Today, different agronomic systems are existing in the world. Management practices
in these systems are effective on crop yield, resources use efficiency and population
of weeds. Mixed culture is one of good methods in sustainable production of
crop. Planting more than one crop caused better resources use, in comparison
with mono-culture (Sobkowicz, 2006). In comparison with
pure culture, intercropping systems has many advantages such as better use of
resources for growth, weed, pest and disease control and increase in stability
of yield in different environmental conditions (Nargis Akter et al.,
2004). In addition, intercropping systems might be wisest selection in determining
compatible plants, minimum competition and highest total yield. This could become
possible by using suitable combination of different varieties (Saka
et al., 2007). One of problems in designing and efficiency of mixed
culture is due to lack of predicting interaction between species composition
and environmental conditions (Fukais and Trenbath, 1993).
Therefore, in mixed culture, the most important factors in selecting plants
include their compatibility, having low competition and producing highest yield.
Also, careful selection of companion crop, can result in nutrient balance, economic
yield stability and sustainability of agricultural systems (Nargis Akter et
al., 2004). In addition, better management and weed control and following
bioenvironmental issues are other advantages of this culture method.
Due to high importance of oilseeds in nutrition, their production and
processing situation was on concern from old time. But, problems in cultivation
and production of these crops have been always a barrier in increase yield
and obtaining sustainable yield. Therefore, due to important situation
of mixed culture in removing some problems in agro-ecosystems and that
researches in this field across the country, particularly in Khuzestan
province was very limited, on the other hand, this study tries to compare
and asses the mixed culture of canola and field bean (a plant that has
suitable status in agricultural systems in the region due to its characteristics),
in different densities of two crops with pure culture of canola.
MATERIALS AND METHODS
This experiment was carried out in the research farm of Ramin Agricultural
and Natural Resources University, located 36 km northwest Ahwaz in 31
degree and 36 min geographic latitude, in 2004-2005. This region is in
semi-arid parts with average annual rainfall rate of 269.9 mm. soil of
experiment location has silt-clay-loam texture, with 0.84% organic matter.
In this research, intercropping of canola (Hyola 401 cv.) and field bean
(local) was investigated. Canola was planted in two 20 and 40 shrubs m-2
densities and field bean was planted in 0, 20, 40 and 60 shrubs m-2
densities. Experimental design was randomized complete blocks, with three
replicate. Each plot include six furrow with 75 cm distance and four meter
length, that one cultivation line of each one of two crops is located
on those. Treatments was different combination of two crops (canola and
field bean) (Table 1). It should be noted that treatment
of pure culture are as control.
Agronomic operations including fertilization, irrigation and harvest
were done based on technical recommendations of research centers in the
region. In order to investigation of weed status, no control was made
against the weed. Field bean was harvested at the end of April and canola
at the beginning of May. Then, samples were taken to laboratory and were
dried and following parameters were measured:
Grain Yield and Yield Components
To determine yield and yield components, after omitting the margins,
in each plot, following parameters were measured:
||Grain yield, silique number, grain per silique and 1000 grain weight
||Biological yield of mixed culture and it components in area unit
||Weight of single shrub in mixture and pure culture
||Different composition in canola mixed field bean
Sampling of weeds, in order to evaluate of mixed culture effects on
weed status, was done. Weeds were collected at the end of February in the
floral stage and labeled. Then their dry weight was measured. In addition,
species composition in different combination of mixed culture and pure culture
Evaluation Indexes of Mixed Culture
Agronomic index of the Land Equivalent Ratio (LER) that was calculated from
formula 3 (Nargis Akter et al., 2004). LER for a canola-field bean intercrop
is the sum of the partial LER values for canola (Lc) and field bean (Lf), in
accordance with Vandermeer (1990).
where, SC is solp crop and IC is intercrop.
Competition Index (dominance factor) which was calculated from formula 4.
In analyzing data, SAS and MSTATC softwares and for drawing graphs. Excel
software, were used.
RESULTS AND DISCUSSION
Canola Yield and Yield Components
Results showed significant difference between treatments in terms
of No. of shrubs per unit area, weight of single shrubs, grain yield,
1000 grain weight, silique No., grain No. per silique and Biological Yield
(Table 2 ).
||Analysis of variance by of canola yield and yield components
mixed with field been
|*, **, Significant at 5 and 1% levels of probability,
||Canola yield and yield components mixed with field bean
|Similar letter(s) in each column shows non-significant
Number of canola shrubs m-2
, was affected seriously by field
bean in mixed culture. Maximum No. of canola shrub was obtained with 40
, in sole crop (Table 3
). With increase
density of canola and field bean, BY of both crop single shrub decreased
and mean comparison showed very decreasing trend in terms of weight of canola
single shrub, in mixed culture.
BY of canola single shrubs, from 18 in sole crop with 40 shrubs per m2,
decreased to 8 g. In mixed with field bean. This decreasing trend, especially
was increased greatly in higher densities of field bean. It seems that BY decreasing
is due to competition in mixed culture (Tsubo et al.,
With increase of canola density, canola BY increased. Highest canola BY was
observed in sole crop with 40 shrubs m-2 (with 627 kg DM ha-1)
and lowest BY was related to mixed culture of 40 canola shrubs and 60 field
bean shrubs. In both density of canola, with increase in relative share of field
bean population, canola BY decreased, especially with 40 canola shrubs m-2.
Cause of canola BY decrease in mixed culture, can be related to interaction
of two crops and competition ability of legumes (Fairys,
1990). Some of other researchers reported no significant difference between
mixed and sole crop (Raji, 2007).
Highest canola grain yield (GY) was obtained in sole crop with 40 canola
shrubs m-2 by 2788 kg ha-1 and lowest GY was obtained
in 40 canola and field bean shrubs m-2 in mixed culture by
551 kg ha-1. Mean of GY in sole crop with 40 canola shrubs
per m2 was five times than mixed culture with the same density
These results agree with reports of Rouber et al.
(2000) on decrease oat grain yield mixed with pea, in relation with sole
crop and Sobkowicz (2006) on triticale mixed field bean.
It also seems that increase in GY in mixed culture with 20 shrubs was due to
decrease competition and interaction between two mixed crop and decrease in
the No. of branches, that agree with results obtained by Finckh
and Karpenstein-Machan (2002).
Mixed culture also decreased canola yield components. In this condition, No.
of silique per plant decreased. Maximum No. of silique per plant was obtained
from sole crop in both density of canola and minimum No. of silique was related
to high densities in mixed culture. This agrees with reports of Sobkowicz
(2006) and Fukais and Trenbath (1993). It seems that
decrease in the No. of silique per plant with increase bean density, is related
to fields bean shading on canola. In addition, the grain No. per silique decreased
in different combinations of mixed culture. Lowest No. of grain per silique
was observed in combination of 40 canola shrubs with 60 bean shrubs m-2,
by 15 grain per silique. Also, highest number of grain per silique was observed
in sole cropping. One thousand grain weight of canola in sole crop was less
than mixed culture.
Bean Yield and Yield Components
Results showed very significant difference between treatments in terms
of shrub No. m-2, single shrub weight, BY, GY, 100 grain weight,
silique No. per shrub, grain No. per silique (Table 4).
It seems that the competition established with increase in density of
both crops in mixed culture.
The weight of single shrub of bean varied in different competition of
mixed culture and showed decreasing trend in mixed culture, in comparison
with sole crop. The highest weight of single shrub of bean was found in
sole crop by 38.5 g and lowest was in mixed culture by 29.84 g (Table
With regarding to results, it seems that intraspecific competition with canola
and interspecific competition between bean shrubs particularly in high densities
could be the reason of decrease in the biological yield of single shrub. This
agrees with the report of Sobkovicz (2006) on intraspecific
competition of triticale with bean. BY in bean sole crop, by 6718 kg ha-1,
showed increase in comparison with mixed culture. Some of researchers have also
reported that yield of both species in mixed culture was lower than sole crop
(Nargis Akter et al., 2004).
||Analysis of variance of bean yield and yield components mixed
|*, **, Significant at 5 and 1% levels of probability,
||Bean yield and yield components mixed with canola
|Similar letter(s) in each column shows non-significant
||GY comparison of field bean single shrub in sole crop, with
The highest GY of field bean was obtained with sole crop by 2525 kg ha-1,
that was higher than different densities mixed with canola. Other compositions
of mixed culture in this experiment, had lower yield than bean sole crop. Especially,
with increase of canola density in mixed culture, lowering of yield became more
intensive (Table 6).
Comparison the BY of mixed culture showed that there was no significant difference
between different compositions of mixed and sole cropping (Table
4). However, combination of 20 canola shrubs mixed with 40 bean shrubs m-2
had highest BY, by 9295 kg ha-1. Cause of this might be due to bean
characteristic and low portion of canola in this mixture composition. This agrees
with results of Carr et al. (1992) on intercropping
Land Equivalent Ratio
Land Equivalent Ratio (LER) had different percentage in seed yield in different
mixture compositions. Minimum LER (69%) was obtained in 40 canola shrubs mixed
with 20 bean shrubs m-2 and maximum LER (204%) was obtained in 20
canola shrubs mixed with 60 bean shrubs mixed with 60 bean shrubs m-2
(Table 7). LER in low density of canola (20 shrubs m-2)
was lower than 40 canola, in all compositions of mixed culture. It seems that
in low densities of canola, with increase of No. of bean shrubs per unit area,
GY of mixture increased and less land was needed to produce GY of sole cropping.
Although, the GY of both crop was higher in sole cropping, but LER increased
except in combinations of canola and bean with 40-20 and 40-40 densities. The
pattern of yield decrease with increase in LER agrees with other mixed culture
experiments (Nargis Akter et al., 2004; Sobkovicz,
2006). Studding LER of BY, showed that LER in low density of canola mixed
with bean, had advantages in relation with sole cropping (Table
Results showed that in different mixtures, due to bean traits and
inter-specific competition, Dominance index was less than 1 or negative.
It shows better dominance of bean in mixture with canola (Table
||LER and dominance in different mixtures of canola and field
||Weed species in sole crop and mixed intercropping
||Weed dry weight in different mixtures of canola and field
|Similar letters shows non significant difference
Weed Biomass and Species
Results showed that mixed culture can be an effective implement for weed
control that agree with results of some of researches (Deksen
et al., 2002). Results of analysis of variance showed significant
difference between different densities of both crops in mixed and sole cropping.
Highest DM of weed was observed in canola sole cropping (Table
8, 9). This agrees with reports of Libman
and Dyck Dik (1993) on decrease in weed biomass in mixed culture in relation
with sole cropping. Results showed also that with increase bean density in mixture,
weed biomass had decreasing trend. It seems that morphological traits of bean
(such as high growth rate, early canopy closure and long term coverage of surface
soil) and competition ability of this crop, had significant effect on decreasing
weed biomass, particularly in early growth season (Siner et
al., 2000). Results of this experiment showed effect of type of farming
system on weed density and species composition. This agrees with Shetty
and Rao (1981).
In mixed culture of canola and bean, weed dry weight and diversity was significantly
decreased (Table 9). It seems that difference between crops
in response, change and renovation in farming options and crop and weed traits
as well as time of emergence, were cause of changes in weed density and their
dominance within crops. In other hand, change in crop density and spatial array
have prevented invrease in population of a particular species, that agrees with
reports of Walker and Buchanan (1982) and Deksen et al.
The existence of interaction between components of one culture pattern
and farming systems, such as presence of different crops, plough systems,
application of different herbicides and management of plant residues,
makes difficult the estimation of equality of reactions of different weed
populations or control strategy in a farming system. In fact, using diversity
of crops will be as a tool to disrupt of balance and stability of weed
communities, increase ability of competition of crop, maintenance the
quality of resources and environment. Using mixed culture in the condition
of experiment region with common farm crops, can be effective in establishing
stability in the agricultural ecosystems in terms of biological, economical
and environmental dimensions.