Abstract:
A field trial was conducted at the Teaching and Research Farm
of the University of Agriculture, Abeokuta (latitude 7°15 N and longitude
3°25 E’) located in the forest-savanna transition zone of south west
Nigeria in 2002 and 2003 to assess the yield and economic potentials of intercropping
two cassava morphotypes (TMS 30572, branching and TME 1, non-branching) and
rice varieties (WAB 189-B-B-B-6-HB, ITA 150 and ITA 321). Significant differences
was observed among the rice varieties as ITA 321 produced the highest grain
yield (3.50 and 3.56 t ha-1) under sole in 2002 and 2003, respectively.
Similarly under intercropping with both cassava cultivars it recorded the highest
grain yield in 2002 and 2003. On the average intercropping significantly reduced
the grain yield of rice intercropped with TMS 30572 and TME 1 in 2002 and 2003.
In 2002, tuber yields of the two cassava cultivars in mixtures were similar
to the yields of their corresponding sole. However, in 2003, sole cassava TMS
30572 and TME 1 produced significantly higher tuber yield than their corresponding
intercrops. Rice/cassava intercrop on the average resulted in land equivalent
ratio (LER) of 1.88 and 1.79 in 2002 and 2003, respectively indicating an advantage
of intercropping rice with cassava. Also a high level of compatibility was observed
as the land equivalent co-efficient in 2002 and 2003 was high especially in
2002 (0.52 and 0.88). The intercropping of rice with cassava gave a higher total
net income of intercropping than sole crop as TMS 30572 intercropped with ITA
321 gave a higher total net income (
INTRODUCTION
Multiple cropping (mixed or intercropping) is an important crop production technique advocated for subsistence agriculture and it offers considerable yield advantage over sole cropping due to efficient utilization of growth resources (Willey, 1979). In the event of an unforeseen environmental hazard affecting the yield of one crop it offers an alternative so providing a more stable food source overall from the same field (Baker, 1980). The pattern of mixed cropping varies considerably from one area to another and even differ among farmers within a location. The common feature is that each system tends to reflect the farmers needs, management ability and resources, economic considerations and convenience (Ntare, 1990; Osiru and Willey, 1972; Willey and Osiru, 1972).
It is the worlds most important staple food crop and more than four-fifths of the world’s rice is produced and consumed by small-scale farmers in low-income and developing countries (FAO, 2003). Upland rice is commonly intercropped with pigeon pea (Mahapatra and Satpathy, 1988), cowpea and lablab (Aggarwal and Garrity, 1987), yam and cassava (Ugwu, 1996). Despite the fact that small scale farmers have failed to accept the recommendation of sole cropping system, most researchers have centred on sole crop, this could be as a result of trying to improve on sole cropping system (FAO, 1999).
Cassava (Manihot esculenta) is an important root crop widely cultivated in sub-saharan Africa. As a major source of energy, it is now gradually replacing maize in livestock feed industries (Omole, 1977; Tewe and Egbunike, 1992; Eruvbetine and Afolami, 1992; Eruvbetine and Oguntona, 1999). Special attributes of the crop include tolerance to low pH, low soil fertility and drought. These features single it out as an ideal crop for the tropics (Wilson and Adeniran, 1976). Cassava is characterized by slow initial growth and longevity hence, it is often found in mixture with short season crops that are harvested before it develops full canopy (Olasantan et al., 1996). Intercrops associated with cassava are highly variable and location specific. It is often intercropped with shorter duration crops such as maize, yam, cowpea, melon and vegetables (Njoku and Odurukwu, 1986; Olasantan, 2001; Olasantan and Bello, 2004). Given the high yield potentials of these new rice varieties (ITA 150, ITA 321 and WAB 189-B-B-B-6-HB) and the cassava TMS 30572, information on their compatibility in intercropping system is lacking.
Several concepts have been developed to evaluate the productivity and efficiency of different intercropping systems. Such concepts include relative crowding effect, RCE (Dewit, 1960), crop equivalent factor, CEF (Donald, 1963), coefficient of agressivity, CA (Mc Gilchrist and Trenbath, 1971), land equivalent ratio, LER (Willey, 1979), competitive ratio, CR (Willey and Rao, 1980), land equivalent coefficient, LEC (Adetiloye et al., 1983), staple land equivalent ratio, SLER (Reddy and Chetty, 1984), area time equivalent ratio, ATER (Hiebsch and Mc Collum, 1987). These concepts measure the productivity of the systems by comparing yields or monetary returns in intercropping with that of sole crop. However, each of the indices has its limitations. Hidlebrand (1976) advised that whichever concept is going to be adopted must be well understood by the farmer such that it can guide him in allocating his limited resources between competing demands. This study was therefore, carried out to evaluate the yield and economic advantages of cassava/rice using LER and LEC and total net income respectively in the forest-savanna transition zone of Nigeria.
MATERIALS AND METHODS
Site Description
The experiment was conducted at the Teaching and Research Farm of the University
of Agriculture, Abeokuta (latitude 7°15 N and longitude 3°25 E’).
The rice experiment was between July and November in 2002 and May and September
in 2003 while the cassava experiment was between July 2002 to June 2003 and
June 2003 to May 2004. Weather data during the period of experimentation are
presented in Table 3. The soil analysis for 2002 showed that
pH was 5.22, organic carbon 1.24% organic matter content 2.14%, total N 0.31%,
P 0.601 (ppm) and K 1.71 (mol kg-1). While in 2003 soil pH was 5.67,
organic carbon 1.01%, organic matter 1.70%, total N 0.61%, P 0.466 (ppm) and
K 1.33 (mol kg-1).
Varieties of Cassava and Rice Used
The cassava varieties used in this study were of two different morphotypes.
TMS 30572, a profusely, branching morphotype and TME 1 the non-branching type.
The rice varieties used were WAB 189-B-B-B-6-HB (an early maturing interspecific
rice hybrid of Oryza glabberimaxOryza sativa cross), ITA 150 (an
early maturing Oryza sativa cross) and ITA 321 (a late maturing Oryza
sativa cross).
Experimental Design and Treatments
The trial was laid out in a factorial arrangement in a randomized complete
block design and replicated three times in each year. The treatments consisted
of three sole rice varieties (ITA 321, ITA 150 and WAB 189-B-B-B-6-HB), two
sole cassava varieties (TMS 30572 and TME 1) and six intercrop combinations
of the two component crops.
Crop Husbandry
The field was ploughed and harrowed fourteen days later in both years. Each
plot size was 9x6.4 m and separated by an alley of 0.5 m. The rice was sown
by dibbling on 13th July, 2002 and 23rd May, 2003 at a spacing of 30x30 cm resulting
in 31 rows of rice per plot while in mixed stands a constant arrangement of
one row of cassava bordering two rows of rice with rows 30 cm apart was used.
Cassava was planted at 90x90 cm. Weeding was done three times before harvesting
rice at 3, 6 and 9 Weeks After Planting (WAP). After the harvesting of rice,
the plots of cassava were weeded 3 times before harvest.
Determination of LER, LEC and Cost Benefit Ratio
In this study, LER and LEC were used to evaluate the agronomic advantage
and economic advantage was determined using Cost benefit ratio. LER was determined
by dividing yields for cassava (TMS 30572 and TME 1) by their respective sole
crop yields and the resulting ratios (relative yields) for the two crops were
added to obtain the LER values (Willey, 1979). LEC was determined as a product
of the relative yield for cassava and rice (Adetiloye et al., 1983).
Statistical Analysis
The data collected were subjected to analysis of variance using the MSTATC
package based on the experimental design adopted on the field. Treatments that
showed significant effect on parameters measured were further separated using
the Least Significant Difference method (LSD) (Steel and Torrie, 1980).
RESULTS
Weather Condition
Table 1 shows the monthly rainfall and average temperature
for 2002 to 2004. In the cropping season of 2002, the wettest months were July
(325.5 mm) and October (297 mm), while in 2003 the wettest months for rice were
June (293 mm) and September (286 mm).
Cassava
In 2002 cropping system had no significant effect on the tuber yield of
cassava cultivars (Table 2). While in 2003 cropping system
had significant effect on the tuber yield of cassava, as sole cassava cultivars
TMS 30572 and TME 1 produced significantly higher tuber yield (34 and 22 t ha-1)
than their corresponding intercrops (Table 3).
Rice
Intercropping significantly reduced the grain yield of rice as sole cropped
rice significantly yielded higher than those intercropped with cassava in both
2002 and 2003 (Table 2 and 3). Among rice
varieties ITA 321 had significantly higher grain yield (3.50 and 3.56 t ha-1)
in 2002 and 2003, respectively in sole crop, while in intercrop ITA 321 intercropped
had significantly higher grain yield than other rice varieties (Table
1 and 2).
| Table 1: | Weather observation for Abeokuta, 2002/2003 and 2003/2004 |
| NA = Not Available | |
| Table 2: | Grain yield, land equivalent ratio, land equivalent coefficient of cassava and rice in sole and intercrop in 2002 |
Intercropping Advantagel
Land Equivalent Ratio (LER)
TMS 30572 had a higher LER (1.88-1.46) when intercropped with rice varieties
than TME 1 (1.80-1.63) in 2002, while TME 1 had higher LER (1.78-1.61) than
TMS 30572 (1.59-1.42) in 2003 (Table 2 and 3).
Land Equivalent Coefficient (LEC)
In respect to intercrop compatibility, rice intercropped with cassava of
different morphotypes in both years recorded LEC values greater than 0.25. In
2002, WAB 189-B-B-B-6-HB had the highest LEC values (0.88 and 0.81) in intercrop
(Table 2 and 3).
| Table 3: | grain yield, land equivalent ratio, land equivalent coefficient of cassava and rice in sole and intercrop in 2003 |
| Table 4: | Cost/benefit analysis of rice/cassava intercrop |
| Price Levels-Rice = WAB 189-B-B-B-6-HB |
|
However, among the rice varieties intercropped with cassava, ITA 150 recorded the highest LEC values (0.62 and 0.79) in 2003.
Cost Benefit Ratio
Results from Table 4 shows the cost/benefit analysis of
rice/cassava intercrop in sole and intercrop, in which the reduction in the
yield of rice was compensated for by the tuber yield of TMS 30572 than the tuber
yield of TME 1 as greater yield obtained from TMS 30572 resulted in a higher
total net income of
DISCUSSION
The success of any intercropping system depends on crop compatibility. It is important to select the intercrop carefully on the basis of their mutual competition and the benefit of association (Singh and Joshi, 1980). The reduction in the grain yield of rice in intercrop when compared with the grain yield of rice planted sole was due to the higher population of rice in sole than in intercrop. Nevertheless the reduction in the grain yield of rice was compensated for by the tuber yield of TMS 30572 than that of TME 1 as greater tuber yield obtained from TMS 30572 resulted to a higher total net income of
The land use advantage (LER>1.00) ranged between 1.46-1.88 and 1.63-1.80 among TMS 30572/Rice and TME 1/Rice respectively, of which rice variety WAB 189-B-B-B- 6- HB intercropped with cassava had a higher LER than other rice in 2002. The relative yield of cassava and rice was low in 2003. The relative yield of cassava and rice was low in 2003. Nevertheless, their was a relative yield advantage of intercropping over sole, as the LER ranged from 1.42-1.59 and 1.39-1.78 among TMS 30572 intercropped with rice and TME intercropped with rice respectively in which ITA 150 intercropped with cassava had a higher LER. The intercropping system of rice/cassava exhibited high level of intercrop compatibility as their LEC exceeded 0.25 (Adetiloye et al., 1983). This shows that rice can be grown in mixture with cassava of different morphotypes.
CONCLUSIONS
Cropping system significantly reduced the grain yield of rice in both years. Thus, the reduction in the grain yield of rice in mixture was more compensated for by the tuber yield of associated TMS 30572 than TME 1. Considering the economic implication, TMS 30572 intercropped with ITA 321 gave a higher total net income (