Economics of aflatoxin control in maize production among smallholder farmers in Oyo State, Nigeria

In Africa, the prevalence of aflatoxin contamination in agricultural production places the stability of food security at risk. This study investigated the socio-economic characteristics of farmers; assessed the prevalence of aflatoxin in maize production; identified the aflatoxin control practices used; and estimated the net returns to users and non-users of the control practices. A multistage sampling procedure was employed to select 240 farmers, comprising users and non-users of aflatoxin control practices. Data were collected on farmers’ socioeconomic characteristics, maize farmland cultivated, the proportion affected by aflatoxin as well as quantity and prices of inputs and output from the maize farms with the aid of pretested structured questionnaire and interview guide in a focus group discussion. Data were analyzed using descriptive statistics and budgeting technique. Results showed that most of the farmers are married (86.7%), with over 20 years of farming experience and active ages of between 41 and 60 years. 42% of their average maize farm of 2.7 ha were affected by aflatoxin contamination. About 28% of the farmers used different types of aflatoxin control practices. A larger proportion (72%) of the farmers did not use any of the control measures. There was a significant difference (p<0.05) in the net returns earned between users and non-users of aflatoxin control practices. It was concluded that use of aflatoxin control practices in maize production should be promoted among farmers in Oyo state as it enhances maize yield and the net returns earned from maize production.


INTRODUCTION
Maize (Zea mays, L.) is one of the major food crops grown across a range of agro ecological zones in Nigeria and is currently the third most traded cereal after wheat and rice, with a total production of about 822 million tonnes on over 160 million hectares of land (Onuk et al., 2010;FAO, 2012).It is produced annually more than any other grain and about 50 species exist, consisting of different colours, textures; grain shapes and sizes (IITA, 2007(IITA, , 2008)).Maize is a source of food for humans and animals with about 80% consumed by man and animals, while 20% is utilized as basic raw material for the production of starch, alcoholic beverages, ethanol, food sweeteners and fuel (Adegboye, 2004;FAO, 2007;FAOSTAT, 2015).It is an important source of carbohydrate, protein, iron, vitamin B and minerals.Maize is predicted to become the crop with the greatest production globally, and in the developing world by 2025 (Rosegrant et al., 2008).
Despite its importance, maize production in Africa is bedevilled with low productivity with average yield of about 1.5 tons/ha (CIMMYT, 1999;De Groote et al., 2003).Low maize yield is often ascribed to various factors such as climate change, price fluctuations, poor storage facilities, and in particular, pests and diseases (Ojo, 2000;Tirado et al., 2010).Among the pest and diseases that currently threatens maize productivity growth is aflatoxin, known to be one of the most potent and dangerous groups of mycotoxins worldwide (IITA, 2012).Aflatoxins are toxic to crops and animals, pose serious risk to human health resulting into food insecurity, hunger, famine and huge economic losses (Cardwell et al., 2001;Stronider et al., 2006;Legreve and Duveiller, 2010;Waliyar and Sudini, 2012;IITA, 2012).
Several maize growing states in Nigeria, including Oyo state, have been identified with the incidence of aflatoxin occurring beyond the acceptable threshold of 247 and 276.1 ppb (Meridian Institute, 2013), and the level and frequency of occurrence are particularly high in 30% of maize in stores (IITA, 2013).According to Udoh et al. (2000), 33% of maize samples from different ecological zones of Nigeria are contaminated with aflatoxins.Thus, tackling aflatoxin contamination has become a priority in maize enhancement programmes among farmers in Nigeria with different measures employed for aflatoxin control.These control measures include timely planting, maintaining optimal plant densities, proper plant nutrition, avoiding drought stress, proper harvesting, and control of other plant pathogens, weeds and insect pests (Bruns, 2003).However, these measures have been used with varying degrees of effectiveness across agro ecological zones in Nigeria (Ogunsunmi, 2005;Adeoye et al., 2011).It therefore becomes imperative to evaluate the economic implications of using Aflatoxin control measures among maize farmers.Thus, the important questions to ask are: What are the socio-economic characteristics of smallholder farmers in maize producing areas?What proportion of maize land is affected by aflatoxin contamination?Which are the control practices employed by maize farmers to control aflatoxin?Are there differences in the costs and returns to maize production between users and non-users of aflatoxin control practices?This paper therefore evaluates the economic implications of aflatoxin control on maize production in Oyo State, Nigeria.Specifically, the paper describes the socioeconomic characteristics of the maize farmers; examines the prevalence of aflatoxin in maize farms; identifies the types of aflatoxin control measures used; and determines the net returns to use of aflatoxin control Ladoye et al. 2437 measures in the study area.

Study area
The study was conducted in Oyo State in Southwestern Nigeria.
The state is located between latitudes 7 °3′ and 9 °12′ north of the equator and longitudes 2° 47′ and 4° 23′ east of the Meridian, and covers a total land area of about 27,249 sq km, with a ratio of almost 1:1 distribution of male to female population (NPC, 2006).
Based on the prevailing climatic conditions and vegetation types, the state has three agro-ecological zones, viz: rainforest, savannah and derived savannah.The rainforest is characterized by high relative humidity and supports the cultivation of tree crops like citrus, oil palm and cocoa as well as arable crops like cassava, yam and maize.The vegetation of the savannah and derived savannah zones mainly supports the cultivation of crops such as cassava, cowpea yam and maize.By virtue of its location between 40°N and 40°S latitude, Nigeria's environment offers suitable growing conditions for the fungi, aflatoxin (Agboola, 1987;Udoh et al., 2000).

Sampling procedure and data collection methods
A multistage sampling technique was employed to select respondents for the study.The first stage involved the purposive selection of three local government areas (LGAs), namely Afijio, Saki East and Ibarapa East where maize is predominantly produced.In the second stage, two villages with relatively higher incidence of maize area affected by aflatoxin were purposively selected from each of the LGAs to give 6 villages.Stratified sampling was used in the third stage to categorize farmers in each village into two: those that control for aflatoxin, and those who did not control for aflatoxin.Finally, between 15 and 25 farmers were randomly selected from each category, based on the proportion of maize farmers in each village, to give a total of two hundred and forty respondents for the study.Primary data were collected using pretested structured questionnaire.Interview guide was also used to complement the questionnaire in focus group discussion sessions.Data collected included farmers' socio-economic characteristics such as gender, age, level of education, farm size, household size and proportion of maize land affected by aflatoxin as well as input-output quantities and prices to use and non-use of aflatoxin control practices.

Data analysis
Data was analysed using descriptive statistics and budgeting technique.The descriptive statistics was used to describe the study variables and it involved the use of means, standard deviation, frequency counts and percentages.The difference between mean tests was used to compare estimates for farmers who controlled for aflatoxin and those who did not.The partial budgeting approach to budgeting technique was used to estimate the costs, returns and gross margin (net profit) to use of aflatoxin control measures as described below.
The gross margin is assumed to be due only to the effects of use of at least one of the aflatoxin control measures and was computed using cost-return analysis.The cost consists of fixed cost (FC) and variable cost (VC).Fixed costs are indirect production costs which are incurred independent of the level of production regardless of the volume of sales or level of output; while variable costs are direct production costs which are consumed directly in the production process and which are used roughly in direct proportion to the level of production.Note that in this study, only the variable cost was used with the assumption that users and non-users of aflatoxin control measures have the same background living within the same geographical area and with similar sociocultural and demographic characteristics, and only differ in their use or non-use of aflatoxin control measures (Upton, 1979;Bamire, 1999;Adeoye et al., 2011).Data were collected on the quantities and prices of variable cost items such as seed, fertilizer, herbicides, pesticides, aflatoxin and labour, while returns to maize production was computed by collecting information on quantities and prices of outputs.
Costs were computed by multiplying the quantity of inputs ( Xj ) used in kg per hectare on each farm by their average prices ( j P ) in Naira (N), that is, Xj Pj , and the summation of variable costs (TVC) for all respondents is given as ∑ Xj Pj , while returns were computed by multiplying the quantity of maize output ( i Q ) in kg per hectare by their market prices and the summation of returns (TR) for all respondents is given as The partial budgeting technique employed to compute the gross margin is specified as: Where i and j represent the number of observations (i, j = 1, 2, 3, 4, …,240); GM is gross margin in (N/ha); TR is total revenue = average quantity of output i in kg/ha ( i Q ) x average price of output i ₦/kg ( i P ), and for all observations, ∑ i P i Q ; TVC is total variable cost = average quantity of inputj used in kg/ha (Xj) x average price of input j in ₦/kg (Pj), and for all observations, ∑ Xj Pj (2) Equation 2 was computed for users and non-users of aflatoxin control measures as well as for the entire sample.

RESULTS AND DISCUSSION
This section presents the results of data analysis based on the objectives of the study.It compares the socioeconomic characteristics of users and non-users of aflatoxin control measures among the smallholder maize farmers in Oyo State, Nigeria; describes the extent of aflatoxin contamination based on the proportion of maize area affected by aflatoxin; reports the different types of aflatoxin control practices used; and estimates the gross margin or net returns to use of the aflatoxin control measures.

Socioeconomic characteristics of maize farmers
The socio-economic characteristics of farmers in the study area, comprising users and non-users of Aflatoxin control measures are shown in The human capital endowment of the farmers is often represented by household size as it reflects potential labour supply for farming services (Afolayan, 2012).The difference between the household size for users (7.55±3.02)and non-users (7.63±3.39) of aflatoxin control practices was not significant at the conventional levels of probability.Majority of the respondents (60%) had a household size of between 6 and 10 members and about 16% had more than 10 members.This suggests that maize farmers in the study area have the opportunity of possibly engaging household members in their farming activities.
The highest percentage of users (45.8%) and nonusers (48.6%) of aflatoxin control practices had secondary education, 43.8 and 41.7% users and nonusers had primary education, respectively.Also, about 4 and 7% of users and non-users of the control practices had tertiary education, while only 6.3 and 2.8% did not have any formal education.The high level of basic education attained by the farmers could be attributed to the free and compulsory primary education policy of the Federal Government of Nigeria for all Nigerians.
The number of years of experience in any setting, including farming, is expected to improve proficiency as a result of knowledge and better skills acquired over time (Bamire et al., 2007;Oyekale and Idjesa, 2009).More than 80% of the respondents had over 10 years of experience in farming.The difference between the mean years of farming experience of users (23.9±11.35)and non-users (24.5±14.12) of aflatoxin control measures was significant (p<0.10).This shows that users of aflatoxin control measures are more experienced in maize farming than non-users.In other words, farmers with more years of farming experience use aflatoxin control practices.

Prevalence of aflatoxin in maize production
The prevalence of aflatoxin infestation, indicated by the proportion of maize land affected by Aflatoxin in the study area, is shown in Table 2.
There was no significant difference between the mean farmland area cultivated by users (4.91±3.22ha) and non-users (4.44±2.84ha) of aflatoxin control measures in the study area.About 86% of the farmers cultivated below five hectares of land, which suggests that most of the respondents are small scale farmers; those that cultivated above 5 hectares constituted 8.3% for the sample, 6.3% for users of aflatoxin control methods and 9.3% for non-users.The size of maize farmland is in agreement with Ojo (2000) that established that the crop production is mainly small scale in size.A larger proportion of the farmers (73%) reported that less than 0.5 hectares of their maize farms was affected by aflatoxin.Also, about 76% of those that controlled aflatoxin and 71% of those that did not use control measure had less than 0.5 hectares of their farms affected by aflatoxin.The difference between the proportion of farmers who used control measures (42%) and those that did not (41%) was not statistically significant (p>0.5).This implies that the proportion of maize farms affected by aflatoxin is as large as those not affected by aflatoxin in the study area as reported by IITA (2013).

Aflatoxin control practices used in Oyo State, Nigeria
The different aflatoxin control practices used by maize farmers in Oyo State are shown in Table 3.There are various control practices employed by maize farmers in Oyo State; traditional, chemical, biological, and a combination of the practices of which the traditional/ biological method had the highest percentage (9%).This classification is in consonance with the study of IITA ( 2013) classifying methods of controlling aflatoxin in food crop.About 67.5% of the farmers did not use any control practice which suggests that most farmers do not control aflatoxin on their maize farms.Out of the remaining 32.5% that controlled for aflatoxin, about 15% used traditional method as the dominant control measure, 11% used chemical methods and only 2% used biological methods.This implies that farmers that controlled for aflatoxin mostly used traditional or local methods that involve drying/use of traditional storage systems to store maize.Use of chemical control measures involved the use of fungicides and herbicides in controlling aflatoxin.
Only few farmers employed the use of biological control measures that involved bio-control of fungal growth in the field in combating aflatoxin infestation.This view was supported by focus group discussion reports and further enunciated by seminal works of Onuk (2010) and Waliyar and Sundini (2012).

Net returns to use of aflatoxin control measures
A comparison of the average costs incurred and net returns (profit) to users and non-users of Aflatoxin control measures in the study area is shown in Table 4. From the table, there was a significant difference between the total revenue earned per hectare by users of aflatoxin control measures (₦299,959.01)and that of non-users (₦247,690.67),implying that use of aflatoxin control measures earned higher revenue than its non-use.However, the difference between the total variable costs of production of users of control measures (₦170,763.69)and that of non-users (₦165,616.99)was not significant (p>0.5),suggesting that the two groups incurred almost similar costs in their maize production operations.An analysis of cost items showed that labour accounted for the highest percentage for both users (48%) and non-users (49%) of aflatoxin control measures; and fertilizer cost accounted for 17% for users and 18% for nonusers of control methods.There was a significant difference (p˂ 0.01) between the mean net returns earned by users of aflatoxin control methods (₦88,719.28)which more than doubled that of non-users (₦43,597.68).The same trend was obtained for the difference between the mean gross margin of users of aflatoxin control measures (₦129,195.92)and that of non-users (₦82,073.68)which was significant at the 5% level of probability.This suggests that users of aflatoxin control measures in maize production earned higher net returns than non-users as supported by Bruns (2003) and Legreye and Duveiller (2010).

CONCLUSION AND RECOMMENDATIONS
Aflatoxin contamination ruins maize harvests, and consequently leads to low productivity, food insecurity, reduces farmers' income generating potentials and destroys the lives and livelihoods of millions of people (Udoh et al., 2001;IITA, 2013).
There is a relatively high prevalence of aflatoxin contamination in the study area, as indicated by the proportion of maize farmland affected by the fungi.Though, maize production generally earns positive net returns to production in the study area, use of aflatoxin control measures provide significant increases in the net returns to farmers' production efforts than its non-use.However, the non-use of aflatoxin control measures by a large percentage of farmers in Oyo State suggests the need for enlightenment programmes aimed at sensitizing farmers on the dangers of aflatoxin on their farms, and in promoting the use of aflatoxin control measures through effective extension services in the study area for increased maize production.Also, a significant proportion of the farmers used the traditional control measures among the different types of control measures, suggesting the need to guide farmers in

Table 1 .
Bamire et al. (2007)ively larger percentage of the farmers in the entire sample were married, while only few 4.6% were single.All users of aflatoxin control measures were married, while 93.2% of non-users were married with only few (6.8%) single.The mean age of users of aflatoxin control methods was 50.64±8.83yearswitha minimum of 26 and maximum of 72 years, while that of non-users of aflatoxin control methods, it was 48.64±14.11yearswitha minimum of 16 and maximum of 80 years.There was no significant difference between the ages of the farmers in the two groups, suggesting that the farmers are generally within the same age group.About 83% of the entire respondents and about 89 and 80% of users and non-users of aflatoxin control measures respectively were 60 years and below.This may suggest that on the average, farmers in the study area are expected to be productive.A larger percentage of the respondents who are users (88.5%) and non-users (77.2%) of aflatoxin control practices were between the ages of 41 and 60 years.This further suggests that most of the respondents are in the active and productive age bracket and supports the findings ofBamire et al. (2007)and Ohajianya et al.
(2010)that farmers within this age range are resourceful and active.

Table 1 .
Socioeconomic characteristics of maize farmers in Oyo State, Nigeria *Significant at p<0.05.

Table 2 .
Prevalence of aflatoxin in the maize farms (% respondents).

Table 3 .
Aflatoxin control practices used in the maize farms (% respondents).

Table 4 .
Average net returns (N) of use and non-use of aflatoxin control measures.