sustainability
Article
Influence of Mowing and Trampling on the Allelopathy and
Weed Suppression Potential of Digitaria ciliaris and
Cyperus microiria
Bienvenu Biramahire 1 , Kwame Sarpong Appiah 1,2 , Seishu Tojo 3, Yoshiharu Fujii 3,* and Tadashi Chosa 3,*
1 United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Fuchu,
Tokyo 183-8509, Japan
2 Department of Crop Science, University of Ghana, Legon, Accra P.O. Box LG 44, Ghana
3 Department of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan
* Correspondence: yfujii@cc.tuat.ac.jp (Y.F.); chosa@cc.tuat.ac.jp (T.C.)
Abstract: A long-term, sustainable solution to weed infestation is extremely desirable because weeds
have the potential to reduce crop productivity and the aesthetic appeal of the environment. In this
study, the impacts of mowing and varying degrees of trampling pressure on the suppression of
weeds, alongside wound-induced changes in the allelopathic potential, of the rhizosphere soil and
the root exudates of southern crabgrass (Digitaria ciliaris) and Asian flatsedge (Cyperus microiria)
were evaluated under both field and greenhouse conditions. The field study results showed that
all trampling treatments induced the relative suppression of weed growth. Grass weeds showed
higher resistance to trampling than broad-leaved weeds. However, laboratory bioassays showed that
light trampling caused a significant increase in the growth-inhibitory effects of southern crabgrass
rhizosphere soil on lettuce. Moreover, mowing (9.11% of control) and trampling (16.4% of control)
Citation: resulted in a marginal increase in the growth-inhibitory effects of root exudates released from southernBiramahire, B.; Appiah,
K.S.; Tojo, S.; Fujii, Y.; Chosa, T. crabgrass. Furthermore, the growth-inhibitory activities of the Asian flatsedge rhizosphere soil were
Influence of Mowing and Trampling significantly reduced after heavy trampling pressure. Moreover, mowing and trampling resulted in
on the Allelopathy and Weed marginal reductions in the growth-inhibitory activities of root exudates released from Asian flatsedge
Suppression Potential of Digitaria against lettuce (i.e., 18.7% and 28.5%, respectively). In general, mowing and varying degrees of
ciliaris and Cyperus microiria. trampling induced contrasting and integrated impacts on weed suppression as well as the allelopathic
Sustainability 2022, 14, 16665. potential of both southern crabgrass and Asian flatsedge.
https://doi.org/10.3390/
su142416665 Keywords: trampling; weed suppression; Digitaria ciliaris; Cyperus microiria; allelopathy
Academic Editor: Khawar Jabran
Received: 28 October 2022
Accepted: 7 December 2022 1. Introduction
Published: 13 December 2022
The application of herbicides and mowing to mitigate the challenges of weed in-
Publisher’s Note: MDPI stays neutral festation often leads to health and environmental problems in the long term [1,2]. For
with regard to jurisdictional claims in instance, intense or prolonged mowing has been reported to further induce grass weed
published maps and institutional affil- infestation [3,4], along with severe accidental injury to mowing machine operators [5,6]. In
iations. addition, mowing needs a long-standing, hardworking labor force [7]. Moreover, excessive
pesticide inputs harm both life on Earth and the whole environment [8]. When humans or
animals become directly or indirectly exposed to synthetic agrichemicals for a long period
of time, they commonly develop several health conditions, including both respiratory and
Copyright: © 2022 by the authors.
Licensee MDPI, Basel, Switzerland. reproductive impairments, diabetes, neurological disorders, and cancer [9]. Furthermore,
This article is an open access article the inappropriate use of pesticides pollutes water bodies, interferes with soil health, and
distributed under the terms and results in the development of pesticide-resistant weeds as well [10]. Hence, there is a strong
conditions of the Creative Commons need for alternate weed control techniques to ensure sustainable weed management.
Attribution (CC BY) license (https:// In previous studies, the potential use of allelopathic species has been explored in the
creativecommons.org/licenses/by/ control of weeds. The extensive and effective implementation of bioherbicides released
4.0/). directly from allelopathic plants or manufactured indirectly from allelopathic compounds
Sustainability 2022, 14, 16665. https://doi.org/10.3390/su142416665 https://www.mdpi.com/journal/sustainability
Sustainability 2022, 14, 16665 2 of 16
could, in fact, be a better and more sustainable means of strengthening global crop produc-
tion, along with a reduction in the health and environmental hazards caused by synthetic
herbicides [10]. Furthermore, studies have been performed on how mechanical stimu-
lation, including trampling, rolling, and roll chopping, can sustainably suppress weeds’
growth [4,11]. Moreover, studies on the effects of human [12,13], animal [14], and ma-
chine trampling [11] on weed control, soil compaction, and vegetation composition have
indicated that light treading pressure possesses more desirable impacts on both weed
suppression and soil health than intense treading pressure [13,15]. This can be linked to
the fact that mechanical stimulation (i.e., touching, cutting, and pressuring), herbivory,
and some environmental factors (such as drought and nutrient availability) induce the
release of volatile organic compounds (VOCs), such as ethylene, which, depending on
its concentration, stimulates or suppresses both growth and senescence in plants [16–18].
It also induces transient increases in the root exudation of organic carbon, amino acids,
ammonium cations, phenolics, and proteins [19–21]. Thus, the desirable weed suppression
impacted by light trampling might not only be due to the outcome of the physical top-down
pressure on weeds but also a complex process involving the influence of allelochemicals
released from touched or wounded plants.
Root exudates are major sources for the direct input of plant chemicals into the
rhizosphere, making them one of the most important sources of allelochemicals released
into the rhizosphere soil [22]. Both mowing and trampling are long-established methods of
weeding that could (along with other mechanical stimulation) hypothetically influence the
allelopathic activity and subsequent suppression of weeds in the field. As an example of the
enhancement in allelopathic compound release through mechanical means, Yang et al. [23]
reported that the use of a mist system on the roots of sorghum (Sorghum bicolor) increased
sorgoleone exudation through the induction of abundant root hair production. Sorgoleone
is a strong allelochemical as well as a potent bioherbicide produced in the root hairs of
sorghum plants [24,25]. Allelochemicals are released into the environment through several
routes, including volatilization, leachates, exudation, and decomposition. Specific bioassays
have been designed to effectively evaluate the growth-inhibitory effects of compounds
released through these routes. These include plant-box [26] and rhizosphere soil [27]
methods for root exudates, the dish pack method [28] for volatiles, and the sandwich
method [29] for leachates. In this study, the plant-box and rhizosphere soil methods were
adopted to assess wound-induced variations in the allelopathic effects of candidate plants.
The objective of this study was to assess the impacts of mowing and varying degrees
of intensity of trampling on the suppression of weed growth, along with variations in
the allelopathic potential, of both the rhizosphere soil and the root exudates of southern
crabgrass (Digitaria ciliaris) and Asian flatsedge (Cyperus microiria). Both Southern crabgrass
(annual plant) and Asian flatsedge (perennial plant) are common, widespread, and noxious
weeds, and they all aggressively grow in open fields, soybean fields, and both upland and
paddy fields [30–32]. In addition, biochemical compounds (i.e., veratric acid, maltol, and
(−)-loliolide) released in the root exudates of crabgrass (Digitaria sanguinalis), which belongs
to the Digitaria family, were reported to inhibit the growth of wheat, maize, and soybean
alongside the growth of soil bacteria, actinobacteria, and fungi [33]. On the other hand,
several terpenes, including α-cyperone, β-selinene, and α-humulene, were extracted from
the tubers and rhizomes of whitehead spikesedge (Cyperus kyllingia), which belongs to the
Cyperus family, and they all indicated growth inhibition effects against lettuce seedlings [34].
This study presents the outcome of preliminary research conducted on common weeds as
an initial stage of a large, ongoing research project.
2. Materials and Methods
All field and greenhouse experiments, along with laboratory bioassays, were con-
ducted at the Tokyo University of Agriculture and Technology, Saiwai-cho, Fuchu, Tokyo,
Japan (35◦41′ N, 139◦28′ E). Southern crabgrass and Asian flatsedge were selected as can-
didate species for laboratory bioassays because the two weeds were the most dominant
Sustainability 2022, 14, 16665 3 of 16
weeds within the field. They also possess stronger stems, which gave them more resistance
and allowed the more successful uprooting of their roots from the soil. All the other weeds
(i.e., oriental water willow (Justicia procumbens), horsenettle (Solanum carolinense), and giant
foxtail (Setaria faberi)) were difficult to pull out of the ground because they had become
extremely broken up, particularly after heavy trampling pressure.
In addition, a greenhouse study was carried out in order to evaluate the potential
allelopathic effects of the candidate species in a controlled environment. In the field,
rainfall (Appendix A) might interfere with the allelopathic potential in the soil by leaching
water-soluble allelochemicals into deeper soil profiles [35]. The greenhouse experiment
also ensured that the growth-inhibitory effects of only the root exudates from Southern
crabgrass and Asian flatsedge were evaluated, and not those from other organisms.
2.1. Planting Conditions and Treatments
This section describes how the weed species were grown in both the field and green-
house studies, along with how they were treated.
2.1.1. Field Study
Beginning in July 2018, the experimental field was established after mowing an un-
cultivated area of land consisting of 24 plots. The soil type was Andosol (also known as
Kuroboku soil), which is a common, humus-rich, light black soil in the Kanto Plain, Central
Japan, developed from volcanic ash, and which was texturally classified as clay loam, with
29.6% of sand, 33.4% of silt, and 23.4% of clay [36,37]. This study used a randomized
complete block design with four replications. The plot size was 1.05 m2 (0.70× 1.50 m), and
the distance between plots was 1.0 m. Treatments consisted of mowing, trampling 25 times
(T25), trampling 50 times (T50), trampling 100 times (T100), and trampling 200 times (T200).
The control plots were left undisturbed. Weed species grew naturally for around three
months before being treated. Mowing and trampling experiments were carried out once
after the weed survey. The weeds were trimmed to 2~5 cm using a shoulder-type lawn
mower (MBC231DWB, Makita Co., Ltd., Kagawa, Japan) and the leaf cuttings were imme-
diately removed from all mown plots. The trampling was conducted by rolling a 69.5 kg
grass roller (SL-003 International Trading Co., Ltd., Yangjiang, China) back and forth from
one end of the plot to the other.
2.1.2. Greenhouse Study
A greenhouse was used to grow southern crabgrass and Asian flatsedge plants both in
the soil (i.e., for assessing the allelopathic influences of the rhizosphere soil) and in the sand
(i.e., for assessing the allelopathic influences of the root exudates). Southern crabgrass was
grown with commercially available seeds (ESPEC MIC Corporation, Aichi, Japan), while
Asian flatsedge was grown with transplants collected from the field. Both species were
grown for around four months. The T15 treatment was included based on the outcome of
the field study, which suggested that light trampling pressure induced higher allelopathic
impacts than heavy trampling pressure.
Soil cultivation (for assessing allelopathic influences of the rhizosphere soil)
Between six and eight Southern crabgrass and Asian flatsedge plants were grown in
clay pots (21 cm dia. × 17 cm depth) using commercially available, pre-fertilized, and
granulated soil (JA Nippi No. 1, Ninon Hiryo Co., Ltd., Tokyo, Japan). Treatments consisted
of mowing, trampling 15 times (T15), trampling 25 times (T25), and trampling 50 times
(T50). The control pots were left undisturbed. All treatments, including the control pots,
were replicated three times. The weeds were trimmed down to 2~5 cm using a garden
shear, and the leaf cuttings were immediately removed from all the clipped pots. To ensure
that each pot received the same amount of trampling force per treatment, trampling was
strictly carried out on the same day by a single person (~50 kg), who evenly stamped on all
weeds with a boot-shod leg.
Sustainability 2022, 14, 16665 4 of 16
Sand cultivation (for assessing allelopathic influences of the root exudates)
Between six and eight southern crabgrass and Asian flatsedge plants were grown in
clay pots (21 cm dia. × 17 cm depth) using commercially available 100% natural river sand
(Miyuki Shoko Co., Ltd., Saitama, Japan). The use of natural river sand allowed the easy
removal of plants from the clay pots without destroying the roots [26]. Treatments consisted
of mowing and trampling 15 times (T15). All control plants were left intact or untouched.
2.2. Field Experiments
This section describes all experiments carried out in the field, including the weed sur-
vey, and the calculation of the frequency percentages of all identified weeds, the calculation
of the multiplied dominance ratio (MDR) of the 5 most frequent weeds, the soil hardness
test, and the gathering of rainfall data as well.
2.2.1. Weed Survey and Calculation of the Frequency Percentage
The assessment of the suppression of weed growth began by documenting and com-
puting the frequency percentage of all spotted weeds within all 24 plots of the experimental
field (two days before treatment). Frequency (%) measurement is an easy, fast, and reliable
method because only the presence or absence of a species is recorded to calculate the
percentage of all sampling units (e.g., quadrants or plots) in which the target species is
found, and it is calculated as follows [38]:
Number of sampling units
Frequency (%) = × 100
Total number of sampling units
The number of sampling units referred to the number of all plots in which a given
weed was found, while the total number of sampling units was 24 (all 24 plots of the
field). In addition, the frequency percentages were used to select the candidate weeds for
multiplied dominance ratio (MDR) calculation and allelopathic activity bioassays.
2.2.2. Multiplied Dominance Ratio (MDR)
One day before treatment, which was considered zero weeks after treatment (0 WAT),
two weeks after treatment (2 WAT), and four weeks after treatment (4 WAT), the percentage
coverage and height of the 5 most frequent weeds were recorded within a 0.25 m2 quadrant
(0.50 × 0.50 m) placed in the center of each plot. In each plot, the height of three mature
individuals per species was randomly measured using a ruler (from soil to shoot apex)
in three different places within the quadrant. The plants measured at 0 WAT were not
marked to ensure randomness; therefore, they could not be recognized at both 2 WAT
and 4 WAT. Afterwards, the MDR was calculated to express the impacts of mowing and
trampling on weed volume [39] for the 5 most frequent weeds. The MDR is a common
weed dominance index, calculated by multiplying the percentage coverage and height of
each target species [40].
MDR (m3 m−2) = coverage (m2 m−2) × height (m)
2.2.3. Soil Hardness Test
Variations in the hardness of the soil are common indicators of changes in the levels
of soil compaction [41,42]. Therefore, at 3 WAT, 6 WAT, and 13 WAT, soil hardness was
recorded using a soil penetrometer (Hardness tester, Fujiwara Scientific Co., Ltd., Tokyo,
Japan) to quantify the impacts of trampling and mowing on soil compaction. Three
consecutive sunny days were awaited to record 10 samples per plot, because the soil
hardness test is conducted best on moist, but not too wet, soil.
Sustainability 2022, 14, 16665 5 of 16
2.2.4. Gathering of the Rainfall Data
The data on daily rainfall in Fuchu, Tokyo, Japan, between 1 September 2018 and
31 December 2018 (Appendix A), were obtained using the Automated Meteorological Data
Acquisition System (AMeDAS) [43].
2.3. Laboratory Bioassays
This section describes the laboratory bioassays (i.e., the rhizosphere soil and plant-box
methods) used to assess the allelopathic potential of rhizosphere soil alongside the root
exudates of the target weed species.
2.3.1. Rhizosphere Soil Method
The allelopathic effects of rhizosphere soil from both field-collected and greenhouse-
grown weed species were investigated using the rhizosphere soil method described by
Fujii et al. [27]. In all field and greenhouse studies, rhizosphere soil was collected on the
fourth day after mowing and trampling. Rhizosphere soil is commonly defined as the soil
adhering to plant roots after being shaken thoroughly [44].
Fifteen mature plants per species per treatment were gently pulled out of the ground by
hand and subsequently taken into the laboratory for soil sampling, along with allelopathic
analyses. Afterwards, all surface soil was shaken off the plants, and the rhizosphere soil
was gently collected from the surface roots using a soft brush. Three grams of soil (sieved
with a 1.0-mm sieve) was placed into a 6-well multi-dish. Subsequently, 5.0 mL of 0.75%
agar was poured on top of the soil. After the gelatinization of the soil–agar mixture, an
additional 3.2 mL of agar was added to the mixture. Lettuce seeds (Lactuca sativa L. var.
Legacy; Takii Company, Kyoto, Japan) were planted on the gelatinized soil–agar mixture.
The six-well multi-dishes were closed and incubated in a dark incubator (NTS Model
MI-25S) at 25 ◦C for 3 days. Subsequently, the lengths of the lettuce radicles were measured.
The percentage of inhibition of rhizosphere soil growth before treatment (i.e., using
intact plants) was determined by considering the growth of lettuce seedlings grown in
the agar medium (gelling temperature 30–31 ◦C, Nacalai Tesque, Kyoto, Japan) as 100%.
Furthermore, changes in the allelopathic effects of rhizosphere soil after treatments were
determined by comparing the length of lettuce seedlings grown in the soil of mown and
trampled plants with the length of lettuce seedlings grown in the soil of intact plants.
2.3.2. Plant-Box Method
The allelopathic effect of root exudates was assessed using the plant-box method
described by Fujii et al. [26]. It was carried out in order to gain further insight into how the
wound-induced changes in root exudation processes influence the allelopathic potential of
the target weeds.
In this context, mature plants were mown or trampled and slowly pulled out of the
pots by hand. The plants were immediately taken into the laboratory for the allelopathic
assessment of root exudates. Afterwards, the roots of the plants were gently and thoroughly
washed with distilled water. Then, the plants were placed into the root zone separating
tubes and fixed in their positions in the plant boxes using cellophane tape. The agar solution
was slowly poured into the boxes (to avoid bubbles) up to the 6.5 cm level. The boxes were
cooled down immediately by dipping them in ice-chilled water (for approximately 30 min)
and leaving them to stand at room temperature for a few more minutes. Lettuce seeds
(Lactuca sativa L. var. Legacy; Takii Company, Kyoto, Japan) were seeded on the surface
of the agar (narrowed tip downward). All boxes were covered with polyethylene and
incubated in a growth chamber (BiOTRON. Type LH-350SP, NK System, Taiwan) at 25 ◦C
for 5 days (12 h of light and 12 h of darkness). After the incubation period, the lengths of
lettuce radicles and hypocotyls were measured.
The percentage of inhibition of root exudate growth before treatment (i.e., using
intact plants) was determined by considering the growth of lettuce seedlings grown on the
agar medium (gelling temperature 30–31 ◦C, Nacalai Tesque, Kyoto, Japan) as 100%. In
Sustainability 2022, 14, 16665 6 of 16
addition, the changes in the allelopathic effects of the root exudates were determined by
comparing the percentage growth inhibition of both mown and trampled plants with that
of intact plants.
2.4. Statistical Analysis
Statistical analyses and graphs were obtained using IBM SPSS Statistics 27 (IBM®
SPSS®, Armonk, NY, USA) along with Microsoft Excel (Microsoft, Redmond, Washington,
DC, USA). Tukey’s HSD test, Dunnett’s test, and analysis of variance (ANOVA) were
conducted. The significance level was 0.05.
3. Results
3.1. Weed Survey
In the field, seventeen weed species were identified before treatment and the frequency
percentages of these species were calculated (Table 1). The five most frequent weed species
were southern crabgrass (Digitaria ciliaris), Asian flatsedge (Cyperus microiria), oriental
water willow (Justicia procumbens), horsenettle (Solanum carolinense), and giant foxtail
(Setaria faberi). The five least frequent weeds were yellow foxtail (Setaria glauca), mulberry
(Morus alba), dallisgrass (Paspalum dilatatum), spotted spurge (Euphorbia maculata), and
annual bluegrass (Poa annua). The five most frequent weed species served to evaluate the
impacts of both mowing and trampling on the MDRs of the weeds.
Table 1. Frequency percentages of weed species identified inside all 24 experimental field plots.
No. Scientific Name Common Name Frequency (%)
1 Digitaria ciliaris Southern crabgrass 95.8
2 Cyperus microiria Asian flatsedge 95.8
3 Justicia procumbens Oriental water willow 95.8
4 Solanum carolinense Horsenettle 75.0
5 Setaria faberi Giant foxtail 70.8
6 Rumex japonicus Japanese dock 66.7
7 Houttuynia cordata Fish-mint 62.5
8 Cayratia japonica Bush killer 54.2
9 Paederia scandens Skunk vine 41.7
10 Plantago lanceolata Ribwort plantain 37.5
11 Oxalis corniculata Sleeping beauty 37.5
12 Taraxacum officinale Dandelion 20.8
13 Poa annua Annual bluegrass 12.5
14 Euphorbia maculata Spotted spurge 12.5
15 Paspalum dilatatum Dallisgrass 8.33
16 Morus alba Mulberry 4.17
17 Setaria glauca Yellow foxtail 4.17
The weed survey was carried out one day before treatment or zero weeks after treatment (0 WAT).
3.2. Multiplied Dominance Ratio (MDR)
A wide-ranging dataset of the multiplied dominance ratios (MDRs) of all the five
most frequent weeds is shown in Table 2. The high variability observed in the MDRs
is related to the larger variations in the elongation (height) along with the expansion
(coverage area) of candidate weed species. In comparison to all the other weeds, it was
found that southern crabgrass was taller and had a larger coverage area, resulting in a
significantly higher MDR. Despite being slightly taller than Asian flatsedge and oriental
water willow plants, horsenettle and giant foxtail still occupied a smaller area inside most
plots, which resulted in their MDRs becoming noticeably lower than the MDR of southern
crabgrass. Additionally, an analysis of variance (ANOVA) of the MDRs also showed that
the difference between species was highly significant. In comparison to the controls, only
mowing induced significant decreases in the MDR of southern crabgrass (a vs. b) at both
2 WAT and 4 WAT. None of the trampling treatments significantly affected the MDRs of any
Sustainability 2022, 14, 16665 7 of 16
target grass weeds (southern crabgrass, Asian flatsedge, and giant foxtail). On the other
hand, the MDR of oriental water willow became significantly reduced due to mowing and
T200 at 2 WAT. Moreover, the MDR of horsenettle was decreased by mowing, T50, T100,
and T200 at 2 WAT. Throughout the study, the most frequent and most abundant weed was
southern crabgrass.
Table 2. Multiplied dominance ratio (MDR) of the five most frequent weed species in the experimental field.
MDR (×100 m3 m−2)
Plant Species
D. ciliaris C. microiria J. procumbens S. faberi S. carolinense
Time Treatment Mean SE Mean SE Mean SE Mean SE Mean SE
0 WAT Control 49.7 20.3 0.843 0.688 0.775 0.379 0.467 0.192 1.19 0.523
Mowing 20.2 8.95 1.33 0.407 0.735 0.208 1.13 0.522 1.92 0.605
T25 34.8 12.5 1.67 0.816 0.568 0.211 2.17 1.73 0.398 0.213
T50 42.8 22.5 1.80 0.888 1.09 0.776 0.391 0.293 1.71 1.48
T100 16.7 5.94 1.56 0.484 1.29 0.355 0.589 0.354 0.888 0.454
T200 38.9 14.9 1.65 0.582 0.349 0.117 11.2 10.9 0.848 0.122
2 WAT Control 58.9 a 21.4 0.835 0.452 0.836 a 0.255 0.733 0.332 0.450 a 0.169
Mowing 0.533 b 0.191 0.849 0.368 0.115 b 0.0674 0.000 0.000 0.0408 b 0.0164
T25 34.2 ab 14.3 0.363 0.0606 0.171 ab 0.0858 0.188 0.0409 0.193 ab 0.114
T50 22.2 ab 5.68 1.07 0.525 0.453 ab 0.248 0.107 0.0645 0.0467 b 0.0467
T100 19.6 ab 2.83 0.829 0.463 0.226 ab 0.0783 0.729 0.586 0.0408 b 0.0238
T200 17.7 ab 6.37 0.317 0.122 0.0417 b 0.0146 3.76 3.55 0.0200 b 0.0115
4 WAT Control 60.4 a 23.4 12.0 11.7 0.445 0.214 1.19 0.889 0.263 0.111
Mowing 0.517 b 0.228 0.570 0.234 0.238 0.188 0.000 0.000 0.118 0.0228
T25 24.0 ab 9.71 0.238 0.0618 0.154 0.0887 0.614 0.301 0.0775 0.0775
T50 19.5 ab 6.79 0.570 0.243 0.152 0.0812 0.127 0.0744 0.0217 0.0217
T100 19.6 ab 4.16 0.584 0.141 0.0950 0.00569 0.477 0.228 0.147 0.0952
T200 15.2 ab 5.71 0.383 0.116 0.0625 0.00250 1.99 1.93 0.0575 0.0225
The means (n = 4) followed by the same letter within time inside each column are insignificantly different (p < 0.05).
0 WAT, 2 WAT, and 4 WAT (weeks after treatment). SE, standard error. Control, intact plants; Mowing, mown
plants; T25, trampling 25 times; T50, trampling 50 times; T100, trampling 100 times; T200, trampling 200 times.
Impacts of Mowing and Trampling on MDR of the Five Most Frequent Weeds
The results of the field study showed that mowing caused sharp and prolonged
reductions in the MDRs of all the weed species. Moreover, it was observed that the various
degrees of trampling induced uneven changes in the MDRs of the weeds (Table 2). In
general, the ANOVA of the MDRs indicated that the differences between treatments and
the species*treatments interaction were all highly significant at both 2 WAT and 4 WAT.
Significant reductions in the MDR induced by both mowing and trampling were recorded
at 2 WAT on horsenettle (mowing, T50, T100, and T200) along with oriental water willow
(mowing and T200). Furthermore, the results indicated that, at both 2 WAT and 4 WAT,
there were changes in the MDR of southern crabgrass induced by both mowing and all
trampling treatments. However, significant changes (reductions) were only noted between
mowing and the control (a vs. b). T25, T50, T100, and T200 were not significantly different
from the control or mowing (ab). Furthermore, the results of the statistical analysis showed
that (in comparison to controls) there were no significant reductions in the MDRs of all
graminoids (i.e., southern crabgrass, Asian flatsedge, and giant foxtail) due to trampling.
On the contrary, at 2 WAT, the MDR of the shrub (oriental water willow) had become
significantly narrowed in T200, while the MDR of the forb (horsenettle) had also been
significantly decreased in T50, T100, and T200. These findings show that graminoids
(especially southern crabgrass) have stronger resistance to trampling than shrubs, along
with forbs.
Sustainability 2022, 14, x FOR PEER REVIEW  8  of  17 
 
at 2 WAT on horsenettle (mowing, T50, T100, and T200) along with oriental water willow 
(mowing and T200). Furthermore, the results indicated that, at both 2 WAT and 4 WAT, 
there were changes in the MDR of southern crabgrass induced by both mowing and all 
trampling  treatments. However,  significant  changes  (reductions) were  only  noted  be‐
tween mowing and the control (a vs. b). T25, T50, T100, and T200 were not significantly 
different from the control or mowing (ab). Furthermore, the results of the statistical anal‐
ysis showed that (in comparison to controls) there were no significant reductions in the 
MDRs of all graminoids (i.e., southern crabgrass, Asian flatsedge, and giant foxtail) due 
to trampling. On the contrary, at 2 WAT, the MDR of the shrub (oriental water willow) 
had become significantly narrowed in T200, while the MDR of the forb (horsenettle) had 
also been significantly decreased in T50, T100, and T200. These findings show that grami‐
Sustainability 2022, 14, 16665 noids (especially southern crabgrass) have stronger resistance to trampling than sh8ruofb1s6, 
along with forbs. 
Resistance is commonly assessed based on the resistance indices, which are the num‐
ber oRf epsaisstsaensc ereisqucoirmedm oton lryedasuscees stehdeb vaesgedetoantiothne croevsiesrta onrc ehienidghicte sb,yw 5h0ic%h a[1r2e,t4h5e].n  Iunm  tbheisr 
sotfupdays,s eressriesqtaunicre dwtoasr eadsusecsesethde dveepgentadtiinogn  coonv  tehreo rnhuemigbhert boyf 5p0a%sse[1s2  (,4tr5a]m. Ipnlitnhgis  tsitmuedsy), 
nreeseidsteadn ctoe wreadsuacses tehses eMdDdRep oefn ad iwnegeodn stpheecineus mbyb e5r0%of. pTahses erses(itsrtaamncpel iinngdticimese fso)rn seoeudtehdertno 
creradbugcreatshs ewMerDe R20o0f paawsseeesd (Ts2p0e0c)i east b2 yW5A0%T .aTnhde broetshi s5t0a npcaessinesd (iTce5s0)f oarnsdo 2u0t0h epransscersa b(Tg2ra0s0s) 
wate 4r eW2A00Tp. Tashsee sre(sTi2st0a0n)caet i2nWdiAceTs afonrd mbootsht o5f0 tphaes ostehse(rT w50e)eadnsd w2e0r0e p2a5s pseasss(eTs2 (0T02)5a)t a4t WboAtTh. 
T2 hWeAreTsi satnadn c4e WindAiTce. sHfoorwmevoesrt,o tfhteh ereostuhletsr wdiede dnsotw sehroew25 ap 5a0s%se sre(Td2u5c)tiaotnb ointh th2eW MADTRa nodf 
A4 WsiaAnT .flHatoswedegvee ri,nt hbeotrhes Tu5lt0s adnidd nTo1t0s0h aotw 2 aW50A%T,r eadlouncgti ownitihn tthhee MDRR ooff Agisaiannt ffloaxttsaeidl gine 
Tin10b0o taht Tb5o0tha 2n dWTA1T00 aantd2 4W WAAT,Ta. lAonltghowuigthh tthhee MheDigRhot fogf itahnet Afosxiatani lfliantsTe1d0g0ea wt baos trhed2uWceAdT, 
tahned p4laWntA dTi.dA nlotht oduieg hantdhe thhuesig shhtoowfetdh esoAmsiea nresfliasttsaendceg etow tarasmrepdliuncge.d O, nth tehpe loatnhtedr ihdannodt, 
mdioesatn hdorthseunsesthtloe,w medossto omrieenretasils wtaantceer two itlrlaomw,p alinndg .mOonstt hgeiaontth feorxhtaainl dp,lamnotss tdhieodrs eshnoertttlley, 
amftoesrt torraimenptlainl wg. aItne rtrwamillpolwed, a pnldotms, othsteg MiaDntRf ogxratadiul aplllayn dtsecdliiendedsh oovretrly tiamftee.r Ttrhaem MpDlinRg a. tI n4 
WtraAmTp lwedasp sloomts,etwhehaMt DloRwgerra tdhuaanl ltyhed eMclDinRed ato v2 eWr tAimTe. .HTohweeMvDerR, tahte4 MWDART iwncarsesaosmede wmhaar‐t
gloinwaelrlyt hwaintht htiemMe DinR thate 2coWnAtrTo.l Hploowtse. ver, the MDR increased marginally with time in the
control plots.
33..33.. SSooiill HHaarrddnneessss TTeesstt 
AAnn AANNOOVVAA ooff ssooiill hhaarrddnneessss iinnddiiccaatteedd tthhaatt tthhee ddiiffffeerreenncceess bbeettwweeeenn ttrreeaattmmeenntt aanndd 
mmeeaassuurreemmeenntt ttiimmeess wweerree aallll hhiigghhllyy ssiiggnniiffiiccaanntt ((FFiigguurree 11)).. AAtt 33 WWAATT,, ssooiill hhaarrddnneessss iinn TT110000 
wwaass ssiiggnniifificcaannttllyy hhiigghheerr ccoommppaarreedd ttoo tthhee ccoonnttrrooll,, mmoowwiinngg,, TT2255,, aanndd TT5500.. FFuurrtthheerrmmoorree,, 
ssooiill hhaarrddnneessss iinn TT220000 wwaass ssiiggnniiffiiccaannttllyy hhigighheerr ccoommppaareredd toto ththee coconntrtorol lanandd mmowowinign.g A. At 6t 
W6 WAAT,T ,oonnlyly TT110000 sshhoowweedd ssigignnififiiccaanntltyly hhiigghheerr ssooiill hhaarrddnneessss tthhaann tthhee ccoonnttrrooll.. SSiiggnniifificcaanntt 
ddiiffffeerreenncceess iinn ssooiill hhaarrddnneessss wweerree nnoott ddeetteecctteedd aatt 1133 WWAATT. . 
 
FFiigguurree 11.. Meeaann ssooiill hhaarrddnneessss ((NN//cmcm2)2. )T. hTeh ceacpappepde dbabras risndinicdaictea tteheth setasntadnadrda redrreorrrso rosf ofofufor urerprleipcali‐-
tciaotniosn (sn (=n 4=0).4 T0)h.e Tmheamnse wanitshwini tehaicnh emacehasmureeamsuernetm tiemnet ftoimlloewfoeldlo bwy etdheb syamthe lseattmere alreet tneor ta sriegniof‐t
significantly different (p < 0.05). 3 WAT, 6 WAT, and 13 WAT (weeks after treatment). Control,
undisturbed plots; Mowing, mown plots; T25, trampling 25 times; T50, trampling 50 times; T100,
trampling 100 times; and T200, trampling 200 times.
3.4. Results of the Allelopathic Potential of Selected Weed Species
This section introduces the results of the evaluation of the allelopathic activity of the
studied weed species.
3.4.1. The Allelopathic Influences of Rhizosphere Soil
The results of the evaluation of the rhizosphere soil for potential allelopathic effects
showed that the field-collected rhizosphere soil of intact southern crabgrass and Asian
flatsedge induced the significant growth inhibition of lettuce radicles at 72.0% and 73.8%,
respectively (Tables 3 and 4).
Sustainability 2022, 14, 16665 9 of 16
Table 3. A summary of one-way ANOVA of growth inhibition percentages of lettuce radicles assessed
using the rhizosphere soil method.
Source of Variance Sum of Squares df Mean of Squares F p-Value
Between treatments 10,600 2 5310 894 0.000 ***
Within treatments 35.6 6 5.94
Total 10,600 8
The table summarizes the outcome of statistical analysis of the allelopathic impacts of the rhizosphere soil from
southern crabgrass along with Asian flatsedge on the growth inhibition of lettuce radicles. Three asterisks (***)
indicate that the treatments were significantly different at the 0.1% level.
Table 4. Dunnett’s test of mean growth inhibition percentages of lettuce radicles assessed using the
rhizosphere soil method.
Treatments Mean (%) SD Pair Comparison MD (%) SE p-Value
Control (agar) 100 2.27 Control vs. D. ciliaris 72.0 1.31 0.000 ***
D. ciliaris 28.0 3.22 Control vs. C. microiria 73.8 1.86 0.000 ***
C. microiria 26.2 1.50 D. ciliaris vs. C. microiria 1.80 0.867 0.430 ns
The table indicates the allelopathic impacts of the rhizosphere soil from southern crabgrass along with Asian
flatsedge on the growth inhibition of lettuce radicles. Three asterisks (***) indicate that the treatments were
significantly different at the 0.1% level. ns: not significant. SD: standard deviation. MD: mean difference. SE:
standard error.
Sustainability 2022, 14, x FOR PEER REVIEWF  urthermore, an ANOVA of variations in the allelopathic activity of field-collected rh10iz  oof-  17 
  sphere soil showed that the differences between species, treatments, and the species*treatments
interaction were all highly significant (Figure 2A).
 
FiFgiugurer e2.2 .MMeaena nlenlegntght hofo lfetletuttcuec erardaidcilcelse sgrgorwown nini nthteh erhrihziozsopsphhereere sosoili loof fsosouuththeerrnn ccrraabbggrraasss (D. 
ci(lDiar. icsi)l ianrids) AansidanA fsliatnsefldagtsee (dCg.e m(Cic.romiriicar)o.i r(iAa)). T(hAe) sTohiel fsroiml f rtohme ftiheledfi; e(Bld); t(hBe) stohiel sfrooilmf rtohme gthreen‐
hogureseen. hTohues ec.aTphpedca bpapresd inbdaricsaitned tihcaet esttahnedsatarndd earrrdoresr roofr sthorfeteh rreeplriecpaltiicoantiso n(ns =(n 9=). 9T)h. Te hmeemaneasn osfo efach 
weeaecdh wspeeecdiessp efocileloswfoelldo wbeyd  tbhye tshaemsaem  leetlteetrt earraer eininsisgignnifiificcaannttllyy ddiiffffeerreenntt (p(p<  <0 .005.0)5. )C. oCnotrnotlr,oinl,t aincttact 
plpalnantst;s M; Moowwiningg, ,mmoowwnn pplalanntsts; ;TT1155, ,trtraammpplliinngg 1155 ttiimeess;; TT2255,, ttrraampplliinngg 2255 ttiimeess;; TT5500,, ttrraampplliinngg 50 
tim50etsi;m Te1s0; 0T,1 t0r0a,mtrpalminpgli 1n0g01 t0i0mteims;e Ts;2T002,0 0tr,atmramplpinlign g20200 0titmimese.s .
3.4.2. The Aleltlteulcoepraatdhicl eInsfilnueTn2c5eas nodf RT5o0otw Eexruedsaigtensifi  cantly shorter concerning southern
crabTghrea srsesthualtns tohfe thcoe nptlraonlst.‐bNoxo msigenthifiocda snhtodwiffeedr etnhcaet twhaes rooobts eerxvueddaatemso onfg intthaectc osonutrtohle, rn 
crmabogwriansgs, aTn2d5 ,inantadctT A10s0iatnre faltamtseendtgseo finAdsuiacnedfl 7at7s.e9d%g ea.ndT h5e8.l9e%ttu gcerorwadthic lienshiinbiTti5o0n ainnd the 
leTtt2u0c0ew  reardeiscilgen, irfiecsapnetclytivtaelllyer  (tThaabnltehse  5c oanntrdo l6s.  aInndad  Fdiigtiuorne, a3n).A ANdOdVitAioonfacllhya,n  agne sAinNthOeVA 
shaollweloepda tthhaict ascotuivtihtyerof greenhouse-collected rhizosphere soil (Figure 2B) indicated that thedifferences between tnr ecartambegnrtasssa nsdigtnhiefiscpaenctileys *itnrheaibtmiteednt sthien tgerraocwtitohn owf elreettaullcesi gwnhifiecna ncot.m‐
pWarehden toth tehreh iczoonstprhoel.r eFusoritlhoefrmsoourteh,e mrnocwraibnggr aasnsdw tarasmuspeldin, gth ienlcertetuacseedra tdhiec legrinowT1th5‐winahsibi‐
tosrigyn eififfceacntstl yofs hsoorutethreinrnc ocmrapbagrrisaosns rwoiotht ethxeucdoantterso lo,nm loewttiuncge, Tra2d5,icalneds Tb5y0 9. .N11o%tr eaantmd e1n6t.s4%, 
respectively (Figure 3A). In contrast, mowing and trampling reduced the growth‐inhibi‐
tory effects of Asian flatsedge against  lettuce radicles by 18.7% and 28.5%, respectively 
(Figure 3B). Moreover, an ANOVA showed  that the differences between species,  treat‐
ments, and the species*treatment interaction were all highly significant. The root exudates 
of both mown and trampled southern crabgrass did not significantly inhibit the growth 
of lettuce seedlings. The growth of lettuce radicles was significantly stimulated by the root 
exudates of trampled Asian flatsedge. In addition, in comparison to the controls, lettuce 
seedlings incubated with mown Asian flatsedge had increased radicle lengths; however, 
all increases were insignificant. 
Table 5. A summary of one‐way ANOVA of elongation percentages of  lettuce  radicles assessed 
using the plant‐box method. 
Species  Source of Variance  Sum of Squares  df  Mean of Squares  F  p‐Value 
D. ciliaris  Between treatments  13,800  3  4610  49.6  0.000 *** 
    Within treatments  743  8  92.9         
    Total  14,500  11             
C. microiria  Between treatments  5460  3  1820  6.37  0.016 * 
    Within treatments  2290  8  286         
    Total  7750  11             
The table summarizes the outcome of statistical analysis of the allelopathic impacts of root exudates 
released by sand‐grown southern crabgrass along with Asian flatsedge on the elongation of lettuce 
radicles. One asterisk (*) and three asterisks (***), respectively, mean that the treatments were sig‐
nificantly different at the 5% level and at the 0.1% level. 
   
Sustainability 2022, 14, 16665 10 of 16
significantly affected the allelopathic effects of the rhizosphere soil of Asian flatsedge from
the greenhouse.
3.4.2. The Allelopathic Influences of Root Exudates
The results of the plant-box method showed that the root exudates of intact southern
crabgrass and intact Asian flatsedge induced 77.9% and 58.9% growth inhibition in the
lettuce radicle, respectively (Tables 5 and 6 and Figure 3). Additionally, an ANOVA showed
that southern crabgrass significantly inhibited the growth of lettuce when compared to
the control. Furthermore, mowing and trampling increased the growth-inhibitory effects
of southern crabgrass root exudates on lettuce radicles by 9.11% and 16.4%, respectively
(Figure 3A). In contrast, mowing and trampling reduced the growth-inhibitory effects
of Asian flatsedge against lettuce radicles by 18.7% and 28.5%, respectively (Figure 3B).
Moreover, an ANOVA showed that the differences between species, treatments, and the
species*treatment interaction were all highly significant. The root exudates of both mown
and trampled southern crabgrass did not significantly inhibit the growth of lettuce seedlings.
The growth of lettuce radicles was significantly stimulated by the root exudates of trampled
Asian flatsedge. In addition, in comparison to the controls, lettuce seedlings incubated with
mown Asian flatsedge had increased radicle lengths; however, all increases were insignificant.
Table 5. A summary of one-way ANOVA of elongation percentages of lettuce radicles assessed using
the plant-box method.
Species Source of Variance Sum of df Mean ofSquares Squares F p-Value
D. ciliaris Between treatments 13,800 3 4610 49.6 0.000 ***
Within treatments 743 8 92.9
Total 14,500 11
C. microiria Between treatments 5460 3 1820 6.37 0.016 *
Within treatments 2290 8 286
Total 7750 11
The table summarizes the outcome of statistical analysis of the allelopathic impacts of root exudates released by
sand-grown southern crabgrass along with Asian flatsedge on the elongation of lettuce radicles. One asterisk (*)
and three asterisks (***), respectively, mean that the treatments were significantly different at the 5% level and at
the 0.1% level.
Table 6. Dunnett’s test of mean elongation percentages of lettuce radicles assessed using the plant-
box method.
Species Treatment Mean (%) SD Pair Comparison MD (%) SE p-Value
D. ciliaris Control (Agar) 100 7.08 Control vs. Intact 68.8 8.16 0.011 *
Intact 31.2 12.2 Control vs. Mowing 77.9 4.99 0.001 **
Mowing 22.1 4.99 Control vs. Trampling 85.2 8.10 0.005 *
Trampling 14.8 12.1 Intact vs. Mowing 9.11 7.63 0.783 ns
Intact vs. Trampling 16.4 9.94 0.553 ns
Mowing vs. Trampling 7.27 7.57 0.881 ns
C. microiria Control (Agar) 100 24.1 Control vs. Intact 58.9 14.3 0.138 ns
Intact 41.1 6.05 Control vs. Mowing 40.2 16.7 0. 292 ns
Mowing 59.8 16.1 Control vs. Trampling 30.5 16.8 0.488 ns
Trampling 69.5 16.3 Intact vs. Mowing −18.7 9.93 0.492 ns
Intact vs. Trampling −28.5 10.0 0. 252 ns
Mowing vs. Trampling −9.77 13.2 0.959 ns
The table indicates the allelopathic impacts of root exudates released by the sand-grown southern crabgrass along
with Asian flatsedge on the elongation of lettuce radicles. One asterisk (*) and two asterisks (**), respectively,
mean that the treatments were significantly different at the 5% level and at the 1% level. ns: not significant. SD:
standard deviation. MD: mean difference. SE: standard error.
Sustainability 2022, 14, x FOR PEER REVIEW  11  of  17 
 
Table 6. Dunnett’s test of mean elongation percentages of lettuce radicles assessed using the plant‐
box method. 
Species  Treatment  Mean (%)  SD  Pair Comparison  MD (%)  SE  p‐Value 
D. ciliaris  Control (Agar)  100  7.08  Control vs. Intact  68.8  8.16  0.011 * 
    Intact  31.2  12.2  Control vs. Mowing  77.9  4.99  0.001 ** 
    Mowing  22.1  4.99  Control vs. Trampling  85.2  8.10  0.005 * 
    Trampling  14.8  12.1  Intact vs. Mowing  9.11  7.63  0.783 ns 
                Intact vs. Trampling  16.4  9.94  0.553 ns 
                Mowing vs. Trampling  7.27  7.57  0.881 ns 
C. microiria  Control (Agar)  100  24.1  Control vs. Intact  58.9  14.3  0.138 ns 
    Intact  41.1  6.05  Control vs. Mowing  40.2  16.7  0. 292 ns 
    Mowing  59.8  16.1  Control vs. Trampling  30.5  16.8  0.488 ns 
    Trampling  69.5  16.3  Intact vs. Mowing  −18.7  9.93  0.492 ns 
                Intact vs. Trampling  −28.5  10.0  0. 252 ns 
                Mowing vs. Trampling  −9.77  13.2  0.959 ns 
The table indicates the allelopathic impacts of root exudates released by the sand‐grown southern 
crabgrass along with Asian flatsedge on the elongation of lettuce radicles. One asterisk (*) and two 
Sustainaabisliteyr2i0s2k2,s1 4(*, 1*6),6 6r5espectively, mean that the treatments were significantly different at the 5% level and1 1 of 16
at the 1% level. ns: not significant. SD: standard deviation. MD: mean difference. SE: standard error. 
 
Figure 3. The percentaFgigeu grero3w. Tthhe spueprcpenretasgseiognro owft hrosuopt perxeussdioanteosf rforootmex suadnadte‐sgfrroomwsna nudn-tgorouwchneudn,t omucohwedn, ,m  own,
and 15‐times trampleda nsdou15th-tiemrnes ctrraambgplreadssso (uDth. ecrinliacrraisb)g aralsosn(gDs. icdiliea rAis)siaalonn fglsaidtseeAdsgiaen (flCa.t mseidcgreoi(rCi.am) aicgroairiina)sta gainst
the elongation of lettuthcee erlaondgiactlieosn. o(fAle)t tSuoceurtahdeicrlne sc. r(Aab) Sgoruatshse;r n(Bc)ra Abgsriaasns; (fBla)tAsesidangefl.a tTsehdeg ef.igTuherefisg udriesspdliaspyl ay the
the means of all three mreepanliscoaftiaollntsh roeef rtehpel ipcaltaionnts‐boof xth me peltahnot-dbo oxumtectohmodeo. utcome.
4. Discussion
4. Discussion  The results of the weed survey and the values of MDR showed that the grass weeds,
The results of tphaertstud w
icu
ye
l
fie
adrleld 
y
.sSu
so
ir
uvtehye ranncdra bthgera vssa, lsutreosn gly dominated all the othemilarly, Kobayashi et al.o[4f0 M,46D] rRe psohrotewd ethda tththaete th
r we egerdassin the no-tillagemergenceso wf gereadsssw,  eeds
particularly southerins h cigrahbergtrhaasnsi,n sbtrrooandg-lleya vdedomweinedasteinds uamll mtheer  aontdhneor- twilleaegde sfi eilnd sthineJ anpoa‐nt.ilIlnatghee tilled
study field. Similarlfiye,l dK,othbeawyaeesdhei mete ragle. n[c4e0a,4lo6n]g rwepithorstpeedci etshcaotm thpoes eitmionerwgaesnccoerr eolfa tgedrasstrso wngelyedwsit h the
is higher than in broraedse‐rlveoaivreodf w weeededsese idns sinutmhemsoeirl oarntdh enwo‐eteidllasegeed bfiaenlkdfso irnb oJathpgarna.s Isna nthdeb rtoilalde-dle aved
field, the weed emewrgeeednsc[e4 7a,4lo8]n. g with species composition was correlated strongly with 
Although larger variations in the MDRs of target weeds were recorded before and
the reservoir of weeadfte srebeodths mino wthineg saonild otrra tmhpel iwnge,erdel asteiveedrbeadnukct ifoonrs binotthhe gMraDsRss aonfda llbwroeaedds‐ were
leaved weeds [47,48r]e.c o  rded at 2 WAT and 4 WAT in all trampled plots. These findings suggest that all
Although largetrra mvaprliinagtiotrneast mine nthtsei mMpDacRtesd o(dfe tpaerngdeint gwoeneidntse nwsietyrea nrdecsopredcieeds) tbheefosurpep arensdsi on of
after both mowing agnrodw ttrha(mi.ep., lhineiggh, treanladticvoeve rreagdeuacrteiao)nins ainll wtheee dMs.DSuRpsp roefs saiolln wofewedeesd wgreorwe trhetch‐rough
orded at 2 WAT anmd e4ch Wanical means such as trampling or treading and rolling has also been reportestudies A[4,T11 i]n.  all trampled plots. These findings suggest that all tram
d i‐n past
pling  treatments  impacFtuerdth e(rdmeopree,nsdoiunthge ronnc rainbgteransssi,taylo  nagnsdid esptheecoiethse) r tghream  siunopidpsre(Asssiioann floatfs edge
growth (i.e., height and gcioanvtefroaxgtaei la),rdeeam) ionn satlrla wtedeehdigsh. eSrurpespisrteasnscieotno torfa mwpeleindg gthroanwtthhe tshruobug(ohri ental
water willow) and the forb (horsenettle), which suggests that the higher resistance of
the graminoids to trampling pressure was due to their morphological characteristics, i.e.,
graminoids’ growing points are commonly under the soil surface, rendering them more
resilient to trampling pressure. In previous studies, it has also been indicated that the
easily bendable stems, greater leaf tensile strength, low-to-ground growing points, and
below-ground reproductive structure of the graminoids—southern crabgrass in particular—
render them more resistant to trampling than shrubs and forbs, which are more vulnerable
and characterized by broad leaves, woody stems, and reproductive structures high on the
plant [45,49,50].
Increases in the soil hardness, largely inside the intensely trampled plots (T100 and
T200), were revealed by the outcome of the soil hardness test, which indicated that the soil
compaction increased with the increasing trampling intensity. Similarly, da Silva et al. [41]
and Panda and Yamamoto [42] also reported that soil compaction depends on the increase
in trampling intensity, and it is signaled by the variations in hydraulic conductivity along
Sustainability 2022, 14, 16665 12 of 16
with soil hardness. The disappearance of significant differences in the soil hardness among
the mown, trampled, and untouched plots (observed at 13 WAT) suggested that the soil
had recovered by the end of the study. Moreover, previous studies have indicated that
soils take between 85 and 165 days (depending on soil type) to recover from short-term
trampling impacts through natural processes [51–55]. In addition, soil compaction occurs
in the time for which soil particles are pressed tightly together, causing the pore space in
between them to become narrower, and the soil bulk density to become higher [56]. Soil
physical stresses due to compaction, along with drought, result in perturbations in the root
exudation processes of stressed plants [57], reductions in root size, deceleration of root
penetration, and decreases in the availability of plant nutrients.
The assessment outcome for the allelopathic potential indicated that both southern
crabgrass and Asian flatsedge significantly inhibited the growth of lettuce radicles by
over 70%. Therefore, both weeds contain compounds that suppress lettuce radicle growth.
Similarly, Ito et al. [58] reported that soil in which southern crabgrass had been grown
inhibited the growth of several crops, especially cucumber. The root exudates and extracts
of the roots and aerial parts of Cyperus rotundus [59] and Cyperus iria [60] were reported to
have phytotoxic effects on tomatoes, cucumbers, rice, and soybeans.
Furthermore, the growth suppression activities of the rhizosphere soil of southern crab-
grass were significantly increased by the lowest trampling intensity under both greenhouse
(T15) and field conditions (T25 and T50). However, the treatments did not significantly
affect the growth-inhibitory effects of the rhizosphere soil of Asian flatsedge. The inhibitory
effect of the root exudates of southern crabgrass was not significantly affected by mowing
and T15. In contrast, T50 and T200, under field conditions, significantly reduced the growth
suppression activities of Asian flatsedge rhizosphere soil. Additionally, trampling and
mowing only slightly decreased the growth-suppressing abilities of Asian flatsedge root
exudates, by 18.7% and 28.5%, respectively. These findings suggest that mowing and
trampling induced uneven influences on the allelopathic potential of the two weed species,
and that mowing and heavy trampling treatments (over T50) significantly increased the
carbon demand, resulting in a lower concentration of allelochemicals available for rhi-
zodeposition. Previous studies have shown that wounding in plants induces a transient
disruption in the root exudation processes due to the turnover of storage compounds
during remobilization [61,62], leading to the utilization of stored assimilates to support the
maintenance respiration [63,64]. In addition, transient increases in the rhizodeposition of
perennial ryegrass (Lolium perenne) following defoliation were reported by Paterson and
Sim [38]. Meanwhile, decreases in the root exudates of timothy (Phleum pratense) [65] and
maize plants [66] were reported after defoliation.
All trampling treatments induced relative growth suppression (i.e., reductions in the
MDR) in all the target weeds. Moreover, a light trampling intensity resulted in higher
increases in the allelopathic potential of the target weeds. These findings suggest that, apart
from the pressing force of the roller, trampling induced the release of allelopathic com-
pounds from the weeds and/or nearby organisms (i.e., volatile organic compounds such as
ethylene and other allelochemicals in root exudates) to affect the growth of surrounding
weed species. Jaffe [16], Chehab et al. [67], and Sunohora et al. [68] found that when plants
such as Plantago asiatica, Cucumis sativus, Mimosa pudica, and Ricinus communis become
mechanically stimulated due to fingers sliding along them or touching or trampling, they
rapidly attempt to overcome the intrusion by undergoing diverse biochemical reactions,
including the release of natural growth inhibitors such as ethylene, jasmonates, and abscisic
acid (ABA), along with several morphological reactions, such as the acceleration of leaf
senescence processes and fast cessation of shoot elongation. These types of touch-induced
responses are commonly termed thigmomorphogenis [16,67]. In addition, similar findings
on the release of phytotoxic compounds (such as organic carbon, phenolics, and sorgeolone)
through the roots of mechanically stimulated or trampled plants have previously been
published [23,61].
Sustainability 2022, 14, 16665 13 of 16
The evaluation of the potential allelopathic effect of root exudates using the plant-box
method showed that after mowing and T15, the growth suppression activity of southern
crabgrass increased, whereas that of Asian flatsedge decreased. These findings indicate
that the differences in allelopathic effects between the two weeds could be due to the
solubility of their root exudates. Hydrophobic compounds cannot travel in water-based
media, including the plant-box and rhizosphere soil methods. Fujii et al. [26] found
that plant species with hydrophobic chemicals possessed decreased allelopathic effects in
water-based media compared to species with hydrophilic chemicals. Root exudates from
Digitaria sanguinalis are largely composed of hydrophilic allelochemicals, such as veratric
acid, maltol, and (−)-loliolide [33]. Meanwhile, root exudates from the rhizomes of Cyperus
species are largely composed of essential oils, such as cyperol, α-cyperone [69], and methyl
esters of acyclic terpenic acids [70], which are hydrophobic.
Moreover, the results showed that changes in the growth suppression activities of
southern crabgrass and Asian flatsedge in the field after both mowing and various degrees
of trampling differed from changes in their growth suppression activities in the greenhouse.
These results suggest that the environmental conditions impacted the variations in the
allelochemical exudation processes from the roots of the two weeds in response to mowing
and varying trampling pressure. Similar to the outcome of this study, Yang et al. [71]
also reported that the root exudation rate of some plant species, such as Pinus koraiensis,
Larix gmelinii, and Betula platyphylla, was influenced by environmental factors, including
the site, temperature, latitude, organic matter content, and moisture content. This short-
term study involved single-year field and greenhouse research; however, it led to key
insights into how and why long-term studies need to be carried out in the future to take
full advantage of the impacts of trampling on the enhancement in the allelopathic potential
of plants, along with suppression of weed growth, sustainably.
5. Conclusions
This is the first study to show that southern crabgrass and Asian flatsedge possess
allelopathic effects on lettuce radicle growth. Mowing and varying trampling intensities
resulted in contrasting impacts on both weed suppression and the allelopathic activity of
southern crabgrass and Asian flatsedge. A forthcoming article will present the long-term
impacts of trampling on weed suppression, alongside the allelopathic potential of cover
crops. Future studies should also focus on identifying and quantifying the allelochemicals
in southern crabgrass, Asian flatsedge, and other plant species for their potential utilization
in sustainable weed management in combination with proper mowing and trampling.
Author Contributions: Conceptualization, B.B., T.C. and Y.F.; methodology, Y.F. and B.B.; software,
B.B. and Y.F.; formal analysis, B.B., K.S.A. and Y.F.; investigation, B.B.; resources, Y.F., T.C. and B.B.;
writing—initial draft preparation, K.S.A. and B.B.; writing—review and editing, K.S.A., S.T., T.C., B.B.
and Y.F.; supervision, Y.F., S.T. and T.C. All authors have read and agreed to the published version of
the manuscript.
Funding: This research was partially supported by JST-CREST, Grant Number JPMJCR17O2.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: The datasets of the present study are available from the corresponding
authors upon reasonable request.
Acknowledgments: The authors would like to express their gratitude to the Japanese Ministry of
Education, Culture, Sports, Science, and Technology (MEXT), Japan, for providing the scholarship to
the first author at the Tokyo University of Agriculture and Technology, Tokyo, Japan.
Conflicts of Interest: The authors declare no conflict of interest.
Sustainability 2022, 14, x FOR PEER REVIEW  14  of  17 
 
Author Contributions: Conceptualization, B.B., T.C. and Y.F.; methodology, Y.F. and B.B.; software, 
B.B. and Y.F.; formal analysis, B.B., K.S.A. and Y.F.; investigation, B.B.; resources, Y.F., T.C. and B.B.; 
writing—initial draft preparation, K.S.A. and B.B.; writing—review and editing, K.S.A., S.T., T.C., 
B.B. and Y.F.; supervision, Y.F., S.T. and T.C. All authors have read and agreed to the published 
version of the manuscript. 
Funding: This research was partially supported by JST‐CREST, Grant Number JPMJCR17O2. 
Institutional Review Board Statement: Not applicable. 
Informed Consent Statement: Not applicable. 
Data Availability Statement: The datasets of the present study are available from the correspond‐
ing authors upon reasonable request. 
Acknowledgments: The authors would like to express their gratitude to the Japanese Ministry of 
Education, Culture, Sports, Science, and Technology (MEXT), Japan, for providing the scholarship 
to the first author at the Tokyo University of Agriculture and Technology, Tokyo, Japan. 
Sustainability 2022, 14, 16665 14 of 16
Conflicts of Interest: The authors declare no conflicts of interest. 
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References (AMeDAS). 
1. Ghanizadeh, H.; Harrington, K.C. Non-Target Site Mechanisms of Resistance to Herbicides. Crit. Rev. Plant Sci. 2017, 36, 24–34.
References  [CrossRef]
2. Hussain, M.; Farooq, S.; Merfield, C.; Jabran, K. Mechanical Weed Control. In Non-Chemical Weed Control; Elsevier Academic
1. GhanizadePhr,e sHs:.;C Hamabrrriidngget,oMnA, K, U.CSA. ,N20o1n8‐;Tpapr.g13e3t –S1i5t5e. MISBeNch9a7n8-i0s-m12s-8 o09f 8R81e-s3i.stance to Herbicides. Crit. Rev. Plant Sci. 2017, 36, 24–34. 
https:/3/.doi.Foyrngn/,1R0..W10.S8.;0M/0o7r3ri5s,2C6.8D9.;.2E0d1w7a.1rd3s1,6T1.J3. E4f.f ect of Burning and Mowing on Grass and Forb Diversity in a Long-Term Grassland
2. Hussain, MEx.;p Feraimroeonqt., ASp.p; lM. Veegr.fiSeclid. 2, 0C04.;, 7J,a1b–r1a0n. [,C Kro. sMsRefc]hanical Weed Control. In Non‐Chemical Weed Control; Elsevier Academic 
Press: 4C. amInbargidakgie, ,H M.; IAna, gUakSiA, S,. ;2K0a1t8o;, Yp.p; K. a1w33a–i,1M5.5; ,S IuSnBakNa w9a7,8T‐.0E‐1ff2ec‐8ts0o9f8T8r1ea‐3d. Pressure Treatment on Vegetation Surrounding Rice
3. Fynn, R.WFields. J. Jpn. Soc. Reveg. Technol. 2017, 43, 183–186. [CrossRef]5. K.So.;g Mlero, Rrr.;isQ, uCe.nDd.l;e Er,dEw.; Baorxdbse, rTge.Jr., EJ.fOfeccctu opaf tBiounranl iAncgc iadnendt sMwoitwh iMngow oinn gGMraascsh iannesdi nFoArubs tDriiavneArsgirtiyc uinltu ar eL.oAnngn‐.TAegrrmic. Grassland 
ExperimenEtn. vAirpopn.l.M Veedg. .2 S01c5i., 2220,0143,7 –71, 411–. 1[C0r.o hsstRtpesf]:/[/PduobiM.oerdg]/10.1111/j.1654‐109X.2004.tb00589.x. 
4. Inagak6i., HW.; Iun, aBg.;aWkui, YS..;;A Koaktio, Y, .Y; N.;i sKhaimwuaria,, MS. M.; SowuninagkPaawttear,n Ts .C Eomffepcatrsis onf: TArneaaldyz PinrgetshseuMreo wTrinegatBmeheanvtio orsno Vf EelgdertlaytiAodnu Sltus orrnoaunnding Rice 
Fields. J. JpIn.c lSinoecd. RPleavneegv. iTa eacMhnootilo. n20C1a7p,t u4r3e,D 1e8v3ic–e1.8IE6E. EhtAtpccse:s/s/d20o2i0.,o8r,g2/11606.2732–12116/6jj3s3r.t.[4C3r.o1s8sR3e. f]
5. Kogler7,. R.;B Qörkuleün, Hd.lRe.r;,E Erd.;e mBior,xFb. Cerognecerp, tJu.a Ol dcecsiugpnaotfiaonnianln oAvcactiivdeelanwtsn wmoitwhe rMmoawchiinneg. DMüzaccehÜinnievser siinte sAi BuilsimtrViaenT eAkngolr. iDcuerlgt.u/Druez. ceAnn. Agric. 
Environ. MUedn.i v2. 0J.1S5c,i .2A2m, 1p;3T7e–ch1nol. 2019, 7, 15–26. [Cro8. FAO. Pesticides and En4v1ir.o hnmttepnst:a/l/Idnociid.oenrtgs:/1
ssRef]
R0o.t5te6r0da4m/1C2o3n2v1e9n6ti6on.1o1n4t1h3e8P3r.i or Informed Consent Procedure for Certain Hazardous
6. Wu, B.; WuC,h eYm.;ic Aalsoaknid, PYe.s;t iNcidiseshiinmInutreran,a Sti.o nMaloTwradine;gF APOat: tReormnse ,CItoalmy,p20a2r2i;sIoSnBN: A9n78a-l9y2z-5i-n1g34 t9h37e- 3M. owing Behaviors of Elderly Adults on 
an  In9c.lineRda niP, Lla.;nTeh apvaia, K  .a;  KaMnoojitai,oNn .; SChaaprmtuar,eN  .;DSienvgihc,eS.. ; GIEreEwEa l,Ac.Sc.e;sSsr iv2a0st2a0v, A8.L, .; 2K1a6u6sh2a3l–, 2J.1A6n63E3x.t enhstivtpesR:/e/vdieowi.oorngt/h1e0.1109/AC‐
CESS.2020.C3o0n4s0e4q1u8en. ces of Chemical Pesticides on Human Health and Environment. J. Clean. Prod. 2021, 283, 124657. [CrossRef]
10. Mehdizadeh, M.; Mushtaq, W. Chapter 9—Biological Control of Weeds by Allelopathic Compounds from Different Plants: A
BioHerbicide Approach. In Natural Remedies for Pest, Disease and Weed Control; Egbuna, C., Sawicka, B., Eds.; Elsevier Academic
Press: Cambridge, MA, USA, 2020; pp. 107–117. ISBN 978-0-12-819304-4.
11. Creamer, N.G.; Dabney, S.M. Killing Cover Crops Mechanically: Review of Recent Literature and Assessment of New Research
Results. Am. J. Altern. Agric. 2002, 17, 32–40. [CrossRef]
12. Cole, D.N.; Bayfield, N.G. Recreational Trampling of Vegetation: Standard Experimental Procedures. Biol. Conserv. 1993, 63,
209–215. [CrossRef]
13. Mihretie, F.A.; Tsunekawa, A.; Haregeweyn, N.; Adgo, E.; Tsubo, M.; Masunaga, T.; Meshesha, D.T.; Tsuji, W.; Ebabu, K.; Tassew,
A. Tillage and Sowing Options for Enhancing Productivity and Profitability of Teff in a Sub-Tropical Highland Environment. Field
Crop. Res. 2021, 263, 108050. [CrossRef]
Total daily rainfall (mm)
2018/9/1
2018/9/6
2018/9/11
2018/9/16
2018/9/21
2018/9/26
2018/10/1
2018/10/6
2018/10/11
2018/10/16
2018/10/21
2018/10/26
2018/10/31
2018/11/5
2018/11/10
2018/11/15
2018/11/20
2018/11/25
2018/11/30
2018/12/5
2018/12/10
2018/12/15
2018/12/20
2018/12/25
2018/12/30
Sustainability 2022, 14, 16665 15 of 16
14. Warren, S.D.; Nevill, M.B.; Blackburn, W.H.; Garza, N.E. Soil Response to Trampling under Intensive Rotation Grazing. Soil Sci.
Soc. Am. J. 1986, 50, 1336–1341. [CrossRef]
15. Burden, R.F.; Randerson, P.F. Quantitative Studies of the Effects of Human Trampling on Vegetation as an Aid to the Management
of Semi-Natural Areas. J. Appl. Ecol. 1972, 9, 439–457. [CrossRef]
16. Jaffe, M.J. Thigmomorphogenesis: The Response of Plant Growth and Development to Mechanical Stimulation. Planta 1973, 114,
143–157. [CrossRef]
17. Hatanaka, A. The Biogeneration of Green Odour by Green Leaves. Phytochemistry 1993, 34, 1201–1218. [CrossRef]
18. Iqbal, N.; Khan, N.A.; Ferrante, A.; Trivellini, A.; Francini, A.; Khan, M.I.R. Ethylene Role in Plant Growth, Development and
Senescence: Interaction with Other Phytohormones. Front Plant Sci 2017, 8, 475. [CrossRef] [PubMed]
19. Bardgett, R.D.; Mawdsley, J.L.; Edwards, S.; Hobbs, P.J.; Rodwell, J.S.; Davies, W.J. Plant Species and Nitrogen Effects on Soil
Biological Properties of Temperate Upland Grasslands. Funct. Ecol. 1999, 13, 650–660. [CrossRef]
20. Paterson, E.; Thornton, B.; Sim, A.; Pratt, S. Effects of Defoliation and Atmospheric CO2 Depletion on Nitrate Acquisition, and
Exudation of Organic Compounds by Roots of Festuca rubra. Plant Soil 2003, 250, 293–305. [CrossRef]
21. Paterson, E.; Thornton, B.; Midwood, A.J.; Sim, A. Defoliation Alters the Relative Contributions of Recent and Non-Recent
Assimilate to Root Exudation from Festuca rubra. Plant Cell Environ. 2005, 28, 1525–1533. [CrossRef]
22. Bertin, C.; Yang, X.; Weston, L.A. The Role of Root Exudates and Allelochemicals in the Rhizosphere. Plant Soil 2003, 256, 67–83.
[CrossRef]
23. Yang, X.; Owens, T.G.; Scheffler, B.E.; Weston, L.A. Manipulation of Root Hair Development and Sorgoleone Production in
Sorghum Seedlings. J. Chem. Ecol. 2004, 30, 199–213. [CrossRef] [PubMed]
24. Czarnota, M.A.; Rimando, A.M.; Weston, L.A. Evaluation of Root Exudates of Seven Sorghum Accessions. J. Chem. Ecol. 2003, 29,
2073–2083. [CrossRef] [PubMed]
25. Trezzi, M.M.; Vidal, R.A. Potential of Sorghum and Pearl Millet Cover Crops in Weed Suppression in the Field: II—Mulching
Effect. Planta Daninha 2004, 22, 1–10. [CrossRef]
26. Fujii, Y.; Pariasca, D.; Shibuya, T.; Yasuda, T.; Kahn, B.; Waller, G.R. Plant-box Method: A Specific Bioassay to Evaluate Allelopathy
through Root Exudates. In Allelopathy New Concept and Methodology; Fujii, Y., Hiradate, S., Eds.; Science Publishers: Enfield, CT,
USA, 2007; pp. 39–56.
27. Fujii, Y.; Furubayashi, A.; Hiradate, S. Rhizosphere Soil Method: A New Bioassay to Evaluate Allelopathy in the Field. In
Proceedings of the 4th World Congress on Allelopathy, “Establishing the Scientific Base”, Wagga Wagga, Australia, 21–26 August
2005; pp. 493–497.
28. Fujii, Y.; Matsuyama, M.; Hiradate, S.; Shimozawa, H. Dish Pack Method: A New Bioassay for Volatile Allelopathy. Thymus 2005,
2, 493–497.
29. Fujii, Y.; Parvez, S.S.; Parvez, M.M.; Ohmae, Y.; Iida, O. Screening of 239 Medicinal Plant Species for Allelopathic Activity Using
the Sandwich Method. Weed Biol. Manag. 2003, 3, 233–241. [CrossRef]
30. Noguchi, K. Upland Weeds and Their Management in Soybean in Japan. In Pest Management in Soybean; Copping, L.G., Green,
M.B., Rees, R.T., Eds.; Springer: Dordrecht, The Netherlands, 1992; pp. 299–307. ISBN 978-94-011-2870-4.
31. Ito, M.; Ichikawa, E. Nitrification Inhibition by Roots of Digitaria adscendens (H. B. K.) Henr. J. Weed Sci. Technol. 1994, 39, 125–127.
[CrossRef]
32. Chozin, M.A.; Yasuda, S. Possibility of Natural Hybridization between Cyperus iria L. and Cyperus microiria Steud. J. Weed Sci.
Technol. 1991, 36, 282–289. [CrossRef]
33. Zhou, B.; Kong, C.-H.; Li, Y.-H.; Wang, P.; Xu, X.-H. Crabgrass (Digitaria sanguinalis) Allelochemicals that Interfere with Crop
Growth and the Soil Microbial Community. J. Agric. Food Chem. 2013, 61, 5310–5317. [CrossRef]
34. Komai, K.; Tang, C.-S. Chemical Constituents and Inhibitory Activities of Essential Oils from Cyperus brevifolius And C. kyllingia. J
Chem Ecol 1989, 15, 2171–2176. [CrossRef]
35. Chou, C.-H.; Leu, L.-L. Allelopathic Substances and Interactions of Delonix regia (Boj) Raf. J. Chem. Ecol. 1992, 18, 2285–2303.
[CrossRef]
36. Jaikaew, P.; Boulange, J.; Thuyet, D.Q.; Malhat, F.; Ishihara, S.; Watanabe, H. Potential Impacts of Seasonal Variation on Atrazine
and Metolachlor Persistence in Andisol Soil. Env. Monit Assess 2015, 187, 760. [CrossRef]
37. IUSS Working Group, W.R.B. World Reference Base for Soil Resources 2014: International Soil Classification System for Naming Soils and
Creating Legends for Soil Maps; FAO: Rome, Italy, 2014; ISBN 978-92-5-108370-3.
38. Booth, B.D.; Murphy, S.D.; Swanton, C.J. Weed Ecology in Natural and Agricultural Systems; CAB International: Wallingford, UK,
2003; ISBN 978-0-85199-528-1.
39. Kobayashi, H. Seasonal Dynamics of Weed Biomass in Upland Fields, Periodically Cultivated Fields and Weeded Fields without
Soil Disturbance: Estimation Based on Plant Coverage and Height. Tohoku Agri. Res. 2000, 53, 93–94.
40. Kobayashi, H.; Nakamura, Y.; Watanabe, Y. Analysis of Weed Vegetation of No-Tillage Upland Fields Based on the Multiplied
Dominance Ratio. Weed Biol. Manag. 2003, 3, 77–92. [CrossRef]
41. da Silva, A.P.; Imhoff, S.; Corsi, M. Evaluation of Soil Compaction in an Irrigated Short-Duration Grazing System. Soil Tillage Res.
2003, 70, 83–90. [CrossRef]
42. Pande, T.N.; Yamamoto, H. Cattle Treading Effects on Plant Growth and Soil Stability in the Mountain Grassland of Japan. Land
Degrad. Dev. 2006, 17, 419–428. [CrossRef]
Sustainability 2022, 14, 16665 16 of 16
43. Japan Meteorological Agency|AMeDAS. Available online: https://www.jma.go.jp/jma/en/Activities/amedas/amedas.html
(accessed on 28 October 2022).
44. Kang, S.; Mills, A.L. Soil Bacterial Community Structure Changes Following Disturbance of the Overlying Plant Community. Soil
Sci. 2004, 169, 55–65. [CrossRef]
45. Hill, R.; Pickering, C. Differences in Resistance of Three Subtropical Vegetation Types to Experimental Trampling. J. Environ.
Manag. 2009, 90, 1305–1312. [CrossRef] [PubMed]
46. Kobayashi, H.; Miura, S.; Oyanagi, A. Effects of Winter Barley as a Cover Crop on the Weed Vegetation in a No-Tillage Soybean.
Weed Biol. Manag. 2004, 4, 195–205. [CrossRef]
47. Rahman, A.; James, T.K.; Grbavac, N. Potential of Weed Seedbanks for Managing Weeds: A Review of Recent New Zealand
Research. Weed Biol. Manag. 2001, 1, 89–95. [CrossRef]
48. Rahman, A.; James, T.K.; Grbavac, N. Correlation between the Soil Seed Bank and Weed Populations in Maize Fields. Weed Biol.
Manag. 2006, 6, 228–234. [CrossRef]
49. Sun, D.; Liddle, M.J. Trampling Resistance, Stem Flexibility and Leaf Strength in Nine Australian Grasses and Herbs. Biol. Conserv.
1993, 65, 35–41. [CrossRef]
50. Kobayashi, T.; Hori, Y.; Nomoto, N. Effects of Trampling and Vegetation Removal on Species Diversity and Micro-Environment
under Different Shade Conditions. J. Veg. Sci. 1997, 8, 873–880. [CrossRef]
51. Greenland, D.J. Soil Management and Soil Degradation. J. Soil Sci. 1981, 32, 301–322. [CrossRef]
52. Dexter, A.R. Amelioration of Soil by Natural Processes. Soil Tillage Res. 1991, 20, 87–100. [CrossRef]
53. Jordan, D.; Li, F.; Ponder Jr, F.; Berry, E.C.; Hubbard, V.C.; Kim, K.Y. The Effects of Forest Practices on Earthworm Populations and
Soil Microbial Biomass in a Hardwood Forest in Missouri. Appl. Soil Ecol. 1999, 13, 31–38. [CrossRef]
54. Elliott, A.H.; Tian, Y.Q.; Rutherford, J.C.; Carlson, W.T. Effect of Cattle Treading on Interrill Erosion from Hill Pasture: Modelling
Concepts and Analysis of Rainfall Simulator Data. Soil Res. 2002, 40, 963–976. [CrossRef]
55. Drewry, J.J.; Paton, R.J.; Monaghan, R.M. Soil Compaction and Recovery Cycle on a Southland Dairy Farm: Implications for Soil
Monitoring. Soil Res. 2004, 42, 851–856. [CrossRef]
56. Reintam, E.; Kuht, J. Weed Responses to Soil Compaction and Crop Management. In Weed Control; Price, A., Ed.; InTech: London,
UK, 2012; ISBN 978-953-51-0159-8.
57. More, S.S.; Shinde, S.E.; Kasture, M.C. Root Exudates a Key Factor for Soil and Plant: An Overview. Pharma Innov. J 2020, 8,
449–459.
58. Ito, M.; Kobayashi, H.; Ueki, K. Allelopathic Potential of Digitaria adscendens: Inhibitory Effects of Previously Grown Soil on
Crop Growth and Weed Emergence. In Proceedings of the 11th Asian Pacific Weed Science Society Conference, Taipei, Taiwan,
China, 29 November–5 December 1987; Volume 2, pp. 607–612.
59. Alsaadawi, I.S.; Salih, N.M.M. Allelopathic Potential of Cyperus rotundas LI Interference with Crops. Allelopath. J. 2009, 23,
297–303.
60. Chopra, N.; Tewari, G.; Tewari, L.M.; Upreti, B.; Pandey, N. Allelopathic Effect of Echinochloa colona L. and Cyperus iria L. Weed
Extracts on the Seed Germination and Seedling Growth of Rice and Soyabean. Adv. Agric. 2017, 2017, 5748524. [CrossRef]
61. Paterson, E.; Sim, A. Rhizodeposition and C-Partitioning of Lolium perenne in Axenic Culture Affected by Nitrogen Supply and
Defoliation. Plant Soil 1999, 216, 155–164. [CrossRef]
62. Danckwerts, J.E.; Gordon, A.J. Long-Term Partitioning, Storage and Re-Mobilization of 14C Assimilated by Lolium perenne
(Cv. Melle). Ann. Bot. 1987, 59, 55–66. [CrossRef]
63. Evans, G.C. The Quantitative Analysis of Plant Growth; University of California Press: Berkeley, CA, USA, 1972; Volume 1.
64. Bokhari, U.G.; Singh, J.S. Effects of Temperature and Clipping on Growth, Carbohydrate Reserves, and Root Exudation of Western
Wheatgrass in Hydroponic Culture1. Crop Sci. 1974, 14, 790–794. [CrossRef]
65. Mikola, J.; Kytöviita, M.-M. Defoliation and the Availability of Currently Assimilated Carbon in the Phleum pratense Rhizosphere.
Soil Biol. Biochem. 2002, 34, 1869–1874. [CrossRef]
66. Nguyen, C.; Henry, F. A Carbon-14-Glucose Assay to Compare Microbial Activity between Rhizosphere Samples. Biol. Fertil. Soils
2002, 35, 270–276. [CrossRef]
67. Chehab, E.W.; Eich, E.; Braam, J. Thigmomorphogenesis: A Complex Plant Response to Mechano-Stimulation. J. Exp. Bot. 2009,
60, 43–56. [CrossRef]
68. Sunohara, Y.; Ikeda, H.; Tsukagoshi, S.; Murata, Y.; Sakurai, N.; Noma, Y. Effects of Trampling on Morphology and Ethylene
Production in Asiatic Plantain. Weed Sci. 2002, 50, 479–484. [CrossRef]
69. Stephane, F.F.Y.; Juleshttps, B.K.J. Terpenoids as Important Bioactive Constituents of Essential Oils. In Essential Oils-Bioactive
Compounds, New Perspectives and Applications; IntechOpen: London, UK, 2020; ISBN 978-1-83962-697-5.
70. Iwamur, J.; Hosotsubo, H.; Hirao, N. Mass Spectra for Molecular Structure(4)Mass Spectra of 2-Alkenoic Acid Methyl Esters.
Mass Spectrosc. 1978, 26, 269–274. [CrossRef]
71. Yang, L.; Wang, X.; Mao, Z.; Jiang, Z.; Gao, Y.; Chen, X.; Aubrey, D.P. Root Exudation Rates Decrease with Increasing Latitude in
Some Tree Species. Forests 2020, 11, 1045. [CrossRef]