Impact of Cereal–Legume Intercropping on Changes in Soil Nutrients Contents under Semi–Arid Conditions

Full text

Citation: Attallah, A.; Hamdi, W.;
Souid, A.; Farissi, M.; L’taief, B.;
Messiga, A.J.; Rebouh, N.Y.; Jellali, S.;
Zagrarni, M.F. Impact of
Cereal–Legume Intercropping on
Changes in Soil Nutrients Contents
under Semi–Arid Conditions.
Sustainability 2024,16, 2725.
https://doi.org/10.3390/su16072725
Academic Editor: Jeroen Meersmans
Received: 18 February 2024
Revised: 21 March 2024
Accepted: 22 March 2024
Published: 26 March 2024
Copyright: © 2024 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
sustainability
Article
Impact of Cereal–Legume Intercropping on Changes in Soil
Nutrients Contents under Semi–Arid Conditions
Amal Attallah 1, Wissem Hamdi 1,*, Amira Souid 1, Mohamed Farissi 2, Boulbaba L’taief 3, AiméJ. Messiga 4,
Nazih Y. Rebouh 5, Salah Jellali 6and Mohamed Faouzi Zagrarni 1
1Higher Institute of the Sciences and Techniques of Waters, Gabes University, Gabes 6029, Tunisia;
amalatallah7@gmail.com (A.A.); amirasouid518@gmail.com (A.S.); zagrarni_m_f@yahoo.fr (M.F.Z.)
2Laboratory of Biotechnology & Sustainable Development of Natural Resources, Polydisciplinary Faculty
of Beni-Mellal, Sultan Moulay Slimane University, Beni-Mellal 23000, Morocco; farissimohamed@gmail.com
3Biology Department, College of Science, King Khalid University, P.O. Box 960, Abha 62223, Saudi Arabia;
lboulaba@yahoo.com
4Agassiz Research and Development Centre, Agriculture and Agri-Food Canada,
Agassiz, BC V0M1A0, Canada; aime.messiga@agr.gc.ca
5Department of Environmental Management, Institute of Environmental Engineering, RUDN University,
6 Miklukho-Maklaya St., 117198 Moscow, Russia; n.yacer16@outlook.fr
6Center for Environmental Studies and Research, Sultan Qaboos University, Al-Khoud 123, Muscat, Oman;
s.jelali@squ.edu.om
*Correspondence: wissemhemdi@yahoo.fr
Abstract: Cereal–legume intercropping systems are not well studied under the semi–arid conditions
of Southern Tunisia. Therefore, the present study aimed to investigate the effect of intercropping
durum wheat (Triticum turgidum ssp. durum L.) with chickpea (Cicer arietinum L.) on crop grain
yield and soil physicochemical proprieties such as carbon (C) and nitrogen (N) availability, microbial
biomass nutrients (C and N) and plant nutrient content (N) in comparison to their monocultures.
Field experiments were conducted during the 2020–2021 (EXP–A) and 2021–2022 (EXP–B) seasons in
Medenine, Tunisia. The results revealed a significant augmentation (p< 0.05) in the total nitrogen pro-
portions (Ntot) within the soil of intercropped durum wheat (DuWh–IR) compared to its monoculture
(DuWh–MC). The observed variations amounted to 32% and 29% during the two growing seasons,
identified as EXP–A and EXP–B. Additionally, the soil of intercropped durum wheat (DuWh–IR)
significantly (p< 0.05) accumulated more total carbon (C
tot
) than the monocrop (DuWh–MC) for
both experiments, showing an increase of 27% in EXP–A and 24% in EXP–B. Simultaneously, the
N
−
uptake of durum wheat significantly increased under the effect of intercropping, showing a rise
of 26% in the EXP–A season and 21% in the EXP–B season. Similarly, the yield of durum wheat
crops was comparatively greater in the intercropped plots as opposed to the monoculture crops, with
variances of 23% in EXP–A and 20% in EXP–B. Intercropping cereals and legumes has the potential
to enhance the soil fertility and crop production in the semi–arid regions of Southern Tunisia and
contribute to environmental sustainability by reducing reliance on nitrogen fertilizers.
Keywords: chickpea; durum−wheat; N−uptake; carbon availability; crop yield
1. Introduction
Tunisia’s soils are undergoing substantial degradation, leading to a loss of fertility
and a decline in the soil’s ability to retain and infiltrate water. This soil degradation is
expected to intensify in the coming years due to rapid population growth and increased
demands for soil production, exacerbated by global phenomena such as climate change.
This prompted Tunisian farmers to adopt modern strategies marked by a notable simplifi-
cation of agroecosystems and the widespread use of chemical inputs. Unfortunately, this
has yielded various adverse environmental effects, as documented by Tribouillois et al. [
1
].
One significant consequence has been the decline in ecosystem services, particularly in
Sustainability 2024,16, 2725. https://doi.org/10.3390/su16072725 https://www.mdpi.com/journal/sustainability

Sustainability 2024,16, 2725 2 of 12
water and soil resources, as highlighted by Glaze-Corcoran et al. [
2
]. These impacts include
the chemical, physical, and biological degradation of soil, eutrophication of surface and
groundwater, and the release of nitrous oxides, contributing to air pollution [3,4].
As a result, there is growing scrutiny of modern agriculture, urging the adoption of
new agronomic solutions that are both efficient and environmentally friendly, aiming to
mitigate negative environmental impacts, address resource scarcity (such as water and
fossil energy), and adapt to climate change [
5
,
6
]. Within this framework, biodiversity
emerges as a pivotal strategy for sustainable agriculture, preserving soil fertility, optimizing
nutrient utilization, managing pest protection, and sustaining overall productivity [7,8].
One potential avenue in this regard is the adoption of intercropping systems. Inter-
cropping involves cultivating multiple crop species simultaneously on a single plot of land,
aiming to enhance the land utilization efficiency and ultimately achieve higher productivity
levels [
9
,
10
]. This agricultural practice is grounded in ecological principles, specifically
facilitation and complementarity [
6
,
8
]. Furthermore, intercropping systems combining
legumes and cereals are widely acknowledged as highly efficient cropping systems with
the potential to optimize the utilization of resources, particularly nitrogen and water [
10
,
11
].
Moreover, these systems have demonstrated increased resilience to abiotic stressors, such
as drought, and offer effective strategies for weed, pest, and disease management without
relying on herbicides [12–14].
Implementing this agricultural cropping system has a significant impact on vari-
ous nitrogen transformation processes by influencing microbial processes, diversity, and
community composition [
15
–
18
]. Consequently, due to the nitrogen fixation facilitated
by legumes, intercropped cereals exhibit a reduced dependence on nitrogen fertilizers
compared to those grown in monoculture.
Numerous studies have highlighted that intercropping systems involving cereals
and legumes demonstrate an enhanced efficiency in utilizing nutrient resources, specifi-
cally carbon (C), nitrogen (N), and phosphorus (P), compared to conventional single–crop
systems [
19
–
22
]. The intercropping system is one of the most useful practices in crop
production, especially in areas with water and nutrient deficiencies in arid and semi–arid
climatic zones. Previous studies have confirmed that this type of land use can result in
higher–than–expected yields due to an increased use of soil nutrients and/or by suppress-
ing crop pests [23–25].
Adopting a chickpea–based intercropping system certainly has the potential to im-
prove the nitrogen nutrition and crop yield for associated cereals through biological ni-
trogen fixation [
26
]. Nevertheless, like other vegetables, the growth and nitrogen fixa-
tion of chickpeas can be influenced by abiotic factors such as drought, phosphorus defi-
ciency,
low–nitrogen
soil, and biotic factors including pests, weeds, and diseases [
27
–
31
].
These stressors are particularly significant in the southern Mediterranean regions, to which
Tunisia belongs, where the impact of these limiting variables is more pronounced [32–34].
The cereal–legume intercropping system is poorly studied in Tunisia, particularly
in the southeastern region characterized by a semi–arid climatic, limited precipitation,
and nutrient–deficient soils. Therefore, the objective of this study was to investigate
crop performance and soil physicochemical proprieties under a durum wheat–chickpea
intercropping system. We hypothesize that this practice enhances carbon (C) and nitrogen
(N) availability, microbial biomass nutrients (C and N), and plant nutrient content (N) in
comparison to the monoculture practice. This hypothesis is based on the premise that
incorporating chickpeas (legumes) into nitrogen–poor soils increases soil nutrient levels
through biological N
2
fixation. Consequently, this process results in increased microbial
biomass and improved nutritional value in the intercropped plants relative to those grown
in monoculture.

Sustainability 2024,16, 2725 3 of 12
2. Materials and Methods
2.1. Experimental Site
Experimental trials were conducted over two agricultural seasons in two distinct
fields within the Medenine region (33
◦
46
′
N and 10
◦
59
′
E) of southeastern Tunisia. EXP–A
represents the agricultural season of 2020–2021, while EXP–B denotes the agricultural
season of 2021–2022. The average annual temperature at both sites ranges from 21.5 ◦C to
22.6
◦
C, with an annual rainfall varying between 167.8 and 241.6 mm. The Mediterranean
climate in Medenine is characterized by a cold winter and an extended, very hot and
dry summer. The soil samples were taken from the top layer (0–20 cm), air–dried, and
sieved (2 mm) in preparation for analyzing certain physicochemical properties before
beginning the experiment. According to Mtimet et al. [
35
], the soil type is classified as
alluvial soil, and exhibits a sandy–loamy texture, comprising 70.2% sand, 20.1% silt, and
8.7% clay fraction. This site has an alkaline pH, registering at 8.02, and possesses low
organic matter (OM) content, measuring 1.21%. CaCO
3
is present, with a content of 21%.
Furthermore, measurements of total phosphorus (P
Tot
), Olsen–P, and total nitrogen (N
Tot
)
reveal deficiencies in these elements. The P
Tot
level was found to be 5.95 mg.kg
−1
. Olsen–P
was recorded at a value of 0.51 mg.kg
−1
, and the NTot level was measured at 3.58 mg.kg
−1
.
2.2. Experimental Device
The study was conducted with a variety of chickpea (Cicer arietinum L. Amdoun) and
a variety of durum wheat (Triticum turgidum ssp. durum L. Simeto) cultivated either in in-
tercropping or in monoculture. The experimental design chosen in our study was in the
form of a split–plot comprising three replications (blocks). Each micro–plot included one
of the following treatments: chickpea monoculture (ChKp–MC), durum wheat monocul-
ture (DuWh–MC), and durum wheat–chickpea intercropping (DuWh–IR and ChKp–IR)
(
micro–plots (4.5 m2)×3 treatments ×3 replications
). The total surface area of the experi-
mental plot was 40.5 m
2
, with each micro–plot allocated 4.5 m
2
, and each micro–plot was
located 1 m from the adjacent micro–plots (Figure 1). The grain density used for both experi-
ments was 100
±
5 grains per m
2
for pure chickpea (ChKp–MC),
250 ±3 grains per m2
for
pure durum wheat (DuWh–MC), 50
±
3 grains per m
2
for intercropped chickpea (ChKp–IR),
and 150
±
5 grains per m
2
for intercropped durum wheat (DuWh–IR). The seeds were sown
in the third week of January for both growing seasons, with occasional manual weeding. Im-
portantly, no chemical fertilizers or herbicides were applied throughout the entire experiment.
For each experiment, before sowing, a 20 cm deep sample was taken from each micro–plot
and mixed to obtain a single sample, designated as the control soil (S–Bulk).
Figure 1. Experimental design including durum wheat–monocrops (DuWh–MC), chickpea–
monocrops (ChKp–MC), and intercrops of durum wheat and chickpea (DuWh–IR and ChKp–IR).
2.3. Plant and Soil Sampling
At the full flowering stage (70 days after sowing), ten plants were sampled from each
monocropped micro–plot, while five plants were sampled from each intercropped micro–

Sustainability 2024,16, 2725 4 of 12
plot. The stems were detached from the roots at the cotyledonary node, subsequently
dried at 60
◦
C for 48 h, and then weighed. Additionally, five soil samples from the
rhizosphere were meticulously collected from the roots of each sampled plant. This soil,
representing the fraction adhering to the roots (1–4 mm), was delicately recovered using a
brush. The collected samples were blended to form a homogeneous mixture, then subjected
to air–drying, followed by sieving to a particle size of 2 mm.
2.4. Measurements
The physicochemical analysis of the soils was conducted using standard methods from
each site. The nitrogen content in both soil and plant samples were determined using the Kjel-
dahl method [
36
]. Soil pH was measured in a soil–water suspension (
soil/water ratio = 1:2.5
)
using a pH meter. Phosphorus availability was assessed using the Olsen method [
37
], and the
total phosphorus content in the soil was determined through the malachite green procedure
following mixed digestion with perchloric and nitric acids [
38
]. Soil organic matter and soil
carbon content were quantified using the Walkley and Black method [
39
], and the proportion
of calcium carbonate (CaCO
3
) in the soil was determined by measuring CO
2
volume based
on the Horton and Newson methods [
40
]. Additionally, the nitrogen and carbon content in
soil microbial biomass (SMB–N and SMB–C) were estimated using the fumigation extraction
(FE) method devised by Vance et al. [41].
2.5. Statistical Analyses
The statistical analyses were performed using XLSTAT (Premium Version, 2019, Addin-
soft, Long Island, NY, USA). Significant differences between mean values at p= 0.05 level
of significance and the influence of treatments (intercropping and monocultures) on the
variables (crop yield, nitrogen content in the soil (Ntot), plant N
−
uptake, soil microbial
biomass fraction (SMB–N), soil carbon content (Ctot), and microbial biomass (SMB–C))
were investigated using the Tukey test.
3. Results
3.1. Crops Yield
The results depicted in Figure 2indicate substantial crop yield variations in response
to crop treatments (intercropping or monoculture) at both experimental sites. During the
first season (EXP–A), there was a notable increase (23%) in the grain yield of durum wheat
within the intercropped system compared to the monoculture. Similarly, during the second
season (EXP–B), the grain yield of intercropped durum wheat showed a significant rise of 20%
compared to the monoculture (Figure 2). Conversely, the grain yield of chickpea exhibited a
significant decrease when intercropped with durum wheat in both EXP–A and EXP–B, with
reductions of 21% and 17%, respectively, compared to its monoculture (Figure 2).
3.2. Nitrogen Content (Ntot) Soil Availability
Figure 3illustrates the variation in soil nitrogen content (N
tot
) in response to treatments
and experimental sites during the two growing seasons. In both experiments EXP–A and
EXP–B, the Ntot soil levels significantly increased for durum wheat under the influence of
intercropping (DuWh–IR), showing a rise of 32% in EXP–A and 29% in EXP B compared
to its monoculture (DuWh–MC). According to Figure 3, there was a notable reduction in
Ntot (p< 0.05) observed in ChKp–IR compared to ChKp–MC across both sites, indicating a
variance of 11% in EXP–A and 7% in EXP–B.
3.3. Soil Microbial Biomass (SMB–N) Variation
A notable increase (p
≤
0.05) in the nitrogen content of the soil microbial biomass
(
SMB–N
) for intercropped durum wheat with chickpea (DuWh–IR) compared to its mono-
culture (DuWh–MC) was observed (Figure 4). This increase was approximately 39% and
36% during the EXP–A and EXP–B growing seasons, respectively. Furthermore, a slight
decrease of approximately 5% in the nitrogen content of the soil microbial biomass for chick-
pea intercropped with durum wheat (ChKp–IR) compared to its monoculture (ChKp–MC)

Sustainability 2024,16, 2725 5 of 12
in EXP–A was noted. However, no significant difference was observed between chickpea
monocrops and chickpea intercrops during the EXP–B growing season.
Figure 2. Grain yield levels (g.m
−2
) of various crops, including chickpea–monocrops (ChKp–MC),
durum wheat–monocrops (DuWh–MC), and intercrops of durum wheat and chickpea (DuWh–IR and
ChKp–IR) were assessed over two years of cultivation (EXP–A and EXP–B). The error bars indicate
the standard deviation. The letters a, b, c, and d represent the significant difference at a probability
p< 0.05 between all treatments in each year.
Figure 3. N
tot
availability in the control soil (S–Bulk) and across the different crop covers (chickpea–
monocrops (ChKp–MC), durum wheat–monocrops (DuWh–MC), and intercropped durum wheat–
chickpea (ChKp–IR and DuWh–IR)) at the flowering stage during two growing seasons (EXP–A and
EXP–B). The values are the average of three replicates. The error bars indicate the standard deviation.
The letters a, b, c, and d represent the significant difference at a probability p< 0.05 between all
treatments in each year.

Sustainability 2024,16, 2725 6 of 12
Figure 4. SMB–N variation in the control soil (S–Bulk) and across the different crop covers (chick-
pea monocrops (ChKp–MC), durum wheat monocrops (DuWh–MC) and intercrops durum wheat–
chickpea (ChKp–AIR) and (DuWh–IR) at the flowering stage during the two growing seasons (EXP–A
and EXP–B). The values are the average of three replicates. The error bars indicate the standard
deviation. The letters a, b, and c represent the significant difference at a probability p< 0.05 between
all treatments in each year.
3.4. Nitrogen−Uptake
The results exhibited in Figure 5indicate a significant decrease (p< 0.05) in nitrogen
uptake (N
−
uptake) for intercropped chickpea (ChKp–IR) compared to its monoculture
(ChKp–MC) for both experiments, with reductions of 13% for EXP–A and 10% for
EXP–B
.
However, there was a significant increase (p
≤
0.05) in N
−
uptake for intercropped du-
rum wheat (DuWh–IR) compared to the durum wheat monoculture (DuWh–MC); these
increases were approximately 26% and 21% for EXP–A and EXP–B, respectively.
Figure 5. N
−
uptake by different crop covers (chickpea monocrops (ChKp–MC), durum wheat
monocrops (DuWh–MC) and intercropped durum wheat–chickpea (ChKp–IR and DuWh–IR)) at the
flowering stage, during the two growing seasons (EXP–A and EXP–B). The values are the average of
three replicates. The error bars indicate the standard deviation. The letters a, b, and c represent the
significant difference at a probability p< 0.05 between all treatments in each year.

Sustainability 2024,16, 2725 7 of 12
3.5. Total Soil Carbon Content (Ctot)
Figure 6demonstrates that the soil carbon levels (Ctot) were significantly higher in the
micro–plots with intercropped durum wheat (DuWh–IR) than in those with monoculture
durum wheat (DuWh–MC) and the bulk soil (S–Bulk) across both experiments (EXP–A
and EXP–B). In EXP–A, the Ctot concentration in DuWh–IR soil was 27% and 60% greater
than in DuWh–MC and S–Bulk, respectively. For EXP–B, the increase in soil carbon content
in DuWh–IR micro–plots was approximately 24% and 68% over DuWh–MC and S–Bulk,
respectively. Nevertheless, there was no notable distinction detected among ChKp–MC,
ChKp–IR, and DuWh–IR in both experiments, with 2.10%, 1.95%, and 2.01% in EXP–A
and 1.74%, 1.62%, and 1.73% in EXP–B, respectively. Moreover, soil from the chickpea
monoculture (ChKp–MC) demonstrated significantly higher carbon levels than those in
the durum wheat monoculture (DuWh–MC) and bulk soil (S–Bulk) in both agricultural
experiments. Specifically, in EXP–A, there was a 30% and 62% increase in total soil carbon
content compared to DuWh–MC and S–Bulk, respectively. However, in EXP–B, increases
in the soil carbon concentration were 24% and 68% relative to DuWh–MC and S–Bulk,
respectively (Figure 6).
Figure 6. C
tot
concentrations in the control soil (S–Bulk) and across the different crop covers (chickpea–
monocrops (ChKp–MC), durum wheat–monocrops (DuWh–MC), and intercropped durum wheat–
chickpea (ChKp–IR and DuWh–IR)) at the flowering stage during two growing seasons (EXP–A
and EXP–B). The values are the average of three replicates. The error bars indicate the standard
deviation. The letters a, b, and c represent the significant difference at a probability p< 0.05 between
all treatments in each year.
3.6. Microbial Biomass (SMB–C) Variation
The carbon content variation in the soil microbial biomass (SMB–C) for the two years
of experiments is demonstrated in Figure 7. During EXP–A, SMB–C concentrations in the
soil cultivated with intercropped durum wheat (DuWh–IR) were significantly higher by
32% and 57% compared to the monoculture durum wheat (DuWh–MC) and the bulk soil
(S–Bulk), respectively. Moreover, SMB–C concentrations obtained from the soil cultivated
with pure chickpea (ChKp–MC) were significantly higher by 34% and 57% compared
to the monoculture durum wheat (DuWh–MC) and the bulk soil (S–Bulk), respectively.
Similarly, the results obtained in EXP–B aligned with those from the first experiment
(EXP–A), indicating a significant increase in SMB–C of approximately 39% and 66% for
the intercropped durum wheat (DuWh–IR) compared to the monoculture durum wheat

Sustainability 2024,16, 2725 8 of 12
(DuWh–MC) and the bulk soil (S–Bulk), respectively. Additionally, for pure chickpea
(ChKp–MC), SMB–C concentrations were notably higher by 36% and 67% compared to the
durum wheat monoculture (DuWh–MC) and the bulk soil (S–Bulk), respectively.
Figure 7. SMB–C content in the control soil (S–Bulk) and across the different crop covers (chickpea–
monocrops (ChKp–MC), durum wheat–monocrops (DuWh–MC) and intercropped durum wheat–
chickpea (ChKp–IR and DuWh–IR)) at the flowering stage during the two growing seasons (EXP–A
and EXP–B). The values are the average of three replicates. The error bars indicate the standard
deviation. The letters a, b, and c represent the significant difference at a probability p< 0.05 between
all treatments in each year.
4. Discussion
4.1. Impact of the Durum Wheat–Chickpea Intercropping on Crop Yield
Cereal–legume intercropping’s effect on the crop yield has been extensively researched
and documented across agricultural studies. This agricultural practice effectively enhances
nitrogen levels in the soil, thereby directly influencing the grain yield [
42
]. These investi-
gations highlight a notable increase in the cereal yield when intercropped with legumes,
compared to being grown using monoculture practices. For instance, studies on maize [
43
]
and durum wheat [
44
] have shown higher yields when intercropped with faba beans and
soybeans, respectively. During both growing seasons (EXP–A and EXP–B), our findings
demonstrated a marked rise in yield for the intercropped durum wheat (DuWh–IR). This en-
hancement was likely due to the efficient symbiotic nitrogen fixation facilitated by chickpea,
resulting in greater nitrogen accumulation in the rhizosphere of the intercropped durum
wheat. Similar increases in wheat yield within intercropping systems have been observed by
Huˇnady and Hochman [
45
], who reported higher grain yields when wheat was intercropped
with faba beans. Furthermore, Chhetri et al. [
46
] documented a 40% yield increase when
wheat was intercropped with beans. This cropping system’s benefits in terms of enhancing
cereal grain yields were reinforced by studies on wheat–maize intercropping, bean–maize
intercropping [
47
], and cowpea–maize intercropping [
48
]. However, findings from the present
study indicate a decrease in the yield of intercropped chickpea (ChKp–IR) when compared to
their sole cultivation. This decline can be attributed to the vigorous interspecific competition
with durum wheat for nitrogen resources, as reported by Latati et al. [49].
4.2. Effect of Intercropping Cereal–Legume Systems on the Availability of Ntot, N−Uptake, and
Variations in N within the SMB–N
The primary findings depicted in Figures 3–5highlight the substantial influence of
the durum wheat–chickpea intercropping system on various aspects, including the total

Sustainability 2024,16, 2725 9 of 12
nitrogen content of the soil (Ntot), nitrogen uptake by plants (N
−
uptake), and nitrogen
present in the microbial biomass (SMB–N).
According to Figure 3, there was a substantial accumulation of Ntot in the rhizosphere
of durum wheat intercropped with chickpea compared to its monoculture and N–deficient
bulk soil across both experiments (EXP–A and EXP–B). This notable rise can most likely be
attributed to the interspecific facilitation of nutrient utilization between durum wheat and
chickpea. Moreover, legumes grown in an intercropping system enhance the availability of
inorganic nitrogen in the rhizosphere through their ability for symbiotic nitrogen fixation
(N2), providing benefits to cereals [
50
,
51
]. These results are consistent with the findings of
Hauggaard-Nielsen et al. [
52
], who noted a higher nitrogen concentration in the soil of peas,
faba beans, and lupins when intercropped with barley compared to their monocultures.
Similarly, Corre-Hellou et al. [
53
] demonstrated elevated nitrogen concentration in the soil
under pea and barley intercropping as opposed to their monocultures.
However, the nitrogen (N
tot
) content in the rhizosphere of monoculture chickpea
remained elevated compared to the levels observed under the influence of intercropping,
probably due to the strong competition from intercropped durum wheat for the absorption
of nitrogen fixed by chickpeas in the soil [
54
]. This increase in N
tot
within intercropped
durum wheat through symbiotic nitrogen fixation was accompanied by a rise in the content
of SMB–N in the rhizosphere of durum wheat (Figure 4). Thus, the SMB–N increase can be
attributed to the transfer of nitrogen from nodules to the soil microbial biomass after nodule
senescence, as reported by Latati et al. [
19
]. Furthermore, these findings align entirely with
those of Tang et al. [
55
], who reported an increase in microbial biomass under the influence
of the wheat/chickpea intercropping compared to their respective monocultures. However,
the low nitrogen content in the microbial biomass obtained in the bulk soil (S–Bulk) may
be explained by the absence of soil tillage and the addition of organic amendments to
stimulate soil microbial activity [56].
Moreover, Figure 5indicates a rise in the plant–absorbed nitrogen content (N
−
uptake)
for durum wheat when in association compared to its monoculture in both experiments
(EXP–A in 2020–2021 and EXP–B in 2021–2022). Our results are consistent with the findings
of Zhang al. [
20
], who reported an enhanced nitrogen content in wheat when cultivated in
an intercropping system with soybeans compared to its monoculture. Likewise, Szumigal-
ski and Van Acker [
57
] observed increased nitrogen concentrations in wheat and canola
crops when intercropped with peas.
4.3. Effect of Cereal–Legume Intercropping Systems on Ctot Content and SMB–C Variation
Our results demonstrated a significant enhancement in the soil microbial biomass
(
SMB–C
) of intercropped durum wheat compared to its monoculture and the bulk soil
(
Figure 6
). This enhancement may be assigned to the combined root exudates from both
chickpea and durum wheat. These findings align with those of Tang et al. [
55
], who observed
enhancements in microbial biomass carbon stocks when durum wheat was intercropped with
chickpea and lentils compared to their respective monocultures. Likewise, Latati et al. [
19
]
documented a rise in the soil microbial biomass for maize and bean intercropping.
Another notable result from this study pertains to the soil carbon (C
tot
) content, which
underwent a significant increase during both cropping seasons (EXP–A and EXP–B) when
durum wheat was intercropped with chickpea, compared to the monoculture and the
bulk soil, as depicted in Figure 7. The significant soil carbon content observed may be
attributed to the increased microbial activity favored by its intercropping with chickpea [
58
].
This occurrence has already been observed in various regions worldwide. For instance,
Chapagain and Riseman in 2014 [
59
] observed similar results in Vancouver, Western Canada,
for barley–pea intercropping, and Scalise et al. [
60
] found the same in an agroecosystem in
Southern Italy for barley and bean intercropping. Thus, it is apparent that soil microbial
biomass plays a crucial role in the mineralization of organic matter and the enrichment of
the soil with carbon, which is an essential element for the proper development of crops.

Sustainability 2024,16, 2725 10 of 12
5. Conclusions
The main results of this field research revealed an increase in durum wheat grain yields
under the intercropping system compared to the monoculture. This increase can be attributed
to a significant bioavailability of nitrogen (N) in the rhizosphere of intercropped durum wheat
in the two sites that were characterized by initially low nitrogen soil contents. Furthermore,
this study validates that intercropping durum wheat with chickpea enhances the soil carbon
content compared to monoculture practices. This improvement stems from heightened
microbial activity in the rhizosphere of the intercropped durum wheat, recognized as a pivotal
mechanism in the mineralization and decomposition of soil organic matter.
Therefore, chickpea exhibits a beneficial impact in the context of interspecific com-
petition in the intercropping system. Consequently, this study affirms the benefits of the
durum wheat–chickpea intercropping system in improving soil fertility and crop yield
compared to a monoculture, leading to a reduction in the reliance on chemical fertilizers.
Finally, durum wheat–chickpea intercropping could offer a pragmatic solution to fostering
sustainable agriculture in semi–arid regions.
Author Contributions: Conceptualization, A.A. and W.H.; methodology, A.A. and W.H.; software,
A.A. and A.S.; validation, A.A., W.H. and M.F.Z.; formal analysis, A.A., M.F. and A.J.M. investigation,
A.A. and W.H.; resources, A.A. and W.H.; data curation, A.A. and S.J.; writing—original draft
preparation, A.S.; writing—review and editing, A.A., N.Y.R., B.L., M.F. and S.J.; visualization, A.A.
and A.S.; validation, N.Y.R.; supervision, W.H. and M.F.Z.; project administration, N.Y.R. and B.L.
All authors have read and agreed to the published version of the manuscript.
Funding: This paper has been supported by the RUDN University Strategic Academic Leadership Program.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Data are contained within the article.
Acknowledgments: The authors extend their appreciation to the Deanship of Scientific Research at
King Khalid University for funding this work through the Small Groups Project under grant number
S.R.G.P./288/44, (formal analysis).
Conflicts of Interest: The authors declare no conflicts of interest.
References
1.
Tribouillois, H.; Dürr, C.; Demilly, D.; Wagner, M.H.; Justes, E. Determination of Germination Response to Temperature and Water
Potential for a Wide Range of Cover Crop Species and Related Functional Groups. PLoS ONE 2016,11, e0161185. [CrossRef]
[PubMed]
2.
Glaze-Corcoran, S.; Hashemi, M.; Saghpour, A.; Jahnazad, E.; Afshar, R.K.; Liu, X.; Herbert, S.J. Understanding intercropping to
improve agricultural resiliency and environmental sustainability. Adv. Agron. 2020,162, 199–256.
3.
Ohyama, T. The role of legume-rhizobium symbiosis in sustainable agriculture. In Legume Nitrogen Fixation in Soils with Low
Phosphorus Availability; Sulieman, S., Phan Tran, L.S., Eds.; Springer: Cham, Switzerland, 2017; pp. 1–20.
4.
Andrés, P.; DoblaS–Miranda, E.; Silva-Sánchez, A.; Mattana, S.; Font, F. Physical, Chemical, and Biological Indicators of Soil
Quality in Mediterranean Vineyards under Contrasting Farming Schemes. Agronomy 2022,12, 2643. [CrossRef]
5.
Zuma, M.; Arthur, G.; Coopoosamy, R.; Naidoo, K. Incorporating cropping systems with eco-friendly strategies and solutions to
mitigate the effects of climate change on crop production. J. Agric. Food Res. 2023,14, 100722. [CrossRef]
6.
Lefebvre, M.; Midler, E.; Bontems, P. Adoption of Environment-Friendly Agricultural Practices with Background Risk: Experi-
mental Evidence. Env. Resour. Econ. 2020,76, 405–428. [CrossRef]
7.
Pansu, M.; Ibrahim, H.; Hatira, A.; Brahim, N.; Drevon, J.J.; Harmand, J.M.; Chotte, J.L.; Blavet, D. Modelling the continuous
exchange of nitrogen between microbial decomposers, the organs and symbionts of plants, soil reserves, and the atmosphere. Soil
Biol. Biochem. 2018,125, 185–196. [CrossRef]
8.
Rebouh, N.Y.; Khugaev, C.V.; Utkina, A.O.; Isaev, K.V.; Mohamed, E.S.; Kucher, D.E. Contribution of Eco-Friendly Agricultural
Practices in Improving and Stabilizing Wheat Crop Yield: A Review. Agronomy 2023,13, 2400. [CrossRef]
9.
Vidal, D.F.; Trichet, P.; Puzos, L.; Bakker, M.R.; Delerue, F.; Augusto, L. Intercropping N–fixing shrubs in pine plantation forestry
as an ecologically sustainable management option. For. Ecol. Manag. 2019,437, 175–187. [CrossRef]

Sustainability 2024,16, 2725 11 of 12
10.
Bouras, F.-Z.; Hadjout, S.; Haddad, B.; Malek, A.; Aitmoumene, S.; Gueboub, F.; Metrah, L.; Zemmouri, B.; Kherif, O.; Rebouh,
N.-Y.; et al. The Effect of Nitrogen Supply on Water and Nitrogen Use Efficiency by Wheat–Chickpea Intercropping System under
Rain-Fed Mediterranean Conditions. Agriculture 2023,13, 338. [CrossRef]
11.
Kherif, O.; Haddad, B.; Bouras, F.-Z.; Seghouani, M.; Zemmouri, B.; Gamouh, R.; Hamzaoui, N.; Larbi, A.; Rebouh, N.-Y.; Latati,
M. Simultaneous Assessment of Water and Nitrogen Use Efficiency in Rain-Fed Chickpea-Durum Wheat Intercropping Systems.
Agriculture 2023,13, 947. [CrossRef]
12.
Corre-Hellou, G.; Crozat, Y. N2 fixation and N supply in organic pea (Pisum sativum L.) cropping systems as affected by weeds
and pea weevil (Sitona lineatus L.). Eur. J. Agron. 2005,22, 449–458. [CrossRef]
13.
Deveikyte, I.; Kadziuliene, Z.; Sarunaite, L. Weed suppression ability of spring cereal crops and peas in pure and mixed stands.
Agron. Res. 2009,7, 239–244.
14.
Amossé, C.; Jeuffroy, M.H.; Celette, F.; David, C. Relay-intercropped forage legumes help to control weeds in organic grain
production. Eur. J. Agron. 2013,49, 158–167. [CrossRef]
15.
Lian, T.; Mu, Y.; Jin, J.; Ma, Q.; Cheng, Y.; Cai, Z. Impact of intercropping on the coupling between soil microbial community
structure, activity, and nutrient–use efficiencies. Peer J. 2019,7, 6412. [CrossRef] [PubMed]
16.
Laranjeira, S.; FernandeS–Silva, A.; Reis, S.; Torcato, C.; Raimundo, F.; Ferreira, L.; Car-nide, V.; Marques, G. Inoculation of plant
growth promoting bacteria and arbuS–cularmycorrhizal fungi improve chickpea performance under water deficit conditions.
Appl. Soil. Ecol. 2021,164, 103927. [CrossRef]
17.
Williams, A.; Birt, H.W.G.; Raghavendra, A.; Dennis, P.G. Cropping System Diversification Influences Soil Microbial Diversity in
Subtropical Dryland Farming Systems. Microb. Ecol. 2023,85, 1473–1484. [CrossRef] [PubMed]
18.
Netthisinghe, A.M.; Galloway, H.O.; Agga, G.E.; Gunter, P.A.; Sistani, K.R. Effects of Cropping Systems on Soil Physicochemical
Properties and Abundances and Spatial Distributions of Nitrogen–Cycling Bacteria. Agronomy 2023,13, 1461. [CrossRef]
19.
Latati, M.; Rebouh, N.Y.; Aouiche, A.; Laouar, M. Modelling the functional role of the micro-organisms in the daily exchanges of
carbon and nitrogen in intercropping system under Mediterranean conditions. Agron. Res. 2019,17, 559–573.
20.
Homulle, Z.; George, T.S.; Karley, A.J. Root traits with team benefits: Understanding belowground interactions in intercropping
systems. Plant Soil 2021,471, 1–26. [CrossRef]
21.
Singh, A.K.; Singh, J.B.; Singh, R.; Kantwa, S.R.; Jha, P.K.; Ahamad, S.; Singh, A.; Ghosh, A.; Prasad, M.; Singh, S.; et al.
Understanding Soil Carbon and Phosphorus Dynamics under GrasS–Legume Intercropping in a Semi-Arid Region. Agronomy
2023,13, 1692. [CrossRef]
22.
Wang, G.; Sheng, L.; Zhao, D.; Sheng, J.; Wang, X.; Liao, H. Allocation of Nitrogen and Carbon Is Regulated by Nodulation and
Mycorrhizal Networks in Soybean/Maize Intercropping System. Front. Plant Sci. 2016,7, 1901. [CrossRef] [PubMed]
23. Willey, R. Intercropping: Its importance and research needs. 1. Competition and yield advantages. Field Crops Abstr. 1979,32, 1–10.
24.
Lal, B.; Rana, K.S.; Rana, D.S.; Shivay, Y.S.; Sharma, D.K.; Meena, B.P.; Gautam, P. Biomass, yield, quality and moisture use of
Brassica carinata as influenced by intercropping with chickpea under semiarid tropics. J. Saudi Soc. Agric. Sci. 2017,18, 61–71.
[CrossRef]
25.
Raza, M.A.; Yasin, H.S.; Gul, H.; Qin, R.; Mohi Ud Din, A.; Khalid, M.H.B.; Hussain, S.; Gitari, H.; Saeed, A.; Wang, J.; et al.
Maize/soybean strip intercropping produces higher crop yields and saves water under semi-arid conditions. Front. Plant Sci.
2022,13, 1006720. [CrossRef] [PubMed]
26.
Vandermeer, J.; van Noordwijk, M.; Anderson, J.; Ong, C.; Perfecto, I. Global change and multispecies agroecosystems: Concepts
and issues. Agric. Ecosyst. Environ. 1998,67, 1–22. [CrossRef]
27.
Hamdi, W.; Noura, Z.; Ernest, K.; Blavet, D.; Seffen, M. Effect of the soils properties on the sorption capacity of phosphorus and
ammonium by alkaline soils of the semi-arid areas. IOSR-JA C 2015,5, 34–42.
28.
Hamdi, W.; Hamdi, N.; Jellali, S.; Seffen, M. Effect of background electrolytes on the adsorption of phosphorus (P) onto southern
Tunisia natural clays. Phys. Chem. Earth 2022,127, 103160. [CrossRef]
29.
Leoni, F.; Lazzaro, M.; Carlesi, S.; Moonen, A.C. Screening suitable legumes for living mulches to support nitrogen dynamics and
weed control in a durum wheat-forage sorghumm crop sequence. Field Crops Res. 2024,307, 109246. [CrossRef]
30.
Huss, C.P.; Holmes, K.D.; Blubaugh, C.K. Benefits and Risks of Intercropping for Crop Resilience and Pest Management. J. Econ.
Entomol. 2022,115, 1350–1362. [CrossRef]
31. Boudreau, M.A. Diseases in intercropping systems. Annu. Rev. Phytopathol. 2013,51, 499–519. [CrossRef]
32.
Brenas, S.V.; Celette, F.; Pissaloux, A.P.; David, C. Biotic and abiotic factors impacting establishment and growth of relay
intercropped forage legumes. Eur. J. Agron. 2016,81, 169–177. [CrossRef]
33. Kchaou, R.; Benyoussef, S.; Jebari, S.; Harbaoui, K.; Berndtsson, R. Forage Potential of Cereal–Legume Mixtures as an Adaptive
Climate Change Strategy under Low Input Systems. Sustainability 2023,15, 338. [CrossRef]
34.
Delhoumi, M.; Zaabar, W.; Ben Rhouma, A.; Achouri, M.S. Effects of agricultural practices and abiotic factors on woo-dlice
diversity across two agroecosystems in Tunisia. Vie et milieu-life and enVironment 2018,68, 253–261.
35. Mtimet, A.; Lasram, M. Atlas Des Sols Tunisiens; Ministère de l’agriculture: Tunis, France, 1999.
36.
Kjeldahl, J. A new method for the determination of nitrogen in organic matter. Zeitschrift für Analytische Chemie 1883,22, 366–382.
[CrossRef]
37.
Olsen, S.R.; Cole, C.V.; Watanabe, F.S.; Dean, L.A. Estimation of Available Phosphorus in Soils by Extraction with NaHCO
3
; USDA
Cir.939; US Department of Agriculture: Washington, DC, USA, 1954.

Sustainability 2024,16, 2725 12 of 12
38.
Valizadeh, G.R.; Rengel, Z.; Rate, A.W. Response of wheat genotypes efficient in P utilization and genotypes responsive to P
fertilization to different P banding depths and watering regimes. Aust. J. Agric. Res. 2003,54, 59–65. [CrossRef]
39.
Walkley, A.; Black, I.A. An examination of the Degtjareff method for determining soil organic matter, and a proposed modification
of the chromic acid titration method. Soil Sci. 1934,37, 29–38. [CrossRef]
40.
Leo, M.W.M. Determination of soil carbonates by a rapidegasometric method. J. Agric. Food Chem. 1963,11, 452–455. [CrossRef]
41.
Vance, C.P.; Uhde-Stone, C.; Allan, D.L. Phosphorus acquisition and use: Critical adaptations by plants for securing a nonrenew-
able resource. New Phytol. 2003,157, 423–447. [CrossRef]
42.
Boulelouah, N.; Berbache, M.R.; Bedjaoui, H.; Selama, N.; Rebouh, N.Y. Influence of Nitrogen Fertilizer Rate on Yield, Grain
Quality and Nitrogen Use Efficiency of Durum Wheat (Triticum durum Desf.) under Algerian Semiarid Conditions. Agriculture
2022,12, 1937. [CrossRef]
43.
Dahmardeh, M.; Ghanbari, A.; Syahsar, B.A.; Ramrodi, M. The role of intercropping maize (Zea mays L.) and cowpea (Vigna
unguiculata L.) on yield and soil chemical properties. Afr. J. Agric. Res. 2010,5, 631–636.
44.
Tang, X.; Yu, Y.; Shen, J.; Van der Werf, W.; Zhang, F. Intercropping legumes and cereals increases phosphorus use efficiency:
A meta-analysis. Plant Soil 2021,460, 89–104. [CrossRef]
45.
Huˇnady, I.; Hochman, M. Potential of legume-cereal intercropping for increasing yields and yield stability for self-sufficiency
with animal fodder in organic farming. Czech J. Gen. Plant Breed. 2014,50, 185–194. [CrossRef]
46.
Chhetri, B.; Sinha, A.C. Advantage of maize (Zea mays)-based intercropping system to different nutrient management practices.
Indian J. Agron. 2020,65, 25–32. [CrossRef]
47.
Lazali, M.; Brahimi, S.; Drevon, J.J. High yields in a low–P tolerant recombinant inbred line of common bean under field conditions.
Rhizosphere 2018,8, 27–33. [CrossRef]
48.
Takim, F.O. Advantages of maize-cowpea intercropping over sole cropping through competition indices. J. Agric. Biodivers. Res.
2012,1, 53–59.
49.
Latati, M.; Pansu, M.; Drevon, J.J.; Ounane, S.M. Advantage of intercropping maize (Zea mays L.) and common bean (Phaseolus
vulgaris L.) on yield and nitrogen uptake in Northeast Algeria. IJRAS 2013,1, 1–7.
50.
Wehmeye, H.; De Guia, A.H.; Connor, M. Reduction of Fertilizer Use in South China Impacts and Implications on Smallholder
Rice Farmers. Sustainability 2020,12, 2240. [CrossRef]
51.
Yong, T.W.; Ping, C.; Qian, D.; Qing, D.U.; Feng, Y.; Wang, X.; Liu, W.; Yang, W.Y. Optimized nitrogen application methods to
improve nitrogen use efficiency and nodule nitrogen fixation in a maize-soybean relay intercropping system. J. Integr. Agric. 2018,
17, 664–676. [CrossRef]
52.
Hauggaard-Nielsen, H.; Gooding, M.; Ambus, P.; Corre-Hellou, G.; Crozat, Y.; Dahlmann, C.; Dibet, A.; von Fragstein, P.; Pristeri,
A.; Monti, M.; et al. Pea-barley intercropping for efficient symbiotic N2-fixation, soil N acquisition and use of other nutrients in
European organic cropping systems. Field Crops Res. 2009,113, 64–71. [CrossRef]
53.
Corre-Hellou, G.; Fustec, J.; Crozat, Y. Interspecific competition for soil N and its interaction with N2 fixation, leaf expansion and
crop growth in pea-Barley intercrops. Plant Soil. 2006,282, 195–208. [CrossRef]
54.
Chen, S.; Waghmode, T.R.; Sun, R.; Kuramae, E.; Hu, C.; Liu, B. Root-associated microbiomes of wheat under the combined effect
of plant development and nitrogen fertilization. Microbiome 2019,7, 1–13. [CrossRef] [PubMed]
55.
Tang, X.; Bernard, L.; Brauman, A.; Daufresne, T.; Deleporte, P.; Desclaux, D.; Souche, G.; Placella, S.A.; Hinsinger, P. Increase in
microbial biomass and phosphorus availability in the rhizosphere of intercropped cereal and legumes under field conditions. Soil
Biol. Biochem. 2014,75, 86–93. [CrossRef]
56.
Chenene, Y.; Blavet, D.; Belalmi, M.; Kaci, G.; Teffahi, M.; Ounane, S.M. Variation of chickpea nodulation in a Mediterranean
agroecosystem: Relationship with soil characteristics and thresholds for significant contribution to plant growth. Agron. Res.
2021,19, 42–56.
57.
Szumigalski, A.R.; Van Acker, R.C. Nitrogen yield and land use efficiency in annual sole crops and intercrops. Agron. J. 2006,98, 1030–1040.
[CrossRef]
58.
Arshad, M. Fortnightly dynamics and relationship of growth, dry matter partition and productivity of maize based sole and
intercropping systems at different elevations. Eur. J. Agron. 2021,130, 126377. [CrossRef]
59.
Chapagain, T.; Riseman, A. Barley–pea intercropping: Effects on land productivity, carbon and nitrogen transformations. Field
Crops Res. 2014,166, 18–25. [CrossRef]
60.
Scalise, A.; Tortorella, D.; Aurelio, P.; Petrov, B.; Gelsomino, A.; Lindstrom, K.; Monti, M. Legume-barley intercropping stimulates soil
N supply and crop yield in the succeeding durum wheat in a rotation under rained conditions. Soil Biol. Biochem. 2015,89, 150–161.
[CrossRef]
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual
author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to
people or property resulting from any ideas, methods, instructions or products referred to in the content.