Content uploaded by Jamal Nasar
Author content
All content in this area was uploaded by Jamal Nasar on Aug 23, 2021
Content may be subject to copyright.
Content uploaded by Shao Zeqiang
Author content
All content in this area was uploaded by Shao Zeqiang on Sep 06, 2020
Content may be subject to copyright.
RESEARCH PAPER
The effect of maize–alfalfa intercropping on the physiological
characteristics, nitrogen uptake and yield of maize
J. Nasar
1
, Z. Shao
1
, A. Arshad
2
, F. G. Jones
1
, S. Liu
1
,C.Li
1
, M. Z. Khan
3
, T. Khan
4
,
J. S. K. Banda
5
,X.Zhou
1
&Q.Gao
1
1 Key Laboratory of Sustainable Utilization of Soil Resources in the Commodity Grain Bases in Jilin Province, Jilin Agricultural University, Changchun, 130118,
China
2 College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China
3 College of Plant Protection, Jilin Agricultural University, Changchun, 130118, Jilin Province, China
4 Department of Mathematics and Statistics, Lanzhou University, Lanzhou, China
5 Zambia Agriculture Research Institute, P/B 7, Chilanga, Zambia
Keywords
chlorophyll content; intracellular CO
2
;
photosynthetic activity; stomatal
conductance; transpiration rate.
Correspondence
X. Zhou and Q. Gao, Key Laboratory of
Sustainable Utilization of Soil Resources in the
Commodity Grain Bases in Jilin Province, Jilin
Agricultural University, Changchun 130118,
China.
E-mail: zhouxue_jlau@163.com;
gyt9962@163.com
Editor
R. Leegood
Received: 13 April 2020; In Revised form:
28 May 2020; Accepted: 17 June 2020
doi:10.1111/plb.13157
ABSTRACT
•In Northeastern China, the intensive cropping system and increased use of chemical
fertilizer has caused severe problems in terms of sustainable agricultural development.
Therefore, to improve agricultural sustainability and crop productivity the farming
system needs to be modified in the region.
•A pot experiment was conducted to evaluate the effect of maize–alfalfa intercropping
on the physiological characteristics, nitrogen (N) uptake and yield of the maize crops
in northeast China in 2017–2018.
•The study findings showed that intercropping under N fertilization progressively
improved the physio-agronomic indices of the maize crop as compared to mono-
cropping. The grain yield, 100 seed weight and biomass dry matter of maize crop
improved in intercropping when it was practiced with N fertilizer. Furthermore, inter-
cropping with N fertilization increased the chlorophyll content of the maize crop at
bell-mouthed, silking, filing and mature stages by 19%, 44%, 12%, and 9% in 2017
and by 23%, 43%, 15%, and 11% in 2018, respectively, as compared with the
monocropping system. Unlike monocropping, intercropping with N fertilization
increased the photosynthesis rate (14% and 15%), stomatal conductance (74% and
98%) and transpiration rate (74% and 75%) in 2017 and 2018, respectively. However,
intercropping reduced intercellular CO
2
(C
i
). Moreover, intercropping with N fertil-
ization increased the maize N content of grain and leaves as well as total N uptake by
49%, 31% and 93% in 2017 and 53%, 34% and 132%, respectively, in 2018 as com-
pared to monocropping.
•In conclusion, our results suggest that maize–alfalfa intercropping with optimal N fer-
tilization provides a practical method for improving growth, yield and N accumula-
tion in the maize crop.
INTRODUCTION
Northeast China is a shared ecozone for agronomy and animal
husbandry, which plays an important role in China’s agricul-
tural industry. The region is characterized by sandy soils, low
vegetation cover and massive wind erosion, which have damag-
ing effects on the local ecological environment (Shao et al.
2020). Similarly, intensive farming and a long-term single
cropping system has created severe problems in terms of the
agricultural ecosystem and loss of biodiversity (Fragoso et al.
1997; Celette et al. 2009; Li et al. 2014). Moreover, the low soil
fertility caused by terrestrial erosion has adversely affected yield
and quality of the crops (Sun et al. 2014; Sun et al. 2018; Liu
et al. 2019). Besides, high soil erosion and overgrazing have
caused a deterioration in grassland production and quality of
forage (Sun et al. 2014; Nasar & Alam 2018). Together with the
intensive use of chemical fertilizers and herbicides, sustainable
agricultural development in the area is facing severe challenges
(Gao et al. 2014; Sun et al. 2014).
Therefore, to improve agricultural sustainability, ensure
the supply of high-quality forage grass and satisfy increasing
meat product demands, the farming system needs to be
modified in northeast China. In this context, introducing
forage grass to the primary crop farming system and estab-
lishing a cereal–legume intercropping system, will enhance
productive resource utilization, leading to an economically
improved and environmentally friendly cropping system (Li
et al. 2001).
Intercropping is the simultaneous cultivation of two or more
crop species on the same piece of land. It is a centuries-old
agricultural practice and still used in modern-day agriculture.
Compared to mono-cropping, intercropping improves the
Plant Biology 22 (2020) 1140–1149 ©2020 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands1140
Plant Biology ISSN 1435-8603
growth and productivity of the crops as a result of the efficient
utilization of available resources (water, light and nutrients)
(Zhang et al. 2013; Nasar et al. 2019). The increased productiv-
ity in an intercropping system is mainly due to the comple-
mentarity and facilitative interactions among intercrops (Li
et al. 2014; Zhang et al. 2014; Raza, et al. 2019b). Complemen-
tarity is achieved through a decrease of interspecific competi-
tion between intercrops having different time, space and
growth characteristics (Hinsinger et al. 2011; Yong et al. 2015;
Raza, et al. 2019c). Moreover, facilitation occurs when one
plant promotes the growth and development of the corre-
sponding neighbour plant in an intercropping system
(Ehrmann & Ritz 2013; Zhang et al. 2014). These complemen-
tarities and interspecific interactions in a cereal–legume inter-
cropping system have resulted in better growth, yield and
higher N uptake for both the cereal and the legume crop (Li
et al. 2001; Zhang et al. 2011; Yong et al. 2015).
Maize (Zea mays L) is an important food and forage crop
grown in northeast China. It is also known as the ‘queen of
cereals’ because it’s many cultivars have very high genetic yield
potentials compared with other cereal crops (Sun et al. 2014).
Alfalfa (Medicago sativa L) is a high-yielding herbaceous
legume, rich in protein, vitamins and minerals, with good
palatability and high digestibility for grazing animals (Sun
et al. 2018). Additionally, being a legume, alfalfa improves soil
fertility and the physio-chemical characteristics of the soil due
to its large rooting structure and N-fixing nodules (Sun et al.
2014) and, as a cover crop, also decreases wind erosion of the
cultivated area, retaining the soil throughout the year (Li et al.
2003). Therefore, maize intercropped with alfalfa not only
secures regional food demand and nutritional quality for the
forage industry, but also provides an environmentally friendly
and a promising agricultural system for the future development
of the region.
Intercropping is practiced globally because of the estab-
lished and anticipated advantages, such as higher crop yield
(Saleem et al. 2011), improved agricultural sustainability
(Borghi et al. 2012), land utilization efficiency (Al-Dalain
2009; Kermah et al. 2017), nutrient acquisition (Banik &
Sharma 2009; Raza et al. 2020) and soil quality improvement
with zero to minimal inputs (Regehr 2014). In contrast,
China has developed high input and high output intensive
cropping systems (Zhang et al. 2013). However, the beneficial
consequences of an intercropping system would provide ade-
quate fertilization, in the sense that soil fertility is essential
for the interspecific interaction between intercrops (Zhang
et al. 2014). Several studies have shown that increased nutri-
ent availability enhances interspecific competition because
taller individuals require more space, absorb more light and
use more nutrients and water (Kheroar & Patra 2013; Adeni-
yan et al. 2014). Nevertheless, sufficient N supply could
reduce competition between intercrops (Zhang et al. 2013).
Also, adequate N supply is crucial for growth of photosyn-
thetic organs and is essential in photosynthesis (Evans 1983;
Yang et al. 2010). Adequate fertilizer N application can
enhance plant enzyme content, chlorophyll content and
enzyme activity of plant leaves, thus promoting photosynthe-
sis and crop yield (Giersch & Robinson 1987).
Therefore, the justification for the following experiment
was to evaluate differences in maize physiological characteris-
tics, yield and N uptake between monocropping and
intercropping (with alfalfa) with and without extra N
fertilization. We hypothesized that intercropping with or
without N fertilization would have significant advantages
over maize monocropping.
MATERIAL AND METHODS
Experimental design and management
The pot experiment was conducted in 2017–2018 in a green-
house of Jilin Agricultural University, Changchun
(125°24’50.38" E, 43°48’28.59" N, 248.5 m a.s.l.), Jilin Province,
China. The area is characterized as a moderate to the semi-arid
region with four distinct seasons. The average annual tempera-
ture and rainfall are 4–6°C and 553–914 mm, respectively, and
130–150 free-frost days annually. The soil used in this experi-
ment was loam, low in organic matter (12.85 mg kg
−1
), total N
(1.51 g kg
−1
), available N (81.29 mg kg
−1
), available P
(18.93 mg kg
−1
), available K (85.76 mg kg
−1
) and pH 6.37.
The experimental treatments were arranged in a complete
randomized design (CRD) with two N fertilization levels
(NL): N0 (no added N) and N1 (2 g N pot
−1
for maize and
0.5 g N pot
−1
for alfalfa), with three planting patterns (PP);
maize monocropping, alfalfa monocropping and maize–alfalfa
intercropping, with four replicates. Medicago sativa L. cv.
Dongmu No. 1 and Zea mays L. cv. Zhengdan 958 were cho-
sen as test crops. All N:P:K fertilizer applications were mixed
with soil before sowing for alfalfa, while for maize 1/3 of the
N:P:K fertilizer was applied as a base application and 2/3of
the N application were used as a top dressing in the small
bell mouth and big bell mouth stages. The NPK fertilizers
were applied according to local fertilization practice. Maize
was treated with 225 kg N ha
−1
, 120 P kg ha
−1
and
60 K kg ha
−1
, while alfalfa received 53 kg N ha
−1
, 135 kg P
ha
−1
and 90 kg K ha
−1
. The fertilizer sources used were urea
(46% N), phosphorus pentoxide P
2
O
5
(46% P) and potas-
sium oxide K
2
O (60% K).
The seeds were sown in pots (length 35 cm, width 20 cm,
height 30 cm) at 2-cm depth with a planting density of 3:5
(maize:alfalfa) (Fig. 1). Maize seeds were sown at a field
planting density of 60,000 plants ha
-1
, while alfalfa seeds were
sown at field seed rate of 15 kg ha
−1
. The bottom of the pots
was covered with marble pebbles to prevent nutrient leaching
and placed at a distance of 0.8 m, and the distance between
maize and alfalfa in intercropping was kept at 5 cm. Both
maize and alfalfa were sown on 15 June 2017 and 10 June
2018 and harvested on 10 October 2017 and 15 October
2018. At the three-leaf stage, maize crops were thinned to a
single plant per pot to aid adaptation to the pot environ-
ment. Plants were regularly watered with tap water to keep
the soil at 60–70% of field water-holding capacity throughout
the growth stage, and soil temperature in each pot was moni-
tored using micro-tensiometers (Nanjing Institute of Soil
Science, Chinese Academy of Sciences). Weeding was done
with a small hand spade, pests and diseases were cautiously
monitored and controlled to abate effects of insecticides of
the non-targeted plant. Further environmental factors, such
as temperature (°C), rainfall (mm), relative humidity (%),
rainfall days, daylight (h), sunshine (h) and irrigation sched-
ule (l pot
−1
) were carefully monitored and recorded during
the entire growing season (Fig. 2).
Plant Biology 22 (2020) 1140–1149 ©2020 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands 1141
Nasar, Shao, Arshad, Jones, Liu, Li, Khan, Khan, Banda, Zhou & Gao Effects of maize-alfalfa intercropping
Data collection
Physiological characteristics, yield attributes and biomass dry
matter
Data on different physiological aspects of maize crops were
recorded at different growth stages (VT, V9, R1 and R6). The
height of the maize plant was measured with a measuring tape.
Stem diameter, cob length and width were measured with Ver-
nier calipers. After harvesting at full maturity, the rows per cob
and number of seeds per row were recorded by manual count-
ing. After threshing, yield attributes of cob weight, grain yield,
grain per cob and 100-grain weight were measured with an
electronic balance. Subsequently, plant samples were sun-dried
for 3 days and then oven-dried at 70 °C for 72 h to obtain the
biomass as dry matter.
Leaf traits
The number of leaves and leaf area were recorded at the co-
growth stage. The number of leaves per plant was recorded by
manual counting. For leaf area, three fully expanded leaves
(top, middle and bottom) were selected to measure length and
width using a tape-measure and taking three reading per leaf.
However, in intercropping, the maize leaves adjacent to the
alfalfa plant leaves were selected to measure leaf area. The fol-
lowing formula was used to calculate leaf area.
LA cm2
¼LWA
where LA,L, W and Aare leaf area (cm), length (cm) and
width (cm) for maize leaf, respectively. The constant coefficient
is 0.73 for maize leaf area (Dervis
¸2013).
Chlorophyll and photosynthetic characteristics
Leaf chlorophyll content (usually at the ninth leaf stage) was
measured using the SPAD Chlorophyll Meter (SPAD-502;
Minolta, Tokyo, Japan) by taking three readings (Zhang et al.
2013). The photosynthetic characteristics of maize leaves
(photosynthesis rate, stomatal conductance, transpiration rate
and intercellular CO
2
) were determined (usually at ninth leaf
stage) between 09:00 h an 11:00 h using a Li-6400XT portable
photosynthesis system (LiCor, Lincoln, NE, USA) at a leaf
temperature of ~27 °C, constant light of 1000 μmol m
−2
s
−1
and CO
2
level of 400 μmol mol
−1
(Ahmad et al. 2013). For the
intercropping system, the alfalfa leaves adjacent to maize leaves
were selected to determine photosynthetic characteristics, with
three readings per leaf.
Grain and leaf N content and total N uptake
The N contents of grain and leaves were determined by wet
digestion (H
2
SO
4
and H
2
O
2
2:1) using the Kjeldahl N determi-
nation apparatus (Zhang et al. 2014). Total N uptake was cal-
culated from the formula below, as suggested by (Nasar & Shah
2017).
Total N uptake ðg pot1Þ¼ Grain N contetnt grain yield
100
þLeaf N contetnt biomass dry matter
100
Statistical analysis
The collected data were analysed using the statistical software
MS statistix 8.1. Graphical analysis was done with Graph Pad
Prism 6.02. The two-way factorial ANOVA was performed with
NL and PP as main factors and their interaction, separately for
2017 and 2018. The mean among treatments was compared
using the Tukey HSD test at P≤0.05 (Zhang et al. 2014). The
modest Pearson’s correlation was applied to determine the
relationship between chlorophyll content, photosynthetic activ-
ity and leaf area of the maize crop.
RESULTS
Effect of intercropping and N fertilization on physio-
agronomic indices of the maize crop
Intercropping and N fertilization had a significant effect on the
physio-agronomic indices of maize crops, except for plant
height where there were no significant changes (P<0.05;
Table 1). Results of the 2-year experiment showed that inter-
cropping significantly (P<0.05) improved the physio-agro-
nomic indices of the maize crop. When compared to
Fig. 1. Schematic diagram of maize–alfalfa intercrop-
ping system. N0, no nitrogen fertilization, N1 nitrogen
fertilization.
Plant Biology 22 (2020) 1140–1149 ©2020 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands1142
Effects of maize-alfalfa intercropping Nasar, Shao, Arshad, Jones, Liu, Li, Khan, Khan, Banda, Zhou & Gao
monocropping, intercropping without N fertilization signifi-
cantly (P<0.05) increased the stem diameter (mm), number
of leaves plant
-1
and leaf area (cm
2
) of the maize crop by 17%,
13%, and 15%, and by 18%, 16% and 18%, respectively, with
N fertilization in 2017. In 2018, intercropping without N fertil-
ization boosted the stem diameter (mm), number of leaves
plant
-1
and leaf area (cm
2
) of the maize crop by 18%, 17% and
19% and by 23%, 21% and 22%, respectively with N fertiliza-
tion. Furthermore, intercropping when compared to
monocropping increased the maize cob length (cm), cob width
(mm), cob weight (g), number of rows cob
-1
and grains row
-1
by 12%, 6%, 9%, 8% and 2%, respectively, without N fertiliza-
tion, and by 15%, 8%, 15%, 10% and 23%, respectively, with
N fertilization in 2017. In 2018, compared to monocropping,
intercropping without N fertilization increased the cob length
(cm), cob width (mm), cob weight (g), number of rows cob
-1
and grains row
-1
by 14%, 7%, 11%, 17% and 20% and by 16%,
12%, 14%, 18%, and 26%, respectively, with N fertilization.
Effect of intercropping and N fertilization on chlorophyll
content and photosynthesis parameters
Intercropping with alfalfa and N fertilization had a significant
effect on the chlorophyll content and photosynthetic activity of
the maize crop (P<0.05; Table 2, Fig. 3). The results showed
that intercropping significantly (P<0.05) improved the
chlorophyll content and photosynthetic activity (i.e. photosyn-
thesis rate (P
r
), stomatal conductance (g
s
) and transpiration
rate (T
r
) of the maize crop and reduced the intercellular CO
2
concentration (C
i
). In 2017, when compared to monocropping,
intercropping without N fertilization increased the chlorophyll
content (%) of the maize crop by 16%, 37%, 11% and 8% and
by 19%, 44%, 12% and 9% at bell-mouthed, silking, filing and
mature stages, respectively, with N fertilization. In 2018, inter-
cropping without N fertilization increased the chlorophyll con-
tent (%) of the maize crop by 17%, 37%, 14% and 10% and by
23%, 43%, 15% and 11% at the bell-mouthed, silking, filing
and mature stages, respectively. The P
r
,g
s
and T
r
of the maize
crop increased by 5%, 60%, and 57%, respectively, in the inter-
cropping system without N fertilization and by 14%, 74% and
76%, respectively, with N fertilization as compared to
monocropping in 2017. In 2018, when compared to
monocropping, intercropping without N fertilization increased
P
r
,g
s
and T
r
by 4%, 82%, and 63%, and by 15%, 98% and
73%, respectively, with N fertilization. Nevertheless, the C
i
response changed in the intercropping production system.
Compared to monocropping, intercropping without and with
N fertilization reduced C
i
by 17% and 20%, respectively, in
2017, and 17% and 21%, respectively, in 2018.
Effect of intercropping and N fertilization on maize crop N
content and N uptake
Nitrogen fertilization and intercropping significantly affected
the N content and N uptake of the maize crop (Fig. 4). Inter-
cropping significantly (P<0.05) improved the N content and
N uptake of the maize crop as compared to monocropping.
Intercropping increased the maize N content (grain and leaves)
and N uptake up to 42%, 27% and 64%, respectively, with no
N fertilization and by 49%, 31% and 93%, respectively, with N
fertilization in 2017 as compared to monocropping. During
2018, intercropping with no N fertilization increased the maize
N content (grain and leaves) and N uptake up to 42%, 30%
and 105%, and 53%, 34% and 132%, respectively, following N
application.
Effect of intercropping and N fertilization on maize yield and
biomass dry matter
Nitrogen fertilization and intercropping had a significant
impact on yield and biomass dry matter of maize and alfalfa
(P<0.05; Table 3). The 2-year results showed that intercrop-
ping increased the yield and biomass dry matter of the maize
crop. When compared to monocropping, intercropping with-
out N fertilization increased the grain yield (g) and 100-grain
weight (g) of the maize crop by 18% and 21%, respectively,
and by 31% and 22%, respectively, with N fertilization in 2017.
In 2018, intercropping without N fertilization increased the
grain yield (g) and 100-grain weight (g) of the maize crop by
45% and 23%, respectively, and by 54% and 24%, respectively,
with N fertilization.
Furthermore, intercropping without N fertilization increased
the biomass dry matter of maize by 13% and 17% with N fertil-
ization as compared to monocropping in 2017. In 2018, inter-
cropping without N fertilization increased the biomass dry
matter of maize by 14% and by 18% with N fertilization as
Fig. 2. Temperature, humidity, rainfall, rainfall days,
daylight and sunshine and irrigation schedule of the
experimental site.
Plant Biology 22 (2020) 1140–1149 ©2020 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands 1143
Nasar, Shao, Arshad, Jones, Liu, Li, Khan, Khan, Banda, Zhou & Gao Effects of maize-alfalfa intercropping
Table 1. Effect of planting pattern and N fertilization on the physio-agronomic indices of the maize crop
Year
Treatments
Plant height (cm)
Stem diameter
(mm)
No of leaves
plant
−1
Leaf area
(cm
2
)
Cob length
(cm)
Cob width
(mm)
Cob weight
(g)
No of rows
cob
−1
No of grains
row
-1
NL PP
2017 N0 Monocrop 252.50 32.10 3.1 c 9.75 0.8 b 299.81 25.9 c 14.62 1.2 c 50.41 1.4 b 203.25 7.2 c 14.75 1.5 b 30.00 3.2 c
Intercrop 253.25 37.75 1.2 b 11.01 0.7 ab 344.44 39.3 bc 16.42 1.1 bc 53.50 1.6 b 222.50 9.1 bc 16.01 0.8 ab 36.25 1.7 bc
N1 Monocrop 252.25 37.25 2.5 bc 11.01 1.1 ab 374.44 14.5 b 18.80 0.5 ab 52.99 0.5 b 250.01 21.5 b 16.01 0.8 ab 38.03 4.3 b
Intercrop 255.75 44.10 2.1 a 12.75 0.4 a 440.01 26.3 a 21.69 1.8 a 57.28 2.3 a 287.57 8.5 a 17.75 1.7 a 46.89 3.3 a
Significance
NL 0.560
ns
0.000*** 0.005** 0.000*** 0.000*** 0.002** 0.000*** 0.036*0.000***
PP 0.271
ns
0.000*** 0.005** 0.001** 0.006** 0.000*** 0.002** 0.036*0.001**
NL x PP 0.471
ns
1.425
ns
1.584
ns
0.468
ns
0.462
ns
0.466
ns
0.243
ns
0.702
ns
0.500
ns
2018 N0 Monocrop 251.72 31.10 0.6 c 9.00 1.4 b 283.35 26.5 c 15.17 0.6 c 49.53 2.9 b 202.67 7.2 c 13.25 1.3 b 29.75 3.6 c
Intercrop 254.07 36.55 2.5 b 10.50 1.3 ab 335.79 38.5 bc 17.22 2.0 bc 52.96 1.0 b 224.22 5.6 bc 15.50 1.3 ab 35.75 1.5 bc
N1 Monocrop 253.93 34.10 2.4 bc 10.75 2.1 ab 349.96 22.6 b 19.30 1.2 ab 53.32 0.8 b 235.70 7.9 b 16.75 0.9 ab 37.50 4.0 b
Intercrop 256.82 42.07 2.8 a 13.00 0.8 a 427.45 29.5 a 22.36 1.0 a 59.56 4.1 a 267.68 16.0 a 19.75 4.3 a 47.25 3.1 a
Significance
NL 0.124
ns
0.002** 0.013*0.000*** 0.000*** 0.002** 0.000*** 0.008** 0.000***
PP 0.105
ns
0.000*** 0.025*0.001*** 0.005** 0.003** 0.001** 0.05
ns
0.001**
NL x PP 0.857
ns
0.286
ns
0.617
ns
0.418
ns
0.515
ns
0.305
ns
0.386
ns
0.766
ns
0.326
ns
Mean values with same letters SD show no significant difference at P≤0.05, Tukey HSD test. N0: no nitrogen, N1: nitrogen fertilization, PP: planting pattern, NL: nitrogen level, *P<0.05, **P<0.01,
***P<0.001 and
ns
P>0.0.5
Plant Biology 22 (2020) 1140–1149 ©2020 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands1144
Effects of maize-alfalfa intercropping Nasar, Shao, Arshad, Jones, Liu, Li, Khan, Khan, Banda, Zhou & Gao
compared to monocropping. When compared to monocrop-
ping, the biomass dry matter of alfalfa in intercropping fell by
10% without N fertilization and by 8% with N fertilization in
2017. Intercropping reduced the biomass dry matter of alfalfa
by 12% without N fertilization and by 7% with N fertilization
as compared to monocropping in 2018.
Correlation analysis of chlorophyll, photosynthetic activity
and leaf area
Pearson’s correlation analysis was used to quantify the relation-
ship of chlorophyll content, photosynthetic activity and leaf
area of the maize crop (Fig. 5). The correlation analysis
revealed a significant and positive correlation of photosynthesis
(Fig. 5A), stomatal conductance (Fig. 5B), intercellular CO
2
(Fig. 5C), transpiration (Fig. 5D) and leaf area (Fig. 5E) with
chlorophyll content in maize.
DISCUSSION
The present study demonstrated that intercropping with alfalfa
significantly improved the growth and yield of a maize crop
compared to monocropping. We also observed that intercrop-
ping enhanced the chlorophyll content and photosynthetic
activity of maize; however, these values were further improved
with the addition of N fertilizer (Table 2, Fig. 3).
Generally, the growth and yield advantages of intercropping
are mainly related to the effective use of available resources
(e.g. water, light and nutrients) (Hinsinger et al. 2011; Mei
et al. 2012; Gao et al. 2014; Raza et al. 2019a). In the current
study, intercropping improved the physio-agronomic attri-
butes of maize, but its effect was more pronounced under N
fertilization as compared to monocropping. Probably, this
might be related to the N fertilization, which helps to improve
plant growth and development (Liu et al. 2018). Also note that
Table 2. Effect of planting pattern and N fertilization on maize chlorophyll content at different growth stages
Year
Treatments
Bell-mouthed stage (%) Silking stage (%) Filling stage (%) Mature stage (%)NL PP
2017 N0 Monocrop 20.31 1.2 c 22.70 1.2 c 42.32 2.2 c 23.48 2.2 c
Intercrop 23.42 1.8 b 31.21 1.3 b 47.03 1.5 b 25.27 1.5 bc
N1 Monocrop 24.21 0.8 b 28.62 0.9 bc 46.21 0.7 b 26.66 0.8 ab
Intercrop 28.83 1.3 a 41.10 6.0 a 52.03 2.1 a 29.07 2.1 a
Significance
NL 0.000*** 0.000*** 0.000*** 0.000***
PP 0.000*** 0.000*** 0.000*** 0.007**
NL x PP 0.330
ns
0.237
ns
0.575
ns
0.760
ns
2018 N0 Monocrop 19.58 1.3 c 23.25 0.8 c 40.44 2.3 c 22.43 2.1 c
Intercrop 22.95 11.2 b 31.77 1.2 b 46.29 2.9 b 24.75 1.3 bc
N1 Monocrop 23.70 2.8 b 29.10 1.7 bc 45.74 1.7 b 26.30 1.4 ab
Intercrop 29.11 3.1 a 41.59 5.2 a 52.79 2.3 a 29.31 1.6 a
Significance
NL 0.000*** 0.000*** 0.000*** 0.000***
PP 0.000*** 0.000*** 0.000*** 0.007**
NL*PP 0.223
ns
0.186
ns
0.778
ns
0.696
ns
The mean values with similar letter SD in the table shows no significant difference at P≤0.05, Tukey HSD test, N0: no nitrogen, N1: nitrogen fertilization,
PP: planting pattern, NL: nitrogen levels, *P<0.05, **P<0.01, ***P<0.001 and
ns
P>0.05
Fig. 3. Effect of intercropping and N fertilization on
photosynthetic activity of maize. A photosynthesis rate,
B stomatal conductance, C intercellular CO
2
, and D tran-
spiration rate for the growing seasons 2017–2018. Bars
are SD and lowercase letters indicate significant dif-
ferences with Tukey HSD test at P<0.05.
Plant Biology 22 (2020) 1140–1149 ©2020 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands 1145
Nasar, Shao, Arshad, Jones, Liu, Li, Khan, Khan, Banda, Zhou & Gao Effects of maize-alfalfa intercropping
in intercropping, one plant promotes the growth, fitness and
survival of the other crop (Zhang et al. 2014). It was previously
reported that appropriate N application to maize–pigeon pea
(Cajanus cajan L) intercropping increased the number of leaves
per plant (15.5), leaf area (508 cm
2
), cob length (15.6 cm), cob
weight (168.7 g), no of rows per cob (16.68), 100-grain weight
(32.02 g), stover yield (7293 kg ha
−1
) and grain yield
(8009 kg ha
−1
) of the maize crop compared to monocropping
(Boregowda 2015).
The existing study evidently shows that intercropping also
increased the chlorophyll content of the maize crop at different
growth stages, but this effect was more evident under N fertil-
ization, as reported in Table 2. Perhaps this was related to the
adequate N fertilization, which helps to advance the enzyme
content, enzyme activity and chlorophyll content of the leaves
(Giersch & Robinson 1987), or might be related to better light
utilization (Ahmad et al. 2013; Raza et al. 2019a). Also, the
belowground rhizospheric interaction in intercropping also
improved iron nutrition, which also enhanced the chlorophyll
content (Zuo et al. 2003; Zhang et al. 2013). Similarly, in
maize–peanut intercropping, chlorophyll content was increased
from 128 to 141 in maize and from 217 to 228 in peanut (Gao
et al. 2010). In another study, maize–soybean intercropping
with N fertilization increased the chlorophyll content of the
maize crop compared to monocropping (Zhang et al. 2014).
Changes in the chlorophyll content are expected to affect
photosynthetic activity, which has a significant impact on the
growth, yield and development of the crop (Ahmad et al. 2013;
Zhang et al. 2013). In the current study, intercropping and N
fertilization improved the photosynthetic activity of the maize
crop (Fig. 3). This might be due to an increase in chlorophyll
content (Ahmad et al. 2013) or to the differences in plant
height, which improved ventilation and light conditions of the
taller plants compared to shorter plants obtained in intercrop-
ping (Zhang et al. 2014; Raza , et al. 2019c). It has been docu-
mented that maize–soybean or cotton intercropping enhanced
photosynthesis rate (μmol CO
2
m
−2
s
−1
), stomatal
conductance (mol H
2
Om
−2
s
−1
) and transpiration rate (μmol
H
2
Om
−2
s
−1
) of the maize crop by 7.6%, 43.53% and 6.60%,
respectively, and reduced the intercellular CO
2
content under
appropriate N application (Zhang et al. 2014).
Nitrogen is a crucial nutrient for plant growth and develop-
ment (Liu et al. 2018). In this study, intercropping increased
the N content and total N uptake of the maize crop compared
to monocropping, but these values were further improved with
N fertilization. This might be due to niche complementarity
and facilitative interaction in intercropping (Li et al. 2003;
Richardson et al. 2009; Shao et al. 2020). Also, the soil root-re-
leased chemicals improved the plant nutrient availability,
which improves plant nutrient status (Li et al. 2009; Rivest
et al. 2010). The increased N concentration and total N uptake
of oat (Avena sativa L) and pea (Pisum sativum L) in the inter-
cropping system with maize was predominantly because of the
belowground interspecific root interaction under the same N
level (Neugschwandtner & Kaul 2015). Also, appropriate N fer-
tilization to maize–soybean intercropping further increased the
N content and N uptake in the maize crop (Zhang et al. 2017).
Previous studies have shown that the increased yield and bio-
mass dry matter of cereal crops in an intercropping system are
closely related to the use of available resources required for
optimum growth (nutrients, water and light) (Latati et al.
2013; Yong et al. 2015; Shao et al. 2020; Raza et al. 2019d).
Consistent with these studies, our results showed that inter-
cropping increased the yield and biomass dry matter of the
maize crop compared to monocropping (Table 3). There
might be several reasons for this: (i) improved growth, chloro-
phyll, N content and photosynthetic characteristics in inter-
cropping, (ii) adequate N fertilization, and (iii) utilization
efficiency of the plant available resources. However, intercrop-
ping reduced biomass dry matter of the alfalfa crop as com-
pared to monocropping. One possible reason could be the
difference in plant height. The limited growth of alfalfa was a
result of shading from the taller maize, since light is needed for
the photosynthetic processes (Wang et al. 2015; Shao et al.
Fig. 4. Effect of intercropping and N fertilization on
maize N content (grain and leaves) and total N uptake. A
maize grain N content, B maize leaf N content, C, total
N uptake of maize crop in the growing seasons
2017–2018. Bars are SD and lowercase letters indi-
cate significant differences with Tukey HSD test at
P<0.05.
Plant Biology 22 (2020) 1140–1149 ©2020 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands1146
Effects of maize-alfalfa intercropping Nasar, Shao, Arshad, Jones, Liu, Li, Khan, Khan, Banda, Zhou & Gao
2020). Previously it was reported that maize–mung bean
(Vigna radiata L) or maize–mash bean (Vigna mungo L) inter-
cropping significantly (P<0.05) improved the grain and yield
of the maize crop (Saleem et al. 2011). Similarly, intercropping
of maize–pea under adequate N fertilization boosted the yield
and biomass dry weight of the maize crop as compared to
Table 3. Effect of planting pattern and N fertilization on yield and 100-seed weight of maize and biomass dry matter of maize and alfalfa
Years
Treatments Grain yield (g pot
−1
) Biomass dry matter (g pot
−1
) Biomass dry matter (g pot
−1
) 100-grain weight (g)
NL PP Maize Maize Alfalfa Maize
2017 N0 Monocrop 95.63 7.1 c 202.51 14.8 c 101.86 7.6 ab 22.71 1.7 c
Intercrop 113.21 6.2 b 229.53 3.7 b 91.26 9.1 b 27.62 2.1 b
N1 Monocrop 107.40 5.7 bc 220.83 8.6 bc 116.37 9.1 a 29.51 1.5 bc
Intercrop 140.72 8.7 a 268.73 7.8 a 107.25 4.5 ab 36.33 2.8 a
Significance
NL 0.000*** 0.000*** 0.002** 0.000***
PP 0.000*** 0.000*** 0.028*0.000***
NL*PP 0.075
ns
0.084
ns
0.830
ns
0.473
ns
2018 N0 Monocrop 91.50 8.0 c 194.20 8.8 c 102.01 8.6 bc 23.13 2.7 c
Intercrop 132.69 1.0 b 234.64 3.3 b 89.34 6.1 c 28.50 2.3 bc
N1 Monocrop 103.65 9.4 c 217.47 7.3 b 118.33 4.1 a 31.33 1.3 b
Intercrop 160.04 5.1 a 271.20 10.4 a 110.20 4.2 ab 38.71 3.2 a
Significance
NL 0.000*** 0.000*** 0.000*** 0.000***
PP 0.000*** 0.000*** 0.005** 0.000***
NL x PP 0.073
ns
0.152
ns
0.469
ns
0.493
ns
Mean values with different lowercase letter SD are significantly different from each other with Tukey HSD test, P(≤0.05). PP: planting pattern, NL: nitrogen
level, N0: no nitrogen, N1: nitrogen fertilizer, *P<0.05, **P<0.01, ***P<0.001,
ns
P>0.05.
Fig. 5. The relationship between chlorophyll and photosynthesis rate (A), stomatal conductance (B), intercellular CO
2
(C), transpiration rate (D) and leaf area
(E).
Plant Biology 22 (2020) 1140–1149 ©2020 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands 1147
Nasar, Shao, Arshad, Jones, Liu, Li, Khan, Khan, Banda, Zhou & Gao Effects of maize-alfalfa intercropping
monocropping (Yang et al. 2018). In another study, maize–-
legume intercropping improved the yield and biomass dry
matter of the maize crop primarily because of the improved
growth indices of the maize crop or better resource utilization
in the intercropping system (Gao et al. 2010).
CONCLUSIONS
The present study showed that intercropping significantly
(P<0.05) improved the growth and yield attributes of the
maize crop as compared to monocropping, but this effect
was more pronounced under adequate N fertilization. The
study also indicated that intercropping with N fertilization
increased the physiological indices of the maize crop, such as
leaf area, chlorophyll, and photosynthetic activity, and thus
improved the yield attributes of maize as compared to
monocropping. Moreover, intercropping with or without N
fertilization improved the N content (grain and leaves) and
N uptake in the maize crop. These improvements in physio-
logical indices and N accumulation of the maize crop by
intercropping significantly (P<0.05) improved the yield and
biomass dry matter. Based on our findings, it is recom-
mended that intercropping under suitable N fertilization is a
better and more sustainable model for promoting plant
growth and development, yield and N requirements of the
maize crop.
ACKNOWLEDGEMENTS
We would like to thank the College of Resources and Environ-
ment, Jilin Agricultural University, for providing the green-
house facility. We also thank Prof. Gao Qiang and Prof. Xue
Zhou of the College of Resources and Environmental Sciences,
Jilin Agricultural University, Changchun, for technical advice
and support throughout the experiment. This work was sup-
ported by the National Natural Science Foundation (31471945;
U19A2035), the Natural Science Foundation of Jilin Province,
China (20190201274JC) and the Science and Technology Pro-
ject of the 13th Five-Year Plan of Jilin Provincial Department
of Education (JJKH20190908KJ).
REFERENCES
Adeniyan O.N., Aluko O.A., Olanipekun S.O., Olasoji
J.O., Aduramigba-Modupe V.O. (2014) Growth and
yield performance of cassava/maize intercrop under
different plant population density of maize. Journal
of Agricultural Science,6,35–40.
Ahmad I., Cheng Z., Meng H., Liu T., Nan W.C., Khan
M.A., Wasila H., Khan A.R. (2013) Effect of inter-
cropped garlic (Allium sativum) on chlorophyll con-
ten, photosynthesis and antioxidant enzymes in
pepper. Pakistan Journal of Botany,45, 1889–1896.
Al-Dalain S.A. (2009) Effect of Intercropping of Zea
mays with Potato Solanum tuberosum, L. on Potato
Growth and on the Productivity and Land Equiva-
lent Ratio of Potato and Zea mays. Agricultural Jour-
nal,4, 164–170.
Banik P., Sharma R.C. (2009) Yield and resource uti-
lization efficiency in baby corn–legume intercrop-
ping system in the eastern plateau of India. Journal
of Sustainable Agriculture,33, 379–395.
Boregowda Y.S. (2015) Growth and yield of maize as
influenced by maize-based intercropping system for
Southern zone of Karnataka. International Quarterly
Journal of Environmental Sciences,7, 335–339.
Borghi
´
E., Crusciol C.A.C., Nascente A.S., Mateus G.P.,
Martins P.O., Costa C. (2012) Effects of row spacing
and intercrop on maize grain yield and forage pro-
duction of palisade grass. Crop and Pasture Science,
63, 1106–1113.
Celette F., Findeling A., Gary C. (2009) Competition
for nitrogen in an unfertilized intercropping system:
The case of an association of grapevine and grass
cover in a Mediterranean climate. European Journal
of Agronomy,30,41–51.
Dervis
¸B. (2013) A coefficient for computing leaf area
in hybrid corn. Journal of Chemical Information and
Modeling,53, 1689–1699.
Ehrmann J., Ritz K. (2013) Plant: Soil interactions in
temperate multi-cropping production systems. Plant
and Soil,376,1–29.
Evans J.R. (1983) Nitrogen and photosynthesis in the
flag leaf of wheat (Triticum aestivum L.). Plant Physi-
ology,72, 297–302.
Fragoso C., Brown G.G., Patr´on J.C., Blanchart E.,
Lavelle P., Pashanasi B., Senapati B., Kumar T.
(1997) Agricultural intensification, soil biodiversity
and agroecosystem function in the tropics: The role of
earthworms. PUBLISHER & PLACE?.
Gao Y., Duan A., Qiu X., Sun J., Zhang J., Liu H.,
Wang H. (2010) Distribution and use efficiency of
photosynthetically active radiation in strip inter-
cropping of maize and soybean. Agronomy Journal,
102, 1149–1157.
Gao Y., Wu P., Zhao X., Wang Z. (2014) Growth, yield,
and nitrogen use in the wheat/maize intercropping
system in an arid region of northwestern China.
Field Crops Research,167,19–30. https://doi.org /10.
1016/j.fcr.2014.07.003.
Giersch C., Robinson S.P. (1987) Regulation of photo-
synthetic carbon metabolism during phosphate limi-
tation of photosynthesis in isolated spinach
chloroplasts. Photosynthesis Research,14, 211–227.
Hinsinger P., Betencourt E., Bernard L., Brauman A.,
Plassard C., Shen J., Tang X., Zhang F. (2011) P for
two, sharing a scarce resource: Soil phosphorus
acquisition in the rhizosphere of intercropped spe-
cies. Plant Physiology,156, 1078–1086.
Kermah M., Franke A.C., Adjei-Nsiah S., Ahiabor
B.D.K., Abaidoo R.C., Giller K.E. (2017) Maize–-
grain legume intercropping for enhanced resource
use efficiency and crop productivity in the Guinea
savanna of northern Ghana. Field Crops Research,
213,38–50. https://doi.org/10.1016/j.fcr.2017.07.
008.
Kheroar S., Patra B.C. (2013) Advantages of Maize-
Legume Intercropping Systems. Journal of Agricul-
tural Science and Techonology,3, 733–744.
Latati M., Pansu M., Drevon J.-J., Ounane S.M. (2013)
Advantage of intercropping maize (Zea mays L.) and
common bean (Phaseolus vulgaris L.) on yield and
nitrogen uptake in Northeast Algeria. International
Journal of Research and Applied Sciences,1,1–7. [on-
line] http://www.knowledgejournals.com.
Li L., Sun J., Zhang F., Li X., Yang S., Rengel Z. (2001)
Wheat/maize or wheat/soybean strip intercropping I.
Yield advantage and interspecific interactions on
nutrients. Field Crops Research,71, 123–137.
Li L., Zhang F., Li X., Christie P., Sun J., Yang S., Tang
C. (2003) Interspecific facilitation of nutrient uptake
by intercropped maize and faba bean. Nutrient
Cycling in Agroecosystems,65,61–71.
Li Y., Ran W., Zhang R., Sun S., Xu G. (2009) Facili-
tated legume nodulation, phosphate uptake and
nitrogen transfer by arbuscular inoculation in an
upland rice and mung bean intercropping system.
Plant and Soil,315, 285–296.
Li L., Tilman D., Lambers H., Zhang F.S. (2014) Plant
diversity and overyielding: Insights from below-
ground facilitation of intercropping in agriculture.
New Phytologist,203,63–69.
Liu Z., Gao J., Gao F., Liu P., Zhao B., Zhang J. (2018)
Photosynthetic characteristics and chloroplast ultra-
structure of summer maize response to different
nitrogen supplies. Frontiers in Plant Science,9,1–13.
Liu Z., Gao F., Yang J., Zhen X., Li Y., Zhao J., Li J.,
Qian B., Yang D., Li X. (2019) Photosynthetic char-
acteristics and uptake and translocation of nitrogen
in peanut in a wheat–peanut rotation system under
different fertilizer management regimes. Frontiers in
Plant Science,10,1–13.
Mei P.P., Gui L.G., Wang P., Huang J.C., Long H.Y.,
Christie P., Li L. (2012) Maize/faba bean intercrop-
ping with rhizobia inoculation enhances productiv-
ity and recovery of fertilizer P in a reclaimed desert
soil. Field Crops Research,130,19–27. https://doi.
org/10.1016/j.fcr.2012.02.007.
Nasar J., Alam A. (2018) Intercropping promote sus-
tainble agriculture and clean environment. Biomedi-
cal Journal of Science & Technical Research,4,2.
https://doi.org/10.26717/BJSTR.2018.04.0001018.
Nasar J., Shah Z. (2017) Effect of iron and molybde-
num on yield and nodulation of lentil. ARPN Jour-
nal of Agricultural and Biological Science,12 [online]:
www.arpnjournals.com.
Nasar J., Alam A., Nasar A., Khan M.Z. (2019) Inter-
cropping induce changes in the above- and below-
ground plant compartments in mixed cropping sys-
tem. Biomedical Journal of Science & Technical
Research,17, 5. https://doi.org/10.26717/BJSTR.
2019.17.003054.
Neugschwandtner R.W., Kaul H.P. (2015) Nitrogen
uptake, use and utilization efficiency by oat-pea
intercrops. Field Crops Research,179, 113–119. [on-
line]: https://doi.org/10.1016/j.fcr.2015.04.018.
Raza M.A., Feng L.Y., Iqbal N., Ahmed M., Chen Y.K.,
Khalid M.H., Bin D.A.M.U., Khan A., Ijaz W., Hus-
sain A., Jamil M.A., Naeem M., Bhutto S.H., Ansar
Plant Biology 22 (2020) 1140–1149 ©2020 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands1148
Effects of maize-alfalfa intercropping Nasar, Shao, Arshad, Jones, Liu, Li, Khan, Khan, Banda, Zhou & Gao
M., Yang F., Yang W. (2019a) Growth and develop-
ment of soybean under changing light environments
in relay intercropping system. PeerJ,7, e7262.
https://doi.org/10.7717/peerj.7262.
Raza M.A., Feng L.Y., van der Werf W., Cai G.R., Bin
K.M.H., Iqbal N., Hassan M.J., Meraj T.A., Naeem
M., Khan I., Rehman Sana ur, Ansar M., Ahmed M.,
Yang F., Yang W. (2019b) Narrow-wide-row plant-
ing pattern increases the radiation use efficiency and
seed yield of intercrop species in relay-intercropping
system. Food and Energy Security,8.
Raza M.A., Feng L.Y., van der Werf W., Iqbal N., Khan
I., Hassan M.J., Ansar M., Chen Y.K., Xi Z.J., Shi
J.Y., Ahmed M., Yang F., Yang W. (2019c) Optimum
leaf defoliation: A new agronomic approach for
increasing nutrient uptake and land equivalent ratio
of maize soybean relay intercropping system. Field
Crops Research,244, 107647. https://doi.org/10.
1016/j.fcr.2019.107647.
Raza M.A., Bin Khalid M.H., Zhang X., Feng L.Y.,
Khan I., Hassan M.J., Ahmed M., Ansar M.,
Chen Y.K., Fan Y.F., Yang F., Yang W. (2019d)
Effect of planting patterns on yield, nutrient
accumulation and distribution in maize and soy-
bean under relay intercropping systems. Scientific
Reports,9,1–14. https://doi.org/10.1038/s41598-
019-41364-1.
Raza M.A., Feng L.Y., van der Werf W., Iqbal N.,
Khan I., Khan A., Din A.M.U., Naeem M., Meraj
T.A., Hassan M.J., Khan A., Lu F.Z., Liu X.,
Ahmed M., Yang F., Yang W. (2020) Optimum
strip width increases dry matter, nutrient accumu-
lation, and seed yield of intercrops under the relay
intercropping system. Food and Energy Security,9
(2); in press.
Regehr, A. (2014). Evaluation of maize and soybean
intercropping on soil quality and nitrogen
transformations in the Argentine Pampa. UWSpa-
ce.http://hdl.handle.net/10012/8149
Richardson A.E., Barea J.M., McNeill A.M., Prigent-
Combaret C. (2009) Acquisition of phosphorus and
nitrogen in the rhizosphere and plant growth pro-
motion by microorganisms. Plant and Soil,321,
305–339.
Rivest D., Cogliastro A., Bradley R.L., Olivier A. (2010)
Intercropping hybrid poplar with soybean increases
soil microbial biomass, mineral N supply and tree
growth. Agroforestry Systems,80,33–40.
Saleem R., Ahmed Z., Ashraf M., Arif M. (2011)
Response of maize–legume intercropping system to
different fertility sources under rainfed conditions.
Sarhad Journal of Agriculture,27, http://www.aup.ed
u.pk/sj_pdf
Shao Z., Wang X., Gao Q., Zhang H., Yu H., Wang Y.,
Zhang J., Nasar J., Gao Y. (2020) Root contact
between maize and alfalfa facilitates nitrogen transfer
and uptake using techniques of foliar
15
N-labeling.
Agronomy,10,2–18.
Sun B., Peng Y., Yang H., Li Z., Gao Y., Wang C., Yan
Y., Liu Y. (2014) Alfalfa (Medicago sativa L.)/Maize
(Zea mays L.) Intercropping Provides a Feasible Way
to Improve Yield and Economic Incomes in Farming
and Pastoral Areas of Northeast China (W.-X. Lin,
Ed.). PLoS One,9, e110556..
Sun T., Li Z., Wu Q., Sheng T., Du M. (2018) Effects of
alfalfa intercropping on crop yield, water use effi-
ciency, and overall economic benefit in the Corn Belt
of Northeast China. Field Crops Research,216,
109–119.
Wang Z., Zhao X., Wu P., He J., Chen X., Gao Y., Cao
X. (2015) Radiation interception and utilization by
wheat/maize strip intercropping systems. Agricul-
tural and Forest Meteorology,204,58–66. https://doi.
org/10.1016/j.agrformet.2015.02.004.
Yang L., Yan J., Cai Z. (2010) Effects of N-applications
and photosynthesis of maize (Zea mays L.) on soil
respiration and its diurnal variation. Frontiers of
Agriculture in China,4,42–49.
Yang C., Fan Z., Chai Q. (2018) Agronomic and Eco-
nomic Benefits of Pea/Maize Intercropping Systems
in Relation to N Fertilizer and Maize Density. Agron-
omy,8,2–14.
Yong T., Liu X., Yang F., Song C., Wang X., Liu W., Su
B., Zhou L., Yang W. (2015) Characteristics of nitro-
gen uptake, use and transfer in a wheat–maize–soy-
bean relay intercropping system. Plant Production
Science,18, 388–397.
Zhang G., Yang Z., Dong S. (2011) Interspecific com-
petitiveness affects the total biomass yield in an
alfalfa and corn intercropping system. Field Crops
Research,124(1), 66–73. https://doi.org/10.1016/j.fc
r.2011.06.006.
Zhang X., Huang G., Bian X., Zhao Q. (2013) Effects of
nitrogen fertilization and root interaction on the
agronomic traits of intercropped maize, and the
quantity of microorganisms and activity of enzymes
in the rhizosphere. Plant and Soil,368, 407–417.
Zhang X., Huang G., Zhao Q. (2014) Differences in
maize physiological characteristics, nitrogen accu-
mulation, and yield under different cropping pat-
terns and nitrogen levels. Chilean Journal of
Agricultural Research,74, 326–332.
Zhang H., Zeng F., Zou Z., Zhang Z., Li Y. (2017)
Nitrogen uptake and transfer in a soybean/maize
intercropping system in the karst region of south-
west China. Ecology and Evolution,7, 8419–8426.
Zuo Y., Li X., Cao Y., Zhang F., Christie P. (2003) Iron
nutrition of peanut enhanced by mixed cropping
with maize: Possible role of root morphology and
rhizosphere microflora. Journal of Plant Nutrition,
26, 2093–2110.
Plant Biology 22 (2020) 1140–1149 ©2020 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands 1149
Nasar, Shao, Arshad, Jones, Liu, Li, Khan, Khan, Banda, Zhou & Gao Effects of maize-alfalfa intercropping
