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1 July 2018 Seedbank Persistence of Palmer Amaranth (Amaranthus palmeri) and Waterhemp (Amaranthus tuberculatus) across Diverse Geographical Regions in the United States
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Abstract

Knowledge of the effects of burial depth and burial duration on seed viability and, consequently, seedbank persistence of Palmer amaranth (Amaranthus palmeri S. Watson) and waterhemp [Amaranthus tuberculatus (Moq.) J. D. Sauer] ecotypes can be used for the development of efficient weed management programs. This is of particular interest, given the great fecundity of both species and, consequently, their high seedbank replenishment potential. Seeds of both species collected from five different locations across the United States were investigated in seven states (sites) with different soil and climatic conditions. Seeds were placed at two depths (0 and 15cm) for 3 yr. Each year, seeds were retrieved, and seed damage (shrunken, malformed, or broken) plus losses (deteriorated and futile germination) and viability were evaluated. Greater seed damage plus loss averaged across seed origin, burial depth, and year was recorded for lots tested at Illinois (51.3% and 51.8%) followed by Tennessee (40.5% and 45.1%) and Missouri (39.2% and 42%) for A. palmeri and A. tuberculatus, respectively. The site differences for seed persistence were probably due to higher volumetric water content at these sites. Rates of seed demise were directly proportional to burial depth (α=0.001), whereas the percentage of viable seeds recovered after 36 mo on the soil surface ranged from 4.1% to 4.3% compared with 5% to 5.3% at the 15-cm depth for A. palmeri and A. tuberculatus, respectively. Seed viability loss was greater in the seeds placed on the soil surface compared with the buried seeds. The greatest influences on seed viability were burial conditions and time and site-specific soil conditions, more so than geographical location. Thus, management of these weed species should focus on reducing seed shattering, enhancing seed removal from the soil surface, or adjusting tillage systems.

Introduction

The high fecundity of Palmer amaranth (Amaranthus palmeri S. Watson) (Korres 2018; Korres and Norsworthy 2017) and waterhemp [Amaranthus tuberculatus (Moq.) J. D. Sauer] (Hartzler et al. 2004; Heneghan and Johnson 2017) and the relatively high frequency of evolving herbicide resistance (Heap 2017; Jhala et al. 2014; Molin et al. 2016; Vencill et al. 2008) are major reasons why these species have become two of the most problematic weeds in U.S. cropping systems (Riar et al. 2013; Webster and Nichols 2012). The excessive proliferation of these species can rapidly enrich the soil seedbank, the persistence of which is the driving force for future weed infestations in agricultural production systems. Seed persistence in soil seedbanks counteracts the effects of unfavorable environmental conditions for seed germination over long periods (Gutterman 1994; Holmgren et al. 2006) and increases the possibility that viable seeds are available when conditions for seed germination and seedling recruitment are optimal (Holmgren et al. 2006).

Weed species that form persistent seedbanks are a concern for future weed management. The persistence of viable seeds in the soil seedbank depends on a wide range of interacting biotic and abiotic factors. These include germination cues, seed dormancy, seed size (Honda 2008; Hulme 1998; Ooi et al. 2007; Thompson et al. 1994), physiological age, predation, and microbial decay, along with environmental conditions, burial depth, and burial duration (Davis et al. 2005; Liebman et al. 2001). High mortality occurs at the seed stage owing to high seed losses and fatal germination (i.e., the condition wherein seeds germinate but fail to emerge) (Cavers 1983; Forcella 2003; Forcella et al. 1992). Consequently, reducing the number of germinable seeds will decrease the number of individuals that will be subjected to weed management operations and the number of escapees that could replenish the soil seedbank. Longevity of seeds in the soil is the most determinant factor for the success of this approach.

The first crucial phase in the formation of a persistent soil seedbank is burial (Fenner and Thompson 2005). Whether buried seeds contribute to soil seedbank persistence and consequently to weed population regeneration depends mainly on the depth from which the seeds are able to germinate (Baker 1989). The persistence and viability of some weed species after long burial periods is well documented (Conn et al. 2006; Telewski and Zeevaart 2002). However, the majority of weed species lose seed viability at relatively short periods after burial (Burnside et al. 1996; Conn et al. 2006; Egley and Chandler 1983; Lutman et al. 2002), particularly small-sized seeds such as A. palmeri (Jha et al. 2014; Sosnoskie et al. 2013), which are more likely to become buried (Peart 1984; Thompson et al. 1994). Omami et al. (1999) found changes in redroot pigweed (Amaranthus retroflexus L.) viability for seeds placed on the soil surface compared with seeds buried at various depths up to 10 cm. He reported that the decline in viability was most rapid for the seeds on the soil surface compared with buried seeds. Schweizer and Zimdahl (1984) discussed the persistence of Amaranthus species seedbank due to longevity of seeds, which, based on the literature, seems to vary considerably from a 12-mo period (Horng and Leu 1974; Omami et al. 1999) up to 4 (Jha et al., 2014; Steckel et al. 2007), 10 (Burnside et al. 1981; Toole and Brown 1946), or even 40 yr (Kivilaan and Bandurski 1981; Quick 1961).

Recent research has sought to address the influence of climate in relation to plant biological characteristics on the establishment and persistence of plant populations (Scott et al. 2014). As stated by Ooi (2012), expanding our knowledge of the response and adaptability of seedbanks to environmental and climatic factors will provide the basis for accurate predictions of species occurrence and future distribution, especially in ecosystems that are exposed to temporarily irregular disturbances.

As mentioned previously, the persistence of viable seeds in the seedbank is affected by a wide range of interacting biotic and abiotic factors that in turn depend on the position of seeds in the soil profile (Omami et al. 1999) and geographic location (Warr et al. 1993). Knowledge of the effects of burial depth and burial duration on long-term seed viability and, subsequently, seedbank persistence of A. palmeri and A. tuberculatus populations originating from different locations and dispersed among diverse regions with different soil and climatic conditions can be used for the development of efficient weed management approaches. This is of particular interest given the high fecundity of both species and their high seedbank replenishment potential.

The aim of this study, therefore, was to assess A. palmeri and A. tuberculatus seed persistence at two soil burial depths over a 3-yr period at various locations by testing the following hypotheses: (1) Was seed viability of A. palmeri and A. tuberculatus affected when seeds were exposed to diverse soil surface and subsurface environments at different experimentation sites? (2) Was seed viability of A. palmeri and A. tuberculatus, hence seedbank persistence of these species, reduced as burial depth and burial duration increased?

Materials and Methods

Seed Material and Seedbank Establishment

Seeds of A. palmeri and A. tuberculatus ecotypes, originating from five different locations (i.e., A. palmeri from Arkansas, Indiana, Missouri, Nebraska, and Tennessee; A. tuberculatus from Indiana, Missouri, Nebraska, Ohio, and Wisconsin), were collected as they matured between mid-September to late October 2013 and sent to the University of Arkansas, Fayetteville, for further processing. Approximately 1 mo after the plant material was collected, a cleaned seed sample from each seed lot was sent to seven experimental sites (i.e., Arkansas, Illinois, Indiana, Mississippi, Missouri, Tennessee, and Wisconsin) for the establishment of the seed burial trials (Figure 1).

At each site, seeds of each species under investigation were buried using polyethylene mesh bags (64 cm2), with 500-micron pore openings (Elko Filtering, Miami, FL). More specifically, 100 seeds from each seed lot were counted and thoroughly mixed with approximately 20 g of soil collected from the burial site and known to be free of both weeds. Soil placed in the bags was sieved though a 1.4-mm (14 mesh) screen to ensure that no alien seeds would be enclosed in the polyethylene bag. The use of the polyethylene bags, particularly for weeds with small-sized seeds such as A. palmeri and A. tuberculatus, ensures that seeds could be retrieved on any sampling occasion. Wijayratne and Pyke (2012) adopted the same approach when investigating the persistence of the small-sized seeds of big sagebrush (Artemisia tridentata Nutt.).

Figure 1.

Experimental sites across Midsouth United States, where Amaranthus palmeri and Amaranthus tuberculatus seed material was exposed to burial trials for a period of 1 to 3 yr before viability test evaluation. Numbers in parentheses represent the latitude and longitude of the experimental sites.

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Figure 2.

Experimental layout in which the randomized arrangement of main plots (i.e., retrieval year), subplots (colored seed bags representing the site by ecotype treatments), and sub-subplot (i.e., burial depth treatment) are depicted along with details for seedbank establishment (dimensions and burial depth of PVC cage).

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Soil was excavated at each experimental site to a 15-cm depth, and polyvinyl chloride (PVC) plastic cylindrical pipe cages (60-cm diameter by 17.5-cm height with openings at both ends; Figure 2) were placed in the opening and filled with excavated soil after installation of the polyethylene bags within the cage. One polyethylene bag containing seeds from one location of origin and one species (one ecotype) was placed in each cage at the 15-cm depth. Polyethylene bags were also placed at the soil surface (0 cm) after the cage was filled with excavated soil, for a total of 10 polyethylene bags. The remaining 2.5 cm of the rim of the cage remained above the soil surface to prevent off-site movement of seed-containing bags but also to ensure that potential stagnant water could percolate through the soil profile. The cages were covered with wire mesh to prevent possible damage of seed bags by rodents and birds. Three replicates were used for this experimental setup for each of A. palmeri and A. tuberculatus species. Eighteen cages (nine for each species) were used in the study in each experimental location (Figure 2).

Seed Germination

Germination tests on A. palmeri and A. tuberculatus seed samples before burial (December 2013) and after the completion of the experiment (December 2017) were conducted as described by Jha et al. (2014), with four replications for each combination of species and ecotype. For the duration of the experiment, seed samples were stored at 4 C with approximately 25% to 30% relative humidity.

For the germination evaluations, a seed lot of 100 seeds per species from each ecotype were placed in separate 9-cm-diameter plastic petri dishes (Fisher Scientific, Suwanee, GA, USA) lined with two layers of Whatman filter paper (Whatman's No. 1, Fisher Scientific), and moistened with 5ml of 1% (v/v) captan fungicide (Captan 4-L, Drexel Chemical, Memphis, TN, USA) solution in deionized water. These were incubated for 18 d with a 14-h photoperiod at 30 C, which is the optimum temperature for Amaranthaceae germination (Steckel et al. 2004). Deionized water was added when necessary to maintain adequate moisture for the incubated seeds. Seed germination was assessed every 6 d, with germination determined by radicle protrusion of at least 1 mm. Nongerminated seeds were checked for viability using both a tetrazolium test, as described below, and a seed crush test (Borza et al. 2007; Sawna and Mohler 2002). The viability of the untreated seed material from each location was evaluated separately; however, germination and viability test results were combined to estimate viability of each seed lot.

Seed Retrieval and Viability (Tetrazolium) Test

Each November, the bags pertaining to the retrieval timing at both depths were extracted by carefully unearthing the PVC cages. The retrieved seed bags from all sites were sent to Fayetteville, AR, where seeds were carefully retrieved and subjected to the tetrazolium test for seed viability evaluation. Soil that had been earlier added to the bags was gently rinsed with tap water, and the remaining content of the bag was placed in a 9-cmdiameter petri dish from which the seeds were retrieved using a pair of forceps (Becton, Dickinson, Franklin Lakes, NJ, USA) and visually inspected using a dissection Accu-Scope 3055 LED Stereo microscope (Accu-Scope, Commack, NY, USA). All seeds were counted and classified as damaged or intact.

Damaged seeds (%) were estimated based on Equation 1:

e01_446.gif

where DS is damaged seeds + seed losses, IS is intact seeds found in the polyethylene seed bag at retrieval year ti , 100 is the total number of seeds placed in the polyethylene seed bag at the beginning of the experiment, and ti is retrieval year. Damaged seeds included broken, shrunk, or malformed seeds (Figure 3) and those lost due to deterioration and futile germination. Any other debris was also discarded.

To facilitate tetrazolium straining, the undamaged seeds were initially placed in petri dishes between two Whatman filter papers that were moistened with 2.5 ml of deionized water for 24 h at room temperature. Immediately after this period, 2.5 ml of 1% w/w solution of 2, 3, 5-triphenyltetrazolium chloride was added to the petri dish to ensure that the seeds were well imbibed into the solution. Seeds remained at room temperature for a 24-h staining period (Forcella et al. 2003). Seeds were then removed from the petri dish and gently crushed and classified as viable if the entire embryo was stained (Association of Official Seed Analysts 1970; Forcella et al. 2003; International Seed Testing Association 1985; Price et al. 2010).

Figure 3.

Amaranthus palmeri seeds as they appeared under a dissection microscope (A) before the seed retrieval and cleaning processes and (B) after the cleaning process. The same criteria were used for A. tuberculatus seeds.

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The percentage of viable seeds (VS) after tetrazolium staining was calculated as the total number of viable seeds, which was the sum of germinated seeds (G) plus those that tested positive with tetrazolium (T) divided by the total number of seeds placed in the polyethylene seed bag (N) and multiplied by 100 (Equation 2) (Borza et al. 2007).

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Damaged seeds were expressed as a percentage of the total seeds found in the polyethylene mesh bags at each retrieval time.

Soil Temperature and Volumetric Water Content

Minimum/maximum soil temperature and volumetric water content (i.e., soil moisture content) were recorded every 15 min using Onset HOBO U12 (Onset Computer, Bourne, MA, USA) data loggers with a soil-temperature probe (TMC6-HD, Onset Computer) and a soil-moisture probe (Onset S-SMD-M005 10HS, Onset Computer) placed at the soil surface and 15 cm below the soil surface throughout the entire experimental period. Data from the data loggers were downloaded to a laptop unit every 6 mo. Logger batteries were checked and were replaced, when necessary, every year.

Experimental Design and Data Analysis

The experiment was conducted as a split-split-plot design with three replications, where year of retrieval was the main plot factor, site by location of origin (ecotype) were subplot factors, and burial depth was the sub-subplot factor. The main plot treatments were randomly assigned, and they were permanent throughout the period of the study. The plot area was 1-m wide by 3-m long, and the subplot was 1m2, although the experiment was limited to a PVC cage, and the sub-subplot was limited within the PVC cage (i.e., 60-cm diameter) (Figure 2).

Seed viability, expressed as a percentage viability of the initial 100-seed population placed in the polyethylene mesh bags between sites by origin locations, years, and burial depths, was analyzed as fixed effects by ANOVA using JMP v. 13.1.0 Pro software (SAS Institute, Cary, NC, USA), whereas replication was set as a random effect. Species were analyzed separately due to different collection origins. Seed damage was expressed as a percentage of the remaining seed population at each retrieval time and was analyzed using the same methods as those used for seed viability data.

Results and Discussion

Viability of Initially Harvested and Stored Seeds

The viability of the seeds from each location of origin was evaluated at the beginning and at the end of the experimental period using germination and tetrazolium tests. Both results were averaged and expressed as percentage viability. The percent viability ranged from 88.5% to 92.5% in 2013 and 89.2% to 94.5% in 2017 for A. palmeri and 88.5% to 94.5% in 2013 and 90.2% to 94.5% in 2017 for A. tuberculatus (Table 1). Barton (1961) reported 25% germination of A. retroflexus seed when stored on moist glass wool at constant temperatures over a period of 8 yr, but 100% viability and germination for the remaining seeds when these were exposed to suitable temperature and relative humidity environments.

Table 1.

Percentage of Amaranthus palmeri and Amaranthus tuberculatus viable seeds before (2013) and at the end of the experimental period (2017) of stored seed lots.

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Effects of Site and Seed Origin (Ecotype) on Seed Damage and Seed Viability

Significant differences (α=0.0001) for seed damage and viability were recorded for both species due to burial site. More specifically, higher seed damage averaged across ecotype, burial treatment, and retrieval year was recorded for the seed that originated from Illinois (51.3% and 51.8%) followed by Tennessee (40.5% and 45.1%), and Missouri (39.2% and 42%) for A. palmeri and A. tuberculatus, respectively. Pakeman et al. (2012) reported that increases in soil moisture resulted in increases of the rate of seed mortality. This might be attributed to the activity of fungal pathogens during moist or flooded conditions (Fogliatto et al. 2010; Liebman et al. 2014). The average volumetric water content values for Illinois and Tennessee were recorded at 0.39 and 0.38, respectively, and were the highest levels among all sites, whereas that of Missouri was at a moderate level equal to 0.22 (Figure 4).

Figure 4.

Monthly soil temperature (averaged over a 15-min concurrent recording period on a daily basis for the entire experimental period) at the top and at 15 cm below the soil surface (left y-axis) and monthly soil volumetric water content at 15 cm below soil surface (right y-axis) for each of the seven sites where the seed material of Amaranthus palmeri and Amaranthus tuberculatus was exposed to burial conditions during 2014–2016. Data presented for Missouri include only two experimental years (2015 and 2016).

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Volumetric water content at field capacity varies among soils, with values ranging from 0.1 or less for sandy soils to 0.4 for clay soils (Sinclair and Bennet 1998). The Indiana and Mississippi sites exhibited high viability, averaged across burial treatments, years, and ecotypes, for both species (i.e., 33.8% and 19.5% for A. palmeri and 33.4% and 27.8% for A. tuberculatus, respectively). Both the Indiana and Mississippi locations, despite their differences in soil temperature, exhibited moderate average volumetric water content, compared with values recorded for Illinois or Tennessee, at 0.32 and 0.29, respectively (Figure 4).

Despite the similarities of soil texture between the experimental sites (Table 2), the moderately higher percentage of sand content at Indiana and Arkansas followed by Tennessee and Mississippi is noticeable. Nevertheless, further research is required to clarify possible relationships among soil type structure, volumetric water content, and seed damage or viability.

Table 2.

Soil series, texture class, and related particle percentages along with organic matter (OM) content and pH for each of the experimental sites where seeds of Amaranthus palmeri and Amaranthus tuberculatus were exposed to burial treatments.

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Annual mean soil temperature at soil surface and 15 cm below the soil surface was recorded at 12.6 and 13.9 C for the Indiana site and at 17.8 and 18.2 C for the Mississippi site, respectively. Webb et al. (1987) reported that amaranth seedling emergence increased as temperature increased from 15.3 to 21.3 C under controlled environmental conditions. He also mentioned that these results corroborate earlier research under field conditions when mean spring soil temperatures were considered.

Larcher (1980) reported that the movement of water through the soil profile and into plant tissue are soil-temperature dependent; water can be extracted more readily from warm than cold soils. The relatively low average soil temperatures (13.5 C) in combination with the low average soil volumetric water content recorded at Missouri (equal to 0.22) possibly resulted in low seed viability for both A. palmeri and A. tuberculatus (Figure 4). High soil moisture levels deplete soil oxygen, causing hypoxic conditions (Wesseling and van Wijk 1957). Orthodox seeds, such as these of the Amaranthaceae family (Hong et al. 1996), maintain their longevity under aerobic conditions and permissible moisture levels; otherwise, seed viability will show the maximum rate of deterioration at a given temperature (Roberts and Ellis 1989).

The effects of site by seed origin (ecotype) averaged over years and burial depth on seed viability were found to be different (α =0.001) for both species (Figure 5; Supplementary Tables S1 and S2). Independently, the origin of the seed, hence the conditions of maternal environment under which the seeds were produced, influences the ability of these species to form a persistent seedbank, even though persistence varies by site (Figure 5; Supplementary Tables S1 and S2). This facilitates the occurrence and distribution of these species, particularly A. palmeri, over a wide range of habitats (Korres et al. 2015) or soil characteristics (Korres et al. 2017). Nevertheless, Penfield and MacGregor (2017) reported that seed-production environment effects are multifaceted and involve a complex and overlapping gene network that acts independently on fruit, seed coat, or zygotic tissues, which can be analyzed through careful physiological, molecular, and genetic approaches.

Figure 5.

Interaction of experimental site by ecotype on seed viability for Amaranthus palmeri and Amaranthus tuberculatus averaged across 2014–2016. Vertical bars represent ± standard error of the mean. Supplemental information is also provided in Supplementary Tables S1 and S2, where the actual values averaged across three replications per treatment and five locations of seed material origins are shown.

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Seed Burial Effects

Burial depth affected (α=0.001) seed damage plus loss for both species. Seeds placed on the soil surface had increased damage and loss compared with seeds buried at 15 cm, independent of the experimental site. Increased damage and loss of unburied seeds at all sites within the same year ranged from 3% to 42% for A. palmeri and 10% to 62% for A. tuberculatus (Figure 6; Supplementary Tables S1 and S2). The rate of unburied seed damage/loss versus that of buried seeds, between consecutive years, was greater for the unburied seeds, particularly for 2014 and 2015 (Figure 6; Supplementary Tables S1 and S2), for both species. As reported by Hulme (1998), seed burial protects seeds from insect predation; however, seeds are susceptible to fungal or bacterial pathogen infection (Blaney and Kotanen 2001; Leishman et al. 2000). In addition, burial of seeds can amend unfavorable environmental effects, reducing seed weathering and increasing seed longevity (Facelli et al. 2005; Wijayratne and Pyke 2012). Crist and Friese (1993) reported that seed decomposition and fungal pathogens were the major factors for the greatest decline of seeds deposited on soil surface compared with buried seeds. Nevertheless, susceptibility of weed seeds to decay by soil microorganisms is species dependent (Chee-Sanford et al. 2006), particularly in regard to the soil microbial community. The manipulation of soil fertility by the incorporation of organic amendments into the soil and/or the choice of cropping system that can influence the composition of fungal and bacterial communities (Davis 2007; Davis et al. 2006; Ullrich et al. 2011) might also affect seedbank longevity and persistence (De Cauwer et al. 2011).

Figure 6.

Interaction of experimental site by burial depth on percentage seed damage and loss averaged across 2014–2016 for Amaranthus palmeri and Amaranthus tuberculatus. Damaged seeds include broken, shrunk, or malformed seeds and those lost due to deterioration or futile germination, which were impossible to count. Vertical bars represent ± standard error of the mean. Supplemental information is also provided in Supplementary Tables S1 and S2, where the actual values averaged across three replications per treatment and five locations of seed material origins are shown.

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Seeds that were not placed in the field but remained under storage conditions had an average viability of 94.8% and 91.1% (±1.3 SE) for A. palmeri and 93.5% and 91.4% (±1.3 SE) and A. tuberculatus for 2013 and 2017, respectively (Table 1). On the contrary, viability of intact seeds rapidly declined the first 12 mo by 80% and 85% for buried and unburied A. palmeri seeds, respectively (Figure 7). Likewise, the percentage loss of viability for buried and unburied A. tuberculatus seeds for the first 12 mo was 78.2% and 84.6%, respectively. Loss of seed viability continued to decrease for both species between 12 and 24 mo burial, reaching the lowest level, at which burial depth had no influence, by the end of the 36-mo experimental period (Figure 7).

The rate at which A. palmeri and A. tuberculatus seeds lost viability over time depended on whether seeds were placed on the soil surface or buried, and it was found to vary among sites. A clear trend in reduction of seed viability was observed for Arkansas, Illinois, Indiana, Missouri, and Tennessee ecotypes compared with Mississippi and Wisconsin ecotypes in the case of A. palmeri (Figure 8). Viability of intact A. palmeri seeds on the soil surface was lower for the entire duration of the study but with some exceptions, as in the case of A. tuberculatus from the Indiana experimental site (Figure 8). Seed burial seemed to act as a longterm conservation mechanism for seedbank persistence in most sites for both species. Amaranthus palmeri seed viability was reduced in Arkansas between 2014 and 2016 for unburied seeds (90.3%) compared with buried seeds (79.4%). Similarly, seed viability declined by 88.7% and 68.4% in Illinois, by 82.4% and 69.2% in Indiana, by 63.1% and 62.2% in Mississippi, and by 60.6% and 43.8% in Wisconsin for unburied and buried seeds, respectively. Conversely, viability was reduced at a slower rate for unburied seeds than for buried seeds in Missouri and Tennessee. Similar trends were recorded for A. tuberculatus (Figure 8).

Figure 7.

Percentage seed viability as affected by burial depth and retrieval time (in months) for Amaranthus palmeri and Amaranthus tuberculatus. Vertical bars represent ± standard error of the mean (i.e., 0.612 and 0.649 for A. palmeri and A. tuberculatus, respectively).

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Figure 8.

Effects of experimental site by burial depth by year on percentage seed viability for Amaranthus palmeri and Amaranthus tuberculatus. Vertical bars represent ± standard error of the mean.

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The effects of burial depth and burial duration on deterioration of seed viability and seedbank longevity have been demonstrated for a range of weed species, such as wild oat (Avena fatua L.) (Miller and Nalewaja 1990), kochia [Bassia scoparia (L.) A. J. Scott] (Zorner et al. 1984), ripgut brome (Bromus diandrus Roth) (Gleichsner and Appleby 1989), weedy rice (Oryza sp.) (Chauhan 2012), giant ragweed (Ambrosia trifida L.) (Harrison et al. 2007), and A. palmeri (Sosnoskie et al. 2013). All of these studies reported findings similar to the work presented here and highlighted the importance of burial duration and depth on seed longevity, seed viability, and seedbank persistence; the deeper the seed burial (up to 30 cm), the greater the seedbank persistence (up to 36 mo burial duration).

As mentioned previously, the first important phase for the development of a persistent soil seedbank is burial (Fenner and Thompson 2005). Small seeds are more likely to become buried, thereby reinforcing the selective advantage of a small seed size, as is found in A. palmeri and A. tuberculatus, two very prolific weed species. The importance of tillage practices was mentioned as a primary tool for the depletion of seedbank persistence (Clements et al. 1996; Cousens and Moss 1990). Various studies (Blackshaw et al. 1994; Ominski and Entz 2001) reported that conservation or zero-tillage systems resulted in reductions of weed populations and seedbank depletion, an approach that could be proven to be quite suitable for A. palmeri and A. tuberculatus. Accumulation of seeds on soil surface in reduced-tillage cropping systems could increase seed mortality due to increased seed predation (Hossain and Begum 2015). Lack of soil disturbance via tillage could also encourage higher predator populations, as it enhances the number, diversity, and/or activity of seed-consuming habitat (Blubaugh and Kaplan 2015). In addition, the removal of weed before seed-set or harvesting weed seed could serve as a prevention method in reducing soil seedbank inputs and depleting weed seedbanks (Walsh et al. 2012, 2013), including those of Amaranthaceae weed species (Norsworthy et al. 2016). The results presented here indicate that the greatest influence of seed viability was burial conditions, time, and site-specific soil conditions, more so than geographical location. Hence, management of these weed species should focus on reducing seed shattering, removing the seed from the soil surface where germination may occur for prolonged periods, enhancing seed predation, or adjusting tillage systems.

Supplementary Materials. To view supplementary material for this article, please visit  https://doi.org/10.1017/wsc.2018.27

Acknowledgments.

Financial support from the United Soybean Board for this research is greatly appreciated. Joe Beeler, David Kincer, Joseph L. Matthews, Shaun Billman, Devin Hammer, Nathan Drewitz, and John Gaska proved invaluable assistance for the completion of this project.

No conflicts of interest have been declared.

References

  1. Association of Official Seed Analysts (1970) Tetrazolium Testing Handbook. Contribution No. 29 to the Handbook of Seed Testing. Washington, DC: Association of Official Seed Analysts. 62 p Google Scholar

  2. Baker HG ( 1989) Some aspects of the natural history of seed banks. Pages 9–21 in Leck MA, Parker TV & Simpson RL eds, Ecology of Soil Seed Banks. New York: Academic Google Scholar

  3. Barton LV ( 1961) Experimental seed physiology. Pp. 561–596 in Proceedings of the International Seed Testing Association 26 at Boyce Thompson Institute for Plant Research, Inc. Yonkers, NY: International Seed Testing Association Google Scholar

  4. Blackshaw RE, Larney GO, Lindwall CW, Kozub GC ( 1994) Crop rotation and tillage effects on weed populations on the semi-arid Canadian prairies. Weed Technol 8:231–237 Google Scholar

  5. Blaney CS, Kotanen PM ( 2001) Effects of fungal pathogens on seeds of native and exotic plants: a test using congeneric pairs. J Appl Ecol 38:1104–1113 Google Scholar

  6. Blubaugh CK, Kaplan I ( 2015) Tillage compromises weed seed predator activity across developmental stages. Biol Control 81:76–82 Google Scholar

  7. Borza JK, Westerman PR, Liebman M ( 2007) Comparing estimates of seed viability in three foxtail (Setaria) species using the imbibed seed crush test with and without additional tetrazolium testing. Weed Technol 21:518–522 Google Scholar

  8. Burnside OC, Fenster CR, Evetts LL, Mumm RF ( 1981) Germination of exhumed weed seed in Nebraska. Weed Sci 29:577–586 Google Scholar

  9. Burnside OC, Wilson RG, Weisberg S, Hubbard KG ( 1996) Seed longevity of 41 weed species buried 17 years in eastern and western Nebraska. Weed Sci 44:74–86 Google Scholar

  10. Cavers PB ( 1983) Seed demography. Can J Bot 61:3578–3590 Google Scholar

  11. Chauhan BS ( 2012) Weedy rice (Oryza sativa) II. Response of weedy rice to seed burial and flooding depth. Weed Sci 60:385–388 Google Scholar

  12. Chee-Sanford JC, Williams MW II , Davis AS, Sims GK ( 2006) Do microorganisms influence seed-bank dynamics? Weed Sci 54:575–587 Google Scholar

  13. Clements DR, Benoit DL, Murphy SD, Swanton CJ ( 1996) Tillage effects on weed seed return and seedbank composition. Weed Sci 44:314–322 Google Scholar

  14. Conn JS, Beattie KL, Blanchard A ( 2006) Seed viability and dormancy of 17 weed species after 19.7 years of burial in Alaska. Weed Sci 54:464–470 Google Scholar

  15. Cousens R, Moss SR ( 1990) A model of the effects of cultivations on the vertical distribution of weed seeds within the soil. Weed Res 30:61–70 Google Scholar

  16. Crist TO, Friese CF ( 1993) The impact of fungi on soil seeds: implications for plants and granivores in a semi-arid shrub-steppe. Ecology 74: 2231–2239 Google Scholar

  17. Davis AS ( 2007) Nitrogen fertilizer and crop residue effects on seed mortality and germination of eight annual weed species. Weed Sci 55:123–128 Google Scholar

  18. Davis AS, Anderson KI, Hallett SG, Renner KA ( 2006) Weed seed mortality in soils with contrasting agricultural management histories. Weed Sci 54: 291–297 Google Scholar

  19. Davis AS, Renner KA, Gross KL ( 2005) Weed seedbank and community shifts in a long-term cropping systems experiment. Weed Sci 53:296–306 Google Scholar

  20. De Cauwer B, D'Hose T, Cougnon M, Leroy B, Bulcke R, Reheul D ( 2011) Impact of the quality of organic amendments on the size and composition of the weed seed bank. Weed Res 51:250–260 Google Scholar

  21. Egley GH, Chandler JM ( 1983) Longevity of weed seeds after 50 years in the Stoneville 50-year buried-seed study. Weed Sci 31:264–270 Google Scholar

  22. Facelli JM, Chesson P, Barnes N ( 2005) Differences in seed biology of annual plants in arid lands: a key ingredient of the storage effect. Ecology 86: 2998–3006 Google Scholar

  23. Fenner M, Thompson K ( 2005) The Ecology of Seeds. Cambridge, UK: Cambridge University Press. 241 p Google Scholar

  24. Fogliatto S, Vidotto F, Ferrero A ( 2010) Effects of winter flooding on weedy rice (Oryza sativa L.). Crop Prot 29:1232–1240 Google Scholar

  25. Forcella F ( 2003) Debiting the seedbank: priorities and predictions. Asp Appl Biol 69:151–162 Google Scholar

  26. Forcella F, Wilson RG, Renner KA, Dekker J, Harvey RG, Alm DA, Buhler DD, Cardina J ( 1992) Weed seedbanks of the U.S. Corn Belt: magnitude, variation, emergence, and application. Weed Sci 40:636–644 Google Scholar

  27. Forcella F, Webster T, Cardina J ( 2003) Protocols for weed seed bank determination in agro-ecosystems. In Labrada R ed, Weed Management for Developing Countries. FAO Plant Production and Protection Paper 120, Addendum 1. Rome: Food and Agriculture Organization of the United Nations Google Scholar

  28. Gleichsner JA, Appleby AP ( 1989) Effect of depth and duration of seed burial on ripgut brome (Bromus rigidus). Weed Sci 37:68–72 Google Scholar

  29. Gutterman Y ( 1994) Strategies of seed dispersal and germination in plants inhabiting deserts. Bot Rev 60:373–425 Google Scholar

  30. Harrison SK, Regnier EE, Schmoll JT, Harrison JM ( 2007) Seed size and burial effects on giant ragweed (Ambrosia trifida) emergence and seed demise. Weed Sci 55:16–22 Google Scholar

  31. Hartzler RG, Battles BA, Nordby D ( 2004) Effect of common waterhemp (Amaranthus rudis) emergence date on growth and fecundity in soybean. Weed Sci 52:242–245 Google Scholar

  32. Heap I ( 2017) The International Survey of Herbicide Resistant Weeds.  www.weedscience.org Accessed: April 2, 2018 Google Scholar

  33. Heneghan JM, Johnson WG ( 2017) The growth and development of five waterhemp (Amaranthus tuberculatus) populations in a common garden. Weed Sci 65:247–255 Google Scholar

  34. Holmgren M, Stapp P, Dickman CR, Gracia C, Graham S, Gutierrez JR, Hice C, Jaksic F, Kelt DA, Letnic M, Lima M, Lopez BC, Meserve PL, Milstead WB, Polis GA, Previtali MA, Richter M, Sabate S, Squeo FA ( 2006) Extreme climatic events shape arid and semiarid ecosystems. Frontiers Ecol Env 4:87–95 Google Scholar

  35. Honda Y ( 2008) Ecological correlations between the persistence of the soil seed bank and several plant traits, including seed dormancy. Plant Ecol 196:301–309 Google Scholar

  36. Hong TD, Linington S, Ellis RH ( 1996) Seed Storage Behaviour: A Compendium. Handbooks for Genebanks No. 4. Rome: International Plant Genetic Resources Institute. P 104 Google Scholar

  37. Hossain MM, Begum M ( 2015) Soil weed seed bank: importance and management for sustainable crop production—a review. J. Bangladesh Agr 13:221–228 Google Scholar

  38. Hulme PE ( 1998) Post-dispersal seed predation and seed bank persistence. Seed Sci Res 8:513–519 Google Scholar

  39. International Seed Testing Association (1985) International rules for seed testing 1985. Seed Sci Tech 13:300–520 Google Scholar

  40. Jha P, Norsworthy JK, Garcia J ( 2014) Depletion of an artificial seed bank of Palmer amaranth (Amaranthus palmeri) over four years of burial. Am J Plant Sci 5:1599–1606 Google Scholar

  41. Jhala AJ, Sandell LD, Rana N, Kruger GR, Knezevic SZ ( 2014) Confirmation and control of triazine and 4-hydroxyphenylpyruvate dioxygenase-inhibiting herbicide-resistant Palmer amaranth (Amaranthus palmeri) in Nebraska. Weed Technol 28:28–38 Google Scholar

  42. Kivilaan A, Bandurski RS ( 1981) The one hundred year period for Dr Beal's seed viability experiment. Am J Bot 68:1290–1292 Google Scholar

  43. Korres NE ( 2018) Agronomic weed control: a trustworthy approach for sustainable weed management. Pages 97–114 in Jabran K & Chauhan BS eds, Non-chemical Weed Control. London: Academic Google Scholar

  44. Korres NE, Norsworthy JK ( 2017) Palmer amaranth (Amaranthus palmeri) demographic and biological characteristics in wide-row soybean. Weed Sci 65:491–503 Google Scholar

  45. Korres NE, Norsworthy JK, Bagavathiannan MV, Mauromoustakos A ( 2015) Distribution of arable weed populations along eastern Arkansas Mississippi Delta roadsides: occurrence, distribution, and favored growth habitats. Weed Technol 29:587–595 Google Scholar

  46. Korres NE, Norsworthy JK, Brye K, Skinner JR V, Mauromoustakos A ( 2017) Relationships between soil properties and the occurrence of the most agronomically important weed species in the field margins of eastern Arkansas—implications for weed management in field margins. Weed Res 57:159–171 Google Scholar

  47. Larcher W ( 1980) Physiological Plant Ecology. 2nd ed. Biederman-Thorson MA trans. Berlin: Springer-Verlag. Pp 206–267  Google Scholar

  48. Leishman MR, Masters GJ, Clarke IP, Brown VK ( 2000) Seed bank dynamics: the role of fungal pathogens and climate change. Funct Ecol 14:293–299 Google Scholar

  49. Liebman M, Miller ZJ, Williams CL, Westerman PR, Dixon PM, Heggenstaller A, Davis AS, Menalled FD, Sundberg DN ( 2014) Fates of Setaria faberi and Abutilon theophrasti seeds in three crop rotation systems. Weed Res 54:1–14 Google Scholar

  50. Liebman M, Mohler CL, Staver CP ( 2001) Ecological Management of Agricultural Weeds. New York: Cambridge University Press. 525 p Google Scholar

  51. Lutman PJW, Cussans GW, Wright KJ, Wilson BJ, Wright GM, Lawson HM ( 2002) The persistence of seeds of 16 weed species over six years in two arable fields. Weed Res 42:231–241 Google Scholar

  52. Miller DS, Nalewaja JD ( 1990) Influence of burial depth on wild oats (Avena fatua) seed longevity. Weed Technol 4:514–517 Google Scholar

  53. Molin WT, Nandula VK, Wright AA, Bond JA ( 2016) Transfer and expression of ALS inhibitor resistance from Palmer amaranth (Amaranthus palmeri) to an A. spinosus × A. palmeri hybrid. Weed Sci 64:240–247 Google Scholar

  54. Norsworthy JK, Korres NE, Walsh MJ, Powles SB ( 2016) Integrating herbicide programs with harvest weed seed control and other fall management practices for the control of glyphosate-resistant Palmer amaranth. Weed Sci 64:540–550 Google Scholar

  55. Omami EN, Haigh AM, Medd RW, Nicol HI ( 1999) Changes in germinability, dormancy and viability of Amaranthus retroflexus as affected by depth and duration of burial. Weed Res 39:345–354 Google Scholar

  56. Ominski PD, Entz MH ( 2001) Eliminating soil disturbance reduces postalfalfa annual weed populations. Can J Plant Sci 81:881–884 Google Scholar

  57. Ooi MKJ ( 2012) Seed bank persistence and climate change. Seed Sci Res 22: S53–S60 Google Scholar

  58. Ooi MKJ, Auld TD, Whelan RJ ( 2007) Distinguishing between persistence and dormancy in soil seed banks of three shrub species from fire-prone southeastern Australia. J Veg Sci 18:405–412 Google Scholar

  59. Pakeman RJ, Small JL, Torvell L ( 2012) Edaphic factors influence the longevity of seeds in the soil. Plant Ecol 213:57–65 Google Scholar

  60. Peart MH ( 1984) The effects of morphology, orientation and position of grass diaspores on seedling survival. J Ecol 72:437–53 Google Scholar

  61. Penfield S, MacGregor DR ( 2017) Effects of environmental variation during seed production on seed dormancy and germination. J Exp Bot 68:819–825 Google Scholar

  62. Price JN, Wright BR, Gross CL, Whalley WRDB ( 2010) Comparison of seedling emergence and seed extraction techniques for estimating the composition of soil seed banks. Methods Ecol Evol 1:151–157 Google Scholar

  63. Quick CR ( 1961) How long can a seed remain alive? Pages 94–99 in, Seeds: The Yearbook of Agriculture 1961. Washington, DC: U.S. Department of Agriculture Google Scholar

  64. Riar DS, Norworthy JK, Steckel LE, Stephenson DO, Eubank TW, Scott RC ( 2013) Assessment of weed management practices and problem weeds in the midsouth United States—soybean: a consultant's perspective. Weed Technol 27:612–622 Google Scholar

  65. Roberts EH, Ellis RH ( 1989) Water and seed survival. Ann Bot 63:39–52 Google Scholar

  66. Sawna JT, Mohler CL ( 2002) Evaluating seed viability by an unimbibed seed crush test in comparison with the tetrazolium test. Weed Technol 16:781–786 Google Scholar

  67. Schweizer EE, Zimdahl RL ( 1984) Weed seed decline in irrigated soil after rotation of crops and herbicides. Weed Sci 32:84–89 Google Scholar

  68. Scott JK, Webber BL, Murphy H, Ota N, Kriticos DJ, Loechel B ( 2014) AdaptNRM Weeds and Climate Change: Supporting Weed Management Adaptation.  www.AdaptNRM.org. Accessed: December 20, 2017 Google Scholar

  69. Sinclair TR, Bennet JM ( 1998) Water. Pages 103–120 in Sinclair TR & Gardner FR eds, Principles of Ecology in Plant Production. Wallingford, UK: CABI Google Scholar

  70. Sosnoskie LM, Webster TM, Culpepper AS ( 2013) Glyphosate resistance does not affect Palmer amaranth (Amaranthus palmeri) seedbank longevity. Weed Sci 61:283–288 Google Scholar

  71. Steckel LE, Sprague CL, Stoller EW, Wax LM ( 2004) Temperature effects on germination of nine Amaranthus species. Weed Sci 52:217–221 Google Scholar

  72. Steckel LE, Sprague CL, Stoller EW, Wax LM, Simmons FW ( 2007) Tillage, cropping system, and soil depth effects on common waterhemp (Amaranthus rudis) seed-bank persistence. Weed Sci 55:235–239 Google Scholar

  73. Telewski FW, Zeevaart JAD ( 2002) The 120-yr period from Dr. Beal's seed viability experiment. Am J Bot 89:1285–1288 Google Scholar

  74. Toole EH, Brown E ( 1946) Final results of the Duvel buried seed experiment. J Agric Res 72:201–210 Google Scholar

  75. Thompson K, Green A, Jewels AM ( 1994) Seeds in soil and worm casts from a neutral grassland. Funct Ecol 8:29–35 Google Scholar

  76. Ullrich SD, Buyer JS, Cavigelli MA, Seidel R, Teasdale JR ( 2011) Weed seed persistence and microbial abundance in long-term organic and conventional cropping systems. Weed Sci 59:202–209 Google Scholar

  77. Vencill WK, Grey TL, Culpepper AS, Gaines C, Westra R ( 2008) Herbicide resistance in the Amaranthaceae. J Plant Dis Prot 21(SP): 41–44 Google Scholar

  78. Walsh M, Newman P, Powles S ( 2013) Targeting weed seeds in-crop: a new weed control paradigm for global agriculture. Weed Technol 27:431–436 Google Scholar

  79. Walsh MJ, Harrington RB, Powles SB ( 2012) Harrington Seed Destructor: a new nonchemical weed control tool for global grain crops. Crop Sci 52:1343–1347 Google Scholar

  80. Warr SJ, Thompson K, Martin Kent M ( 1993) Seed banks as a neglected area of biogeographic research: a review of literature and sampling techniques. Prog Phys Geog 17:329–347 Google Scholar

  81. Webb DM, Smith CW, Schulz-Schaeffer J ( 1987) Amaranth seedling emergence as affected by seeding depth and temperature on a thermogradient plate. Agron J 79:23–26 Google Scholar

  82. Webster TM, Nichols RL ( 2012) Changes in the prevalence of weed species in the major agronomic crops of the southern United States: 1994/1995 to 2008/2009. Weed Sci 60:145–157 Google Scholar

  83. Wesseling J, van Wijk WR ( 1957) Soil physical conditions in relation to drain depth. Pages 461–504 in Luthin JN ed, Drainage of Agricultural Lands. Madison, WI: American Society of Agronomy Google Scholar

  84. Wijayratne UC, Pyke DA ( 2012) Burial increases seed longevity of two Artemisia tridentata (Asteraceae) subspecies. Am J Bot 99: 438–447 Google Scholar

  85. Zorner PS, Zimdahl RL, Schweizer EE ( 1984) Effect of depth and duration of seed burial on kochia (Kochia scoparia). Weed Sci 32: 602–607 Google Scholar

© Weed Science Society of America, 2018. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
Nicholas E. Korres, Jason K. Norsworthy, Bryan G. Young, Daniel B. Reynolds, William G. Johnson, Shawn P. Conley, Reid J. Smeda, Thomas C. Mueller, Douglas J. Spaunhorst, Karla L. Gage, Mark Loux, Greg R. Kruger, and Muthukumar V. Bagavathiannan "Seedbank Persistence of Palmer Amaranth (Amaranthus palmeri) and Waterhemp (Amaranthus tuberculatus) across Diverse Geographical Regions in the United States," Weed Science 66(4), (1 July 2018). https://doi.org/10.1017/wsc.2018.27
Received: 8 February 2018; Accepted: 24 April 2018; Published: 1 July 2018
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