These companies are at the forefront of seed feminization and strain development. Many seed banks have created highly-popular strains known for specific benefits or effects, such as providing greater mental clarity and focus, or for higher THC content.

A marijuana seed bank is a business which specializes in not only storing and selling cannabis seeds, but also on feminizing seeds to reduce the chance of male plants developing and maximize yields for commercial and individual growers.

Maximum Yield Explains Marijuana Seed Bank

As more and more states legalize marijuana, growers big and small find that they need to locate a reliable source of cannabis seeds. Generally, this is done through a marijuana seed bank – a company that develops cannabis strains, stores seeds, and then sells those seeds to commercial and individual growers. However, there’s more to it than that.

The problem is that when left to nature, seeds tend to produce a 50/50 split between male and female plants. Growers then spend time and resources growing plants, half of which must be discarded when it becomes apparent that they are male. Seed feminization reduces the percentage of male to female seeds by a significant amount.

Finally, a marijuana seed bank can also offer growers access to auto-flowering seeds. These plants grow to maturity quickly, in as little as eight weeks. The growing process is greatly simplified, and the yield is maximized, ensuring a better return on investment for growers.