Introduction

Agricultural sector in sub-Saharan Africa (SSA) has continued to be an essential instrument for sustainable development, rural poverty reduction and a reliable source of self-sufficiency in food for the region (World Bank, 2008; Olwande et al., 2009). However, agricultural productivity in the region has continued to decline over the last three decades and poverty levels have increase (Olwande et al., 2009). Currently, agricultural production growth in SSA lags behind that of other regions in the world, and is well below that required to achieve food security and poverty goals. Many farmers in the region are facing declining crop yields, which have adverse effects on the region’s economic growth (Hassan and Karanja, 1998). A major constraint to higher productivity among farmers in the region is “soil infertility” related mainly to low nutrient status of the soils and continuous cultivation without planned replenishment of depleted soil nutrients (Wanyama et al., 2009). Increasing agricultural productivity in the SSA; especially in Nigeria is an urgent necessity; and one of the fundamental ways of improving agricultural productivity is through introduction and optimal use of suitable agricultural technologies.

Increasing rate of food production is a major solution to the challenge of food insecurity in the world. Food production in which production of food crops and cash crops among others are needed to combat hunger. In agriculture, food crops are produced under the arable crop farming. The production of arable crops requires meagre resource inputs in terms of land, capital and labor, therefore small holder farmers that have access to little input resources delve into its production.

With the increasing population and pressure on the available grains and vegetables, the capacity of the small holder farmers to produce and the current low productivity of most cultivated land in SSA due to decline in the soil fertility, the output (supply) cannot meet demand for the arable crops. Measures and various improved technologies have been put in place to increase the productivity of available resources especially land; whose supply is in fixed and whose quality has declined with time of usage (Krautkraemer, 2005). In order to ensure that there is continuous and increased food production for the ever increasing population, some of the technologies that have been adopted include; improved varieties of seeds, irrigation system, improved cultural practices, use of organic and inorganic fertilizers.

Inorganic fertilizer has been widely used to improve the fertility of soil and hence its productivity. There is need to apply fertilizer to improve the soil fertility because of continuous cropping of the same land over long periods of time. This has come about because of fragmentation of available smallholder farmland in Nigeria; hence, limited crop rotation (Raufu, 2010). The importance of fertilizer technology in crop nutrition (FAO, 1984) justifies government policy on fertilizer pricing and subsidy in the last few years. Between 1976 and 1979, fertilizer attracted a 75% subsidy wholly borne by the Federal Government (Tanko and Mbanasor, 2000). In the period between 1980 and 1985, Federal Government share was reduced to 50%, while States Government was required to absorb the 25%. However, in 1997 - 1999, the Federal Government withdrew all subsidies on fertilizer and later re-introduced a 25% subsidy on mineral fertilizer in June 1999 (Evbuomwan, 1991; CBN, 1999; Tanko and Mbanasor, 2000). Osun State like other parts of Nigeria have suffered gross soil nutrient mining due to continuous cropping, coupled with low soil nutrient levels and poor nutrient conservation practices accentuated by mounting population growth and land scarcity. In the State, intensive cropping is gradually replacing the traditional shifting cultivation that is associated with long period of land fallowing. The fluctuating pattern in food production due to reduced length of fallow on land have prompted farmers in the State to amend the soil with different materials (organic and inorganic) in order to enhance plant growth and increase crop yield. Adding nutrients to the soil through fertilizer application is crucial in sustainable agriculture; as it compensates for nutrients depleted through harvested crops.

Various factors and constraints are at play in the both micro and macroeconomic environment that the farmer operates.  Factors in the macroeconomic environment, socio-psychological factors and socio-economic factors all affect a farmer’s decision on what to use or not to. Farmers’ incentives and disincentives to use any new technology are determined by his personal beliefs about the permissiveness of his environment. An optimum production innovation is achieved only when a farmer perceives the recommended practices to be, for him technically feasible, physically possible and socially compatible.

In spite of the early adoption of fertilizer technology by arable crop farmers in States in Nigeria, arable crop outputs have not shown encouraging growth rate (CBN, 2003). Large proportion of arable crop outputs like cassava and its products, cowpea, maize, yam, vegetables like tomatoes, pepper and garden egg are brought in from the neighboring States to complement local production, which is applicable to Osun State. On the other hand, the past efforts of Osun State Government in ensuring the availability of fertilizer and at a subsidized rate to farmers in the State has not yielded the intended objective, given the present low productivity among crop farmers in the State (CBN, 2010). Therefore, following the current situations of low growth rate of arable crop outputs, rapid population growth and unintended objective from the highly publicized fertilizer subsidy program in the State; there is need to uncover factors that determine the use of fertilizer among arable crop farmers in Osun State. Specifically examining the socio-economic characteristics of small holder arable crop farmers in the State will reveal the main factors underlying the use of fertilizer among them. Along with this, identifying the factors that affect demand for fertilizer and the major constrain to fertilizer use will help in informing the policy maker on the next approach to food insecurity in terms of soil infertility. The study will also enlighten the government on the basic needs of farmers or fundamental issues to be addressed for farmer to fully utilize the improved technology of use of fertilizer. A study like this carried out on the behavior of fertilizer consumer, in this case; smallholder arable crop farmers in Osun State will facilitate the fertilizer producers and suppliers in the State to capture the market for more sales by knowing how best they can serve their consumers. Then, generally the problem of food insecurity in the State can be addressed on the side of soil infertility.

Materials and Methods

This study was carried out in Osun State, Nigeria. Osun State is one of the six States that make up the South West Geo-political zone in the South-western part of Nigeria. The State experiences approximately eight months (March to October) of bimodal rainfall and four months (November to February) of dry season each year, the average annual rainfall ranges from 1,125mm in derived savannah to 1,475mm in the rain-forest belt. The mean annual temperature ranges from 27.2°C in the month of June to 39.0°C in December. The area is mainly agrarian. Food crops grown in the area include maize (Zea mays), yam (Dioscorea spp.), cassava (Manihot esculenta), cocoyam (Colocasia spp.), rice (Oryza sativa) and vegetable (Amaranthus spp.). The permanent crops include cocoa (Theobroma cacao), kolanut (Cola nitida) and oil palm (Elaeis guinensis). These crops are usually mixed or intercropped. The State is made up of 30 Local Governments Areas (LGAs) which are distributed into three agro-ecological zones by the State’s Agricultural Development Program (OSSADEP) namely; Ife-Ijesa (rainforest), Osogbo and Iwo zones (derived savannah), with six administrative zones.

The forest zone is characterized by vegetation with rainfall averaging 1,475 mm perannum. The soils of the area are mainly derived from undifferentiated basement complex rocks with pebble beds and to a lesser extent coarse granite parent material. The topography is mainly undulating plains, dissected plains and patches of nearly level to gently undulating plains. Arable crops cultivated include maize (Zea mays), cassava, okra (Hibiscus esculentus), and chilli pepper (Capsicum sp.). The derived savannah zone is located at the northern part of the state and it is characterized by savannah vegetation. The topography is mainly gently undulating plains with undulating dissected plains. Annual rainfall is about 1,125 mm per annum. The soils of the area are derived mainly from quartzite and basement complex rocks. The main crops cultivated are maize, cassava, okra, soybean (Glycine max) and cowpea (Vigna unguiculata).

The selection of respondent farmers was multistage. In the first stage, two of the agro-ecological zones in the State; Osogbo and Iwo were purposively selected based on land use, the zones are noted for arable crop farming being derived savannah zone. Second stage involves selection of four Local Government Areas (LGAs) each from the two agro-ecological zones; three villages from each of the four LGAs, five farmers from each village were selected using systematic random selection at each sampling stage. A total of 120 respondents were interviewed.

Both primary and secondary data were used for the study. Primary data was collected on the socio-economic status of the farmers, price and quantity of inputs and outputs, farm size, with the use of well-structured questionnaire. Secondary data were obtained from records and documents on recommended agronomic practices on fertilizer usage from Osun State Agricultural Development Programs (OSSADEP) and Ministry of Agriculture and Natural Resources.

Descriptive statistics was used to determine the socio-economic characteristics of smallholder farmers in arable crop production. Logistic regression analysis was used to determine factors influencing the use of fertilizer and the major constraints to its use among smallholder arable crop farmers in the State respectively. The logistic regression model derives its name from the logistic probability function (Gujarati, 2004) expresses the quantitative dependent variable. A structural relationship is specified, the quantity of fertilizer used, ranging from zero (i.e. non use of fertilizer) to different levels of fertilizer use, was regressed on the socio-economic factors, and other independent variables such as level of output of the farmer, farmers family size, farmers’ income from other farm enterprise, size of farmland, price of fertilizer which is the principal variable as quantity demanded of a commodity is proportional with its price ceteris paribus. Following Amanze et al., (2010), since the dependent variable in this study is both qualitative (i.e. probability of use) and quantitative, coefficient of multiple determination was not used in deciding the level of significance rather Chi squared (χ²) was used. (Ohajianya et al., 2007).

The model specified equation is stated below:

Ln Y = Ln (P/1-P) …………………………………………………. (i)

Ln (P/1-P) = b₀ + b₁ X₁ + b₂ X₂ + …… b₁₃ X₁₃ + e ……………… (ii)

Where Y = use of fertilizer and its non-use dummy, use of fertilizer is 1 and 0 for non-use; P = Probability of use of fertilizer; Ln = Natural logarithm function

b₀ = Constant; b₁ – b₁₃ = Logistic regression coefficients

X₁ = Total output of the farm in naira (₦); X₂ = Gender [male (1) and female (0)]

X₃ = Age of the farmer (years); X₄ = Level of education; X₅ = Farm size (hectares)

X₆ = Number of farmland; X₇ = income from other farm enterprise (₦)

X₈= Total income from off-farm employment (₦); X₉ = Years of education (years)

X₁₀ = Price of fertilizer (₦); X₁₁ = Family size; X₁₂ = Total cost of land

X₁₃ = Total cost of crop input; e = Stochastic error term.

Results and Discussion

Socio-economic characteristics of smallholder farmers in arable crop production

Age of the farmers ranged between 26 and 85 years with mean age of 52 years. This showed that the farmers were relatively advanced in age (Table 1). This agrees with the findings of Amanze et al., (2010) who reported that the smallholder arable crop production farmers were relatively old in arable crop farmers in Imo State. This buttress the fact that agriculture is seen as an occupation for the aged while the young look for white-collar jobs in the urban areas. Younger farmers are more adventurous while older farmers are laggards and tend not to accept new inventions until there is proof of its effectiveness (Onuoha and Nnadi, 1999). The resultant effect according to Orebiyi, et al (2002) is that, there will be a decrease in agricultural productivity in the long run when the ageing farmers can no longer perform. The arable crop farming is gender biased; male (78.3%) while female (21.7%), the enterprise is male dominated. This is the peculiarity in the study area, where the female is disallowed from laborious work and obligated to attend to milder activities in the community. This confirms the earlier conclusions of Obasi (2007) and Orebiyi et al., (2002) that women are more involved in the less laborious activities. Majority (95.8%) of the farmers was married with mean household size of 7 (Table 1). Having large household size is advantageous because it substitutes for labor cost (Obinne 1989; Ezeh, 2006). About 25% of the respondents had no formal education while 34.2% completed primary school. Less than 15% of the farmers had tertiary education with mean years of education of 9 which is the drop out from secondary school in Nigeria. This shows that relatively the farmers had access to and acquired formal education to a certain extent which in turn reveals the level of development of the grassroots in the country. The finding indicates that most respondents were not learned and this means that there is low tendency of adopting and assimilating of agricultural innovations or technologies among arable crop farmers in the study areas. The modal farm size ranged between 2.01 and 3.00 hectares of land. The mean farm size was 2.54 hectares of land which falls within the range of land holding of small scale farmers and they use low level of fertilizer. This is a confirmation that smallholder farmers are operating on a smallholding (Ezeh et al. 2008). The low holding of farm size was due to partitioning in the inheritance process and probably due to land reform. And this invariably will lead to more intensive land use systems. This implies farmers are forced to shorten fallow periods, increase investment on land and manage soil fertility through the addition of fertilizer.

Table 1 Socio economic characteristics of respondents Source –Field survey, 2014

Factors influencing the use of fertilizer among the small holder farmers

The result of the estimation of the factors influencing the use of fertilizer is presented in Table 2. The variables relating to total farm output (N) (X₁), level of education (X₄), farm size (X₅), number of farmland owned (X₆) and total cost of crop inputs (X₁₃) were significant at 5% level, implying that these variables are the important factors influencing farmers’ use of fertilizer in arable crop production in the study area.  The level of education was significant, implying that farmers with higher education use fertilizer more than farmers with low level of education and that education is a major factor influencing the use of fertilizer among smallholder arable crop farmers. This could be attributed to the fact that higher education enables the farmer to know and want to harness the benefits of the use of improved inputs such as fertilizer in crop production. The farm size was significant and positive. This result is similar to the findings of Amanze et al. (2010). This can be explained in terms of scale of operation, it has been established from literature that a higher scale of operation results in a high production efficiency and mostly a positive returns to scale, so farmers with large farmlands are disposed to using all necessary input including fertilizer indicating that farmers with larger farm size use more fertilizer than farmers with small farm size, this variable has direct relationship with the variables total output in naira, number of farmland owned and total cost of crop input which are also significant at 5%.

Table 2 Estimates of the influences of selected variables on the probability of use of fertilizer among smallholder arable crop farmers in Osun State

Constraints to fertilizer use in Osun State

From the logistic regression result, age of farmer (X₃), family size (X₁₁), income from other farm enterprise (X₇), and price of fertilizer (X₁₀), are highly insignificant at 5% significant level and can constitute the constraints to the use of fertilizer. Age of farmers has positive coefficient and it is insignificant, older farmers tend not to use fertilizer due to their cultural and traditional knowledge of practicing agriculture and suspected  health risk of fertilizer consumption.  Most farmers perceived price of fertilizer as being a deterrent to its use.  Fertilizer prices keep on increasing and do not offer farmers much incentive to its use. A major characteristics of sole farming as a production organization is that the farmers household and the farm are not separated in terms of asset and liability thus, the farm family size can be a major constraint because the farmer will distribute his total income between his household and the farm and the higher the family size the more he spends to cater for them which may cut back on the total amount invested in farming. High income from other farm enterprise would make a farmer to shift attention from farming hence invest less and use less of fertilizer.

Conclusion and Recommendations

The result of the study indicated that total farm output in naira, level of education, farm size, number of farmland owned and total cost of farmland were important factors influencing farmers’ use of fertilizer in arable crop production in the study area. Education plays a major role in fertilizer use and is very significant. It can be concluded that a formal educational institution is a major platform of creating awareness of the immense benefit of adopting and using new technologies even in agricultural production, aside formal institution, any means of educating farmers such as extension services, public awareness programs will enhance the use of fertilizer among arable crop farmers, resulting in increase in agricultural productivity and food security of the country. Thus, it is recommended that government and other policy makers therefore need to increase farmers’ knowledge and skills through aforementioned avenues.

Since the study had identified farm size as the major constraints militating against efficient use of fertilizer. Aftermath of land tenure system led to fragmentation of farmlands. It is recommended that Federal Government should expedite action in enforcing the land use Decree of 1978 and more liberal in making land available for agricultural production and the land tenure system can be reviewed in favor of agricultural production.

The descriptive analysis of the socio economic characteristic of respondents reveals that the population of arable crop farmers in study areas was getting old; as such there is an urgent need to encourage youth into arable crop production in the area. Rural infrastructure such as roads, electricity and telecommunication should be established and/or properly maintained where available in the rural areas by the governments at all levels. This will encourage the youths to stay in the rural areas.

In educating and training of relatively younger farmers, the government and other policy makers need to increase knowledge and skills of young farmers through avenues such as field days and schools, increase extension contact with farmers or any other means of building capacity. Also farmers should be train on how to keep proper and adequate farm record and need to separate family labour from farm business should be discussed in the training session.

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