Profitability of Cowpea Intercropped With Maize in West Africa Guinea Savanna

An on-farm trial was conducted over a 2-year period in Tibali in the Savelugu district of Northern region of Ghana to evaluate the productivity and economic returns of hybrid and open pollinated maize (OPV) either in pure stands or intercropped with erect and trailing cowpea. The maize varieties used were medium maturing (110 days) whie the cowpea varieties were early maturiing (70 days). The experiment was conducted in a randomized complete block design with 14 treatments (sole pan53, sole Etubi, sole mamaba, sole obatampa, sole erect cowpea, sole trailing cowpea, erect cowpea + pan53, erect cowpea+etubi, erect cowpea+mamaba, erect cowpea+obatampa, traing cowpea + pan53, traling cowpea+etubi, trailing cowpea+mamaba and trailing cowpea + obatampa) replicated on 10 farms. Intercropping had better productivity and economic returns than sole cropping. Intercropping maize with trailing cowpea type had better productivity and economic return than intercropping with erect type of cowpea. Intercropping the OPV maize with cowpea had better productivity and economic return than intercropping hybrid maize with cowpea. Farmers may either intercrop OPV maize with trailing cowpea type or hybrid maize variety Pan 53 maize with trailing cowpea type for better productivity and economic return.


Introduction
Intercropping maize with cowpea is one of the most popular mixed cropping combinations under small-holder rain-fed agriculture in the tropics (Abdulraheem & Emmanuel, 2014).Maize-cowpea intercropping has been practiced by small-scale farmers in the West Africa Guinea and Sudan savannah zone for years (Norman, 1975).Small scale farmers in Northern Ghana practice intercropping of maize and cowpea using open pollinated varieties of maize.Intercropping practice helps to increase profit margin of the farmers, restore farm biodiversity (Jackson et al., 2007;Mucheru-Muna et al., 2010) and decrease the dependency on chemical herbicides in weed control (Banik et al., 2006).
The production of hybrid maize in Northern Ghana is gaining popularity in recent years with about 10,000 farmers producing hybrid maize in the pure stands on 21,000 ha of land in the three Northern regions of Ghana (Lambrecht & Ragasa, 2016).
However, quantitative data on the effect of intercropping hybrid maize with legumes, especially in Guinea and Sudan Savanna zones of West Africa is limited.We therefore, hypothesized that intercropping cowpea with hybrid maize will not affect yield and profit of the farmer.

Experimental Site
The experiment was conducted at Tibali (9.66853° N and longitude 0.84728° W) a suburb of Savelugu District in Northern region of Ghana during the 2014 and 2015 cropping seasons.The mean total annual rainfall ranges from 800-1200 mm and occurs between May and October with a dry season characterized by harmattan winds  Where, La and Lb are the partial LER or crop species a and b respectively; Ya and Yb are the individual crop yields in the intercrops; Sa and Sb are their sole crop yields.

Economic Measurements
Farmers would most likely choose and adopt an alternative method or practice if the net benefit is higher than what is currently being used.It was therefore very necessary to compare the extra costs with the extra benefits of the new treatments.Partial budgeting is a method of organizing experimental data and information about various alternative treatments carried out.
The cost of all the variable inputs and seasonal operational cost that prevail in the study area of the cropping seasons on all the treatments were considered.Variable cost included amount paid by farmers for land preparation, planting, cost of materials such as seed, labour for weeding, harvesting and carting of farm produce to the house.The gross income was also estimated from the sale of harvested farm produce.The value or net return per hectare for each treatment was then calculated as the difference between the gross income and total cost of production.There were no charges on capital cost such as land, interest on capital, depreciation on farm equipment and other overheads.

Statistical Analysis
The General Linear Model of Statistical Analysis System Package (SAS, 2011) was used to analyze yield data.
The analysis was done on yearly basis and the model used was: Where, Y ijkl is an observation, µ is experimental mean, B i is block effect, T j is cowpea intercropping effect and e ijkl is residual error.Standard errors and P-values were used to determine differences among treatments.
Treatment means of significant differences were determined at probability of 0.05.

Results and Discussion
Table 1.Effect of intercropping on grain yield and land equivalent ratio

Yield and Productivity
The intercropping affected maize grain yield with sole Pan 53 recording higher (P < 0.01) grain yield than the other maize varieties in both seasons (Table 1).Similarly, to the maize grain yield, the intercropping affected cowpea grain yield with erect type of sole cowpea yielding more (P < 0.01) grain yield than the other cowpea type in both seasons.The seasonal differences grain yields may possibly due to the rainfall distribution (Figure 1).In 2014 growing season, the grain filling stage coincided with the peak of the rainfall in the month of August for which optimum yield production was obtained as compared to that of the 2015 growing season which was in September with low amount of rainfall.The land equivalent ratios of all the intercrops were greater than one which shows better productivity compared to their sole crops.
Though there were similar yield reductions in grain yield of both maize and cowpea in their intercrop, all their LER were above one, which clearly showed that there was an advantage in intercropping over the sole cropping.

Economic Returns
The net returns of the maize-cowpea intercropping are shown in Table 2. Generally, all the intercrops had relative higher net returns as compared to their respective soles in both seasons.Trailing cowpea intercropped with Pan 53 variety recorded the highest net return per hectare, whilst erect cowpea type intercrop with Mamaba maize variety had the least net return per hectare in both seasons.However, on the average intercropping the OPV (Obantapa) with any of the cowpea type had better net return per hectare compared to the intercropping the hybrid with any type of the cowpea in both growing seasons.
The increase in net return of the intercropping may possibly be due to the high LER values of the intercropping (Dhima et al., 2007).Similarly, more net income was obtained from intercropping bush beans with sweet maize (Santalla et al., 2001) and maize-legume intercropping (Yilmaz et al., 2008;Mucheru-Muna et al., 2010;Ngwira et al., 2012).

Conclusion
Intercropping maize with cowpea had better productivity and net returns than the sole cropping.Intercropping OPV maize variety with cowpea had better productivity and net return than intercropping hybrid maize with cowpea.Farmers may either intercrop OPV (e.g.Obatanpa) with trailing type or Pan 53 hybrid maize variety with trailing type of cowpea for better productivity and economic return.

Table 2 .
Net returns of maize and cowpea affected by the intercropping systems