African Crop Science Journal
African Crop Science Society
ISSN: 1021-9730 EISSN: 2072-6589
Vol. 9, Num. 3, 2001, pp. 487-497
African Crop Science Journal, Vol. 9. No. 3, pp. 487-497
EFFECT OF MAIZE DENSITY, BEAN CULTIVAR AND BEAN SPATIAL
ARRANGEMENT ON INTERCROP PERFORMANCE
A. MUTUNGAMIRI, I.K. MARIGA and O.A. CHIVINGE
Department of Crop Science, University of Zimbabwe, P.O.Box MP 167, Mount
Pleasant, Harare, Zimbabwe
Received 17 August, 2000
Accepted 9 March, 2001
Code Number: cs01068
On-farm trials to determine the optimum combination of maize (Zea mays L.)
density, bean (Phaseolus vulgaris L.) cultivar and bean spatial arrangement
to produce high yields of the intercrop combination were conducted in Chinyika
Resettlement Area (CRA) and at Domboshava Training Centre (DTC) during the 1996/97
and 1997/98 rainy seasons. The effects of maize at 37, 000 and 24, 000 plants
ha-1, bean cultivars 'Natal Sugar' and 'Carioca',
and bean arranged in one or two rows between rows of maize or bean planted in
the same row as maize were evaluated in a completed factorial arrangement. Maize
density, bean cultivar, bean spatial arrangement and their interactions significantly
(P<0.01) affected maize and bean grain yields at both locations for the two
seasons. Changing the maize density from 90 x 45 cm (24000 plants ha-1)
to 90 x 30 cm (37000 plants ha-1) increased maize yield by 28 and
39% and reduced bean yields by 11 and 18% in the respective seasons. Maize yield
was 19% less when intercropped with Natal Sugar than with Carioca. Same row
and one row bean cultivar arrangements produced similar maize yields. Land equivalent
ratios (LER) were greater than one for all but one intercrop arrangements at
CRA but less frequently at DTC. The maize density of 90 x 30 cm with Carioca
in the same row as maize produced the highest LER value at all sites, 1.73 at
Chinyudze, and 1.53 at Domboshava. The same treatment gave the highest
gross return ofZ$12 649 ha-1 at CRA. Carioca planted in the same
row as maize at the maize density of 37,000 plants ha-1 is the most
ideal approach to dryland maize/bean intercropping since it achieved high yields
and allows easy weeding.
Key Words: Bean/maize, intercropping, plant arrangement, Zimbabwe
Des études en champs pour déterminer les combinaisons optimales
de densité de variétés de maïs (Zea mays L.),
et l'arrangement spatial de haricots (Phaseolus vulgaris L.) pour
des rendements élevés de la culture intercalaire étaient
conduites à Chinyika Resettlement Area (CRA) et a Domboshava Training
Centre (DTC) durant les saisons pluvieuses de 1996/97 et 1997/98. L'impact
de plantes de maïs à 37000 et 24000 plantes ha-1 et des
variétés de " Natal sugar" et "carioca" de haricots plantées
dans et entre les lignes de maïs était évalué dans
une disposition du type factoriel. La densité de maïs et de haricots,
leurs arrangements spatiaux et leurs intéractions ont affecté
de manière significative (P<0.01) leurs rendements aux deux endroits
pour les deux saisons. La substitution de la densité de maïs de
90 x 45 cm (24000 plantes ha-1) par 90 x 30 cm (37000 plantes ha-1)
a augmenté le rendement de maïs de 28 et 39% et a réduit
le rendement de haricots de 11 et 18% pour les saisons pluvieuses de 1996/97
et 1997/98, respectivement. Le rendement de maïs était réduit
de 19% quand il était cultivé ensemble avec le "Natal sugar" qu'avec
"carioca". La même ligne et une ligne de haricots ont produit des rendements
en maïs identiques. Le taux de terres équivalentes était
supérieur à 1 partout à l'exception de la combinaison
(maïs - haricots) au CRA. La densité de 90 x 30 cm avec carioca
sur la même ligne que le maïs a produit la valeur la plus élevée
de taux de terre equivalent aux deux endroits. La valeur du taux de terres équivalentes
était de 1,73 à Chinyudze et 1,53 à Domboshava. Ce même
traitement a produit un prix de revient de Z$ 12649 ha-1 à
CRA. Le haricot "Cariora" planté sur la même ligne que le maïs
avec une densité de 37000 plantes ha-1 représenté
l'approche idéale pour les maïs / haricots intercalés
de régions arides parce qu'elle permet de réaliser un rendement
élevé et un facile sarclage.
Mots Clés: Haricots/maïs, culture intercalée, arrangement
des plantes, Zimbabwe
Maize/bean is a predominant cropping system in most parts of Africa (Francis
et al., 1982). Productivity of a cropping system comprising intercrops
of two or more species depends upon the degree of complementarity between
them. Enhancing productivity of maize and bean intercrops requires improving
the interspecies complementarity or reducing competition effects (Rezende
and Ramalho, 1994). This might be achieved through manipulation of plant arrangements,
plant densities and planting compatible cultivars (Rao and Mittra, 1990).
Ofori and Stem (1987) proposed that the growth and yield of the legume component
is reduced markedly when intercropped with high densities of the cereal component.
In a maize/bean intercrop system, increasing maize density three-fold, from
18, 000 to 55, 000 plants ha-1, reduced bean leaf area by
24% and seed yield by 70% (Gardiner and Craker, 1981).
Spatial arrangement of component crops is one of the most important agronomic
factors that determine whether an intercrop system will be advantageous or
not with regard to yield gains (Natarajan and Shumba, 1990). Row arrangements,
in contrast to arrangements of component crops within rows, improves the amount
of light transmitted to the lower legume. Such arrangements can enhance legume
yields and efficiency in cereal/legume intercrop systems (Mohta and De, 1980).
Most intercropping research in Zimbabwe has focused on spatial arrangement
of inter-row intercrops with little attention to intra-row intercropping (Mutungamiri,
1999). The adoption of inter-row intercropping practices by small-scale farmers
is rather limited perhaps because the practice is relatively labour-intensive.
In contrast, intra-row intercropping may reduce total labour demand since
planting of both species can be done simultaneously, and other cultural practices,
such as weeding by ox-drawn cultivators, are possible (Nyakanda et al.,
1995). Smallholder farmers in Zimbabwe practise intra-row intercropping
to facilitate ox-drawn cultivation and to protect beans from rain drop impact,
thereby minimising bean flower dropping (Munguri, 1996).
Cultivars which minimise intercrop competition and maximise complementary
effects are suitable for intercropping (Rao and Mittra, 1990). Productivity
of the intercrop can be enhanced through selection of bean cultivars suitable
for intercropping as they have different growth habits and growth durations,
which may result in different interactions with maize in the intercrop. In
Zimbabwe, farmers tend to mostly grow one specific bean cultivar, Natal Sugar,
despite considerable evidence indicating that other bean varieties exhibit
superior adaptation to dryland maize/bean intercropping (Mariga and Munetsi,
1990). Maize cultivars with short internodes and broad leaves shade beans
relatively more than cultivars of a similar height with long internodes and
narrow leaves. Tall cultivars generally give more shadding to understorey
crops (Davis and Garcia, 1983).
This study was undertaken to determine the optimum combination of maize density,
bean cultivar and bean spatial arrangement suitable for high yields of the
maize/bean intercrop combination.
MATERIALS AND METHODS
The experiment was conducted during the 1996/97 and 1997/98 rainy seasons
at Chinyudze in Chinyika Resettlement Area (CRA) and at Domboshava Training
Centre (DTC). The Resettlement lies between 32° 05' and
32° 44' East and between 18° 00' and 18° 20'
South in the eastern part of Zimbabwe. Its altitude ranges from 1,200 m above
sea level in the west to 1,700 m in the east. The Training Centre is situated
at 31° 10' East and 18° 25' South in central
Zimbabwe at an altitude of 1,500 m above sea level. Both CRA and DTC are high
potential areas with mean annual rainfall in the range of 700 - 1000 mm. The
trials were planted in the first week of December in both seasons.
The effects of maize population, bean cultivars, and bean spatial arrangement
were evaluated in a complete 2 x 2 x 3 factorial arrangement in a randomised
complete block design. An early maturing (140 days) 3- way maize hybrid "SC5Ol"
was planted at 90 x 30 cm and 90 x 45 cm for plant densities of 37,000
and 24,000 plants ha-1. The indeterminate, bushy bean cultivars
were Natal Sugar and Carioca. Bean spatial arrangements included: one (SAl)
or two (SA2) rows between rows of maize and bean planted in the same row as
maize (SA3). Within row spacing of bean was 10 cm giving population densities
of 111,111 for the one row and within row arrangements and 222,222 for the
two row arrangement. Sole crop treatments included maize at the two planting
arrangements and the two bean cultivars planted at 45 x 10 cm spacing. Thus,
16 treatments were tested in three replicates.
Intercrop plots had four maize rows, 6 m long (21.6 m2) and three,
four or six rows of beans for spatial arrangements one row, within row and
two rows, respectively. Pure stand plots had either four rows of maize or
eight rows of beans. The harvested area for maize comprised the two central
rows excluding 1 m at each end (7.2 m2). The harvested area for
beans in sole stands comprised the four central rows excluding 1 m at each
end (7.2 m2). The intercrop harvested area for beans was either
(3.6 m2) for one and two or (7.2 m2) for within row.
Compound D fertiliser (8% N, 14% P205, 7% K20
and 6.5% S) was station placed (dolloped) on maize at planting at 300
kg ha-1. Ammonium nitrate (34.5% N) was topdressed at 250 kg ha-1
at five weeks after crop emergence (WACE). The trials were hand weeded
using a hoe, twice at two and five WACE. Dipterex (2.5% trichlorfon
a.i.) was applied to maize at five WACE to control maize stalk borer (Busseola
Grain yields of beans and maize were determined at 12.5 % moisture content.
Analysis of variance was performed on grain yield and monetary value for all
treatments using the MSTATC Statistical computer package. Farm-gate prices
for maize (Z$l ,200 for 1996/97 and Z$2,400 t -1 for 1997/98) and
bean (Z$7,000 for 1996/97 and Z$12,000 t-1 for 1997/98) were used
in the analysis of monetary benefits. Biological performance of the intercrop
treatments was evaluated using the land equivalent ratio (LER) method (Mead
and Willey, 1980).
The three main effects, maize density, bean cultivar and bean spatial arrangement,
had significant (P<0.01) effects on maize and bean grain yields during
both seasons. There were also significant (P<0.01) interaction effects
of maize density x bean cultivar, maize density x bean arrangement, and bean
cultivar x bean arrangement on maize and bean grain yields in both seasons.
Bean yield. Bean yields were generally more with lower maize density
x bean cultivar interaction effects at DTC in 1996/97 and Chinyudze in 1997/98
(Table 1). At DTC, Carioca performed
poorly and gave the least yields with the lower maize density. At Chinyudze,
the interaction effects were significant because the magnitude of cultivar
effects differed for the two maize densities. Interaction effects of maize
spacing x bean spatial arrangement were significant (P<0.01) for bean grain
yields during both seasons at DTC and Chinyudze. At both maize densities,
two rows of beans between maize rows out-yielded the other bean spatial arrangements
at both sites in 1996/97 season (Table 2).
However, with maize a spacing of 90 x 30 cm, one row and same row arrangements
produced similar yields whilst the one row achieved the lowest bean yield
at 90 x 45 cm maize spacing at DTC in the 1996/97 season. At Chinyudze the
same row arrangement achieved similar bean yields at both maize densities,
but higher and lower yield levels than the one and two row arrangements, respectively.
The two row arrangement of Natal Sugar out-yielded all the other combinations
at both sites in the 1996/97 season (Table
3). One row of Carioca produced the lowest yield at DTC. Two rows of Carioca
and Carioca planted in the same row with maize gave similar yields. At Chinyudze,
one row and same row arrangements of Carioca gave similar yields at this site.
Carioca generally achieved higher bean yields than Natal Sugar at the three
spatial arrangements in the 1997/98 season (Table
4). At Chinyudze, Natal Sugar and Carioca produced similar yields at the
one row arrangement, but, at the two row and same row arrangements, Carioca
out-yielded Natal Sugar. The two row arrangement achieved the highest bean
yields for each variety at both sites (Table
4). A serious outbreak of Ascochyta phaseolorum in Carioca at DTC
resulted in low bean yield in the 1996/97 season.
Maize yield. Maize density x bean cultivar interaction effects were
significant (P<0.01) for maize yields at DTC and Chinyudze in the 1996/97
season (Table 5). At both
sites and at both maize densities, maize intercropped with Carioca resulted
in higher maize yields than with Natal Sugar. Maize yields were significantly
(P<0.05) lower at 90 x 45 cm spacing than at 90 x 30 cm at both
sites for both bean cultivars. At each site, maize at 90 x 30 cm intercropped
with Carioca gave the highest yields.
Interaction effects of maize density x bean spatial arrangement on maize yield
were significant (P<0.0l) at DTC and Chinyudze in the 1996/97 season (Table
6). Maize at 90 x 30 cm spacing with one row of beans produced the highest
maize yields at both sites. Maize planted in the same row with beans and maize
with one row of beans in between at the 90 x 45 cm maize density gave similar
yields at DTC. The three spatial arrangements at 90 x 30 cm maize spacing
resulted in higher maize yields than at 90 x 45 cm maize spacing. The lowest
maize yields were achieved for treatments of maize spaced at 90 x 45 cm and
intercropped with two rows of beans at DTC, and with beans in the same row
Significant (P<0.01) bean cultivar x bean spatial arrangement interaction
effects at DTC and Chinyudze in the 1996/97 season were observed in the different
maize grain yields responses in the presence of the two factors (Table
7). At DTC, the presence of two rows of Natal Sugar and maize in the same
row resulted in similar maize yields which were significantly (P<0.05)
lower than that of the one row arrangement. The intercrops with Carioca resulted
in higher maize yields than with Natal sugar at Chinyudze. The one row arrangement
with Carioca gave the highest maize yields at each site.
At both locations in the 1997/98 season, one row arrangement at 90 x 30
cm maize density resulted in the highest maize yield (Table
8). At DTC, one row and two row arrangements at 90 x 45 cm resulted in
similar maize yields. Two rows and same row arrangements at 90 x 30 cm at
Chinyudze resulted in similar yields. The 90 x 45 cm spacing achieved lower
maize yields than the 90 x 30 cm spacing at all bean spatial arrangements.
For either bean variety, intercropping with maize at 90 x 30 cm resulted
in higher maize yields than at 90 x 45 cm at Chinyudze in 1997/98 season (Table
9). Carioca with maize at 90 x 30 cm resulted in the highest maize yields;
with maize at 90 x 45 cm Carioca also resulted in higher maize yields. Carioca
planted in the same row with maize gave the highest maize yield compared to
other arrangements at DTC in 1997/9 8 season (Table
10). Significant bean cultivar x bean arrangement interaction effects
on maize were apparent.
In the 1996/97 season, at Chinyudze, the partial LER values for maize show
that sole crop maize at 90 x 30 cm out-yielded maize in all the maize/bean
intercropping combinations, but, at DTC, sole crop maize exhibited a lower
yield than intercrop maize with one row of Carioca in between maize rows (Table
11). The partial LER values for beans generally indicate that two rows
of beans in between maize rows gave higher yields than the other spatial arrangements.
In the 1996/97 season intercropping had an advantage over monocropping at
Chinyudze whilst most of the treatments had LER values below 1 at DTC. The
partial LER values for beans were notably lower at DTC compared to those for
Chinyudze. In the 1997/98 season the sole crop maize at the standard maize
spacing of 90 x 30 cm out-yielded maize in all the maize bean intercropping
combinations. SC5O1 at 90 x 45 cm with two rows of Natal Sugar gave the highest
LER value of 1.56 and SC5O1 at 90 x 45 cm with one row of Natal Sugar gave
the lowest LER value of 0.97.
At DTC, treatment 4 (SC5O1 at 90 x 45 cm + 2 rows Natal Sugar) gave the
highest return of Z$6,746 but was significantly different (P>0.05) from
the return produced by treatment 5 (SC5O1 at 90 x 30 cm + 1 row Carioca (Table
12). The sole crop treatments generally gave lower returns than the intercrop
treatments except for sole crop maize at 90 x 30 cm which gave similar yields
as the intercrop treatments at Chinyudze. Treatment 10 (SC5O1 at 90 x 30 cm
+ Carioca in the same row as maize) produced the highest return of Z$12,649
at Chinyudze. This treatment was not significantly different from treatment
1 (SC5O1 at 90 x 30 cm + I row Natal Sugar).
Results from this research clearly show that farmers must strive to achieve
the currently recommended 37,000 plants ha-1 in maize, sole or
intercropped, in order to optimise total productivity.
The three parameters tested in this trial did not exhibit simple relationships.
The bean spatial arrangements of two bean rows in between maize rows and beans
planted in the same row as maize gave lower maize yields than where beans
were planted in alternate rows with maize. The results therefore suggest that
a bean spatial arrangement of one bean row in between maize rows was less
competitive to maize in the intercrop. In addition, the first two bean spatial
arrangements place the bean plants closer to the maize plants, thus increasing
inter-component plant competition. The closer intimacy increased the effects
of competition on maize. However, the one row arrangement hinders the use
of ox-drawn cultivation of the maize crop and is thus unlikely to be adopted
by farmers except on very small farms were hand-weeding is most appropriate
or at least by non-cattle owners.
Natal Sugar depressed maize yields more than Carioca. Similar results were
reported by Mariga and Munetsi (1990). An ideal legume would be one with a
reduced competitive effect on the companion cereal, but at the same time showing
high productivity. Farmers are more likely to consider using Carioca since
it is less competitive to maize which they consider to be their main crop.
However Carioca's high susceptibility to disease during wet weather
may necessitate the development of alternative bean cultivars for dryland
Plots comprising of 90 x 45 cm maize density with two rows of beans in between
gave the highest bean yields compared to other intercrops. Here the bean population
had the advantage of high density and reduced competition from maize. Mwaipaya
(1990) suggested that beans are more likely to benefit from the fertiliser
applied to the maize in this arrangement. However, this planting arrangement
too may not be attractive to farmers since it hinders ox-drawn cultivation
and besides, maize yields were significantly reduced in this treatment. Improved
technologies that increase productivity (yields) of the secondary crop but
reduce yields of the main crop are unlikely to be adopted by farmers. However,
in the case of small-holder farmers in Zimbabwe where farmers only intercrop
part of their maize crop, the monetary value of minor intercrops may sometimes
more than compensate for the reduction in maize yields. For example, the market
prices for maize and beans in the year 2000 were Z$5, 500 and Z$35, 000 to
Z$40, 000 ton-1 for the respective crops. This particular planting
arrangement should also be attractive to non-cattle owners who cannot use
ox-drawn cultivators. In the 1997/98, season the 90 x 30 cm maize density
with two rows of Carioca in between maize rows and Carioca in the same row
with maize gave the highest gross outputs. An argument commonly advanced against
intercropping in Zimbabwe is that it makes weeding difficult but with beans
planted in the same row as maize, weeding should be easy as it permits use
of oxen drawn cultivators which are commonly used in the small-holder sector.
Labour demand is also reduced as planting of both component crops can be done
at the same time.
Most LER values at DTC were below 1. This was not due to treatment effects
but was caused by high rainfall which resulted in rotting of some bean pods
and maize kernels. This observation shows the importance of the contribution
of the minor legume to the overall intercrop LER value. The results at Chinyudze,
however, indicate that maize/bean intercropping is more efficient than growing
sole crops of maize and beans. This probably suggests that intercropping facilitated
more efficient exploitation of available resources by the crops, resulting
in greater total yields and gross return.
The bean cultivar Carioca planted in the same row as maize and at the recommended
maize spacing of 90 x 30 cm is the suitable crop density for dryland maize/bean
intercropping since it achieved high yields and also facilitates weeding. Reducing
maize density to 24,700 plants ha-1 for maize/bean intercropping
or sole cropping is not recommended. For non cattle owners and those who would
want to carry out maize/bean intercrop on a small area the spatial arrangement
of two bean rows in between maize rows at the 90 x 30 cm is recommended. Similar
studies in future should involve detailed economic analysis and farmer evaluations.
More work should be focused on the spatial arrangement of the legume to generate
data for a more definitive recommendation.
This study was part of an MPhil study programme of the first author. The authors
are grateful to the Rockefeller Foundation'Forum on Agricultural Resource
Husbandry for funding the study.
Davis , J.H.C. and Garcia, S. 1983. Competitive ability and growth habit
of indeterminate beans and maize for intercropping. Field Crops Research
Francis, C.A., Prager, M. and Tejada, G. 1982. Effects of relative planting
dates in bean (Phaseolus vulgaris L.) and maize (Zea mays
L.) intercropping patterns. Field Crops Research 5:45-54.
Gardiner, T.R. and Craker, L.E. 1981. Bean growth and light interception
in a bean/maize intercrop. Field Crops Research 4:313-320.
Mariga, I.K. and Munetsi, M. 1990. Performance of cereal-bean intercrops
on sandy soils on the Zimbabwean highveld: Preliminary results. Zimbabwe,
Journal of Agriculture Research 28: 139-144.
Mead, R. and Willey, R.W. 1980. The concept of a land equivalent ratio
and advantages in yields from intercropping. Experimental Agriculture
Mohta, N.K. and De, R. 1980. Intercropping maize and sorghum with
soyabean. Journal of Agricultural Science 95:117-122.
Munguri, M.W. 1996. Inorganic fertilizer and cattle manure management
for dryland maize production under low input condition. Master of Philosophy
Thesis, University of Zimbabwe. 170 pp.
Mutungamiri, A. 1999. Effect of spatial arrangement, plant density, maize
and bean genotype on maize/bean intercrop performance. Master of Philosophy
Thesis, University of Zimbabwe. l56 pp.
Mwaipaya, A.M. 1990. Intercropping research experience in Zambia. In:
Research Methods for Cereal/Legume Intercropping. Proceedings of a Workshop
on Research Methods for Cereal/Legume Intercropping in Eastern and Southern
Africa. Waddington, S.R.,Palmer, A.F.E. and Edje, O.T. (Eds.), pp.184-189.
CIMMYT, Harare, Zimbabwe.
Natarajan, M. and Shumba, E.M. 1990. Intercropping research in Zimbabwe:
Current status and outlook for the future. In: Research Methods for Cereal/Legume
Intercropping. Proceedings of a Workshop on Research Methods for Cereal/Legume
Intercropping in Eastern and Southern Africa. Waddington, S.R., Palmer,
A.F.E. and Edje, O.T. (Eds.), pp. 190-193. CIMMYT, Harare, Zimbabwe.
Nyakanda, C., Mashingaidze, A.B. and Kurambwa, G. 1995. Effect of maize/groundnut
intra-and inter-row spatial arrangements on yield and weed pressure. Transactions
of the Zimbabwe Scientific Association 69:20-23.
Ofori, F. and Stem, W.R. 1987. Cereal-legume intercropping systems. Advances
in Agronomy 41:41-89.
Rao, L.J. and Mittra, B.N. 1990. Evaluation of groundnut (Arachis
hypogea) genotypes for intercropping with two types of pigeon pea (Cajanus
cajan). Journal of Agricultural Science 115:337-342.
Rezende, G.D.S.P. and Ramalho, M.A.P. 1994. Competitive ability of maize
and common bean (Phaseolus vulgaris) cultivars intercropped in different
environments. Journal of Agricultural Science 123:185-190.
© Copyright 2001, African Crop Science Society
The following images related to this document are available: