Interspecific facilitation of nutrient acquisition by intercropped maize
and faba bean
Li, L., Zhang, F. S., Li, X. L., Christie, P., Sun, J. H., Yang, S. C., & Tang, C. (2003). Interspecific facilitation of
nutrient acquisition by intercropped maize and faba bean. Nutrient Cycling in Agroecosystems, 65, 61-71.
Published in:
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Download date:16. Jun. 2017
Nutrient Cycling in Agroecosystems 65: 61–71, 2003.
 2003 Kluwer Academic Publishers. Printed in the Netherlands.
61
Interspecific facilitation of nutrient uptake by intercropped maize and
faba bean
1,2
1,
1
1,3
2
2
Long Li , Fusuo Zhang *, Xiaolin Li , Peter Christie , Jianhao Sun , Sicun Yang and
4
Caixian Tang
1
Department of Plant Nutrition, China Agricultural University, 100094 Beijing, People’ s Republic of China;
Gansu Academy of Agricultural Sciences, Institute of Soils and Fertilizers, 730070 Lanzhou, People’ s
Republic of China; 3 Department of Agricultural and Environmental Science, The Queen’ s University of
Belfast, Newforge Lane, Belfast BT9 5 PX, UK; 4 Soil Science and Plant Nutrition, The University of
Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia; * Author for correspondence (e-mail:
zhangfs@ mail.cau.edu.cn; phone: 186 -10 -62892499; fax: 186 -10 -62891016)
2
Received 24 November 2000; accepted in revised form 3 August 2001
Key words: Multiple cropping, Nitrogen, Phosphorus, Potassium, Root barrier, Root interactions
Abstract
Interspecific complementary interactions in N, P and K uptake between intercropped maize (Zea mays L. cv.
Zhongdan No. 2) and faba bean (Vicia faba L. cv. Linxia Dacaidou) were investigated in a field experiment. A root
barrier study was also set up in which belowground partitions were used to determine the contribution of
interspecific root interactions to crop nutrient uptake. Nitrogen uptake by intercropped faba bean was higher than
(no P fertilizer) or similar to (33 kg P ha 21 of P fertilizer) that by sole faba bean during the early growth stages
(first to third sampling) of faba bean, and was similar to (no P fertilizer) or higher than (33 kg P ha 21 of P
fertilizer) that by sole faba bean at maturity. Nitrogen uptake by intercropped maize did not differ from that by sole
maize at maturity, except when P fertilizer was applied. Intermingling of maize and faba bean roots increased N
uptake by both crop species by about 20% compared with complete or partial separation of the root systems.
Intercropping also led to some improvement in P nutrition of both crop species. Maize shoot P concentrations were
similar to those of sole maize during early growth stages and became progressively higher until they were
significantly higher than those of sole maize at maturity. Intercropping increased shoot P concentration in faba
bean at the flowering stage and in maize at maturity, and increased P uptake by both plant species at maturity.
Phosphorus uptake by faba bean with root intermingling (no root partition) was 28 and 11% higher than with
complete (plastic sheet) and partial (400 mesh nylon net) root barriers, respectively. Maize showed similar trends,
with corresponding P uptake values of 29 and 17%. Unlike N and P, K nutrition was not affected by the presence
of root barriers.
Introduction
Total biomass and grain yields of intercropped maize
and faba bean were significantly higher than those of
maize and faba bean in the corresponding sole crops
on a calcareous soil in a field study by Li et al. (1999).
According to Vandermeer (1989), intercropping advantage depends on the net effect in the trade-off
between interspecific competition and facilitation.
However, most of the research on intercropping ad-
vantage in terms of interspecific interactions has been
¨
focused mainly on interspecific competition (Bohringer and Leihner 1997; Braconnier 1998; Dauro and
Mohamedsaleem 1995; Dupraz et al. 1998; Helenius
and Jokinen 1994; Piepho 1995; Jolliffe and Wanjau
1999). Although interspecific facilitation (or positive
interaction) in which one plant species enhances the
survival, growth, or fitness of another has been demonstrated in many natural plant communities (Callaway and Pugnaire 1999), there have been few studies
62
on facilitation (especially of nutrient uptake) in intercropping systems. Effects on P availability that may
qualify as facilitation have been reported by Gardner
and Boundy (1983), Horst and Waschkies (1987) and
Ae et al. (1990). Ae et al. (1990) showed that pigeon
pea could increase P uptake by associated sorghum.
Gardner and Boundy (1983) and Horst and Waschkies
(1987) indicated that white lupin could increase P
uptake by intercropping with wheat. In addition, some
work has been conducted on the N budget in intercropping systems between cereals and legumes in
which the cereals obtain some part of the N from the
associated legumes (Midmore 1993; Stern 1993).
Cereals, on the other hand, can compete for N in the
rhizosphere of cereal / legume mixtures, leading to N
depletion in the rhizosphere of the legumes, and this
stimulates increased N 2 fixation by the legumes
(Boucher and Espinosa 1982).
There is only one cropping season in most areas of
northwest China due to temperature limitations. Many
relay intercropping systems with early spring sowing
of crops with later sown crops, such as faba bean /
maize, wheat / soybean and wheat / maize have therefore been widely adopted by farmers, and these play
an important role in the food production of this
region. In a previous paper (Li et al. 1999), we
reported some beneficial effects of maize and faba
bean intercropping on crop yields and suggested that
these resulted mainly from interactions between the
root systems of the two crop species. This paper
presents data on crop nutrient uptake from the same
field site. The objectives of the study were to (i)
examine the possible occurrence of interspecific
facilitation of nutrient uptake between faba bean and
maize, and (ii) evaluate the contribution of interspecific root interactions to facilitation of nutrient
uptake in the maize / faba bean association.
Materials and methods
Study area
The field experiment was conducted in 1997 at Jingyuan village, Jingyuan county, Gansu province, China
(378059 N, 1048409 E) at an altitude of 1645 m above
sea level. Annual mean temperature is 6.6 8C and the
frost-free period is 160–170 days. Total solar radiation averages 6162 MJ m 22 year 21 . The region is
classified as arid with a continental climate and has
200–250 mm of annual precipitation and 2369 mm of
potential evaporation. The soil in the experimental
field contained 7.20 g kg 21 organic matter, 0.51 g
kg 21 N, 6.4 mg kg 21 Olsen-P and 170 mg exchangeable K kg 21 soil. The soil is classified as an Aridisol
with a pH of 8.2.
The major field experiment
The experimental design was a split-plot with three
replicates in which the main plot treatments were
fertilizer P (33 kg P ha 21 as triple superphosphate)
and no fertilizer P. Sub-plot treatments consisted of
sole maize (Zea mays L. cv. Zhongdan No. 2), sole
faba bean (Vicia faba L. cv. Linxia Dacaidou) and
maize / faba bean relay intercropping. Relay intercropping plots consisted of three strips (six rows of maize
and six rows of faba bean) with two rows of maize
plants grown in alternating 1.2-m wide strips with two
rows of faba bean. There were 18 plants per row for
maize or 21 plants for faba bean in the intercropping.
The maize inter-row spacing was 0.40 m, the faba
bean inter-row spacing was 0.20 m and the distance
between maize and adjacent faba bean rows was 0.30
m in the intercropping treatment. The sole cropping
plots consisted of 6 rows with 24 plants per row for
sole maize or 16 rows with 31 plants per row for sole
faba bean. The maize inter-row spacings were 0.80 m
and 0.40 m for wide and narrow rows, respectively,
and the corresponding faba bean inter-row spacings
were 0.3 m and 0.15 m, with alternating wide and
narrow row spacing in the plots. All plots were 3.6 3
6 m, giving an area of 21.6 m 2 (Figure 1). A 0.4-m
wide ridge between plots was built to separate the
plots from each other, and there was a 0.5-m wide
irrigation furrow plus two 0.4-m ridges between
blocks. The densities of sole maize and faba bean
were 10.12 and 22.95 plants m 22 , respectively. Twothirds of each intercropped area was occupied by
maize and one-third by bean. The densities of intercropped maize and faba bean were therefore 6.75 and
7.64 plants m 22 , respectively, so that the overall
proportional density of each crop species was equal in
both the sole and intercropping treatments.
Seeds were sown on 27 March (faba bean) and 16
April (maize). Faba bean was harvested on 25 July
and maize on 20 September. All plots were given a
basal application of 225 kg N ha 21 as urea. Both the
N and P fertilizers were evenly broadcast and incorporated into the top 20 cm of the soil prior to sowing. All
plots were irrigated during the growing season to
prevent water stress. Six irrigation events (with a
63
Figure 1. Diagram showing the arrangement of the rows of maize (1) and faba bean (s) in the field experiment and the positions of the
partitions in the microplots: (a) sole maize, (b) sole faba bean, and (c) maize and faba bean intercropping.
water depth of 70 mm on each occasion) were carried
out on April 20, May 18, June 13, July 10, August 1
and September 3, respectively for intercropping plots
and sole maize. Only the first four irrigation events
were used for sole faba bean.
limit adverse effects on the main experiment (Figure
1). Roots did not penetrate the nylon mesh at final
harvest.
The root barrier study
In this experiment, there were three treatments: (i)
sole cropping pea (Pisum sativum), (ii) sole cropping
faba bean and (iii) faba bean / pea intercropping.
Fertilizer N and P were applied at total rates of 225
and 33 kg ha 21 . The peas were sown on 25 March and
harvested on 5 July, while the faba beans were sown
on 27 March and harvested on 25 July. The areabased density of pea was 56 plants m 22 under both
intercropping and monocropping treatments.
A root barrier study was conducted in the treatments
receiving P fertilizer: (i) an impermeable plastic sheet
partition inserted into the ground between adjacent
strips of maize and faba bean to a depth of 0.70 m to
prevent interspecific root interactions, (ii) a 400 mesh
nylon net partition (nominal aperture of 37 m) inserted
into the ground between the two crop species to
prevent direct root contact but allow interactions by
mass flow and diffusion, and (iii) a control treatment
with no partition between the two crop species to
allow complete intermingling of their root systems.
The root barriers were inserted just after wheat emergence. Final harvesting dates for faba bean and maize
were the same as in the main field experiment. The
length of each root barrier was restricted to 1 m to
The faba bean /pea intercropping study
Data collection
Above-ground parts of 10 faba bean, 10 pea and 4
maize plants were harvested from each plot at 20-day
intervals from faba bean emergence (5 May). Shoot
dry matter yield was measured by oven drying at 65
8C. At the final harvest, grain yields and above-ground
64
dry matter of maize, faba bean and pea at maturity
were determined by harvesting two rows of maize,
two rows of faba bean and two rows of pea in the
intercropping treatment, from two rows of maize in
the sole maize, and from four rows of faba bean and
pea in the sole faba bean and pea treatment. All of the
plants from 1 m were harvested in the root barrier
study at maturity and the aboveground yield and
biomass were determined as described above. Further
information on the experiments and the yield data has
been given by Li et al. (1999).
Nitrogen, P and K concentrations were determined
on ground subsamples of oven-dried plant material
after digestion in a mixture of concentrated H 2 SO 4
and H 2 O 2 . Nitrogen was measured by the microKjeldahl procedure, P by the vanadomolybdate method and K by flame photometry.
Results
Main field experiment
Shoot nutrient concentrations
There was no significant difference in N concentration
between intercropped and sole maize, except at the
5th sampling (12 August) when the N concentration
was lower in the intercropped maize. This indicates
that the N concentration in maize was not increased
by the associated faba bean. Intercropping also did not
affect shoot N concentration in the faba bean during
its entire growth period (Table 1).
At the early stages of maize growth (20 days after
maize emergence), shoot P concentration was significantly lower in the intercropped than in the sole
maize. Shoot P concentrations in the intercropped
maize subsequently increased and exceeded those of
sole maize after faba bean was harvested; the concentration in the intercropped plants increased by 11%
at the final harvest. Intercropping increased the P
concentration in faba bean at the flowering stage
compared to the sole faba bean. However, at maturity
the P concentration in the intercropped faba bean did
not differ from that in the sole faba bean (Table 1).
Statistical analysis
Analysis of variance was performed using a split-plot
model to test for significance of treatments by analysis
of variance (ANOVA) and means were compared by
least significance difference (LSD) (SAS Institute
1985).
Table 1. Concentrations (% of dry matter) of N, P and K in shoots of maize and faba bean grown in the sole and intercropping systems in the
field at different harvest dates.
Crop
Nitrogen
Maize
Faba bean
Phosphorus
Maize
Faba bean
Potassium
Maize
Faba bean
1
Cropping system
Sampling date
25 May
15 June
5 July
25 July
12 August
3 September
20 September
Sole
Intercropped
Significance 2
Sole
Intercropped
Significance
3.69
3.58
NS
3.03
3.31
NS
4.77
4.62
NS
1.32
1.45
NS
2.03
2.22
NS
2.37
2.33
NS
ND 1
ND
ND
2.53
2.64
NS
2.46
1.50
**
H3
H
H
0.803
0.886
NS
H
H
H
0.98
1.03
NS
H
H
H
Sole
Intercropped
Significance
Sole
Intercropped
Significance
0.377
0.356
*
0.265
0.266
NS
0.280
0.263
NS
0.088
0.118
**
0.194
0.192
NS
0.158
0.191
NS
ND 1
ND
ND
0.210
0.206
NS
0.112
0.122
NS
H
H
H
0.108
0.129
NS
H
H
H
0.128
0.142
*
H
H
H
Sole
Intercropped
Significance
Sole
Intercropped
Significance
3.79
3.81
NS
3.12
2.91
NS
4.01
3.82
NS
1.33
1.32
NS
3.83
3.22
NS
1.36
1.34
NS
ND
ND
ND
1.38
1.39
NS
1.74
1.14
NS
H
H
H
1.35
0.98
*
H
H
H
1.38
1.07
*
H
H
H
ND, not determined. 2 Significance of difference between intercropped and sole by analysis of variance; **, P,0.01; *, P,0.05; NS, not
significant. 3 H, after final harvest of faba bean.
65
Intercropping did not reduce maize shoot K concentration before 12 August (Table 1), indicating that
there was no significant competition from faba bean
for K when the two crops co-existed. However, after
the final harvest of the faba bean, shoot K concentrations in the intercropped maize were lower than in
the sole maize, especially at sampling on 3 September
and 20 September when the differences were significant (P # 0.05). There was no significant intercropping effect on faba bean shoot K concentration
throughout its growth period.
Nutrient uptake
Without P fertilizer, significant differences in N acquisition between intercropped and sole faba bean
were observed at all harvests. By contrast, with P
fertilizer application, there was no difference at the
first three harvests. At maturity, intercropping increased N uptake of faba bean by 29% without P
fertilizer and by 58% with 33 kg P ha 21 . Nitrogen
uptake by intercropped maize was not increased by
associated faba bean, with the exception of P-fertilized plots at final harvest (Table 2). Application of P
fertilizer tended to increase N uptake, especially of
intercropped maize.
Phosphorus uptake of intercropped faba bean was
significantly higher than of sole faba bean except at
the first sampling with P fertilizer application. The
difference became significant (P , 0.05) only at the
second sampling (15 June). At maturity, it was 56%
and 18% higher than of sole faba bean in the plots
with P fertilizer and without P fertilizer, respectively
(Table 3). There was no difference in P uptake
between intercropped and sole maize during early
stages of growth (seedling stage), but on the second
sampling date (15 June: elongation stage) P uptake by
intercropped maize was significantly lower than that
by sole maize where P fertilizer was applied. On the
third sampling date (5 July) the difference in P uptake
between intercropped and sole maize had declined,
and this trend continued until the fifth sampling date
(3 September, grain filling stage). During the last 20
days of the grain filling stage, P uptake of intercropped maize was significantly higher than that of
sole maize (Table 3). Application of P generally
increased P uptake irrespective of cropping system or
crop species.
Potassium uptake of intercropped faba bean was
slightly higher than of sole faba bean only at maturity.
Potassium uptake of intercropped maize was similar
to that of sole maize on the first two sampling dates,
but was then lower than that of sole maize and
eventually similar to sole maize (Table 4).
Root barrier study
Nitrogen
There were no significant differences in maize or faba
bean plant N concentration (weighted mean for shoot
and grain) among the three partition treatments in the
root barrier study (Table 5). This supports the conclusion that the supply of N was adequate for both crops
and consequently there were no interspecific N interactions in the field experiment. Without any root
partition, N uptake by faba bean was 22% and 18%
higher than with the plastic sheet partition and the
nylon mesh partition, respectively. Similarly, N uptake by maize without any root partition was 22% and
20% higher compared with plastic sheet and nylon
mesh. The nylon mesh partition, which prevented
Table 2. Nitrogen uptake (g N m 22 ) by faba bean and maize grown without fertilizer P or with 33 kg fertilizer P ha 21 in the sole and
intercropping systems (Experiment 1).
P fertilizer application
Cropping system and crop species
Sampling date
25 May
No P fertilizer
33 kg P ha 21
LSD 20.05
No P fertilizer
33 kg P ha 21
LSD 0.05
1
Sole faba bean
Intercrop faba bean
Sole faba bean
Intercrop faba bean
Sole maize
Intercrop maize
Sole maize
Intercrop maize
5.54
7.44
7.35
7.64
1.21
0.25
0.25
0.28
0.31
0.04
15 June
4.69
9.98
7.01
7.33
2.44
4.9
4.7
5.5
5.1
0.8
5 July
14.3
27.8
21.0
23.1
9.8
17.6
12.4
19.3
20.4
4.6
25 July
28.3
36.4
27.2
43.0
8.8
ND 3
ND
ND
ND
ND
12 August
1
H
H
H
H
H
31.7
26.2
34.2
24.3
11.9
3 September
20 September
H
H
H
H
H
16.5
20.5
22.5
21.3
4.3
H
H
H
H
H
26.0
26.4
26.4
35.8
7.0
H, after final harvest of faba bean. 2 LSD 0.05 , least significant difference by analysis of variance at the 0.05 level. 3 ND, not determined.
66
Table 3. Phosphorus uptake (g P m 22 ) by faba bean and maize grown without fertilizer P or with 33 kg fertilizer P ha 21 in the sole and
intercropping systems (Experiment 1).
P fertilizer application
Cropping system and crop species
No P fertilizer
Sole faba bean
Intercrop faba bean
Sole faba bean
Intercrop faba bean
33 kg P ha
21
LSD 20.05
No P fertilizer
33 kg P ha 21
Sole maize
Intercrop maize
Sole maize
Intercrop maize
LSD 0.05
1
Sampling date
25 May
15 June
5 July
25 July
12 August
3 September
20 September
0.48
0.53
0.65
0.70
0.15
0.02
0.03
0.03
0.03
0.01
0.31
0.73
0.47
0.69
0.16
0.29
0.30
0.32
0.25
0.06
1.42
1.91
0.88
1.97
0.69
1.44
1.26
2.14
1.58
0.65
2.19
2.58
2.33
3.64
0.65
ND 3
ND
ND
ND
ND
H1
H
H
H
H
1.75
1.52
2.35
2.41
0.52
H
H
H
H
H
1.71
2.93
3.48
3.14
0.92
H
H
H
H
H
3.33
4.07
3.53
4.44
0.55
H, after final harvest of faba bean. 2 LSD 0.05 , least significant difference by analysis of variance at the 0.05 level. 3 ND, not determined.
direct root-to-root contact but would have allowed
mass flow and diffusion of substances between the
rhizospheres of the two crops, did not increase N
uptake by either crop species (Table 5).
Phosphorus
Although P concentration in faba bean shoots was not
affected by the root partitions, P uptake by intercropped faba bean was lowered by the plastic sheet
partition inserted between faba bean and maize roots
(Table 5). Phosphorus uptake by faba bean using the
nylon mesh partition was intermediate between that
for the plastic sheet partition and no partition. Both P
concentration in the maize shoots and P uptake by the
maize were higher without any root partition than
with the plastic sheet or nylon mesh partition (Table
5).
Potassium
There were no significant root partition effects on
maize or faba bean shoot K concentrations and uptake
in the root barrier study (Table 5). This suggests that
there were no interspecific root interactions between
maize and faba bean because of an adequate supply of
soil K for both species.
The faba bean /pea intercropping study
Nutrient concentration
Nitrogen concentration in intercropped faba bean was
significantly lower than in sole faba bean at the third
sampling (5 July), indicating that faba bean intercropped with pea was completely different from faba
bean intercropped with maize as described above. In
contrast, P concentration in intercropped faba bean
Table 4. Potassium acquisition (g K m 22 ) by faba bean and maize grown without fertilizer P or with 33 kg fertilizer P ha 21 in the sole and
intercropping systems (Experiment 1).
P fertilizer application
Cropping system and crop species
Sampling date
25 May
No P fertilizer
33 kg P ha 21
LSD 20.05
No P fertilizer
33 kg P ha 21
LSD 0.05
1
Sole faba bean
Intercrop faba bean
Sole faba bean
Intercrop faba bean
Sole maize
Intercrop maize
Sole maize
Intercrop maize
5.5
6.1
7.8
7.3
1.8
0.27
0.28
0.28
0.32
0.07
15 June
5.2
7.9
6.7
7.9
3.1
4.11
4.02
4.59
4.05
0.68
5 July
10.8
14.6
9.4
12.8
3.6
35.9
22.2
34.1
25.2
10.0
25 July
16.5
19.5
13.4
22.9
6.6
ND 3
ND
ND
ND
ND
12 August
1
H
H
H
H
H
28.3
18.2
35.3
18.1
5.7
3 September
20 September
H
H
H
H
H
24.8
22.9
41.5
23.9
8.6
H
H
H
H
H
36.2
28.2
37.8
36.7
7.1
H, after final harvest of faba bean. 2 LSD 0.05 , least significant difference by analysis of variance at the 0.05 level. 3 ND, not determined.
67
Table 5. Nutrient concentration (% of dry matter) and uptake (mg nutrient m 21 per 2 rows) in the above-ground parts of maize and faba bean
with three types of below-ground partition. All plants received 33 kg P ha 21 and 225 kg N ha 21 and were harvested at maturity (25 July for
faba bean and 20 September for maize).
Nutrient concentration 1
Nutrient and partition type
Maize
Nitrogen
Plastic sheet
Nylon net
No partition
Phosphorus
Plastic sheet
Nylon net
No partition
Potassium
Plastic sheet
Nylon net
No partition
Nutrient acquisition
Faba bean
Maize
Faba bean
2
2.734a
2.701a
2.672a
14.2b
14.6b
17.3a
24.0b
23.3b
28.8a
0.115b 2
0.126ab
0.134a
0.227a
0.240a
0.227a
2.78c
3.25b
3.58a
1.19b
1.32ab
1.52a
1.069a 2
1.072a
1.120a
1.419a
1.212a
1.404a
25.8a
27.4a
29.6a
7.59a
6.58a
9.30a
0.992a
0.910a
1.091a
1
Weighted averages based on the proportions of straw and grain. 2 Within each column, means followed by the same letter are not significantly
different by LSD at the 0.05 level.
was significantly higher than in sole faba bean at the
same sampling. No significant difference in K concentration between intercropped and sole faba bean
was observed at any sampling occasion (Table 6).
There was no significant difference in N, P and K
concentration between intercropped and sole pea.
Nutrient uptake
Although intercropping improved P uptake by faba
bean intercropped with pea at final harvest (25 July),
it did not increase N uptake by faba bean intercropped
with pea, and this is different from N uptake by faba
bean intercropped with maize (Table 7). This may be
Table 6. Nutrient concentrations (%) in faba bean and pea grown with 33 kg fertilizer P ha 21 and 225 kg fertilizer N ha 21 in the sole and
intercropping systems.
Nutrient and crop species
Nitrogen
Faba bean
Pea
Phosphorus
Faba bean
Pea
Potassium
Faba bean
Pea
Cropping system
Sampling date
25 May
15 June
5 July
25 July
Sole
Intercropped
LSD 0.05
Sole
Intercropped
LSD 0.05
3.11
2.68
1.61
3.44
3.91
0.47
1.54
1.41
0.71
2.57
2.58
1.12
2.77
1.92
0.84
1.74
1.82
0.90
2.52
1.86
1.27
H
H
H
Sole
Intercropped
LSD 0.05
Sole
Intercropped
LSD 0.05
0.276
0.267
0.125
0.291
0.311
0.180
0.101
0.121
0.022
0.193
0.200
0.273
0.119
0.232
0.081
0.214
0.220
0.118
0.218
0.186
0.057
H
H
H
Sole
Intercropped
LSD 0.05
Sole
Intercropped
LSD 0.05
3.33
3.40
1.82
4.19
4.39
0.07
1.44
1.60
0.70
2.79
3.11
1.60
1.26
1.41
0.45
1.40
1.40
0.39
1.24
1.70
0.75
H
H
H
68
Table 7. Nutrient acquisition (g m 22 ) by faba bean and pea grown with 33 kg fertilizer P ha 21 and 225 kg fertilizer N ha 21 in the sole and
intercropping systems.
Nutrient and crop species
Nitrogen
Faba bean
Pea
Phosphorus
Faba bean
Pea
Potassium
Faba bean
Pea
Cropping system
Sampling date
25 May
15 June
5 July
25 July
Sole
Intercropped
LSD 0.05
Sole
Intercropped
LSD 0.05
7.4
6.4
0.9
10.1
9.8
6.1
7.0
6.0
3.6
17.9
16.9
4.9
21.0
13.6
14.1
15.0
15.2
8.8
27.2
26.7
10.6
H
H
H
Sole
Intercropped
LSD 0.05
Sole
Intercropped
LSD 0.05
0.65
0.64
0.08
0.85
0.79
0.81
0.47
0.52
0.03
1.35
1.29
1.66
0.88
1.46
1.04
1.85
1.84
1.31
2.33
3.64
0.81
H
H
H
Sole
Intercropped
LSD 0.05
Sole
Intercropped
LSD 0.05
7.8
8.2
6.7
6.8
9.4
9.0
13.4
21.8
12.2
10.9
19.4
20.2
12.2
12.8
H
H
H
why faba bean / pea intercropping is less successful
than faba bean / maize intercropping (Li et al. 1999).
Discussion
Improved P nutrition in intercropped maize and
faba bean
The present study demonstrates that intercropping
facilitated P nutrition in both faba bean and maize.
Firstly, P concentration was higher in the intercropped
plants than in the sole cropping plants during the
flowering (15 June) and pod-setting (5 July) stages for
faba bean and grain filling (3 September) to mature
(20 September) stages for maize. Secondly, intercropping increased total uptake of P by faba bean at all
sampling stages except at first sampling and by maize
at later stages, irrespective of P fertilization. Thirdly,
when faba bean and maize grew together, both P
concentration and P uptake in maize, and P uptake in
faba bean were significantly higher when their roots
were not separated than when their roots were partitioned by a plastic sheet.
Similar facilitation in P nutrition has been found in
wheat / lupin associations (Horst and Waschkies 1987)
and sorghum / pigeon pea intercropping (Ae et al.
1990). In these two studies, legumes only improved
the P nutrition in cereals. However, the present results
indicate that intercropping improved not only P nutrition in maize but also in faba bean. If the improvement in P nutrition in wheat / lupin and sorghum /
pigeon pea intercropping is termed ‘asymmetrical’
facilitation [(1, 0) or (1, 2)] (Crawley 1997), then
the P nutrition improvement in maize / faba bean may
be considered as ‘symmetrical’ (1, 1). In other
words, there was mutual interspecific facilitation in P
nutrition in maize / faba bean intercropping.
Various mechanisms can be proposed for the facilitation in P nutrition by intercropping. The improved P
nutrition in maize could have resulted from an increased uptake of P released during the decomposition
of root residues of faba bean. It was evident that P
concentration and uptake in maize were increased
mainly by intercropping at later growing stages after
the faba bean had been harvested. Alternatively,
although the crops received fertilizer N (urea), faba
bean, as a legume, was better nodulated when intercropped than in monoculture (Table 8) and may have
fixed more atmospheric N 2 . When fixing N 2 , legume
plants take up more cations than anions and release
H 1 from the roots (Tang et al. 1997). The H 1 ions
released are particularly important in dissolving P in
calcareous soils. Furthermore, root nodulation and N 2
69
fixation of legumes have been shown to increase when
the legume is intercropped with a species unable to fix
N 2 (Boucher and Espinosa 1982; Stern 1993; Sangakkara 1994). In the present study, N uptake in faba
bean by intercropping presumably increased through
improved N 2 fixation (discussed below). Total acid
production was found to be highly correlated with
total N 2 fixation in legumes by Tang et al. (1997).
Therefore, the increase in N 2 fixation in intercropped
faba bean may have led to increased proton excretion
by faba bean, and this may have contributed to the
mobilization of sparingly soluble phosphate in the
rhizosphere and thus improved P nutrition in both
crop species.
The improvement in maize P nutrition by intercropping could also result partly from the increased volume of soil exploited by the maize roots for P absorption. The root barrier study showed that P uptake in
maize was greater without separation of its roots from
faba bean roots than when the roots of the two crops
were partitioned with nylon mesh. This was consistent
with the higher intercrop yields obtained when maize
and legume roots intermingled in the soil compared to
separate planting of the two species (May and Misangu 1982), or when the roots of the species were
partitioned by a plastic sheet (Li et al. 1999). In
addition, there is evidence of interspecific nutrient
transfer through vesicular-arbuscular mycorrhizal hyphae (Chiariello et al. 1982). In a tallgrass prairie
plant community, P is also transferred among neighbouring species by mycorrhizal hyphal interconnections and there is differential transfer among co-occurring species (Walter et al. 1996). Interspecific P
transfer via vesicular-arbuscular mycorrhizal hyphae
to an inefficient P acquisition species from an efficient
one may therefore be one of the mechanisms of
interspecific P uptake facilitation in faba bean / maize
intercropping.
Table 8. Weight of single root nodules (mg nodule 21 ) in sole faba
bean and faba bean intercropped with maize grown with different
fertilizer N and P treatments (kg ha 21 ) at the Jingtan site in 1998.
Treatment
Intercropped
faba bean
Sole faba
bean
0 N/0 P
0 N / 53 P
300 N / 0 P
300 N / 53 P
LSD 0.05
19.4
23.7
14.0
16.7
16.9
14.2
8.4
12.4
2.9
The symmetrical facilitation in P uptake between
intercropped maize and faba bean has not been found
in most of the legume / cereal intercropping systems
investigated. Although overall P uptake exceeds sole
cropping in most of the intercropping studies reported, an increase in nutrient uptake by one species is
usually at the expense of a decrease in the other
species. For example, in cassava / peanut intercropping, cassava acquired more P while peanut acquired
less compared to the respective sole cropping systems, although overall P acquisition by intercropping
was higher than that in the sole cropping (Manson et
al. 1986). Impaired P acquisition by maize intercrop¨
ped with cowpea was found by Hardter
and Horst
(1991). In maize / mung bean intercropping, P absorption decreased by 5–43% in maize and by 31–58% in
mung beans as a result of intercropping (Chowdhury
and Rosario 1992). Therefore, the symmetrical interspecific facilitation in P acquisition between intercropped species that we found in the maize / faba bean
intercropping has important implications for intercropping ecology and plant community ecology.
Increased N uptake by intercropped faba bean
Intercropping increased N uptake by faba bean in the
present study. High concentrations of nitrate can
impair nodulation and depress N 2 fixation in legumes
(Unkovich and Pate 1998; Tang et al. 1999). Growing
cereals, e.g. maize in the present study, would efficiently utilize soil nitrate and thus there would be less
adverse effect on N 2 fixation by legumes. In our other
experiment on faba bean / maize intercropping, intercropping increased the weight of single nodules of
faba bean under combined fertilizer treatments of 0 kg
N / 53 kg P, 300 kg N / 0 kg P and 300 kg N / 53 kg P
ha 21 (Table 8). A greater stimulus for nodulation in
beans was also noted when the beans were intercropped with maize (Boucher and Espinosa 1982),
and the nodulation and nodule activity of plants in
close proximity to maize or cassava was higher than
in that of central rows in mung bean / maize and mung
bean / cassava intercropping (Sangakkara 1994). In
pea / barley intercropping, the intercropping advantage
was mainly due to the complementary use of soil
inorganic and atmospheric N sources by the intercropped pea and barley, resulting in reduced competition for inorganic N, rather than a facilitative effect, in
which symbiotically fixed N 2 was made available to
the barley (Jensen 1996). Furthermore, there was no
70
significant difference in N uptake between intercropped and sole maize in the present study, indicating
that N transfer from faba bean to maize was not
significant or the fertilizer N was adequate for optimal
maize growth.
This study also shows that root partitioning by
plastic sheet or nylon mesh decreased N uptake in
faba bean compared to the freely intermingling roots,
indicating that the intermingling of roots played an
important role in the increase in N uptake by faba
bean. The increase in N uptake by root intermingling
resulted mainly from the enhancement of the volume
of soil exploited by the roots rather than a rhizosphere
effect. Many other studies have employed root barrier
partitions to separate the effects of shoot and root
interactions (Chamblee 1958; Assemat et al. 1981;
Willey and Reddy 1981; Regnier et al. 1989; Perera et
al. 1992).
Conclusions
Interspecific belowground interactions played an important role in the acquisition of N and P by faba bean
and maize in the intercropping system. Nitrogen
acquisition was higher by intercropped faba bean than
by sole faba bean during the early growth stages
where no P fertilizer was applied and at maturity
where P fertilizer was applied. Intermingling of maize
and faba bean roots was advantageous to N acquisition by both plant species. Intercropping also led to an
improvement in P nutrition in both maize and faba
bean. Intercropping significantly enhanced P nutrition
in faba bean at the flowering stage and in maize before
maturity, important stages for grain development.
Unlike N and P, K nutrition was not affected by a
rhizosphere effect. The findings of this study may
have important implications where land resources and
fertilizer supply are limited, and where intercropping
systems can improve efficiency of resource use and
should therefore be recommended.
Acknowledgements
We are grateful to the Major State Basic Research
Development Programme of the People’s Republic of
China (Project number G1999011707) and the National Natural Science Foundation of China (Project
number 30070450) for generous financial support.
References
Ae N., Arihara J., Okada K., Yoshihara T. and Johansen C. 1990.
Phosphorus uptake by pigeon pea and its role in cropping
systems of the Indian subcontinent. Science 248: 477–480.
Al Niemi T.S., Kahn M.L. and McDermott D. 1997. P metabolism
in the bean-Rhizobium tropici symbiosis. Plant Physiol. 113:
1233–1242.
Assemat L., Morishima H. and Oka H.I. 1981. Neighbour effects
between rice and barnyard grass strains. Acta Oecologia 87:
551–559.
¨
Bohringer
A. and Leihner D.E. 1997. A comparison of alley
cropping and block planting systems in sub-humid Benin. Agrofor. Syst. 35: 117–130.
Boucher D.H. and Espinosa J. 1982. Cropping system and growth
and nodulation responses of beans to nitrogen in Tabasco,
Mexico. Trop. Agric. (Trinidad) 59: 279–282.
Braconnier S. 1998. Maize-coconut intercropping: effects of shade
and root competition on maize growth and yield. Agronomie 18:
373–382.
Callaway R.M. and Pugnaire F.I. 1999. Facilitation in plant community. In: Pugnaire F.I. (ed.), Handbook of Functional Plant
Ecology. Marcel Dekker, New York, pp. 623–648.
Chamblee D.S. 1958. Some above- and below-ground relationships
of an alfalfa-orchard grass mixture. Agron. J. 50: 434–437.
Chiariello N., Hickman J.C. and Mooney H.A. 1982. Endomycorrhizal role for interspecific transfer of phosphorus in a community of annual plants. Science 217: 941–943.
Chowdhury M.K. and Rosario E.L. 1992. Phosphorus utilization
efficiency as affected by component population, rhizobial inoculation and applied nitrogen in maize / mungbean intercropping.
Exp. Agric. 28: 255–263.
Crawley M.J. 1997. Plant Ecology. Blackwell Science, Cambridge,
UK, pp. 512–513.
Dauro D. and Mohamedsaleem M.A. 1995. Shoot and root interactions in intercropped wheat and clover. Tropic Agric. (Trinidad)
72: 170–172.
Dupraz C., Simorte V., Dauzat M., Bertoni G., Bernadac A. and
Masson P. 1998. Growth and nitrogen status of young walnuts as
affected by intercropped legumes in a Mediterranean climate.
Agrofor. Syst. 43: 71–80.
Gardner W.K. and Boundy K.A. 1983. The acquisition of phosphorus by Lupinus albus L. IV. The effect of interplanting wheat and
white lupin on the growth and mineral composition of the two
species. Plant Soil 70: 391–402.
¨
Hardter
R. and Horst W.J. 1991. Nitrogen and phosphorus use in
maize sole cropping and maize / cowpea mixed cropping systems
on an alfisol in the northern Guinea savanna of Ghana. Biol.
Fertil. Soils 10: 267–275.
Helenius J. and Jokinen K. 1994. Yield advantage and competition
in intercropped oats (Avena sativa L.) and faba bean (Vicia faba
L.): application of the hyperbolic yield-density model. Field
Crops Res. 37: 85–94.
Horst W.J. and Waschkies C. 1987. Phosphorus nutrition of spring
wheat (Triticum aestivum L.) in mixed culture with white lupin
¨ Bodenkd. 150: 1–8.
(Lupinus albus L.). Z. Pflanzenernahr
Jensen S. 1996. Grain yield, symbiotic N 2 fixation and interspecific
competition for inorganic N in pea-barley intercrops. Plant Soil
182: 25–38.
Jolliffe P.A. and Wanjau F.M. 1999. Competition and productivity
in mixtures: some properties of productive intercrops. J. Agric.
Sci. (Cambridge) 132: 425–435.
71
Li L., Yang S.C., Li X.L., Zhang F.S. and Christie P. 1999.
Interspecific complementary and competitive interactions between intercropped maize and faba bean. Plant Soil 212: 105–
114.
Manson S.C., Leihner D.E. and Vorst J.J. 1986. Cassava-cowpea
and cassava-peanut intercropping. III. Nutrient concentrations
and removal. Agron. J. 78: 441–444.
May K.W. and Misangu R. 1982. Soybean-cereal intercropping and
its implications in soybean breeding. In: Keswani C.L. and
Ndunguru B.J. (eds), Intercropping in Semi-Arid Areas. International Development Research Centre, Morogoro, Tanzania, pp.
79–83.
Midmore D.J. 1993. Agronomic modification of resource use and
intercrop productivity. Field Crops Res. 34: 357–380.
Perera K.K., Ayres P.G. and Gunasena H.P.M. 1992. Root growth
and the relative importance of root and shoot competition in
interactions between rice (Oryza sativa) and Echinochloa crusgalli. Weed Res. 32: 67–76.
Piepho H.P. 1995. Implications of a simple competition model for
the stability of an intercropping system. Ecol. Model. 80: 251–
256.
Regnier E.E., Stoller E.W. and Nafziger E.D. 1989. Common
cocklebur (Xanthium strumarium) root and shoot interference in
soybeans (Glycine max). Weed Sci. 37: 308–313.
Sangakkara R. 1994. Growth, yield and nodule activity of mungbean intercropped with maize and cassava. J. Sci. Food Agric.
66: 417–421.
SAS Institute 1985. SAS User’s Guide: Statistics. Version 5. SAS
Institute, Cary, North Carolina.
Stern W.R. 1993. Nitrogen fixation and transfer in intercrop systems. Field Crops Res. 34: 335–356.
Tang C., McLay C.D.A. and Barton L. 1997. A comparison of
proton excretion of twelve pasture legumes grown in nutrient
solution. Austr. J. Exp. Agric. 37: 563–570.
Tang C., Unkovich M.J. and Bowden J.W. 1999. Factors affecting
soil acidification under legumes. III. Acid production by N 2 fixing legumes as influenced by nitrate supply. New Phytol. 143:
513–521.
Unkovich M.J. and Pate J.S. 1998. Symbiotic effectiveness and
tolerance to early season nitrate in indigenous populations of
subterranean clover rhizobia from S. W. Australian pastures. Soil
Biol. Biochem. 30: 1435–1443.
Vandermeer J.H. (ed.) 1989. The Ecology of Intercropping. Cambridge University Press, Cambridge, UK.
Walter L.E.F., Hartnett D.C., Hetrick B.A.D. and Schwab A.P.
1996. Interspecific nutrient transfer in a tallgrass prairie plant
community. Am. J. Bot. 83: 180–184.
Willey R.W. and Reddy M.S. 1981. A field technique for separating
above-ground and below-ground interactions in intercropping: an
experiment with pearl millet / groundnut. Exp. Agric. 17: 257–
264.