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p>The seed bank is the resting place of weed seeds and is an important component of the life cycle of weeds. Seed banks are the sole source of future weed populations of the weed species both annuals and perennials that reproduce only by seeds. For this reason, understanding fate of seeds in the seed bank can be an important component of overall weed control. When weed seeds enter the seed bank, several factors influence the duration for which seeds persist. Seeds can sense the surrounding environment in the seed bank and use these stimuli to become dormant or initiate germination. Soil and crop management practices can directly influence the environment of seeds in the soil weed seed bank and can thus be used to manage seed longevity and germination behavior of weed seeds. J. Bangladesh Agril. Univ. 13(2): 221-228, December 2015</p
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J. Bangladesh Agril. Univ. 13(2): 221–228, 2015 ISSN 1810-3030
Soil weed seed bank: Importance and management for sustainable
crop production- A Review
M. M. Hossain* and M. Begum
Department of Agronomy, Bangladesh Agricultural University, Mymensigh-2202, Bangladesh
*Email: mmhshakil@yahoo.com
Abstract
The seed bank is the resting place of weed seeds and is an important component of the life cycle of weeds. Seed
banks are the sole source of future weed populations of the weed species both annuals and perennials that
reproduce only by seeds. For this reason, understanding fate of seeds in the seed bank can be an important
component of overall weed control. When weed seeds enter the seed bank, several factors influence the duration for
which seeds persist. Seeds can sense the surrounding environment in the seed bank and use these stimuli to
become dormant or initiate germination. Soil and crop management practices can directly influence the environment
of seeds in the soil weed seed bank and can thus be used to manage seed longevity and germination behavior of
weed seeds.
Keywords: Weed seed bank, Deposit, Distribution, Withdrawal
Introduction
The weed seed bank is the reserve of viable weed seeds present on the soil surface and scattered
throughout the soil profile (Singh et al., 2012; Begum et al., 2006). It consists of both new weed seeds
recently shed, and older seeds that have persisted in the soil from previous years. In practice, the soil’s
weed seed bank also includes the tubers, bulbs, rhizomes, and other vegetative structures through which
some of our most serious perennial weeds propagate themselves. Agricultural soils can contain
thousands of weed seeds and a dozen or more vegetative weed propagules per square foot (Menalled,
2013).
The weed seed bank serves as a physical history of the past successes and failures of cropping systems,
and knowledge of its content (size and species composition) can help producers both anticipate and
ameliorate potential impacts of crop weed competition on crop yield and quality. Eliminating “deposits” to
the weed seed bank also called seed rain-is the best approach to ease future weed management
(Menalled, 2008).
Weed seed banks are particularly critical in farming systems, which rely on cultivation as a primary means
of weed control. Because a cultivation pass generally kills a fixed proportion of weed seedlings present, a
high initial population will result in a high density of weeds surviving cultivation and competing with the
crop. Initial weed population is directly related to the density of seeds in the seed bank (Brainardet al.,
2008; Teasdale et al., 2004); thus, effective cultivation-based weed control requires either a low seed
bank density (Forcella et al., 2003) or multiple cultivation passes to achieve adequate weed control.
Types of seed bank
This review focuses on soil seed banks which are the most common and important in agricultural
systems, although aerial seed banks also exist. Aerial seed banks are those where the seeds remain on
the mother plant for some time after maturation allowing for more dispersal strategies. Some of these
strategies includes dispersal by weeds seeds clinging to the fur of animals (e.g. Arctium minus Bernh and
Xanthium strumarium L.) or relying on passage through the digestive tract as is the case for many fruit
bearing shrubs and trees, or shake off the mother plant as it is blown away from its point of origin by wind
(e.g., Kochiascoparia L.). Aerial seed banks tend to be of greater importance in pasture, orchard, or
natural settings than in agricultural fields (Gulden and Shirtliffe, 2009).
222 Importance and management for sustainable crop production
Soil seed banks are typically characterized by their longevity and are determined by how long an
individual seed may reside within it in a viable state. This longevity depends primarily on plant species.
Transient seed banks are those where seeds only survive for a short time in the seed bank (no more than
a couple of years) as is the case with Kochiascoparia (L.) and Taraxacumofficinale (Weber). Seed banks
of these species require almost annual renewal, while other species such as Amaranthusretroflexus (L.)
and Chenopodium album (L.) form a persistent seed bank with the ability to remain viable in the soil for
many decades. It is important to understand the seed bank characteristics of a species as these provide
clues to choose appropriate practices to manage the seed banks.
Purpose of seed bank
Weed seeds are an important component of the weed life cycle as they are the origin of future
populations, and are particularly important in annual and simple perennial species like
Taraxacumofficinale Weber which reproduce by seed only (Gulden and Shirtliffe, 2009). As a rule,
perennial species usually rely on seeds to establish new colonies some distance away from the mother
plant. Around the mother plant, colony expansion is the result of vegetative reproduction. Seed banks
serve many purposes. They allow species such as annual weeds to survive the harsh environmental
conditions of winter. They enhance the survival of a species by buffering against harsh environmental
conditions or highly effective control methods and allowing them to germinate over a period of many
years. This ability slows the genetic shift of a weed population exposed to intense selection pressures by
ensuring that all the seedlings that germinate in any one year are not all from similar genetic backgrounds
(Gulden and Shirtliffe, 2009).
Fate of weed seeds in the seed bank
Weed seeds can have numerous fates after they are dispersed into a field (Fig. 1). Of the many seeds in
the seed bank, very few will actually emerge and produce a plant. Most seeds will die, decompose or be
eaten before ever germinating. Of those that do germinate, some will die before a mature plant is
produced (Menalled, 2013). Seed predation is typically greatest when weed seeds remain on the surface
and there is sufficient residue cover for predators (i.e. no-till). Generalist predators such as common
ground beetles or crickets can reduce weed seed emergence by 5 to 15%(White et al., 2007). Larger
animals such as rodents and birds can also consume significant amounts of weed seeds.
Fig. 1. Fate of weed seeds. Inputs to the seed bank are shown with black arrows and losses with white arrows
(Source: Menalled, 2013).
Hossain and Begum 223
When buried and not available to predators, attack by pathogens is more common. Mortality of
Avenafatua (L.) seed increased as soil moisture content increased from 6 to 24% with maximum mortality
values reaching 55 and 88% after two years of the study (Mickelson and Grey, 2006). The attack of the A.
fatua seeds by soil pathogens was suspected to be the main reason for increase in seed mortality with
higher soil moisture contents. With Setariaviridis seeds less than 1% of seeds buried in bags were viable
after six years(Thomas et al., 1986).
Two other mechanisms of seed mortality in the seed bank are lethal germination and desiccation. Lethal
germination occurs when seeds germinate from a deep depth and seedlings exhaust their seed reserves
and die before reaching the soil surface. Many weed seeds such as Kochiascoparia (L.) can sense their
depth of burial to limit lethal germination. Seed desiccation is also another important mechanism where
extreme environmental conditions in summer and winter. Dry seeds by design are very resistant to
desiccation and can remain viable for up to 2000 years. However, desiccation tolerance is lost quickly
when seeds are subjected to frequent and short-term wetting and drying conditions before germination is
complete. The end result is higher seed mortality (Gulden and Shirtliffe, 2009).
Seed dormancy
Seed dormancy prevents germination during conditions that would otherwise be ideal for germination.
Most weed seeds are dormant at the time of maturity which is referred to as primary dormancy. However,
seeds can cycle in and out of a dormant state because of environmental conditions. This process is
referred to as secondary dormancy and regulates seasonal germination in weed seeds (Baskin and
Baskin, 1998). Secondary seed dormancy prevents germination at a time of year when the life cycle of a
plant could not be completed and this ensures that summer annual species germinate primarily in the
spring and winter annual weeds germinate primarily in the fall. This process is regulated by seasonal
changes in soil temperatures. For most summer annual weeds that germinate in the spring, the cold of
winter will break dormancy and allow the seed to germinate in the spring. On the other hand, winter
annual weeds such as stinkweed and shepherd’s purse require the heat of summer to break dormancy.
This allows them to germinate in the early fall and form a rosette before winter.
Types of seed dormancy
Seed dormancy is controlled by several mechanisms. An immature embryo at the time of seed maturation
will not allow germination. This is a form of primary dormancy and occurs in A. fatua (Gulden and
Shirtliffe, 2009). A period of ‘after ripening’ is required before seeds are able to germinate. Another
mechanism for seed dormancy is physical dormancy where a hard seed coat prevents uptake of water.
This is an important mechanism for extended persistence in the soil seed bank. Weed families with high
levels of seeds with impermeable coats include the pea family e.g., Abutilon thoephrasti (L.) and
members of the goosefoot family such as Chenopodium album (L.). Seeds from these species can readily
survive several decades in the soil seed bank (Radosevich et al., 1997). Finally, seed dormancy may also
be due to physiological changes. This is the mechanism for secondary or cyclical seed dormancy and this
mechanism is regulated by many factors (Baskin and Baskin, 1998).
Secondary seed dormancy is controlled by factors like temperature, light, oxygen, and certain bio-
chemicals. Light and temperature are capable of both inducing and breaking secondary seed dormancy
(Gulden et al., 2003) Light quality and temperature also convey information about the presence of other
plants and the burial depth of weed seeds. In small seeded species like A. retroflexus, a flash of white
light (as faint as full moon light) is often sufficient in breaking seed dormancy as the seed is close to the
surface. This is one mechanism by which day-time cultivation increases seed germination. In other
species such as A. fatua for example, high levels of white light prevent germination as this indicates that
the seed is not buried sufficiently deep for optimum seedling establishment. Light only penetrates a few
millimeters into the soil profile. In some small seeded species, the fluctuations in daily temperature which
decrease into the soil profile provide an indication of depth of burial. Temperature variations are
particularly important in small seeded weeds that can emerge successfully only from shallow depths. Low
oxygen concentrations are also indicative of burial depth and induce seed dormancy in many species. In
addition, there are also a number of chemicals that remove seed dormancy. Most notably, nitrate nitrogen
224 Importance and management for sustainable crop production
and some chemicals that are found in smoke. When these chemical signals are released by dead
vegetation and during a fire, they indicate niche availability. In the 1960s research was conducted that
attempted to regulate germination in the wild by adding nitrate-nitrogen fertilizer. The idea was that
nitrate-nitrogen added to the soil would cause wild oat seeds to germinate which could then be killed with
a tillage operation (Sexsmith and Piman, 1967). Ultimately this technique failed because of the large
amount of nitrate nitrogen fertilizer required and the inconsistency of the effect. The plant hormone
gibberellic acid also removes seed dormancy and this compound has been used to induce germination in
dormant volunteer canola (Brassica napusL.) seed in soil in the greenhouse with some success(Thornton
et al., 1998); however, the high cost of producing this compound make this method unpractical under field
situations.
Dormancy is a complex mechanism that controls when a seed will germinate. However, seed dormancy
characteristics and the persistence of the seed in the seed bank (Table 1) are not always related
(Thompson et al., 2003). One reason for this is that seed dormancy can only regulate germination when
the conditions necessary for germination are present. In many cases, however, ideal conditions do not
exist and seeds that are not dormant cannot germinate. Although seed dormancy is an important
mechanism for most weed species, there are important weed species such as Kochia and Dandelion that
essentially possess no seed dormancy.
Table 1. Longevity of different weed species in the seed bank (Source: Conn et al., 2006)
Weed species Maximum longevity (years)
Calamagrostiscanadensis (Michx.) Beauv. 8-14
Hordeumjubatum L. 7-8
Elytrigiarepens (L.) Nevski 4-6
Avenafatua L. 4-6
Dracocephalumparviflorum Nutt. > 20*
Stellaria media (L.) Vill. > 20
Galeopsistetrahit L 2-3
Chenopodium album L. > 20
Spergulaarvensis L. 18-20
Descurainiasophia (L.) Webb ex Prantl. 16
Polygonumpensylvanicum L. 14-18
P. aviculare L. 10-14
P. convolvulus L. 6-8
Matricariamatricarioides (Less.) C.L. Porter > 20
Potentillanorvegica L. 12-14
Capsella bursa-pastoris (L.) Medicus > 20
N.B.: * about 60% of the seed were still viable after 20 years.
The actual seed longevity in the soil depends on an interaction of many factors, including intrinsic
dormancy of the seed population, depth of seed burial, frequency of disturbance, environmental
conditions (light, moisture, temperature), and biological processes such as predation, allelopathy, and
microbial attack (Davis et al., 2005; Liebman et al., 2001). Understanding how management practices or
soil conditions can modify the residence time of viable seeds can help producers minimize future weed
problems. For example, seeds of 20 weed species that were mixed into the top 6 inches of soil persisted
longer in untilled soil than in soil tilled four times annually (Mohler, 2001a), which likely reflects greater
germination losses in the disturbed treatment.
Distribution of weed seed in the seed bank
Weed seeds disperse both horizontally and vertically in the soil profile. While the horizontal distribution of
weed seeds in the seed bank generally follows the direction of crop rows, type of tillage is the main factor
determining the vertical distribution of weed seeds within the soil profile. In plowed fields, the majority of
weed seeds are buried four to six inches below the surface (Cousens and Moss, 1990). Under reduced
tillage systems such as chisel plowing, approximately 80 to 90 percent of the weed seeds are distributed
in the top four inches. In no-till fields, the majority of weed seeds remain at or near the soil surface.
Clements et al. (1996) have shown that soil texture may influence weed seed distribution in the soil profile
under these different tillage systems (Fig. 2).
Hossain and Begum 225
Fig. 2. Vertical distribution of weed seeds in a loamy sand soil (top) and a silty loam soil (bottom)
(Source: Clements et al., 1996)
Understanding the impact of management practices on the vertical distribution of seeds is important
because it can help us predict weed emergence patterns. For example, in most soils small-seeded weeds
such as Kochiascoparia (L.), Cirsiumarvense (L.), and Chenopodium album (L.) germinate at very shallow
depths (less than 0.5 inch). Large seeded weeds such as Helianthus annus (L.) have more seed reserves
and may germinate from greater depths.
Evaluating the weed seed bank
One way to estimate a field's weed seed bank is to wait and see what weeds emerge during the first
season. However, knowing something about seed bank content before the season starts can help the
farmer prevent severe weed problems before they develop. Davis (2004) recommended the following
simple procedure for scouting the weed seed bank:
A little effort in understanding weed seed bank can give valuable information about what weeds to expect
in a given growing season, weed density, and when most weed germination will take place. To get a
weed preview, germinate of weeds is the best. For summer annual weeds, March–April is a good time to
sample weed seed banks. Using a soil probe or a garden trowel, 20 samples to a 2” depth in a ‘W’ pattern
need to be collected from the field. Soil should be placed in a dish, in a warm place (> 65 º F) and kept
moist. Within one to two weeks, weed seedlings will be emerged and need to be identified (Davis, 2004).
For a more representative sampling, sufficient soil samples should be collected to fill several dishes, or
seedling flat. The larger the sample, the more closely the observed weed emergence will reflect field
weed seed bank status.
Management of weed seed bank
Soil and crop management: Reducing the input of seeds into seed bank is the most obvious way to
reduce the weed seed bank. Any method that reduces the size and number of weeds producing seed will
also reduce the number of seeds “deposited” into the seed bank. Of course, the weed seed bank can be
managed by using other methods that increase the death of the seeds in it, or encourage germination
when the weeds can then be easily controlled. Although most agronomic practices have an indirect effect
on the weed seed bank, only a few key methods directly affect weed seed input, seed bank persistence
and germination from the seed bank.
Herbicides: Herbicides have, and continue to be, the most effective weed management tool of the 20th
century. Herbicides are very effective at reducing weed populations and at the same time the number of
seeds added to the soil seed bank (Hossain et al. 2014c). Weed seed bank densities tend to be greater in
organic management systems than in systems reliant on herbicides, although this is not always the case
as other factors such as crop rotation also strongly influence weed seed production. In production
systems that use herbicides as the principal tool to manage weeds, seed bank densities are typically
226 Importance and management for sustainable crop production
between 1000 and 4000 seeds m-2 (Blackshaw et al., 2004a; Clements et al., 1996). When herbicide
tolerant crops are used extensively in cropping systems, weed seed banks will be near the low end of this
range, however, despite lower weed seed bank densities in these systems, weed seedling emergence
still remains significant in following years. Pre-harvest applications of glyphosate can decrease seed
production and impact seed viability in late flowering weeds. However, the slow action of glyphosate
means that weeds must be managed well before the plant sheds its seed near maturity.
Crop rotation: Crop rotation is also an effective means of managing the weed seed bank. Introducing
perennial crops in annual cropping systems tends to deplete the soil seed bank of annual species over
time. This method is more effective on weed species which have low levels of longevity such as kochia
and many of the grassy weeds like wild oat and green foxtail. Likewise, crop competition is also important
for decreasing weed seeds being recruited to the seed bank. Studies near Saskatoon, SK conducted in
the late 1970s showed that seed bank populations were greatest in summer fallow (about 1600 seeds m-
2) versus wheat stubble (about 500 viable seeds m-2) (Archibold, 1981). Weed seed bank additions are
high in fallow fields in part due to incomplete weed control by tillage and the absence of a competitive
crop (Archibold and Hume, 1983).
Chaff collection: Chaff collection is an effective method for reducing inputs into the weed seed bank.
Weed seeds generally weigh less than crop seeds and therefore end up in the chaff fraction which is
typically spread evenly across the field. Even for large weed seeds such as wild oat, chaff collection can
prevent upwards of 90% of the weed seed numbers added to the seed bank during the harvest operation
(Shirtliffe and Entz, 2005).
Tillage: Tillage was the main method for managing weeds, until the introduction of herbicides. The
degree of soil inversion and depth of tillage, strongly affected the vertical distribution of weed seeds in the
soil seed bank. When using a moldboard plow, 37% of the viable weed seed bank was found in the top 5
cm of the soil profile and 74% under no-till(Clements et al., 1996). Using a chisel plow resulted in 61% of
the seed near the soil surface. Deep buried seeds that remain undisturbed can persist in the soil seed
bank for decades as they avoid some of the seed viability hazards previously described. Therefore, tillage
slows the rate of turnover of the seed bank. In practical terms this could impact the rate of development of
herbicide-resistant weed populations, with a slower shift in conventional tillage situations than under no-
till. However, experimental evidence of this is lacking. Some soil inversion and burial of weed seeds
occurs during the seeding operation in no-till. Since disc openers reduce the amount of soil disturbance
compared to hoe openers, one would therefore expect a reduction in seed burial. However, a study
conducted in Saskatchewan found that the seed bank persistence of volunteer canola was similar after
three years under conventional and no-till (Gulden et al., 2004). Canola seed could only have persisted
for three years if it was buried (Liebman et al., 2001); therefore, these results suggest that even a single
pass with a low disturbance disc opener resulted in some seed burial, even in the no-till system. There
are few studies that compare the degree of seed bank burial with different types of seed openers. A study
in Manitoba showed that average seedling emergence of all weed species studied was from a greater
depth in conventional-till than no-till management (Fenner and Thompson, 2005). In general, lower weed
populations were reported by farmers that practice no-till in western Canada, which is indicative of lower
weed seed banks (Blackshaw et al., 2008). In Ontario, weed seed banks were almost two times greater
under chisel plow management compared to no-till (duCroixSissons et al., 2000).
Tillage can promote weed seed germination by several mechanisms. Soil disturbance with tillage will
expose weed seeds to a flash of light that releases seeds from dormancy. Furthermore, soil disturbance
through tillage also results in nitrogen mineralization which can promote some seed germination. To
reduce the impact of tillage on weed seed germination, tillage in the dark or using a cultivator covered
with light impermeable material has been tried but with variable success because of the inherent
variability in weed seed populations for germination. This method depends on the actual placement of the
seed after tillage and other factors such as nitrogen mineralization which can promote germination
independent of light because of the presence of high nitrate levels (Mickelson and Grey, 2006).
Hossain and Begum 227
Surface accumulation of seeds under reduced tillage would increase predator access to seeds and
therefore could increase their removal rates. Lack of soil disturbance via tillage could also encourage
higher predator populations. No till fields increase the number, diversity, or activity of seed-consuming
fauna as compared to conventionally tilled fields (Blubaugh and Kaplan, 2015) may be due to increased
habitat (Baraibar et al., 2009) or decreased mortality rate (Shearin et al., 2007).
Mulching: The mulch of dead plant residue (often call “trash”) on the soil surface also impacts the seed
bank in no-till systems. Crop residues create micro-environments that provide cover for animals that feed
on them. In addition, residues have a moderating effect on temperature fluctuations in the soil, which in
turn can impact seed dormancy of many of the smaller seeded broadleaf weeds that use daily
temperature fluctuations to gauge burial depth. Crop residues of plant species such as rye (Secalecereale
L.), clover (Trifoliums pp. L.) and recently incorporated canola contain allelopathic chemicals which inhibit
seed germination (Moyer et al., 2000; Vera et al., 1987). The effectiveness of allelopathic chemicals
diminishes over time as the chemicals are leached form the crop residue and degrade due to soil
moisture, light and microbial activity. Large-seeded weed species tend to be less susceptible to
allelopathic compounds than small-seeded species. It is not clear whether this is due to the lower surface
area to volume ratio of larger seeds or whether it is due to reduced concentrations of allele-chemicals at
the deeper depths from which large seeded weed species tend to germinate.
Fertilization: Similar to crops, weeds also respond well to inorganic fertilizers fertilization (Blackshawet
al., 2003; Blackshawet al.,2004b). Over the long-term, weed seed banks of many species can be reduced
by up to 50% by correct timing and placement of nitrogen fertilizer with spring banding at time of seeding
being most effective6. Interestingly banding nitrogen fertilizer greatly reduced green foxtail and stinkweed
populations, especially under a no-tillage cropping system (O'Donovan et al., 1997). Fall-applied nitrogen
that is broadcast on the surface maximizes the competitive ability of weeds by allowing more access to
the fertilizer which enhances weed populations and the weed seed bank. Composting manures before
application reduces the viability of weed seeds, minimizing weed seed inputs into the seed bank
(Menalled, 2008).
Conclusion
One of the most important, yet often neglected weed management strategies is to reduce the number of
weed seeds present in the field, and thereby limit potential weed populations during crop production. This
can be accomplished by managing the weed seed bank. There are many fates and processes that occur
in the weed seed bank, many of which are not very well understood. The sheer difficulty of monitoring a
process that occurs mostly underground has deterred weed scientists from gaining a full understanding of
the weed seed bank. Nevertheless, current knowledge about weed seed banks has shown some potential
management options. Reducing inputs to the seed bank is an important component of seed bank
management, while other strategies like using a no-till cropping system can be used to directly affect
germination, persistence and mortality of weed seeds. Managing weed seed banks would be an important
component of integrated weed management.
References
Archibold, O.W. 1981. Buried viable propagules in native prairie and adjacent agricultural sites in central Saskatchewan. Can. J.
Bot. 59: 701-706.
Archibold, O.W. and Hume, L. 1983. A preliminary survey of weed input into fallow fields in Saskatchewan. Can. J. Bot. 61: 1216-
1221.
Baraibar, B., Westerman, P.R., Carrión, E. and Recasens, J. 2009. Effects of tillage and irrigation in cereal fields on weed seed
removal by seed predators. J. Appl. Ecol. 460: 380–387.
Baskin C.C. and Baskin, J.M. 1998. Seeds: Ecology, biogeography, and evolution of dormancy and germination. San Diego:
Academic Press. 666p.
Begum, M., Juraimi, A.S., Rastan, S.O.B.S., Amartalingam, R. and Man, A.B. 2006.Seedbank and seedling emergence
characteristics of weeds in rice field soils of the muda granary area in north-west peninsular Malaysia. BIOTROPIA.
13 (1): 11 – 21.
Blackshaw R.E., Brandt, R.N., Janzen, H.H. and Entz, T. 2004b. Weed species response to phosphorous fertilization. Weed Sci. 52:
406-412.
Blackshaw R.E., Brandt, R.N., Janzen, H.H., Entz T., Grant, C. and Derksen, D.A. 2003. Differential response of weed species to
added nitrogen. Weed Sci. 51: 532-539.
228 Importance and management for sustainable crop production
Blackshaw R.E., Harker, K.N., O’Donovan, J.T., Beckie, H.J. and Smith, E.G. 2008.Ongoing development of integrated weed
management systems on the Canadian Prairies. Weed Sci. 56: 146-150.
Blackshaw R.E., Molnar, L.J. and Janzen, H.H. 2004a. Nitrogen fertilizer timing and application method affect weed growth and
competition. Weed Sci. 52:614-622.
Blubaugh, C.K. and Kaplan, I. 2015. Tillage compromises weed seed predator activity across developmental stages. Biol. Control
81: 76–82.
Brainard, D.C., Bellinder, R.R., Hahn, R.R. and Shah, D.A. 2008.Crop rotation, cover crop and weed management effects on weed
seedbanks and yields in snap bean, sweet corn and cabbage. Weed Science. 56: 434–441.
Clements, D.R., Benoit, D.L., Murphy, S.D. and Swanton, C.J. 1996. Tillage effects on weed seed return and seedbank composition.
Weed Sci. 44: 314-322.
Conn, J.S., Beattie, K.L. and Blanchard, A. 2006. Seed viability and dormancy of 17 weed species after 19.7 years of burial in
Alaska. Weed Sci. 54: 464-470.
Cousens, R. and Moss, S.R. 1990. A model of the effects of cultivations on the vertical distribution of weed seeds within the soil.
Weed Res. 30: 61–70.
Davis, A.S. 2004.Managing weed seedbanks throughout the growing season [Online].New Agriculture Network Vol. 1 No. 2.
Davis, A.S., Renner, K.A. and Gross, K.L. 2005. Weed seedbank and community shifts in a long-term cropping systems experiment.
Weed Sci. 53: 296–306.
duCroixSissons M.J., van Acker, R.C., Derksen, D.A. and Thomas, A.G. 2000. Depth of seedling recruitment of five weed species
measured in situ in conventional- and zero-tillage fields. Weed Sci. 48:327-332.
Fenner, M. and Thompson, K. 2005.The ecology of seeds. Cambridge, UK: Cambridge University Press. 250 p.
Forcella, F. 2003. Debiting the seedbank: Priorities and predictions. p. 151–162. InBekkeret al. (eds.) Seedbanks: Determination,
dynamics and management. Aspects of Applied Biology 69.Association of Applied Biologists, Welles Bourne, UK.
Gulden R.H., Thomas, A.G. and Shirtliffe, S.J. 2003 Secondary seed dormancy prolongs persistence of volunteer canola (Brassica
napus) in western Canada. Weed Sci. 51: 904-913.
Gulden R.H., Thomas, A.G. and Shirtliffe, S.J. 2004. Secondary dormancy, temperature, and seed burial depth regulate seedbank
dynamics in Brassica napus. Weed Sci. 52: 382-388.
Gulden, R.H. and Shirtliffe, S.J. 2009. Weed Seed Banks: Biology and Management. Prairie Soils & Crops J. 2: 46-52.
Hossain, M.M., Begum, M., Hashem, A, Rahman, M.M., Bell, R.W. Haque, M.E. 2014c. Yield response of mustard as influenced by
weed management practice under conservation agriculture system. Bangladesh J. Weed Sci. 4 & 5, 87-92.
Liebman, M., Mohler, C.L. and Staver, C.P. 2001 Ecological management of agricultural weeds. Cambridge, UK: Cambridge
University Press. 532 p.
Menalled, F.D. 2008. Weed Seedbank Dynamics & Integrated Management of Agricultural Weeds. Agriculture and Natural
Resources (Weeds), 200-708SA
Menalled, F.D. 2013. Manage the Weed Seed Bank—Minimize "Deposits" and Maximize "Withdrawals". Available at: extension.org
http://www.extension.org/pages/18527/manage-the-weed-seed bankminimize-deposits-andmaximize-withdrawals#. VkG6
Xl53C1t
Mickelson, J.A. and Grey, W.E. 2006.Effect of soil water content on wild oat (Avenafatua L.) seed mortality and seedling
emergence. Weed Sci. 54: 255-262.
Mohler, C.L. 2001a. Weed life history: identifying vulnerabilities. Cambridge University Press, New York. p.40–98.
Moyer J.R., Blackshaw, R.E., Smith, E.G. and McGinn, S.M. 2000. Cereal cover crops for weed suppression in a summer fallow-
wheat cropping sequence. Can. J. Plant Sci. 80: 441-449.
O' Donovan, J.T., McAndrew, D.W. and Thomas, A.G. 1997. Tillage and nitrogen influence weed population dynamics in barley
(Hordeumvulgare L.). Weed Technol. 11: 502-509.
Radosevich, S., Holt, J. and Ghersa, C. 1997. Weed ecology: Implications for management. New York: John Wiley & Sons, Inc.
589p.
Sexsmith J.T. and Piman, V.J. 1967.Effect of nitrogen fertilization on germination and stand of wild oats. Weed Res. 11: 99-101.
Shearin, A., Reberg-Horton, S. and Gallandt, E. 2007. Direct effects of tillage on the activity and density of ground beetle
(Coleoptera: Carabidae) weed seed predators. Environ. Entomol. 36: 1140–1146.
Shirtliffe S.J. and Entz, M.H. 2005 Chaff collection reduces seed dispersal of wild oat (Avenafatua) by a combine harvester. Weed
Sci. 53: 465-470.
Singh, A., Kaur, R., Kang, J.S. and Singh, G. 2012.Weed dynamics in rice-wheat cropping system. Global J. Biol. Heal. Sci., 1(1): 7-
16.
Teasdale, J.R., Magnum, R.W., Radhakrishnan, J. and Cavigelli, M.A. 2004. Weed seedbank dynamics in three organic farming
crop rotations. Agronomy J. 96: 1429–1435.
Thomas, A.G., Banting, J.D. and Bowes, G. 1986. Longevity of green foxtail seeds in a Canadian prairie soil. Can. J. Plant Sci. 66:
189-192.
Thompson K., Ceriani, R.M., Bakker, J.P., and Bekker, R.M. 2003. Are seed dormancy and persistence in soil related? Seed Sci.
Res. 13: 97-100.
Thornton, M.A., Peters, N.B.C., West, T.M. and Thomas, T.H. 1998. A novel way to control volunteer oilseed rape (Brassica
napus).Asp. Appl. Biol. 51: 191–196.
Vera, C.L., McGregor, D.I. and Downey, R.K. 1987. Detrimental effects of volunteer Brassica on production of certain cereal and
oilseed crops. Can. J. Plant Sci. 67: 983-995.
White S.S., Renner, K.A., Menalled, F.D. and Landis, D.A. 2007. Feeding preferences of weed seed predators and effect on weed
emergence. Weed Sci. 55: 606-612.
... Soil seed banks are characterized based on resilience and persistence of the seeds (Freitas, 1990) or longevity of the seeds present (Garwood, 1989;Ken-Thompson et al., 1997). Within the soil seed bank, several factors influence the duration of seed dormancy due to seed sensitivity to their environment (Hossain and Begum, 2015). In an agro-system, agricultural soil can contain a huge number of weed seeds (Menalled, 2013) which is vital in weed management. ...
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Soil seed bank is a natural storage for seeds deposited at various soil depths. In this study, the soil seed bank of a yam field and fallow field within the University of Port Harcourt were examined using seedling emergence method to identify and record the floristic composition of both fields through their emergent seedlings. Soil samples from eight points for each field totaling sixteen points were collected and at three soil depths (0-5cm, 5-10cm, and 10-15cm). The soil samples were transferred to Centre for Ecological Studies, University of Port Harcourt for preparation and monitored for four weeks. Statistical analysis was done for the data generated using one-way ANOVA in addition to their graphical representation. From the result, the fallow field showed higher species abundance (emergence seedlings) but was not significantly different at a 5% level of probability from the yam field at all depths. Species diversity index revealed high diversity at 10cm depth for yam field and 5cm depth for the fallow field while the lowest was at 15cm depth for the fallow field. Agricultural tillage of the yam field led to lower species density, abundance, and composition due to seed destruction and deepening of seeds down the soil depths. Soil seed bank provided the vegetation history of the fields and information necessary for weed management.
... Weeds are an important factor influencing crop production through competition for environmental resources (light, water, and nutrients in the soil) and cause heavy yield losses [1]. According to Nishimoto [2], weeds cause 14% of the damage to global agricultural production, and this may lead to crop yield losses of 25-30% in developing nations. ...
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Background: Numerous pesticides and herbicides used in excess cause oxidative stress in plants. These chemicals protect plants from weeds and pests, but they also have very negative side effects, making them common abiotic stressors. One of the most significant nutritional crops in the world is the wheat plant. Conditions of herbicide stress have a negative impact on the plant's phonological phases and metabolic pathways. Plants primarily make an effort to adjust to the environment and develop oxidative homeostasis, which supports stress tolerance. Methods: When controlling broadleaf weeds that emerge after cereal crop plants have been planted, bromoxynil is frequently used as a selective-contact herbicide. This study looked at the effects of the cyanobacteria Arthrospira platensis and Nostoc muscorum aqueous extracts, tryptophan, and bromoxynil (Bh) alone or in combination on wheat plant growth parameters. Both tryptophan and cyanobacterial extract were used as chemical and natural safeners against Bh application. The antioxidant activity and transcriptome studies using qRT-PCR were assayed after 24, 48, 72, 96 h, and 15 days from Bh application in the vegetation stage of wheat plants (55 days old). Results: In comparison with plants treated with Bh, wheat plants treated with cyanobacteria and tryptophan showed improvements in all growth parameters. Following application of Bh, wheat plants showed reduced glutathione content, as well as reduced antioxidant enzyme activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione-s-transferase. The combination of different treatments and Bh caused alleviation of the harmful effect induced by Bh on the measured parameters. Additionally, the expression of glutathione synthase and glutathione peroxidase, in addition to those of three genes (Zeta, Tau, and Lambda) of the GST gene family, was significantly upregulated when using Bh alone or in combination with different treatments, particularly after 24 h of treatment. Conclusion: The current study suggests using cyanobacterial extracts, particularly the A. platensis extract, for the development of an antioxidant defense system against herbicide toxicity, which would improve the metabolic response of developed wheat plants.
... Soil and crop management practices can directly influence the environment of seeds in the seed bank and can thus be used to manage seed longevity and germination behaviour (Kumar et al., 2019) Weed management, be it herbicide treatment or other cultural practices have more impact on weed seed production in rice field; weed management exposes more impact than tillage on weed seed production in maize-soybean rotation (Perron and Legere 2000). Herbicides are considered more effective in reducing weed populations and the number of seeds added to the weed seed bank (Hossain et al., 2015). It also inhibits the germination and growth of dominant weed species in top soil seed banks. ...
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Weed seed bank in soil serves as the reservoir of weed seeds which emerge whenever conditions become conducive and affects crop growth. In the present study, a field experiment was performed at Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai, India, during Kharif 2021 and Rabi 2022 to determine weed seed bank present in soil by direct seed extraction using the sieving method at discrete depths of 0-5 cm, 5-10 cm and 10-15 cm after rice harvest with reference to different weed management practices imposed and its effect on weed population in succeeding crop. The average proportion of weeds that emerged in the field ranged from 9 to 38 % of the total weed seed bank. Weed management practices followed during the preceding crop greatly influenced weed seed germination. The higher weed seed reserve (1384 m-2) and consequent weed population (528 no’s m-2) were found at a depth of 0-5 cm in unweeded plots. The lower weed seed density (536 m-2) and weed population (94 no’s m-2) were found in pre emergence application of Pyrazosulfuron + Pretilachlor and early post emergence application of Bispyripac sodium. The results from the present study confirmed that herbicide treatment considerably minimized the weed seed density and population, which will assist in predicting weed infestation and appropriate timing of weed control.
... The seed bank is the primary source of weeds, represents a critical stage in the weed life cycle, and the weed population is inextricably linked to its seed bank. Knowledge of the size and composition of the soil weed seed bank is critical for forecasting future weed infestations and management techniques, weed seed production after the cropping season, calculation of crop-weed competition and crop yield loss, as well as agricultural economics [2]. There are relatively few research that investigate the influence of CA principles on the dynamics of weed seed banks. ...
... Seeds with the potential genetic variations that determine high crop productivity are biologically important for sustainable crop production. Indeed, from this perspective, seeds are the basic prerequisite for food and energy security [10,11]. Specifically, resilient seeds can realize maximum productivity, thereby contributing to sustainable crop production as well [12,13]. ...
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Maize is the third most common cereal crop worldwide, after rice and wheat, and plays a vital role in preventing global hunger crises. Approximately 50% of global crop yields are reduced by drought stress. Bacteria as biostimulants for biopriming can improve yield and enhance sustainable food production. Further, seed biopriming stimulates plant defense mechanisms. In this study, we isolated bacteria from the rhizosphere of Artemisia plants from Pohang beach, Daegu, South Korea. Twenty-three isolates were isolated and screened for growth promoting potential. Among them, bacterial isolate SH-6 was selected based on maximum induced tolerance to polyethylene glycol-simulated drought. SH-6 showed ABA concentration = 1.06 ± 0.04 ng/mL, phosphate solubilizing index = 3.7, and sucrose concentration = 0.51 ± 0.13 mg/mL. The novel isolate SH-6 markedly enhanced maize seedling tolerance to oxidative stress owing to the presence of superoxide dismutase, catalase, and ascorbate peroxidase activities in the culture media. Additionally, we quantified and standardized the biopriming effect of SH-6 on maize seeds. SH-6 significantly increased maize seedling drought tolerance by up to 20%, resulting in 80% germination potential. We concluded that the novel bacterium isolate SH-6 (gene accession number (OM757882) is a biostimulant that can improve germination performance under drought stress.
... They found that 5 samples were almost the same as those from 30 samples and reliable to a large extent and at the same time very desirable as far as the required time and money are concerned. Distribution of the weed seed bank vertically in the soil profile depends on the type of tillage and is the main factor determining the vertical distribution of weed seeds within the soil profile (Hossain and Begum, 2015). The present work depends on the use of germination method technique for enumerating seed in the soil seeds bank according to Forcella et al. (2003). ...
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All right reserved. No part of this publication may be reproduced, stored in a retrievel system, or transmitted, in any form or by any means, electric, mechanical, photocoping, recording or otherwise, without the prior permission of the copyright owner (Faculty of Agriculture, Cairo University). 297 Bull. Fac. Agric., CairoUniv., 71:279-288(2020).__________ _____ __ ____ PRELIMINARY STUDY ON GERMINABLE SUMMER WEED SEED BANK AT GIZA ABSTRACT Despite efforts to eliminate weeds, they continue to thrive. Weed persistence is reliant upon the soil seedbank. Knowledge of the soil seedbank is continually expanding, but with the rising threat of herbicide-resistant weeds in agriculture, weed scientists have, in the past, focused their management tactics to more short-term solutions that tackle the aboveground problems, rather than long-term solutions. Uptill now, there are few studies about weed seed bank in Egypt. For this reason establishing weed seed bank studies about vertical and horizontal distribution patterns is needed for weed management in Egypt. The present study was carried out during 2018 and 2019 summer seasons to evaluate the magnitude of the non-dormant weed seed bank of summer annual weeds in five different basins in Giza research station. Weed seed germination was kept under observation for a period of six weeks and the germinated seeds were counted weekly and removed after that. The results indicated that most of weed seeds were concentrated in the above 0-5 cm layer followed by 5-10 cm layer and the least were found in 10-15cm layer from soil surface. Most of weed seeds germinated in 1 st and 2 nd weeks, and decreased gradually in the next weeks, where about 95% of weed seeds in soil profile were germinated in the first five weeks. The existed weed flora contained 15 species which differ in their richness from one basin to another. The highest number of germinated weed seeds were recorded in basin 12 (498.8 and 408.1 seedling/kg of soil) in 1 st and 2 nd seasons, respectively, while the least number of germinated weed seeds were found in basins 19 (45.7 and 64.0 seedlings/kg of soil) in 1 st and 2 nd seasons, respectively. By using ANOVA statistical analysis, experimental error decreased by taking 3-4 soil samples, to give adequate accuracy for soil seed bank determination than taking one soil sample. The relationship between number ofseedlings/m 2 and CV% was linear equations: "CV%=-0.26 × Number of seedlings + 29.53" and "CV%=-0.4 × Number of seedlings + 31.103" in the first and second summer seasons, respectively. In conclusion weed seed bank determination in soil is a key for sustainable agriculture in Egypt. The present study throws light of vertical or horizontal distributions in soil profile in seed bank as a good tool for improving weed management in cropping system in Egypt.
... In all agricultural production systems, limiting the weed seed bank is an important step in a successful weed control program. It is a nonspecific and elementary measure in every weed control strategy because it defines its direction, with the aim of successfully controlling aboveground weed infestations [18]. Techniques such as tillage fallow and false seedbeds manage the weed seedbank directly. ...
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Herbicide application has long been considered the most efficient weed control method in agricultural production worldwide. However, long-term use of agrochemicals has numerous negative effects on crops and the environment. Bearing in mind these negative impacts, the EU strategy for withdrawing many herbicides from use, and modern market demands for the production of healthy and safe food, there is a need for developing new effective, sustainable, and ecological weed control measures. To bring a fresh perspective on this topic, this paper aims to describe the most important non-chemical weed control strategies, including ecological integrated weed management (EIWM), limiting weed seed bank, site-specific weed management, mechanical weeding, mulching, crop competitiveness, intercropping, subsidiary crops, green manure, and bioherbicides.
... Hay tres "reglas de oro" sustentadas por estudios científicos para la falsa siembra: (Hossain & Begum, 2016;Marks & Nwachuku, 1986). (Garnica et al., 2017). ...
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Esta sección de la gaceta informativa de Manejo Ecológico Integral de Arvenses busca brindar con más detalle información técnica, ecológica, geográfica, social y económica sobre prácticas específicas entre las mencionadas en números anteriores. En este número de la gaceta informativa se explorarán detalles sobre la falsa siembra, haciendo énfasis en información técnica y ecológica, recomendaciones específicas para México y regiones particulares del país. La falsa siembra consiste en preparar la tierra, mediante una labor superficial, para favorecer la germinación de las arvenses antes de la siembra del cultivo. Esta estrategia de manejo se ha usado de manera tradicional por miles de años.
Chapter
After the emergence of agriculture, the environment became populated not only by cultivated species, but also by species with undesirable characteristics, called weeds. These spontaneous plants have characteristics that differentiate them from other plants and allow them to successfully invade, establish, and persist in agricultural environments. The ability to reproduce sexually through seeds and/or asexually through vegetative structures has allowed weeds to reproduce easily, increasing their ability to exploit agricultural environments. Moreover, the high production of propagules, the presence of dispersal mechanisms, and the dormancy of these reproductive structures have allowed weeds to persist and overcome adversities caused by man and the environment. Knowing the morphophysiological characteristics of weed species and the possibility of grouping species according to their similarities, such as taxonomic classifications, as to habitat, life cycle, and growth habit, helps in the positioning of management techniques. Even if their weed communities have been altered by human action and the environment, weeds will always be present in agricultural environments, so there is a need to live with their presence, avoiding their negative effects, but trying to make the most of their contributions.
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Conservation agriculture practice based on increased residue retention are being developed in Bangladesh but the optimum weed control for crops in the cropping sequence is still not defined. The present experiment aimed to determine the effectiveness of increased residue retention relative to pre-and post-emergence herbicide treatment on weed control and yield of mustard planted after rice. An on-farm experiment was conducted at Durbachara village, Mymensingh district during post rice season (October 2014 to January 2015). Mustard cv. BARI sharisha-14, was sown with six tillage and weed control practices viz., Conventional tillage + farmer's weeding practice (Control); Roundup (RU) + Strip tillage (ST); RU + ST + Pre-emergence (PE) herbicide (Pendimethalin); RU + ST + Post-emergence (PO) herbicide (Oxadiazon); RU+ ST + PE + PO; RU+ ST + weed-free (WF), and two levels of rice residue viz., R20: 20% residue and R50: 50% residue. Conventional tillage produced higher weed density and biomass compared to strip tillage. WF retained 50% residue yielded the highest (1.72 tha-1) which was 67% higher compared to control retained 20% residue (1.03 tha-1). Although WF retained 50% residue yielded the highest, the highest BCR (4.39) was calculated from RU+ ST + PE + PO retained 50% residue which was 7% higher compared to WF with 50% residue.
Chapter
Concerns over environmental and human health impacts of conventional weed management practices, herbicide resistance in weeds, and rising costs of crop production and protection have led agricultural producers and scientists in many countries to seek strategies that take greater advantage of ecological processes and thereby allow a reduction in herbicide use. This book provides principles and practices for ecologically based weed management in a wide range of temperate and tropical farming systems. After examining weed life histories and processes determining the assembly of weed communities, the authors describe how tillage and cultivation practices, manipulations of soil conditions, competitive cultivars, crop diversification, grazing livestock, arthropod and microbial biocontrol agents, and other factors can be used to reduce weed germination, growth, competitive ability, reproduction and dispersal. Special attention is given to the evolutionary challenges that weeds pose and the roles that farmers can play in the development of new weed-management strategies.
Article
Field experiments were established in fall 1999 and 2000 near Huntley, MT, to determine the effects of soil water content on wild oat seed mortality and seedling emergence. Four supplemental irrigation treatments were implemented from June through September to establish plots with varying soil water content. Wild oat seed mortality during the summer increased linearly as soil water content increased. For seed banks established in 1999 (1999SB), seed mortality increased, on average, from 36 to 55% in 2000, and 15 to 55% in 2001 as soil water content increased from 6 to 24%. For seed banks established in 2000 (2000SB), seed mortality increased, on average, from 38 to 88% in 2001 and 53 to 79% in 2002 as soil water content increased from 6 to 24%. Increasing soil water content likely increased the activity of microorganisms that cause mortality in wild oat seeds. The increasing seed mortality rates (due to increasing soil water content) resulted in greater annual declines of wild oat seed banks and 2-yr cumulative decline rates. Total season emergence percentage was not affected by irrigation treatment. Results show that weed seed bank decline is more rapid in moist than in dry soils and suggest that management practices that increase or conserve soil moisture will also increase the rate of wild oat seed bank decline.
Book
The new edition of Seeds contains new information on many topics discussed in the first edition, such as fruit/seed heteromorphism, breaking of physical dormancy and effects of inbreeding depression on germination. New topics have been added to each chapter, including dichotomous keys to types of seeds and kinds of dormancy; a hierarchical dormancy classification system; role of seed banks in restoration of plant communities; and seed germination in relation to parental effects, pollen competition, local adaption, climate change and karrikinolide in smoke from burning plants. The database for the world biogeography of seed dormancy has been expanded from 3,580 to about 13,600 species. New insights are presented on seed dormancy and germination ecology of species with specialized life cycles or habitat requirements such as orchids, parasitic, aquatics and halophytes. Information from various fields of science has been combined with seed dormancy data to increase our understanding of the evolutionary/phylogenetic origins and relationships of the various kinds of seed dormancy (and nondormancy) and the conditions under which each may have evolved. This comprehensive synthesis of information on the ecology, biogeography and evolution of seeds provides a thorough overview of whole-seed biology that will facilitate and help focus research efforts.
Article
What determines the number and size of the seeds produced by a plant? How often should it reproduce them? How often should a plant produce them? Why and how are seeds dispersed, and what are the implications for the diversity and composition of vegetation? These are just some of the questions tackled in this wide-ranging review of the role of seeds in the ecology of plants. The authors bring together information on the ecological aspects of seed biology, starting with a consideration of reproductive strategies in seed plants and progressing through the life cycle, covering seed maturation, dispersal, storage in the soil, dormancy, germination, seedling establishment, and regeneration in the field. The text encompasses a wide range of concepts of general relevance to plant ecology, reflecting the central role that the study of seed ecology has played in elucidating many fundamental aspects of plant community function.
Article
Field experiments were initiated at Alliance and Hairy Hill, Alberta, in 1989 to investigate the effects of conventional tillage, zero tillage, and four levels of nitrogen fertilizer on continuous barley production. In both tillage systems, the nitrogen was banded 6 to 8 cm deep between alternate barley rows. Herbicides were used for weed control each year. The influence of tillage and nitrogen on weed seed population dynamics was determined in 1991 and 1992. In the zero-tillage system, a large proportion of the weed seeds were present either at the soil surface or at the 5- to 10-cm depth. Green foxtail, the dominant species at Alliance, was also present at Hairy Hill where field pennycress was dominant. Green foxtail was consistently associated with low (residual) nitrogen and, in most cases, with conventional tillage. At both locations, green foxtail populations tended to decrease to very low levels as nitrogen rate increased, especially in zero tillage. At Hairy Hill, field pennycress populations in the soil seedbank were higher in zero tillage compared with conventional tillage, but plants that emerged from the soil seedbank in the field in spring were lower in zero tillage. Field pennycress populations were highest under low nitrogen. The results indicate that banding nitrogen has the potential to be an effective tool for green foxtail and field pennycress management in conventional- and zero-tillage systems, resulting in less dependence on herbicides for their control.
Article
Differences in the depth of weed seedling recruitment due to agronomic management practices, such as reduced tillage, have implications for weed competitive ability and management strategies. Depth of seedling recruitment of Avena fatua, Triticum aestivum, Setaria viridis, Polygonum convolvulus, and Echinochloa crus-galli was measured in sim in 1997 and 1998 prior to seeding (preseeding) and before in-crop spraying (prespray) in a total of 44 zero-tillage and 44 conventional-tillage fields located across approximately 3 million ha of southern Manitoba, Canada. For the monocot species, depth of recruitment was measured from the soil surface to the intact seed coats, which marked the point of germination. For P. convolvulus, a dicot, greenhouse studies were conducted prior to sampling in the field to identify a reliable morphological marker indicating the point of germination. For all species, mean recruitment depth was found to be significantly shallower in zero- vs. conventional-tillage fields and significantly shallower in the preseeding vs. the prespray period. There were relatively few differences in mean recruitment depth among weed species. Within a sampling period and tillage system, for example, the greatest difference in mean recruitment depth between species was less than 1.2 cm, and the maximum mean recruitment depth across species, sampling times, and tillage practice was very shallow (less than 4.2 cm). Locating weed seedling recruitment depth is the first step in characterizing weed seedling recruitment microsites. Results indicate this information should be specific to tillage and sampling time.