Vol.2, No.2, 49-55 (2011) Agricultural Sciences
Copyright © 2011 SciRes. Openly accessible at http: //www.scirp.org/journal/AS/
Nematode infestation and N-effect of legumes on soil
and crop yields in legume-sorghum rotations
Vincent Bado1*, Abdoulsalam Sawadogo2, Bouma Thio2, André B ationo3, Karim Traoré2,
Michel Cescas4
1Africa Rice Center (AfricaRice), Sahel Regional Station , Saint Louis , Senegal; *Corre sponding Author: V.Bado@cgiar.org
2Institut de l'Environnement et de Recherches Agricoles, Bobo-Dioulasso, Burkina Faso;
3The Tropical Soil Biology and Fertility Institute of International Center for T ropical Agriculture, Nairobi, Kenya;
4Département des Sols et Génie Agroalimentaire (FSSA), Université Laval Ste Foy Québec, Qué bec, Canada.
Received 28 June 2010; revised 24 March 2011; accepted 31 March 2011.
The effects of cowpea (Vignaunguiculata) and
groundnut (Arachis hypogea) on succeeding
sorghum yields, soil mineral N and nematode in-
festation were studied during five cropping sea-
sons (2000 to 2004) in a weakly acid Ultisol of
the agronomy research station of Farakô-Balo-
cated in the Guinean zone of Burkina Faso, West
Africa. A factorial 5 × 5 design of five crop rota-
tions with five fertilizer treatments in a split-plot
arrangement with four replications was used.
Sorghum yields were affected by the two factors
(rotation with legumes a nd fe rti l izer a ppl ications)
during the four years. But interactions were not
observed between the two factors. Monocrop-
ping of sorghum produced the lowest yields and
legume-sorghum rotations increased sorghum
yie l d s by 50% to 300%. Groundnut-sorghum and
cowpea-sorghum rotations increased soil mi-
neral N by 36% and 52%, respectively. Crop ro-
tation influenced nematode infestation but the
effects on soil and sorghum root infestation dif-
fered according to the rotation. The cowpeasor-
ghum rotation increased soil and sorghum root
infestationby nematodes while groundnut-sor-
ghum decreesed the nematode population. The
soil of the cowpea-sorghum rotation contained
1.5 to 2 times more nematodes than the soil of
the monocropping of sorghum. In contrast, the
soil of the groundnut-sorghum rotation con-
t ai ned from 17 to 19 tim es fewer nematodes than
that of themonocropping of sorghum. However,
nematode infestation did not affect any of the
succeeding sorghum yields. It was concluded
that the parasitic effect of nematodes was lim-
ited by the predominance of positive N-effects
on the development of succeeding sorghum.
Keywords: Legume; Nematode; Nitrogen; Crop
Rotation; Sorghum
In sub-Saharan Africa, crop yields are limited by
many factors such as nutrient deficiencies. Soils have
inherently low levels of nutrients because of low soil
organic matter levels and limited use of nutrient inputs
by farmers. Nitrogen (N) and phosphorous (P) deficien-
cies are the main soil fertility constraints in most of the
soils of West Africa [1]. Chemical fertilizers are im-
ported from developed countries and remain expensive
for poor small holders who therefore never use them or
only occasionally apply small quantities. While 73
kg·ha-1 of chemical fertilizers are used by farmers in
Asia, only 8 kg·ha-1 are used in Africa [2]. N2-fixing
legume crops can help improving soil fertility as sources
of nitrogen. Some legume crops such as groundnut
(Arachis hypogea L.) and cowpe a (Vignaunguiculata (L.)
Walp) are traditionally cultivated by farmers in rotation
or intercropping with cereals. Legume crops can supply
N for non-fixing cereals via biological nitrogen fixation.
In cropping syste ms, N2-fixing legumes can supply N to
the subsequent crops through fallen senescent leaves and
below ground parts, leading to an increase in succeeding
crop yield [3-5]. However, the improvement of soil N
content by legumes also creates favourable conditions
for the development of soil fauna such as parasitic ne-
matodes that could affect the succeeding crop. Some
legumes such as groundnut can reduce the population of
nematodes, while other legumes can increase nematode
infections [3]. In legume-cereal rotations, we can hypo-
thesize that a high population of parasitic nematodes
induced by a previous legume could probably reduce the
V. Bado et al. / A gricultural Sciences 2 (2011) 49-55
Copyright © 2011 SciRes. Openly accessible at http: //www.scirp.org/journal/AS/
development, N absorption (or N-effect) and the yields
of the succeeding crop. Conversely, legumes that can
reduce nematode infestation such as groundnut should
probably have a better N-effect on the succeeding crop.
Little research has been oriented on the interaction of
N-effect and nematode induced by legumes on soil and
succeeding crop. This research aimed to study the com-
bined effect of the two factors (N and nematode infesta-
tion) on soil and succeeding crop.
The study was undertaken through field experiments
carried out over five year s (2000-2004) at the agrono mic
research station of Farakô-Ba (4°20'West, 11°6'North
and 405 m altitude), located in the Guinean savannah
zone of Burkina Faso. This agro ecological zone has one
rainy season per year, starting in May-June and ending
in October. During the five cropping seasons of the ex-
periment, annual rainfall during the cropping seasons
varied from 1058 mm in year 2000 to 639 mm in year
2002 (Table 1). In general, planting dates occurred in
June and harvesting was carried out in October. The ex-
periment was laid down on a six -year-old fallow area on
an Ultisol, a weakly acid (pH/KCl: 5.6) sandy soil (74%)
with low clay (7%) and organic carbon (0.6%) contents.
Available P (P-Bray I: 5.6 mg·kg–1), Ca, Mg and ex-
changeable K and exchange capacity (ECEC: 1.8 coml.
+ kg–1 soil) were very low.
Two legume crops: groundnut (Arachis hypogea L.)
and cowpea (Vignaunguiculata (L) Walp) were used.
Improved varieties of groundnut (RMP-12) and cowpea
(KVX-61-1) recommended by the national agronomic
research institute (INERA) for the Guinean savannah
zone were sown with, respectively, planting densities of
62,500 and 125,000 plants per hectare. An improved
variety of sorghum (Sariaso) with a planting density of
62,500 plants per hectare was used.
A factorial 5 × 5 experiment in a split-plot experi-
mental design with randomised block arrangement and
four replications was used. The five crop rotations (Ta-
ble 2) were used as first factor in the main plots. Each
main plot was split intofive sub plots for different fer-
tilization treatments (PK, NPK, NPK + Dolomite, NPK
+ Manure and Control) employed as second factor.
Chemical fertilizers were applied at rates of 14 kg N ha–1,
10 kg P ha–1 and 11 kg K ha–1 to the two legumes using
complex NPK fertilizer, triple super phosphate and po-
tassium chloride. For the manure-containing treatments,
three tonnes per hectare of air-dried cattle manure were
applied. Cattle manure contained 1.8%, 18.40%, 0.31%
and 0.16%, respectively, of N, C, P and K. In the dolo-
mite-containing treatments, one tonne ha–1 of dolomite
(249 kg ha–1 of Ca and 114 kg ha–1 of Mg) were used.
Except for urea, all fertilizer s were applied at sowing.
Nitrogen fertilizers were split on sorghum plots: 14 kg
N–1 with NPK fertiliser at sowing and 23 kg N ha–1 40
days after sowing (DAS). Legumes were not inoculated.
As regards farmer ’s traditional practices, the residues of
Table 1. Monthly and annual rainfall at Farakô-Ba during the five years of the ex-
2000 60 172 236 309 241 41 1059
2002 58 65 184 175 125 32 639
11 3
11 8
Table 2. Rotation of the three crops of the six treatments during the five years (2000-2004) of ex-
Crop rotations
Sorghum-groundnut Sorghum Groundnut Sorghum Groundnut Sorghum
V. Bado et al. / Agricultural Sciences 2 (2011) 49-55 51
Copyright © 2011 SciRes. Openly accessible at http: //www.scirp.org/journal/AS/
sorghum and legumes are exported at the end of each
season. Only the senescent leaves and residues of roots
of the below ground parts remain as a source of organic
residues recycled in the soil.
The N-effects of legumes were evaluated by soil N
mineralization (
) during the first two
months of the second cropping season (2001) after one
season of rotation. Soil samples were taken in the first
20 cm layer at sowing, 9, 20, 30, 40 and 53 days after
sowing. All sub-plots of the five fertilizer treatments
were sampled. Soil samples were taken in sorghum
plots of three rotations (sorghum-sorghum, cowpea-
sorghum and groundnut-sorghum). Mineral N was ex-
tracted with 1M KCl solution and measured by the col-
orimetric method [6].
Nematode populations were assessed dur ing the crop-
ping season of 2001. All sub-plots of the five fertilizer
treatments were sampled. Soil samples were taken in
sorghum plots of the three rotations (sorghum-sorghum,
cowpea-sorghum and groundnut-sorghum). Soil and root
samples of sorghum were removed at 30 and 90 days
after sowing, and nematodes were extracted and meas-
ured using the methodology described by Seinhorst [7].
Many zero values and high coefficient of variation were
observed, particularly on sorghum root infestation by
nematodes. Thus, logarithmic function Eq.1 was used
for data transformation before statistic analysis [8].
y = log x + 1 (1)
x was the number of nematodes and y the transformed
Agronomic data of sorghum yields were first analyzed
per year using the Fisher test for comparison of treat-
ment effects [8]. Then, the global effects of the four
years were analyzed using the year as a factor. The rota-
tions and fertilizers were used as first and second factors,
3.1. Nematode Infestation
The effects of crop rotations on soil and sorghum
roots infestation by nematodes are presented on (Table
3). Fourgroups of nematodes (Pratylenchus, Scutel-
lonema, Helycotylenchus and Trychodorus) were identi-
fied in the soil. The two most important groups identi-
fied in the soil were Helicotylenchus (55%) and Scute-
lonema (34%). But only two groups (Pratylenchus and
Scutelloma) were identified on sorghum roots. However,
sorghum roots were mainly infested by Pratylenchus
(80%) and Scutelonema (20%) at 30 days after sowing
and by Pratylenchusonly at 90 days after sowing. But
soil and roots infestation by nematodes was not affected
by fertilizer application (data not shown). Only crop
rotation affected soil and roots infestation (p < 0.01) by
nematodes and interactions were not observed between
these two factors. Otherwise, variation in the populations
of nema t ode s wa s due to crop r ot a tions.
Groundnu t and cowpea had opposite effects in the soil
and on the succeeding sorghum root infestation by
nematodes. Compared to the groundnut-sorghum rotation,
a cowpea-sorghum rotationincreased soil (p < 0.01) and
sorghum roots (p < 0.01) infestationby the three groups
of nematodes (Pratylenchus, Scutellonema, Helycotylen-
chus). The soil of the cowpea-sorghum rotation contained
1.5 to 2 times more nematodes than the soil used for-
mono cropping of sorghum. As for cowpea-sorghum ro-
tation, the monocropping of sorghum also increased the
population of Pratylenchus and Scutellonemain the soil
and differences were not observed between the two rota-
tions. On the other hand, groundnut decreased the inci-
dence of the four nematodes in the soil. In ground-
nut-sorghum rotations, the soil contained from 17 to 19
times fewer nematodes than cowpea-sorghum and Môn
3.2. Soil Mineral Nitrogen
For all rotation treatments, soil mineral N decreased
rapidly during the season (Fi g u re 1 ). The first rains of the
season induced a resurgence of microbial activity leading
to a “mineralization flush” of soil organic nitrogen and
increases in mineral N. The mineral N decline can be ex-
plained by the decrease of the mineralization of soil or-
ganic residues, by N uptake by plants, N leaching and
other losses of N. The mineralization of soil organic resi-
dues started with the first rains of the season and de-
creased over time, as indicated by mineral N decreases.
Throughout the season, fertilizer applications did not
affect soil mineral N. However, soil mineral N was af-
fected (p < 0.05) by crop rotation at the start of season (1 -
20 days after sowing) and no interaction was observed
between fert il ize r a nd rotation. During thi s fi rst pe riod ( 1 -
20 days after sowing), the presence of legumes in the
cropping systems increased soil mineral N (p < 0.05) and
differences were not observed between the two legumes
(Fig ure 1). At sowing, soil mineral N varied from 4 2 k g N
ha–1 in monocropping of sorghum to 55 and 62 kg N ha–1
when sorghum was rotated with groundnut and cowpea,
respectively. Otherwise, groundnut-sorghum and cow-
pea-sorghum rotations increased soil mineral N from 36%
and 52%, respe cti vely.
3.3. Sorghum Yields
During the first season (absence of rotation effect),
only the effects of fertilizers were measured. The effects
52 V. Bado et al. / Agricultural Sciences 2 (2011) 49-55
Copyright © 2011 SciRes. Openly accessible at http: //www.scirp.org/journal/AS/
Table 3. Effects of crop rotation with legumes (groundnut-sorghum, cowpea-sorghum) and monocropping of sorghum on soil
(nematodes/dm3 of soil) and sorghum roots (nematodes/g) infestationby nematodes at 30 and 90 days after sowing in 2001.
Daysaftersowing Croprotations Pratylenchus Scutellonema Helycotylenchus Trychodorus Total
Nematodes in
the soil
Groundnut-sorghum 5 c 130 c 97 c 62 b 158 c
157 ab
1138 ab
3157 a
55 bc
3212 a
Sorghum-sorghum 175 a 1228 a 843 b 377 a 1220 b
53 c
135 c
510 c
905 c
518 a
1213 a
3532 a
5880 a
407 ab
940 ab
1892 b
3360 b
Nematodes in
sorghum roots
Groundnut-sorghum 8 c 4 c 0 0 12 c
389 a
60 ab
449 a
160 ab
72 a
232 ab
4 c
4 c
90 Cowpea-sorghum 109 a 0 0 0 109 a
69 ab
69 ab
Values affected by the same letter in the same column are not significantly different at p < 0.05, according to Fisher’s test
19 2030 40 53
D a ys after sowing
Kg N ha-1
Figure 1. Effects of monocropping of sorghum, cowpea-sorghum and groundnut-sorghum
rotations on soil mineral N during the 53 days after sowing in year 2001.
of rotations were evaluated over the next four years
(2001-2004). Sorghum grain yields were affected (p <
0.001) by fertilizer applications, crop rotations and years
(Fi g u re s 2 and 3). However, interactions were not ob-
served between rotations and fertilizers, indicating that
previous legumes (rotations) affected sorghum yields
whether fertilizers are applied or not, and conversely.
Interaction was not observed between year and fertilizer,
showing good responses to fertilizer whatever the rain-
fall in a given seaso n.
During the first year, sorghum produced high yields
even when fertilizers were not applied wh ile yields were
very low during the final two years (Fi gu re 2). This can
be explained by the positive effects of the previous fal-
low in the first year of cultivation and the subsequent
nutrient decrease. In the absence of fertilizer, soil nutri-
ents are exported, leading to declining fertility and yield
decrease during the next four years [9]. Chemical NPK
fertilisation alone increased sorghum grain yields in the
presence of this low soil fertility, thereby indicating
good response to chemical fertilizer [1,9,10]. Applica-
tion of chemical NPK fertilizer associated with manure
produced the highest yields during the five years of this
experiment. Similar results relating to the beneficial ef-
fects of chemical and organic fertilizers on crop yields
have been reported, although they are usually attributed
to the role of organic materials both in correcting soil
acidity and acting as a source of nutrients [1,9,11].
Kg N ha
V. Bado et al. / Agricultural Sciences 2 (2011) 49-55 53
Copyright © 2011 SciRes. Openly accessible at http: //www.scirp.org/journal/AS/
2000 2001 2002 2003 2004
Grain yields (kg ha-1)
Figure 2. Effect of fertilizer applications on three rotations (cowpea-sorghum, groundnut-sorghum and sorg-
hum-sorghum) on sorghum grain yields during four years (2001-2004).
Cow- So r g
Cr op Rota tion s
Grain Yields (kg ha-1)
Cow- So r g
Cr op Rota tion s
Grain Yields (kg ha-1)
Cr op Rota tion s
Grain Yields (kg ha-1)
Cow- So r g
Cr op Rota tion s
Grain Yields (kg ha-1)
Figure 3. Effect of monocropping of sorghum and rotations with legumes (groundnut-sorghum and cow-
pea-sorghum) on sorghum grain yields during four years (2001-2004). Cow-Sorg = cowpea-sorghum; Grou-Sorg =
groundnut-sorghum; Sorg -Sorg = sorghum-sorghum.
Ye ar 2001
Year 2002
Ye ar 2003
Ye ar 2004
Grain yields (kg ha
Grain yields (kg ha
Grain yields (kg ha
Grain yields (kg ha
Grain yields (kg ha
54 V. Bado et al. / Agricultural Sciences 2 (2011) 49-55
Copyright © 2011 SciRes. Openly accessible at http: //www.scirp.org/journal/AS/
An interaction was only observed between years and
rotation. The distribution of rainfall seemed to be more
important than the quantity of water received during the
season. For example, the highest grain yields were ob-
tained in 2001 and 2002 when there was good distribu-
tion of rains, particularly in September and August, even
though the total rainfall was lowest of the five years of
the experiment.
Mono cropping of sorghum produced the lowest
yields during the four years, and rotation of sorghum
with legumes increased sorghum yields by from 50% to
300% compared to monocropping (Figure 3). The ef-
fects of legumes were particularly noticeable during the
first year of rotation (2001). Sorghum grain yields in-
creased from 0.9 tonnes ha–1 in monocropping of sor-
ghum to 1.7 and 2.0 tonnes ha–1 when sorghum was ro-
tated with groundnut and cowpea, respectively. Except
for one year (2002), sorghum yields were higher in
cowpea-sorghum than a groundnut-sorghum rotation.
The two legumes increased soil mineral N during the
first weeks of the cropping season. Legume residues
provided more organic N, a source of mineral N for the
succeeding crop [12]. Despite the exportation of legume
shoots, the remaining crop residues and the below
ground part of legumes can improve organic matter of
the topsoil. Compared to sorghum, the residues of leg-
umes are of better quality. As shown by soil mineral N,
they better contributed to supplying more N in leg-
ume-sorghum rotations. Giller et al. [13] estimated that
15% to 20% of the nitrogen of legumes is recycled for
the succeeding crop by legume residues. The positive
interaction between organic and mineral N can justify
the effecti veness of legume on N upt ake by sorghum.
Our data confirmed the differences between the two
legumes on soil and roots infestation by nematodes. As
observed by other studies, cowpea increased nematode
infestation [14], while groundnut decreased the popula-
tion of nematodes [3,15,16]. The biological effects of
legumes are complex [17] but our results showed that
the N-effect seemed to be the most important factor
governing sorghum response to crop rotation. Nitrogen
and P are known to be the most limiting factors of Al-
fisols and Ultisols of West Africa [1,5]. Legumes can
also improve other soil properties such aspH of acid
soils, microbial N and fungal biomass in the rhizosphere
[17]. In the sensitive rainfed ecosystem of West Africa,
the mineral N supplied by legume residues at the start of
the season as a basal source of N can explain the good
development and yields of sorghum. The good soil con-
ditions created by legume residues such as cowpea can
assist the development of nematodes. The infestation by
nematodes was lowest in a groundnut-sorghum rotation,
probably because groundnut is not a favourable host for
nematodes of sorghum [3]. Despite high infestation
(cowpea) or reduction in nematode population (ground-
nut), nematodes didn’t affect sorghum yields and no re-
lationship was observed between sorghum yields and
nematode densities in soil or sorghum roots. The better
growth of sorghum in legume-sorghum rotations domi-
nated or limited the effects of nematodes. The quantity
and quality (organic N) supplied by the residues of leg-
umes improve soil N, biological properties and avail-
ability of other nutrients, leading to better growth and
good health for the succeeding sorghum. As reported
inprevious work, subsequent cereal yields are usually
increased in legume-cereal rotations [3,4,18] as a con-
sequence of mineral N provided by mineralization of
legume residues [19-22] and the improvement of soil
biological properties and availability of nutrients [17].
Then, despite the increase of the population of nema-
todes, the succeeding sorghum benefits from good nu-
triational conditions and has quicker and better growth,
particularly during the first period of the season. Other-
wise, the highest yields in cowpea-sorghum rotations
explained the predominance of N-effect on the negative
effects of parasitic nematodes.
Compared to the monocropping of sorghum, the two
legumes (cowpea and groundnut) increased N uptake by
succeeding sorghum as a consequence of organic N sup-
plied by legume residues (fallen senescent leaves and
below ground parts). Groundnut remains the most effec-
tive legume for reducing nematode infestation. Cowpea,
on the other hand, increased nematode infestation, but
because of the predominance of the N-effect of legume
residues and the improvement in physical, chemical and
biological conditions of the soil by legume residues,
nematode infestation did not affect the productivity of
the succeeding sorghum.
This study was partly funded by the International Atomic Energy
Agency (IAEA) under IAEA Contract BKF-10952. This research was
conducted as part of FAO/IAEA Coordinated Research Project on
Tropical Acid Soils. The authors are grateful to IAEA, FAO/IAEA
division and Dr. F. Zapata, Project Officer for his assistance.
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