Abstract: An economic analysis was done using the partial budget procedure to evaluate economic performance of maize (Zea mays L.) under incorporated legumes and nitrogen in Northern Guinea Savanna zone of Nigeria. Results showed that plots without nitrogen fertilizer produced maize at loss throughout the three years of study and their average data except in 2006 where a very little profit was made. Maize production using 120 kg N ha–1 gave the highest gross margin and profit per naira (₦) invested throughout the three years of study with an exception of 2005 where there was a loss. However, in the three year average data, application of 90 kg N ha–1 in maize production gave the best profit per naira (₦) invested, which made incurring of extra cost of 30 kg N ha–1 from application 120 kg N ha–1 of no benefit. The most profitable green manure method for maize production was lablab green manure which gave the highest gross margin and profit per naira (₦) invested. When using nitrogen fertilizer and green manure on maize production was compared, incorporation of any of the legumes was better economically than any of the nitrogen levels. The results of this study suggest that using incorporated legumes in maize production was more profitable than using nitrogen fertilizer.
INTRODUCTION
Maize is the most widely and popular cereal in Nigeria that has found its usage in every home either as food for human beings or feed for animals and importantly, raw material for food industries. World total cereal production in 2012 showed that maize was the first most important cereal in Nigeria followed by sorghum and rice as stated by FAO. Africa produced 7.9% of the world’s total from 34.7 million ha. Nigeria which came second after South Africa in Africa produced 8.7 million Mt from 5.7 million ha which represented 1% of the world’s total in 2012. Nigeria’s production is very low compared with 273.8 million t produced by USA in 2012. This study was conducted in Savanna zone of Nigeria that accounts for over 70% of the maize production in the country (Uyovbisere et al., 2001). The reason cannot be farfetched because the average yield per hectare in Nigeria is still very low to the tune of 1500 kg ha–1 in 2012 as stated by FAO. However, in sub-Saharan African countries, low crop yield has been linked to challenges such as poor planting materials, soil infertility, erosion, climate change and improper use of agro-chemicals or excessive use of high external inputs (Ibeawuchi et al., 2009).
Maize is one of the crops that depend substantially on nitrogen for growth and development. It has been established that among all the essential nutrients, nitrogen seems to have the most pronounced effect on plant growth and development (Lombin, 1988). As importance as nitrogen is in plant life, it is low in soils of Nigerian Guinea Savanna. The soils of this zone are characterized with low organic carbon, total nitrogen, available phosphorus, effective Cation Exchange Capacity (CEC) and exchangeable cations as well as clay and silt contents (Singh, 1987). It has been observed that nitrogen is most important constraint to increased maize production in the Guinea Savanna of Nigeria (Singh et al., 2001). Hence, application of nitrogenous fertilizer becomes inevitable to guarantee increased maize production for maximum yield. It should be noted that the growth and productivity of any plant rest on degree of effectiveness of such a plant to absorb and mobilize the nutrients that are available in the soil for plant growth and dry matter accumulation (Adesoji, 2015). The efficient use of mineral fertilizers without compromising the fertility and productivity of soil is the major key to boost crop production (Adesoji, 2015).
The judicious use of mineral fertilizers ensures high crop yields but their use for long time causes deleterious effects on soil health and environment (Adesoji et al., 2015). However, a large number of Nigerian farmers apply little or no chemical fertilizers because of their unavailability at right time, poor distribution network, high cost, fear of adulteration and risks from erratic and limited rainfall especially in Nigerian Guinea Savanna (Adesoji et al., 2010). Average fertilizer use rate in 2012 in Nigeria was 4.8 kg ha–1, which is far lower than the average fertilizer use rate of 62 and 131.1 kg ha–1 for South Africa and United States of America, respectively (World Bank, 2015). The consequences of these are low crop yields, low economic returns and soil nutrients mining. With above mentioned challenges associated with the use of chemical fertilizers, it is worthwhile to explore the use of renewable alternative that optimizes the utilization of biological wastes which are environment friendly to generate plant nutrients for optimal crop production (Adesoji, 2015). Green manure is a good alternative because of its efficient capacity to generate organic matter which is a main force in the sustainability of soil fertility and productivity. Green manure has been reported to increase soil organic matter, available nitrogen, concentration of nutrients near the soil surface in available form and reduces the N loses through leaching and soil erosion (Sultani et al., 2007). The system of incorporating plant materials into soils after a short period of fallow is a good option for the improvement of soil physical, chemical and biological properties for safe and healthy soils.
Farming is a business and should be profit oriented. No farmer will venture into any new technology or innovation that he is not sure of its profitability. The information on economic benefits of maize production using green manure and nitrogenous fertilizer is scanty in this study area. Hence, there is a need to determine the profitability of the tested levels or types of the added inputs because a particular level or a type of an input that gave a maximum yield may not be viable economically which will make its adoption by farmers very difficult. Green manuring technology is not a well familiar technology among farmers in Guinea Savanna zone of Nigeria. The reasons for this may not be far away from some reasons like that the technology has not been well disseminated to farmers by extension workers, small farmers cannot afford to grow them at the expense of food crops in their limited land holdings (Rao and Mathuva, 2000) and some disincentive factors as stated by Fabunmi and Agbonlahor (2012) are costs of labour for establishment, maintenance and incorporation, zero output value and time and land value to cultivate the manure crops. However, profitability of any new technology or innovation is an impetus for an easy adoption by farmers. Therefore, this study was conducted to evaluate the economic benefits of maize production using incorporated legumes and nitrogen fertilizer.
MATERIALS AND METHODS
Three field trials were carried out in the rainy seasons of 2005-2007 at the Research Farm of the Institute for Agricultural Research, Samaru (11°11'N, 07°38' E, 686 m above mean sea level) in the Northern Guinea Savanna ecological zone of Nigeria. The annual rainfall for the duration of the study was 790.4, 1086.7 and 900.4 mm for 2005, 2006 and 2007, respectively. The physico-chemical analysis of the top soil (0-30 cm depth) of the experiment site before planting in 2005 as determined by standard procedures showed that the soil was loam with the following properties: pH (0.01 M CaCl 2), 5.0, organic carbon, 5.3 g kg–1, total nitrogen, 0.53 g kg–1, available phosphorus, 12.25 mg kg–1 and exchangeable cations (cmol kg–1) of Ca 2+, 1.80, Mg2+ , 0.36, K+, 0.14, Na+, 0.11 and CEC, 4.8 cmol kg–1. The treatments consisted of two maize varieties (SAMMAZ 12 and SAMMAZ 27), five levels of N (0, 30, 60, 90 and 120 kg N ha–1) and three green manure crops (Lablab purpureus, Mucuna pruriens and Glycine max (L.) Merrill) and a weedy fallow. The experiment was laid out in a split-plot design with nitrogen and variety as main plot treatment and green manure as the sub plot treatment. The experiment was replicated three times.
Leguminous green manure crops were planted on the flat with narrower inter-row spacing of 37.5 cm. The Lablab was sown at 2 stands per hole at 20 cm within row and mucuna was sown at a stand per hole at 20 cm within row. The soybean was planted drilled. The leguminous green crops were incorporated at 49 days (7 weeks) after planting. After 3 days of incorporation, maize seeds were planted with two or three seeds per hole at a spacing of 25 cm on the ridges of 75 cm apart. The maize seedlings were thinned to one seedling per stand at two weeks after sowing. The experimental plot consisted of six ridges of 4.5 m apart and 4 m long (gross plot) and net plot was 3 m×3 m. The green manure crops were fertilized using 20 kg P2O5 ha–1 and 10 kg N ha–1 to boost their growth. Nitrogen fertilizer as urea (46% N) was applied to the maize at 2 and 6 Weeks After Sowing (WAS) according to treatment. Basal applications of 60 kg P2O5 ha–1 and 60 kg K2O ha–1 were carried out at sowing. Weeds were controlled using Paraquat (Gramaxone) at 3 L ha–1 to kill weeds that were not properly incorporated and hoe weeding was done at 6 WAS.
Data collected from the observations were subjected to statistical analysis of variance (ANOVA) as described by Gomez and Gomez (1984) using SAS package version 9.0 of statistical analysis (SAS., 2002). The differences among treatment means were separated using Duncan’s Multiple Range Test (Duncan, 1955). Effects were considered statistically significant at 5% level of probability. Economic analysis was done using the partial budget procedure to determine the treatment combination that would give acceptable returns at low risk to farmers (CIMMYT., 1988). Economic analysis of the data was done based on the prevailing market prices of inputs, operation and outputs. The concepts used in the partial budget analysis are defined as follows:
| • | Total Revenue (TR) in ₦ per hectare = Q×P |
| • | Total Variable Cost (TVC) in ₦ per hectare = sum of the cost of labour and variable inputs, such as fertilizers, seeds and chemicals |
| • | Gross Margin (GM) in ₦ per hectare = GR-TVC |
| • | Gross margin per ₦ invested = GM/TVC |
| Q | = | Yield of maize for each treatment (Kg ha–1) |
| P | = | Average price of maize (₦) |
| GR | = | Gross revenue (₦) |
| TVC | = | Total variable cost (₦) |
RESULTS
Table 1 shows the costs and returns analysis on investment of growing maize using nitrogen fertilizer and green manure in 2005. Production of maize on plots without nitrogen fertilizer brought a loss of ₦11,108 and 24 k loss per naira(₦) invested. Production of maize using 30 kg N ha–1 was most profitable with ₦7,329 and a profit of 15 k per naira (₦) invested. This was followed by production of maize using 60 kg N ha–1 which gave a gross margin of ₦7,165 and a profit of 13 k per naira invested while using 90 kg N ha–1 to produce maize brought a gross margin of ₦2,754 and 5 k profit per naira (₦) invested. Production of maize in 2005 using 120 kg N ha–1 brought a loss of ₦668 and 1 k loss per naira (₦) invested. In green manure, growing of maize on weedy fallow gave the least gross margin of ₦10,782 and a profit of 35 k per naira (₦) invested. Maize production using mucuna green manure was found most profitable with a gross margin of ₦23.980 and a profit of 64 k per naira (₦) invested while incorporation of lablab produced maize which gave a gross margin of ₦21,034 and a profit of 56 k per naira (₦) invested. Production of maize using incorporated soybean gave a gross margin of ₦16,816 and a profit of 45 k per naira (₦) invested (Table 1).
Table 2 shows the costs and returns analysis on investment of growing maize using nitrogen fertilizer and green manure in 2006. Maize production on plots without nitrogen fertilizer produced a loss of ₦11,108 and 24 k loss per naira (₦) invested. The gross margin and profit per naira (₦) invested increased with each increment of nitrogen up to the highest rate, 120 kg N ha–1.
| Table 1: | Costs and returns analysis on investment of growing maize using nitrogen and green manure in 2005 |
| 1$: ₦199 (2015 autonomous exchange rate), GR: Gross revenue, TVC: Total variable cost | |
| Table 2: | Costs and returns analysis on investment of growing maize using nitrogen and green manure in 2006 |
| 1$: ₦199 (2015 autonomous exchange rate), GR: Gross revenue, TVC: Total variable cost | |
Maize production using 120 kg N ha–1 resulted in a gross margin of ₦120,004 and a profit of ₦1.65 per naira (₦) invested. In green manure in 2006, production of maize on weedy fallow plots resulted in gross margin of ₦53,208 and a profit of ₦1.51 per naira (₦) invested. Incorporation of Mucuna produced maize with a gross margin of ₦114,758 and a profit of ₦2.65 per naira (₦) invested while incorporation of Lablab produced maize with a gross margin of ₦124,535 and a profit of ₦2.83 per naira (₦) invested. Production of maize by incorporation of soybean gave a gross margin of ₦110,201 with a profit of ₦2.52 per naira (₦) invested (Table 2).
Table 3 shows the costs and returns analysis on investment of growing maize using nitrogen fertilizer and green manure in 2007. Production of maize on plots without nitrogen fertilizer produced a loss of ₦23,472 and 39 k loss per naira (₦) invested. Application of 30 kg N ha–1 up to the highest rate of 120 kg N ha–1 resulted in increase in gross margin and profit per naira (₦) invested. Application of 120 kg N ha–1 resulted in a gross margin of ₦33,456 and a profit of 44 k per naira (₦) invested. In green manure in 2007, production of maize on weedy fallow gave a gross margin of ₦18,357 and a profit of 51 k per naira (₦) invested. Maize production using Mucuna green manure gave a gross margin of ₦48,068 and a profit of ₦1.07 per naira (₦) invested while production of maize using incorporated lablab gave a gross margin of ₦48,953 and a profit of ₦1.08 per naira (₦) invested. Production of maize using incorporated soybean gave a gross margin of ₦41,589 and a profit of 92 k per naira (₦) invested (Table 3).
Table 4 shows the costs and returns analysis on investment of growing maize using nitrogen fertilizer and green manure in 2005-2007. The results showed that non application of nitrogen fertilizer in maize production brought a loss of ₦9,053 and 17 k loss per naira (₦) invested while using 30 kg N ha–1 to produce maize in 2005-2007 brought a gross margin of ₦24,235 and 42 k gain per naira (₦) invested.
| Table 3: | Costs and returns analysis on investment of growing maize using nitrogen and green manure in 2007 |
| 1$: ₦199 (2015 autonomous exchange rate), GR: Gross revenue, TVC: Total variable cost | |
| Table 4: | Costs and returns analysis on investment of growing maize using nitrogen and green manure in 2005-2007 (average data) |
| 1$: ₦199 (2015 autonomous exchange rate), GR: Gross revenue, TVC: Total variable cost | |
| Table 5: | Grain yield with green manure types and nitrogen levels |
| Means followed by the same letter(s) within the same column and treatment are not significantly different at 5% level of probability using DMRT | |
Production of maize using 60 kg N ha–1 resulted in a gross margin of ₦41,288 and a profit of 66 k per naira (₦) invested. Production of maize using 90 kg N ha–1 produced a gross margin of ₦48,572 and a profit of 74 k per naira (₦) invested which was higher than gross margin per naira (₦) invested of any other level of N application. Although, production of maize using 120 kg N ha–1 gave a highest gross margin of ₦51,104 but it had lesser profit per naira (₦) invested of 73 k than that of 90 kg N ha–1 which had a profit per naira (₦) invested of 74 k. In green manure in 2005-2007, production of maize on weedy fallow gave a gross margin of ₦28,112 and a profit of 83 k per naira invested. Maize production using incorporated mucuna gave a gross margin of ₦62,992 and a profit of ₦1.51 per naira (₦) invested while incorporation of lablab produced maize with a gross margin of ₦65,456 and a profit of ₦1.54 per naira (₦) invested. Production of maize by incorporating soybean produced gross margin of ₦56,758 and a profit of ₦1.35 per naira (₦) invested. The gross margin per naira (₦) invested in average data (2005-2007) for mucuna, lablab and soybean was 81.9, 85.5 and 62.7% better than gross margin per naira (₦) invested of weedy fallow, respectively (Table 4).
Maize grain yield performance was better in 2006 than 2005 and 2007 because of even distribution of rainfall in 2006 (Table 5). In 2005 and 2007, the rainfall in month of September was poor and unevenly distributed and coincided with the flowering and grain filling period of the crop. Hence, this seriously affected grain filling and consequently grain yield.
DISCUSSION
Maize performance was poor in 2005 and 2007 which could be attributed to poor rainfall and uneven distribution of rain in the month of September. Worst still, this poor rainfall pattern coincided with flowering and grain filling stages of maize. Hence, maize performance was negatively affected, which made grain yields obtained in 2005 and 2007 to be less than that of 2006. Consequently, a better maize grain yields in 2006 than that of 2005 and 2007 because the rain was better and well distributed.
Economic analysis of maize production using nitrogen indicated that application of 120 kg N ha–1 recorded in most cases highest gross margin, however, application of 90 kg N ha–1 gave in most cases the highest profit per ₦ invested. This is an indication that application of 90 kg N ha–1 fetched more profit in terms of naira invested which means the more the naira invested, the more the profit per ₦ invested. Results of the experiment revealed that the application of 120 kg N ha–1 added to the cost of production but did not add significantly to the output. This is obvious because increasing N rate from 90-120 kg N ha–1 did not lead to corresponding increase in grain yield or economic benefits to warrant the extra cost that may be incurred for additional 30 kg N ha–1. Therefore, application of 90 kg N ha–1 was found to be economic viable rate. This result is in consonance with report of Buah et al. (2009), who also found that increasing N rate beyond 90 kg N ha–1 did not give corresponding increase in yield and net benefit to justify the extra cost that may be incurred.
The economic analysis indicated that lablab green manure is the most profitable followed by mucuna green manure which was next in terms of profitability and this was closely followed by soybean green manure. It has been reported that mucuna and lablab were preferred because of reduced labour requirements and increased net benefits compared to continuous cropping (Fischler and Wortmann, 1999). It was further reported that an efficient management of green manures increases their productivity and can reduce labour costs, which therefore leads to increase in net benefits. In the same vein, the economic analysis conducted by Hirpa (2013) indicated that cowpea green manure gave the highest net benefits compared with other green manure types. Similarly, Fabunmi and Agbonlahor (2012) reported that green manure generated from drum variety of cowpea at 80,000 plants ha–1 was the most economically profitable manure in the production of maize.
Results of the study clearly showed that incorporation of lablab, mucuna and soybean gave greater gross margin per ₦ invested than values recorded for any of the N rates. Therefore, investment in maize production using green manure revealed lesser cost of production of maize and higher profit than investment in maize production using N. This might be the reason due to which, Sharma and Behera (2009) reported that legume biomass N has various indirect benefits such as addition and increased availability of other nutrients, improvement in nutrient use efficiency, physical and biological properties of soil. All these presented a better soil performance beyond N-release for an enhanced yield with a lesser cost of production. Consequently, this ensures a sustainable productivity of maize. Similarly, in a study conducted in Tanzania, the partial budget analysis showed that green manure gave a net incremental benefit of Tsh 478,654 A–1 in comparison to chemical fertilizers used by farmers in maize production (William et al., 2012). These benefits were further attributed to increase in marketable yields and savings from the reduction in the costs of chemical fertilizers and labour (William et al., 2012).
CONCLUSION
Economic analysis of maize production revealed that application of 120 kg N ha–1 gave highest gross margin but application 90 kg N ha–1 gave the highest gross margin per naira (₦) invested. The partial budgeting study on maize production using green manure showed that lablab green manure consistently recorded the greatest gross margin and gross margin per naira (₦) invested. This was closely followed by mucuna green manure and lastly by soybean green manure in term of profitability. When incorporation of lablab, mucuna and soybean was compared with application of nitrogen in terms of profitability, incorporation of lablab, mucuna and soybean gave greater gross margin per naira (₦) invested than values recorded for any of the N rates.