Influence of different soil management practices on ground-flora vegetation in an almond orchard

Abstract

This paper reports a survey on the weed flora and seed bank in an almond orchard sited in Apulia region (Southern Italy), where the following soil management practices have been compared for over 30 yrs: no-tillage, keeping the soil totally weed-free throughout the year by using pre-emergence herbicides to prevent plant emergence or post-emergence herbicides in case of weeds already emerged; no-tillage, with post-emergence herbicides; no-tillage, with mowing of natural weed flora in spring; cover cropping, with faba bean sown in November and green manured in springtime; conventional soil tillage. The different management techniques influenced significantly the weed flora in experimental plots, both in terms of quantity and quality. The seed bank was clearly impoverished after the long-term applications of pre-emergence herbicides, both in terms of richness and of diversity. During the fall period, the plots of conventional tillage or pre-emergence herbicides had less natural ground-flora than the others. During springtime, prior to the sward control practices, the plots treated by foliar herbicides or mowing had the highest total weed cover. We conclude that post-emergence weed control by mowing or using chemical herbicides or the green manure of the cover crop may be proposed to reduce impact to the soil and to promote the growth of abundant and sufficiently diversified and balanced flora. If appropriately managed, this flora can provide potential ecological services, without competing with the orchard, as suggested by the literature. During the autumn, natural flora can uptake soil nitrogen thus preventing leaching in the rainy season. In springtime, after the sward has been destroyed, natural flora can supply a substantial amount of biomass to the soil. Indicator species analysis was also used to find the species characterizing each treatment and some of their combinations. Weeds belonging to the
Poaceae
botanical family were significantly associated with post-emergence herbicides and mowing treatments. These species produce a substantial amount of biomass and have bunched roots; consequently, they supply beneficial effects by improving porosity and structure of the soil and reducing erosion hazard.

Full text

Influence of different soil management
practices on ground-flora vegetation in
an almond orchard
M. Fracchiolla
1
*, M. Terzi
2
, L. Frabboni
3
, D. Caramia
3
, C. Lasorella
1
, D. De Giorgio
4
,
P. Montemurro
1
and E. Cazzato
1
1
Department of Agricultural and Environmental Science, University of Bari, Bari, Italy.
2
Italian National Council of Research—Institute of Biosciences and Bioresources, Bari, Italy.
3
Department of Agricultural, Food and Environmental Science, University of Foggia, Foggia, Italy.
4
Agricultural Research Council Research, Unit for Cropping Systems in Dry Environments, Bari, Italy.
*Corresponding author: mariano.fracchiolla@uniba.it
Accepted 22 June 2015 Research Paper
Abstract
This paper reports a survey on the weed flora and seed bank in an almond orchard sited in Apulia region (Southern
Italy), where the following soil management practices have been compared for over 30 yrs: no-tillage, keeping the soil
totally weed-free throughout the year by using pre-emergence herbicides to prevent plant emergence or post-emergence
herbicides in case of weeds already emerged; no-tillage, with post-emergence herbicides; no-tillage, with mowing of
natural weed flora in spring; cover cropping, with faba bean sown in November and green manured in springtime; con-
ventional soil tillage. The different management techniques influenced significantly the weed flora in experimental plots,
both in terms of quantity and quality. The seed bank was clearly impoverished after the long-term applications of pre-
emergence herbicides, both in terms of richness and of diversity. During the fall period, the plots of conventional tillage
or pre-emergence herbicides had less natural ground-flora than the others. During springtime, prior to the sward control
practices, the plots treated by foliar herbicides or mowing had the highest total weed cover. We conclude that post-emer-
gence weed control by mowing or using chemical herbicides or the green manure of the cover crop may be proposed to
reduce impact to the soil and to promote the growth of abundant and sufficiently diversified and balanced flora. If ap-
propriately managed, this flora can provide potential ecological services, without competing with the orchard, as sug-
gested by the literature. During the autumn, natural flora can uptake soil nitrogen thus preventing leaching in the
rainy season. In springtime, after the sward has been destroyed, natural flora can supply a substantial amount of
biomass to the soil. Indicator species analysis was also used to find the species characterizing each treatment and
some of their combinations. Weeds belonging to the Poaceae botanical family were significantly associated with post-
emergence herbicides and mowing treatments. These species produce a substantial amount of biomass and have
bunched roots; consequently, they supply beneficial effects by improving porosity and structure of the soil and reducing
erosion hazard.
Key words: almond orchards, cover crop, diversity, mowing, no-tillage, weeds, herbicides
Introduction
Adequate weed management may have positive conse-
quences on agriculture sustainability, enhancing agro-ecosys-
tem productivity and also by improving ecological services
(Gerowitt et al., 2003). The uncontrolled presence of
natural flora in tree orchards, like in any crop, increases com-
petition especially for water and nutrients, with a subsequent
reduction of yields and fruit quality. However, weed flora,
where appropriately managed, may have many beneficial
effects on the agro-ecosystem. Previous studies on the most
common tree crops in the Mediterranean region, including
olives (Montemurro et al., 2002; Corleto and Cazzato,
2008b;Simoesetal.,2014), wine grapes (Corleto and
Cazzato, 2008a; Ferrara et al., 2012), table grapes (Novello
et al., 1997), citrus (Colloff et al., 2013) and almond orchards
(Ramos et al., 2010), support reducing tillage intensity and
the permanent or temporary presence of sward, either
sown or natural, especially to preserve soil fertility and to
increase the agro-ecosystem’s diversity (Marshall et al.,
Renewable Agriculture and Food Systems: Page 1 of 9 doi:10.1017/S1742170515000241
©Cambridge University Press 2015

2003;Norris,2005; Colloff et al., 2013). The ground flora
reduces the soil erosion hazard (Hernandez et al., 2005;
Ramos et al., 2010; Chauhan et al., 2012)andimprovesthe
chemical, physical and microbiologic fertility of the soil
(Ramos et al., 2011;Sorianoetal.,2014).
Remarkable results in almond orchards are reported in
Spain by Ramos et al. (2010), suggesting that the tempor-
ary presence of weeds and the abandoning of frequently
tilled management enhance soil properties. In a research
on insect pollinators, almond orchards with living
ground cover showed positive relationship between
native bee abundance and the richness of ground cover
plants (Saunders et al.).
The weed communities should ideally combine ad-
equate and positive effects on the agro-environment
with only marginal negative competitive effects on
orchard (Fracchiolla et al., 2013). Such effects clearly
depend upon the eco-physiological and morphological
traits of species and their abundance in weed communities
(Altieri and Letourneau, 1982; Marshall et al., 2003;
Barberi et al., 2010). Consequently, proper weed manage-
ment should not only take into account the efficacy of
weed control but also how the practices affect the weed
population (Naylor and Drummond, 2002). This is the
reason why integrated weed management (Swanton and
Murphy, 1996) considers weeds not as a mere ‘target’
but as a community that ‘needs to be managed’that is
composed by individuals interacting with each other,
with the crop and with all agro-ecosystem components
(Clements et al., 1994; Soriano et al., 2014).
The effects of different management techniques on
weed composition have been shown in many cropping
systems (Zanin et al., 1997; Fried et al., 2012) and tree
crops, such as citrus (Mas et al., 2007), apple orchards
(Minãrro, 2012), grapevines (Montemurro et al., 1994;
Gago et al., 2007) and olive groves (Allen et al., 2006;
Fracchiolla et al., 2013). The results are obviously corre-
lated to the geographic location of the tested fields, al-
though all trials show a marked influence of cultural
practices on weed community composition.
The effects on weed flora are expected to be more stable
if the practices have been carried out over a long period of
time. Therefore, the aim of this paper is to compare the
influence of different soil management practices, pro-
tracted over more than 30 yrs in an almond orchard, on
the diversity and composition of weed communities and
soil seed bank. The experimental field was located in the
South of Italy, under a typical Mediterranean climate,
and it was managed with practices with few or no disturb-
ing activities to the soil.
Materials and Methods
The research was conducted in an experimental field in-
cluding an almond varietal collection, located in ‘La
Piantata’experimental farm near Bari (South-East of
Italy), of the Agricultural Research Council of Italy.
Plant spacing was 7 × 7 m
2
and the crop was rainfed.
The soil had a clay texture and a topsoil nearly 0.30 m
depth. Within a long-term study started in 1976, the fol-
lowing soil management practices were compared:
.Residual herbicide (ReH): no-tillage, keeping the soil
totally weed-free throughout the year by using residual
herbicides (pre-emergence) to prevent plant emergence
or foliar (post-emergence) herbicides in the case of
weeds already emerged (see Appendix).
.Foliar herbicide (FoH): no-tillage, with post-emergence
chemical weed control in spring, using foliar herbicides
(post-emergence of weeds) (see Appendix).
.Mowing (Mow): no-tillage, with mowing of natural
weed flora in spring.
.Cover cropping (Cov): cover cropping, with faba bean
(Vicia faba L. var. minor Beck) sown in November
and green manured in springtime at bloom stage.
.Conventional tillage (Til): conventional soil tillage,
using traditional techniques in the area where the ex-
perimental field is located.
Plots were of 147 m
2
(strip 7 m wide that included one row
of almond plants 21 m long) and were arranged in the
field following the randomized block experimental
design with four replicates. All the treatments were
applied to the whole plots, whereas a central area of 56
m
2
(a strip 4 m wide that included a central row of
almond plants 14 m long) was identified for soil sampling
and flora survey.
Herbicides were diluted in 400 liters ha
−1
of water and
applied with a hand pump sprayer backpack. Active
ingredients and doses are listed in the Appendix.
For mowing, a tractor driven rotary cutting with blades
mounted on a horizontal axle was used, to cut weeds to a
height of about 5 cm above the ground.
In the conventional tillage treatment, several plough-
ings were performed each year: deep ploughings (about
20 cm depth), from late autumn to early winter to increase
the water storage and shallow disk ploughings (10 cm
depth) for weed removal in the other periods.
Seed bank analysis
In October 2010, for each replicate and within the sam-
pling area, 10 soil samples were taken randomly and
from a depth between 0 and 30 cm, using circular soil
probe apparatus of 5 cm in diameter.
For the determination of the seed bank, the direct ob-
servation of the plantlets emerging from each soil
sample was applied (Roberts and Neilson, 1982).
Soil samples were placed into trays where the soil did
not exceed 4 cm depth and was periodically wetted.
Trays were kept in the greenhouse for 25 months, under
such conditions as not to exceed an internal temperature
of 35°C during the hottest periods. Irrigation was period-
ically stopped to simulate drought periods, so the soil was
2 M. Fracchiolla et al.

mixed up and newly wetted, so as to favor the interruption
of dormancy of most seeds (Cantele et al., 1996). In the
hottest months (July and August), trays were not irrigated
so as to prevent the emergence of new plantlets and avoid
their quick decline with the subsequent loss of data. The
plantlets emerging from each tray were identified,
counted and removed. The data collected for each
species were expressed in terms of number of seeds per
square meter of soil.
Flora field surveys
In October 2010–2011 and in May 2011–2012, namely at
the end of the peak vegetative growth periods and prior to
control practices, weed communities were assessed on the
sampling area (56 m
2
) for each replicate. Percent covers of
species were visually estimated; sporadic species were
recorded with the arbitrary value of 0.5%. This paper pro-
vides the means of cover data recorded for the October
(autumn) and May (spring) surveys of each year.
Taxonomic nomenclature refers to Conti et al. (2005).
Numerical analysis
For each treatment, the floristic richness (S) of the seed
bank and autumn and spring weed flora was calculated
as the mean number of vascular plant species and families.
The richness was expressed as the mean number of taxa
found in the sampling area (56 m
2
) of each replication.
The diversity of each treatment was estimated by the
Shannon–Wiener index (H) which combines evenness
and richness of species. The index was calculated as
follows: H=−∑p
i
ln p
i;
where p
i
is the proportion of indi-
viduals (for seed bank) or cover (for field surveys) of the
ith species.
For each treatment, the mean sum of the plant cover
values in each replicate was indicated as the ‘total weed
cover’. This index was used to roughly estimate the struc-
ture (biomass, stratification, coverage) of weed communi-
ties. Occasionally, the total weed cover value exceeded
100% because individual plants can overlap one to each
other.
All the values were square root transformed to ensure
the homogeneity of variances and submitted to the
analysis of variance. The means were compared using
the Duncan’s test. Tables show the mean data, non-
transformed, of replicates.
The indicator species analysis (ISA) (Dufrêne and
Legendre, 1997) was used to find the species characteriz-
ing each treatment and some of their combinations.
The ISA recently arranged within a statistical frame-
work of methods for assessing the association between
species and site groups (De Cáceres and Legendre,
2009), has been widely used in ecology. The strength of
the association between a species and a group of sites is
measured by the indicator value index (IndVal). The
highest IndVal of a species along a site typology identifies
the group of sites for which that species can be considered
as an indicator species (IS) (Dufrêne and Legendre, 1997).
The IndVal of species ifor the group of sites jare calcu-
lated as follows: IndVal
ij
=A
ij
×B
ij
× 100; where A
ij
is
the ratio between the mean abundance of species iin the
sites of group jand the mean abundance of species i
along all the groups of sites. B
ij
is the ratio between the
number of sites of cluster jwhere the species iis present
and the total number of sites in that group. The
maximum value of the index (IndVal = 100) is reached
for species that are present in only one group and in all
of its sites.
The method can be adapted for a randomized block
experimental design, as in our case, by a pre-relativization
by species within each replicate (i.e., blocked ISA)
(McCune and Grace, 2002; McCune and Mefford,
2011). The IndVal were tested for statistical significance
(P≤0.05) by using a Monte Carlo test, with 5000
permutations.
To find the IS associated with more than one treatment,
the treatments were hierarchically clustered (flexible-beta
method, β=−0.25, with Bray–Curtis distance measure)
on the basis of both autumn and spring species mean
cover. The cluster analyses for autumn and spring data
gave very similar results; only the dendrogram for the
autumn survey was shown. Significant IS were calculated
for the clusters of treatments obtained for every level of
the dendrogram. Each significant IS was then assigned
to the treatment or group of treatments for which it
yielded the highest IndVal (Dufrêne and Legendre,
1997; McCune and Grace, 2002).
All the multivariate analyses described above were
carried out by using the software pc-ord v.6.11
(McCune and Mefford, 2011).
Results
The cluster analysis (Fig. 1) clearly differentiated the re-
sidual herbicide from the other treatments. The second
partitioning level of the dendrogram separated the foliar
Figure 1. Cluster analysis [flexible beta (β=−0.25), Bray–
Curtis distance measure] of the treatments based on the
autumn weed surveys. ReH, residual herbicide; FoH, foliar
herbicide; Mow, mowing; Cov, cover crop; Til, conventional
tillage.
3Influence of different soil management practices on ground-flora vegetation

herbicide and mowing treatments from the crop covering
and conventional tillage. The last two treatments were
separated at the third partitioning level, whereas foliar
herbicide and mowing were the most floristically similar
treatments.
The residual herbicide was characterized by the lowest
diversity, richness and total weed cover, both in autumn
and spring surveys (Tables 1 and 2). Also for the seed
bank, the values of the Shannon–Wiener and richness
indexes were statistically different and lower than in all
the other treatments (Table 3). The number of seeds in
the seed bank for the residual herbicide was the lowest
one, significantly different from all the others with the ex-
ception of the foliar herbicide (Table 3).
Regarding the other treatments, in the autumn survey,
the lowest total weed cover was recorded for the conven-
tional tillage, whereas the lowest richness value was
calculated for the foliar herbicide (Table 1). During
spring surveys (Table 2), the highest mean total weed
cover was found for the foliar herbicide and mowing.
The lowest mean numbers of botanical species and fam-
ilies (richness) were found in the mowing. The
Shannon–Wiener index values calculated for foliar herbi-
cide, mowing, conventional tillage and cover cropping
(Table 2), were not statistically different from each other.
Regarding the seed bank, except for the residual herbi-
cide, all the other treatments showed no statistically differ-
ent values of richness, diversity and number of seeds
(Table 3).
IS analysis
In the autumn surveys, the residual herbicide was not
associated with any IS, whereas Avena sterilis,Bromus
Table 1. Autumn surveys: effects of different systems of treatments on total weed cover, richness and diversity
1
.
Treatments
2
ReH FoH Mow Cov Til
Total weed cover (%) 2.7 c 56.8 a 52.3 a 54.4 a 30.9 b
Richness (no. of species) 4.8 c 9.2 b 13.2 a 14.8 a 13.0 a
Richness (no. of families) 4.2 c 9.2 b 11.0 ab 12.2 a 11.2 ab
Shannon–Wiener index 1.6 1.9 1.9 1.8 2.0
1
Values followed by different letter in each row are significantly different from each other at P< 0.05 (Duncan test).
2
ReH, residual herbicide; FoH, foliar herbicide; Mow, mowing; Cov, cover crop; Til, conventional tillage.
Table 2. Spring surveys: effects of different systems of treatments on total weed cover, richness and diversity
1
.
Treatments
2
ReH FoH Mow Cov Til
Total weed cover (%) 19.0 d 115.3 a 109.0 a 41.0 c 72.0 b
Richness (no. of species) 6.2 c 15.5 a 11.2 b 12.2 ab 14.5 ab
Richness (no. of families) 4.5 c 9.2 a 7.0 b 8.7 ab 9.5 a
Shannon–Wiener index 0.8 b 1.9 a 1.7 a 2.1 a 2.3 a
1
Values followed by different letter in each row are significantly different from each other at P< 0.05 (Duncan test).
2
ReH, residual herbicide; FoH, foliar herbicide; Mow, mowing; Cov, cover crop; Til, conventional tillage.
Table 3. Seed bank: effects of different systems of treatments on total number of seeds, richness and diversity
1
.
Treatments
2
ReH FoH Mow Cov Til
Total number of seeds (n m
−2
) 2524 b 7890 ab 11.678 a 8884 a 9897 a
Richness (no. of species) 6.0 b 15.5 a 16.2 a 15.7 a 13.0 a
Richness (no. of families) 5.0 b 12.0 a 11.5 a 12.2 a 11.5 a
Shannon–Wiener index 1.4 b 2.2 a 2.2 a 2.5 a 2.0 a
1
Values followed by different letter in each row are significantly different from each other at P< 0.05 (Duncan test).
2
ReH, residual herbicide; FoH, foliar herbicide; Mow, mowing; Cov, cover crop; Til, conventional tillage.
4 M. Fracchiolla et al.

sterilis and Calendula arvensis characterized the other
treatments. The number of species associated with the
clusters Cov + Til and FoH + Mow were eight and five,
respectively, with seven IS of single treatments (Fig. 1,
Table 4). The highest IndVal were recorded for
Convolvulus arvensis,Cynodon dactylon,Diplotaxis
muralis and Hordeum murinum (associated with the
cluster FoH + Mow) and Amaranthus retroflexus (Cov +
Til), Lathyrus sp. (Cov) and Heliotropium europaeum (Til).
In the spring surveys, only two significant IS (Arenaria
leptoclados and Erigeron Canadensis) were recorded for
the residual herbicide. A. sterilis and B. sterilis were asso-
ciated with the other four treatments (Table 5). The clus-
ters Cov + Til and FoH + Mow were characterized by an
equal number of IS. The highest IndVal were recorded for
H. murinum,Galium aparine and Sherardia arvensis (FoH
+ Mow) and Fumaria capreolata,Lamium amplexicaule
and Veronica hederifolia (Cov + Til). Among the single
treatments, the conventional tillage was floristically differ-
entiated by four significant IS (C. arvensis,Diplotaxis eru-
coides,Lolium rigidum,Senecio vulgaris); two IS were
recorded for mowing and foliar herbicide.
The data concerning the seed bank (Table 6) showed
that only A. leptoclados was significantly associated with
the residual herbicide, whereas the other treatments had
five significant IS, among which C. arvensis (IndVal =
93.8) and Portulaca oleracea (93.8) with the highest
IndVal. The significant IS associated with Fow + Mow
were Euphorbia helioscopia,B. sterilis and Sonchus olera-
ceus, whereas Capsella bursa-pastoris characterized Cov
+ Til. Few other significant IS resulted associated with
single treatments. However, we cannot exclude that the
lower number of species with significant treatment asso-
ciations in the seedbank is due to a greater variability
observed in data recorded in the soil sampling than in
those of aboveground visual surveys.
Discussion and Conclusions
Among the five treatments compared in this paper, the re-
sidual herbicide was the most differentiated for low levels
of total weed cover, richness and diversity. The ISA
selected very few species significantly associated with
this treatment. Moreover, the seed bank, which showed
slight differences among the other treatments, was
clearly impoverished after the long-term applications of
residual herbicides. On the other hand, another study
(De Giorgio and Lamascese, 2005) on the almond tree
productivity in the same experimental plots, recorded
the highest yield for this treatment (4.86 kg per tree).
For the foliar herbicide, cover cropping and conventional
Table 4. Autumn surveys: mean cover percentage and the highest indicator value (IndVal) of weed species significantly (P≤0.05)
associated with a treatment or a group of treatments.
Species
Mean cover percentage (%)
IndVal Treatments
1
ReH FoH Mow Cov Til
Avena sterilis L. 0.0 27.0 25.0 5.0 1.5 100.0 FoH, Mow, Cov, Til
Bromus sterilis L. 0.2 13.8 12.3 3.4 0.4 97.5 FoH, Mow, Cov, Til
Calendula arvensis L. 1.0 4.0 3.4 4.4 6.5 83.3 FoH, Mow, Cov, Til
Convolvulus arvensis L. 0.0 1.1 2.0 0.0 0.0 100.0 FoH, Mow
Diplotaxis muralis (L.) DC. 0.0 2.9 9.8 0.0 0.0 100.0 FoH, Mow
Hordeum murinum L. 0.0 4.0 1.9 0.0 0.0 100.0 FoH, Mow
Cynodon dactylon (L.) Pers. 0.1 3.4 26.6 0.0 0.3 98.9 FoH, Mow
Galium aparine L. 0.0 3.3 0.5 0.5 0.0 88.1 FoH, Mow
Amaranthus retroflexus L. 0.0 0.3 1.5 31.3 13.0 96.4 Cov, Til
Glebionis segetum (L.) Fourr. 0.0 0.0 0.0 1.7 0.4 87.5 Cov, Til
Lamium amplexicaule L. 0.0 0.0 0.0 0.6 0.2 87.5 Cov, Til
Chenopodium album L. 0.0 0.0 0.8 1.1 0.9 79.8 Cov, Til
Senecio vulgaris L. 0.3 0.0 0.0 0.9 1.6 79.2 Cov, Til
Diplotaxis erucoides (L.) DC. 0.2 0.0 2.6 5.5 4.8 77.3 Cov, Til
Portulaca oleracea L. 0.0 0.4 0.6 0.9 0.9 75.0 Cov, Til
Medicago minima (L.) L. 0.3 0.6 0.5 0.7 0.9 70.9 Cov, Til
Lathyrus sp. 0.0 0.0 0.0 0.5 0.0 100.0 Cov
Fumaria capreolata L. 0.1 0.0 0.0 1.0 0.0 95.0 Cov
Fallopia convolvulus (L.) Á. Löve 0.6 5.6 0.4 0.1 0.5 78.7 FoH
Lolium rigidum Gaudin 0.0 1.5 0.0 0.0 0.6 71.2 FoH
Erodium malacoides (L.) L’Hér. 0.0 0.0 1.7 0.1 0.0 87.5 Mow
Sonchus oleraceus L. 0.0 0.0 0.6 0.3 0.0 76.8 Mow
Heliotropium europaeum L. 0.0 0.0 0.1 0.0 1.0 95.2 Til
1
ReH, residual herbicide; FoH, foliar herbicide; Mow, mowing; Cov, cover crop; Til, conventional tillage.
5Influence of different soil management practices on ground-flora vegetation

Table 5. Spring surveys: mean cover percentage and the highest indicator value (IndVal) of weed species significantly (P≤0.05) asso-
ciated with a treatment or a group of treatments.
Species
Mean cover percentage (%)
IndVal Treatments
1
ReH FoH Mow Cov Til
Arenaria leptoclados (Rchb.) Guss. 13.9 0.0 0.0 0.0 0.0 100.0 ReH
Erigeron canadensis L. 1.6 0.0 0.0 0.0 0.0 75.0 ReH
Bromus sterilis L. 0.3 35.6 33.1 3.9 3.0 98.7 FoH, Mow, Cov, Til
Avena sterilis L. 0.0 42.5 47.5 6.3 3.1 93.8 FoH, Mow, Cov, Til
Hordeum murinum L. 0.1 15.8 14.4 0.0 0.0 99.1 FoH, Mow
Galium aparine L. 0.1 7.9 2.4 0.0 0.0 97.6 FoH, Mow
Sherardia arvensis L. 0.0 1.8 2.1 0.1 0.1 95.9 FoH, Mow
Medicago minima (L.) L. 0.1 3.3 1.9 0.1 0.1 92.6 FoH, Mow
Geranium dissectum L. 0.0 2.6 0.8 0.0 0.0 87.5 FoH, Mow
Convolvulus arvensis L. 1.3 3.0 5.4 0.0 0.8 72.6 FoH, Mow
Lathyrus sp. 0.0 1.4 0.9 0.0 0.0 62.5 FoH, Mow
Fumaria capreolata L. 0.0 0.0 0.0 7.4 17.5 100.0 Cov, Til
Lamium amplexicaule L. 0.0 0.0 0.0 4.4 15.1 100.0 Cov, Til
Veronica hederifolia L. 0.1 0.0 0.0 2.0 7.3 96.5 Cov, Til
Capsella bursa-pastoris (L.) Medik. 0.0 0.4 0.0 0.6 2.9 92.5 Cov, Til
Glebionis segetum (L.) Fourr. 0.0 0.9 0.3 7.0 3.3 89.8 Cov, Til
Stellaria media (L.) Vill. 0.0 0.8 1.1 3.3 3.1 79.7 Cov, Til
Scandix pecten-veneris L. 0.0 0.0 0.1 0.6 0.5 65.5 Cov, Til
Vicia sativa L. 0.0 1.4 0.0 0.0 0.0 100.0 FoH
Papaver rhoeas L. 0.0 6.9 0.0 3.9 0.1 64.1 FoH
Euphorbia helioscopia L. 0.0 0.5 5.1 0.0 0.0 91.8 Mow
Malva sylvestris L. 0.0 0.0 0.8 0.0 0.0 75.0 Mow
Senecio vulgaris L. 0.0 0.0 0.0 0.1 5.2 97.7 Til
Diplotaxis erucoides (L.) DC. 0.0 0.0 0.0 0.6 8.0 92.9 Til
Lolium rigidum Gaudin 0.0 0.9 0.0 0.1 2.6 84.8 Til
Calendula arvensis L. 0.3 1.3 1.3 1.4 4.5 59.7 Til
1
ReH, residual herbicide; FoH, foliar herbicide; Mow, mowing; Cov, cover crop; Til, conventional tillage.
Table 6. Seed bank: average number of seeds per square meter and indicator value (IndVal) of weed species significantly (P≤0.05)
associated with a treatment or a group of treatments.
Species
Number of seeds (n m
−2
)
IndVal Treatments
1
ReH FoH Mow Cov Til
Arenaria leptoclados (Rchb.) Guss. 1095 178 242 25 64 91.1 ReH
Calendula arvensis L. 0.0 331 1720 548 153 93.8 FoH, Mow, Cov, Til
Portulaca oleracea L. 0.0 1363 2331 943 1070 93.8 FoH, Mow, Cov, Til
Diplotaxis erucoides (L.) DC. 0.0 382 102 713 267 81.2 FoH, Mow, Cov, Til
Medicago disciformis DC. 0.0 675 382 242 1121 81.2 FoH, Mow, Cov, Til
Lamium amplexicaule L. 0.0 420 242 611 1580 75.0 FoH, Mow, Cov, Til
Bromus sterilis L. 51 420 790 166 38 80.8 FoH, Mow
Sonchus oleraceus L. 102 446 280 267 153 53.0 FoH, Mow
Euphorbia helioscopia L. 0 191 76 38 0 40.6 FoH, Mow
Capsella bursa-pastoris (L.) Medik. 0 0 38 484 229 61.2 Cov, Til
Fumaria capreolata L. 89 25 115 650 127 72.7 Cov
Lolium rigidum Gaudin 0 0 102 166 0 59.4 Cov
Erodium malacoides (L.) L’Hér. 0 0 204 25 0 67.9 Mow
Amaranthus retroflexus L. 0 0 166 280 1248 70.3 Til
1
ReH, residual herbicide; FoH, foliar herbicide; Mow, mowing; cov, cover crop; Til, conventional tillage.
6 M. Fracchiolla et al.

tillage, the yields per tree ranged between 4.05 and 3.56 kg;
whereas the lowest yield was recorded for the mowing
(2.72 kg per tree) (De Giorgio and Lamascese, 2005).
Although these data referred to are the means of the
period 1988–2000 (De Giorgio and Lamascese, 2005)
and need to be updated, we might conclude that the treat-
ment providing the lowest level of diversity (i.e., the less
sustainable practice) is the most productive. However, em-
phasis should be placed on the off-farm environmental
benefits of adopting conservative agriculture techniques
that provide adequate level of biodiversity and low
impact to the soil (Holland, 2004). From this point of
view, the agroecological role of weed flora communities
(Buhler, 2002; Chauhan et al., 2012) should be prioritized
and weed management should be integrated with other
cultural practices in order to optimize the whole cropping
system rather than solely weed control (Elmore, 1996;
Bàrberi, 2002).
During autumn months, the residual herbicide and
conventional tillage were the less infested (cf. Table 1:
total weed cover). This effect does not constitute a
benefit (Montemurro and Fracchiolla, 2013); as a
matter of fact, the presence of the sward in the autumn-
winter period does not cause any damage and is rather de-
sirable because it prevents soil erosion processes that are
particularly common in many Mediterranean areas
(García-Ruiz, 2010; Novara et al., 2011). Moreover, it is
important to consider the high capacity of the natural
flora to takeup soil nitrogen (Blackshaw et al., 2003)
thus preventing in the rainy season leaching processes
that might cause pollution (Constantin et al., 2010).
In springtime, prior to sward control operations, the
plots treated by foliar herbicide and mowing showed the
highest total weed cover, thus supplying a substantial
amount of biomass to the soil, after sward had been
destroyed. Among the species associated with these treat-
ments, a large contribution to the total weed cover come
from three Poaceae: B. sterilis,A. sterilis and H. murinum.
These species produce a substantial amount of biomass
and have bunched roots; consequently they supply benefi-
cial effects by improving porosity and structure of the soil
and reducing erosion hazard. However, they can strongly
compete with almond trees for soil water, particularly in
rainfed orchards placed in Mediterranean conditions
with pronounced summer drought. The lowest yield,
recorded for the mowing treatment by De Giorgio and
Lamascese (2005), is explained as a consequence of a
greater competition for water. In this respect, a realistic
proposal that could be verified by further studies would
be to keep the orchard fully free of weeds during the
drought period to minimize the negative effects of water
competition, while benefiting from the positive effects of
the sward (Ramos et al., 2010; Fracchiolla et al., 2013).
Besides the ‘timing’, another core concern is the techni-
ques of weed removal. Post-emergence weed control by
mowing or using chemical herbicides or the green
manure of the cover crop may be proposed to reduce
impact to the soil and to promote the growth of abundant
and sufficiently diversified and balanced flora. Although
the research has not regarded the effects on the agro-
ecological system and on the physico-chemical soil prop-
erties, this flora can definitely have beneficial effects,
following the indications provided by the literature.
This paper reports data of a trial that has merely
involved the comparison of single weed control practices
repeated for several years. On the other hand, several
studies support the idea that each single practice should
be considered only as a component of a more general
system of diversified strategies of integrated weed man-
agement (Buhler, 2002; Chauhan et al., 2012). For
example, mowing could be adopted to quickly suppress
groundcover at the beginning of the drought period and
chemical weeding can be used to cheaply control subse-
quent regrowing. The sowing of the cover crop could be
performed to promote natural soil fertility and to intro-
duce a further different management technique in the
whole cropping system. One remaining question is the
effects, both on- and off-farm, of adopting a combination
of management practices on weed flora, productivity and
biodiversity for a sustainable rural land use.
Acknowledgements. We would like to thank Prof. F.S.
D’Amico (University of Bari) and the anonymous refer-
ees for their useful suggestions and comments.
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Appendix
List of herbicides (active ingredients) used for the residual
herbicides and foliar herbicides treatments. For each year,
applications are indicated by the active ingredient [month,
dose (kg ha
−1
)].
Residual herbicide treatment: 1976 –Bromacil (January,
2.0); Propyzamide + Simazine (November, 1.0+ 1.5). 1977
–Diclhobenil (October, 3.375). Paraquat (February, 0.47).
1979 –Paraquat (February, 0.47); Chlopropham + Diuron
(February, 2.45 + 2.45); Dalapon (May, 0.04). 1980 –
Bromacil (January, 2.0); Propyzamide + Simazine (1.0 +
1.5). 1981 –Diclhobenil (October, 3.375). 1983 –Paraquat
(February, 0.47); Chlopropham + Diuron (March, 2.45 +
2.45). 1984 –Bromacil (January, 2.0); Paraquat (May,
0.925). 1985 –Propyzamide + Simazine (February, 1.0 +
1.5); Paraquat (May, 0.925); Diclhobenil (October, 3.375).
1986 –Paraquat (April, 0.925). 1987 –Paraquat (March,
0.47); Chlopropham + Diuron (April, 0.245 + 0.245);
Paraquat (May, 0.47). 1988 –Bromacil (February, 2.0);
Propyzamide + Simazine (November 1.0 + 1.5). 1989 –
Diclhobenil (October, 3.375). 1990 –Chlopropham +
Diuron (October, 2.45 + 2.45). 1992 –Glyphosate +
Simazine (February, 1.08 + 3.0). 1993 –Glyphosate +
Simazine (January, 1.08 + 3.0). 1994 –(February,
Glyphosate + Simazine, 1.08 + 3.0). 1995 –Glyphosate +
Simazine (May, 1.08 + 3.0). 1996 –Glyphosate + Simazine
(November 1.08 + 3.0). 1997 –Paraquat (April, 0.925).
1998 –Glyphosate (October, 1.54). 1999 –Glyphosate
(April, 1.23). Glyphosate (October, 1.5). Oxadiazon +
Glyphosate (November, 0.5 + 0.25). 2000 –Glyphosate
(May, 1.23); Oxadiazon + Glyphosate (October, 2.0 +
1.0). 2001 –Oxadiazon + Glyphosate (January, 2.0 +
1.0); Oxadiazon (May, 1.7); Diquat + Paraquat (May,
0.35 + 0.7); Oxadiazon (November, 1.7). 2002 –Diquat +
Paraquat (May, 0.35 + 0.7); Diquat + Paraquat (October,
0.13 + 0.33). 2003 –Glyphosate (April, 1.53); Diquat +
Paraquat (July, 0.04+ 0.12); Oxadiazon + Glyphosate
(September, 2.0 + 1.0). 2004 –Diquat + Paraquat (April,
0.32 + 0.67). 2005 –Oxadiazon + Glyphosate (February, 2.0
+ 1.0); Diquat + Paraquat (April, 0.13 + 0.33). 2006 –
Oxadiazon + Glyphosate (April, 2.0 + 1.0); Glyphosate +
Oxyfluorfen (October, 0.9 + 0.07). 2007 –Glyphosate +
Oxyfluorfen (April, 0.9 + 0.07); Glyphosate (October,
0.108). 2008 –Glyphosate + Oxyfluorfen (May, 0.9 +
0.07); Glyphosate (November, 0.108). 2009 –Glyphosate
+ Flazasulfuron (May, 0.108 + 0.06). 2010 –Glyphosate
+ Flazasulfuron (May, 0.108 + 0.06).
Foliar herbicide treatment: 1976 –Paraquat (May, 0.925).
1977 –Paraquat (May, 0.925). 1978 –Paraquat (May,
0.925). 1979 –Paraquat (May, 0.925). 1980 –Paraquat
(May, 0.925). 1981 –Paraquat (April, 0.925). 1982 –
Paraquat (May, 0.925). 1983 –Paraquat (April, 0.925).
1984 –Paraquat (May, 0.925). 1985 –Paraquat (May,
0.925). 1986 –Paraquat (May, 0.925). 1987 –Paraquat
(May, 0.925). 1988 –Paraquat (February, 0.925). 1989 –
Paraquat (May, 0.925). 1990 –Paraquat (April, 0.925).
1991 –Paraquat (May, 0.925). 1992 –Paraquat (May,
0.925). 1993 –Paraquat (May, 0.925). 1994 –Paraquat
(January, 0.925). 1995 –Diquat + Paraquat (May, 0.35 +
0.7). 1996 –Diquat + Paraquat (November, 0.35 + 0.7).
1997 –Paraquat (April, 0.925). 1998 –Diquat + Paraquat
(May, 0.35 + 0.7). 1999 –Paraquat (May, 0.925). 2000 –
Paraquat (May, 0.925). 2001 –Paraquat (May, 0.925).
2002 –Diquat + Paraquat (May, 0.29 + 0.6). 2003 –
Diquat + Paraquat (November, 0.29 + 0.6). 2004 –
Diquat + Paraquat (May, 0.29 + 0.6). 2005 –Diquat +
Paraquat (May, 0.29 + 0.6). 2006 –Diquat + Paraquat
(April, 0.29 + 0.6); Glufosinate ammonium (December,
0.9). 2007 –Glufosinate ammonium (October, 0.9). 2008 –
Glufosinate ammonium (May, 0.9); Glufosinate ammo-
nium (September, 0.9). 2009 –Glufosinate ammonium
(May, 0.9). 2010 –Carfentrazone ethyl (May, 0.19).
9Influence of different soil management practices on ground-flora vegetation