Pattern of Inorganic Fertilizer use among Food Crop Farmers in Ogun State, Nigeria

Asian Journal of Agricultural Sciences 4(1): 26-31, 2012 ISSN: 2041-3890 Maxwell Scientific Organizational, 2012 Submitted: August 01, 2011 Accepted: October 10, 2011 Published: January 25, 2012 Pattern of Inorganic Fertilizer use among Food Crop Farmers in Ogun State, Nigeria 1 A.O. Otunaiya, 2 P.A. Okuneye and 1 J.O.Y. Aihonsu 1 Department of Agribusiness and Farm Management, College of Agricultural Sciences, Olabisi Onabanjo University, Yewa Campus, Ayetoro, Ogun State, Nigeria 2 Department of Agricultural Economics and Farm Management, University of Agriculture, Abeokuta, Ogun State, Nigeria Abstract: If the world s 1.5 billion ha of farm land were farmed organically, enough food would be available for only about 2.4 billion people, leaving more than half the world s 6.5 billion people without food. Improved use of inorganic fertilizer has been adjudged as a possible solution to food insecurity in Nigeria. This study seeks to analyse the pattern of inorganic fertilizer use among the food crop farmers in Ogun State, Nigeria. A multistage sampling procedure was employed to select 554 food crop farmers from 88 farming communities in 44 cells, within 14 blocks of the four zones of the agricultural landscape of Ogun State, structured by the Ogun State Agricultural Development Programme (OGADEP). Data were analysed using descriptive techniques. Results show that only a quarter (25.6%) of the sampled farmers used fertilizer during the cropping season, at an average of 28 kg per farmer per year and 21 kg/ha of land cultivated. The analysis of difference of means shows that the average quantity of fertilizer used by food crop farmers varies with respect to sex, level of education, extension contacts, crop-mix, and use of tractor services, herbicides, insecticides as well as farm size and fragmentation. Key words: Inorganic fertilizer, food crop farmers, Nigeria. INTRODUCTION Inorganic fertilizers are chemical combinations of the nutrients that plants must have to grow, and available in a form they can use. The main nutrients in inorganic fertilizers are three essential elements: Nitrogen (N), Phosphorus (P), and Potassium (K) (Louis, 1997). Organic manure is an alternative avenue of soil replenishment. However, organic farming is less efficient and lower yielding than farming with inorganic fertilizers, especially in Nigeria (Otunaiya, 2010). This is partly because inorganic fertilizers deliver far more essential nutrients per unit weight than does organic matter. Also, Africa s depleted soils can no longer deliver enough organic matter to maintain soil health (IFDC, 1996). If the world s 1.5 billion hectares of farm land were farmed organically, enough food would be available for only about 2.4 billion people, leaving more than half the world s 6.5 billion people without food. Organic sources of mineral nutrients are certainly not available in sufficient quantities to feed sub-saharan Africa s current population of about 750 million-and that population will be 1.1 billion by 2020. Inorganic fertilizer seems to be the only practical way to provide enough plant nutrients to restore Africa s nutrient-depleted soils and feed Africa human population (Ahemba, 2009). To feed her growing population, Nigeria must increase food production by 4% per year for the next 10 years. To accomplish this challenge, the use of inorganic fertilizer must increase from an average of 10 to 50 kg/ha; since organic sources of soil nutrients will not be sufficient (Okoloko, 2006). This means that the use of inorganic fertilizers must increase at the rate of 18% per year, which is significantly more than the increases observed in South Asia (13%) and Southeast Asia (9%) from the early 1960s to the late 1980s (Yanggen., 1998; EPAT, 1993; Harold et al., 1994). It becomes imperative therefore, to analyse the pattern of inorganic fertilizer use among the food crop farmers in the study area. RESEARCH METHODOLOGY Study area and data collection method: The study was carried out in Ogun State, in the southwest geo-political zone of Nigeria. The State has a landmass of about 16,369.40 Km 2 (Ogun State Central Department of Statistics, 2008). The study was conducted in year 2010 using farm-level cross-sectional data for food Corresponding Author: A.O. Otunaiya, Department of Agribusiness and Farm Management, College of Agricultural Sciences, Olabisi Onabanjo University, Yewa Campus, Ayetoro, Ogun State, Nigeria 26

Table 1: Average quantity of inorganic fertilizer use and average application rate Sample Inorganic fertilizer use Average rate of use Total sample QFERT (Kg) 27.4813 554 FERTRATE (3.1685) 21.2233 (2.0354) Non users QFERT (Kg) - 412 (Kg/ha) - Inorganic fertilizer QFERT (Kg) 107.2156 Users 142 FERTRATE (9.6428) (Kg/ha) 84.1297 (5.2060) Figure in parenthesis are the standard error of estimate crop farmers in the study area. The main instrument for collecting the primary data was scheduled interview with the use of structured questionnaire Sampling technique: Multi-stage random sampling technique was adopted in this study. The sampling frame was based on the division of Ogun State into agricultural zones by OGADEP; each of which is further sub-divided into blocks, cells (circles) and sub-cells (villages). The first stage of the sampling process entailed a random selection of two-third of the blocks in each of the four agricultural zones in the state, depending on the total number of blocks in each zone. This was followed by an independent simple random selection of 50% of the cells in each of the blocks, and 25% of sub-cells (farming communities) in each of the selected blocks in stage 1 and 2, respectively. In the final stage, one food crop farmer was interviewed in 10% of residential buildings randomly selected from each of the sub-cells selected in stage 3. This process enabled the drawing of 554 food crop farmers across the four agricultural zones of the State. Analysis of pattern of inorganic fertilizer use: Patterns of fertilizer use was analysed by descriptive techniques. This include computation of descriptive statistics (means, standard error of means, etc) which were then summarized and presented in simple tables to show the variation in fertilizer use across socio-economic groups. Frequency distributions were also used to describe the type and mode of application of fertilizer used in addition to the description of demographic and socio-economic characteristics of the food crop farmers/farms, in the study area. Inorganic fertilizer use pattern among Arable Crop Farmers : This study provides a basic analysis of the use of inorganic fertilizer by food crop farmers in Ogun State. A farmer is considered to use inorganic fertilizer if it procured and applied any quantity of inorganic fertilizer on any cropped land within the last two production seasons. Inorganic fertilizer use pattern of farmers relate, interaction to their socio-economic characteristics, their spatial distribution, the crop enterprise mix and farm characteristics of the farmers, and how these considerations affect quantity (kg) and rate of inorganic fertilizer use (kg/ha) by the farmers. Rate of use of inorganic fertilizer is traditionally the indices by which inorganic fertilizer use is compared across farms. However, in this study, the average quantity of inorganic fertilizer used ause care must be exercised in interpreting the values for the rate of inorganic fby farmers is reported with the average rate of inorganic fertilizer use. This is becertilizer use given the way the estimates were generated. Following Knepper (2002) Farmers who responded to the survey questions indicated the total area they planted to food crops and total inorganic fertilizer use. Since the total inorganic fertilizer purchase is not necessarily applied to the total area planted, the calculation of the rate of inorganic fertilizer use may be prone to errors especially where farmers do not know the actual area fertilized. RESULTS AND DISCUSSION Average quantity and average rate of inorganic fertilizer use: The average quantity and the average rate of inorganic fertilizer use in Ogun state are shown in Table1. Arable crop farmers in the state used an average of 27.5 kg of inorganic fertilizer per production year while they had an average inorganic fertilizer rate of use of 21 kg/ha. However, among the food crop farmers that used inorganic fertilizer, the mean inorganic fertilizer quantity used was 107 kg. Moreover, the rate of use among users was 84 kg/ha. Obviously, the average rate of inorganic fertilizer use (i.e., 21 kg/ha) in Ogun State is relatively higher than the average rate of use for Nigeria which is put at mere 10 kg/ha (Okoloko, 2006). However, this use rate is far lower and insignificant when compared with the world average put at 90 kg/ha (IFDC, 1996). Farmers socio-economic characteristics and the Inorganic fertilizer use pattern: In the traditional agricultural production system practiced by food crop farmers in Ogun State, the farmers socio-economic characteristics are important factors that could affect the use or non-use of productive resource like inorganic fertilizer on the farm. The summary description of farmers by their socio-economic characteristics and the inorganic fertilizer use pattern are provided in Table 2. The results show that male farmers used more inorganic fertilizer (29.8 kg) than female (16.0 kg) but had fairly equal mean rate of use of 21.4 kg/ha and 20.3 kg/ha, for male and female farmers, respectively. The t-test statistics showed that sex significantly affect the mean quantity of inorganic fertilizer use; while for the rate of inorganic fertilizer use, sex was not a significant influence. Table 2 further reveals that farmers within the 27

Table 2: Farmers socio-economic characteristics and the inorganic fertilizer use pattern Average quantity Average fertilizer inorganic rate of use of Farmers socio Use (kg) (kg/ha) economiccharacteristics QFERT FERTRATE Sex Female 16.0082 a 20.3413 a (4.63462) (5.09471) Male 29.8861 b 21.4094 a (3.69939) (2.22069) t-value -1.660; p#0.10-0.192 Age (Years) Below 30 31.2984 a 24.5430 a (12.44776) (7.52068) 31-40 28.2408 a 26.5506 a (5.71335) (4.82259 41-50 23.6788 a 18.8148 a (5.21750) (3.87180) 51-60 33.9997 a 19.7841 a (9.01357 (4.09471) Above 60 21.9948 a 19.1579 a (4.37348) (4.17317) F-value 0.552 0.577 Education Non formally 15.8448 a 10.9727 a (5.45270) (3.34377) Primary 18.3649 a 18.3340 b (2.80918) (2.64362) Secondary 50.25088 b 31.6850 b (9.95714) (4.70525) Tertiary 79.5372 c 54.6167 c (24.25898) (18.25775) F-value 9.807; p#0.01 6.859; p#0.01 Extension Contact None last 1 year 15.5043 16.2563 (2.39099) (2.14349) At least once/year 75.2811 41.3647 (11.58624) (5.08839) t-value -7.967; p#0.01-5.021; p#0.01 Frequency of extension contact None 15.5043 a 16.2563 a (2.39099) (2.14349) 1-2 times 67.1627 b 31.2963 a (13.50724) (5.20110) At least 3 times 103.208 c 1 75.1948 b (21.61164) (11.479) F-value 34.505; p#0.01 21.729; p#0.01 Figures in parentheses are standard errors of means. a, b, c : Duncan test showing Average quantity and average rate of use within each socioeconomic grouping having different superscripts are significantly different age group 51-60 had highest average quantity of inorganic fertilizer use (34 kg) while farmers above 60 years old had the least average quantity of inorganic fertilizer use (i.e., 22 kg). With respect to the rate of use, farmers within the age bracket 31-40 years old had the highest rate of inorganic fertilizer use (27 kg/ha) while those in the 41-50 years age group had the least rate of use (19 kg/ha). The analysis of variance of means showed that there were no significant differences between farmers age group on the one hand, and the mean quantity of inorganic fertilizer use (kg) and the rate of use (kg/ha) on the other hand. Education is one of the major socio-economic factors that are likely to influence output and productivity of farmers as well as quantity of inorganic fertilizer use and the rate of use. Table 2 shows that mean quantity of inorganic fertilizer used by the farmers in the state increased as their level of formal education improved. Farmers that attained tertiary education used an average of 80kg of inorganic fertilizer per year while farmers without any formal education used only 15 kg. Likewise, the rate of inorganic fertilizer use also increased with the level of farmer s education. The highest rate of use (55 kg/ha) was observed among farmers that attained tertiary level education. The F statistics showed that farmers educational attainment is associated, albeit significantly, with the mean quantity of inorganic fertilizer use as well as the mean rate of inorganic fertilizer use. It is noteworthy that extension contact increased the use of inorganic fertilizer as well as the rate of use (Table 2). Farmers that had no contact with extension agent in the last one year used only 16 kg of inorganic fertilizer while those that had at least a visitation per year used 75 kg for the production period. Also the rate of use for non-visited farmers and visited farmers were 16 and 41 kg/ha, respectively. The t-tests conducted show that there were significant association between the number of visitations by extension agents and the average quantity and average rate of inorganic fertilizer used. Food crop enterprise mix and Inorganic fertilizer use pattern: The crop mixtures range from two to as many as five, apart from the mono crop farmers. Table 3 shows the crop mix and inorganic fertilizer use pattern in Ogun State. The table shows that food crop farmers rarely use inorganic fertilizer when melon is included in the crop mix. The mean quantity of inorganic fertilizer use and rate of use were highest in cassava, maize, vegetable and others mix farms, 133 kg and 54 kg/ha, respectively. The analysis of equality of means between various crop mix shows that there were no significant differences between various crop mixes with respect to the rate of inorganic fertilizer use. Conversely, there were significant differences between enterprise mix and quantity of inorganic fertilizer use. Use of other inputs and inorganic fertilizer use pattern: Access to other farm inputs such as tractor services, Herbicides and Insecticides is an indicator of farmers level of knowledge about improved technologies. Farmers use of other inputs and inorganic fertilizer use pattern is presented in Table 4. Farmers that utilized tractor services used 118 kg of inorganic fertilizer at the rate of about 50 kg/ha while farmers that utilized manual methods of land preparation used only 21 kg at the rate of 19 kg/ha. This shows that the use of tractor services enhances inorganic fertilizer use. The t-value shows that the use of tractor services 28

Table 3: Crop mix and inorganic fertilizer use pattern Average quantity Average rate of inorganic of use fertilizer (kg) (kg/ha) Crop mix (QFERT) (FERTILIZER) Cassava and Maize 13.3824 a 14.0126 a (6.63782) (8.24832) Cassava, Maize 4.2857 a 12.5000 a and Yam1 (8.07420) (9.22779) Cassava, Maize 13.9054 a 22.3888 a and Vegetable (6.30980) (10.28912) Cassava, Maize 52.2776 a 26.4656 a and Others (28.64376) (10.28811) Cassava, Maize, 7.0436 a 28.1744 a Melon and Yams (7.04359) (28.17438) Cassava, Maize, 12.5000 a 6.2500 a Melon and vegetable (12.50000) (6.2500) Cassava, Maize, 15.3846 a 10.9890 a Yams and vegetable (15.38462) (10.98901) Cassava, Maize, 133.3333 b 54.1667 a Vegetable and others (88.19171) (29.16667) Cassava, Maize, 9.3750 a 7.6299 a Melon, Yams and others (5.53163) (5.04075) Other mix 25.0000 a 10.4167 a (25.00000) (10.41667) F-value 2.351*** 0.547 Figures in parentheses are standard errors of means. a, b, c :Duncan test showing Average quantity and average rate of use within the crop mix having different superscripts are significantly different Table 4: Use of inputs and inorganic fertilizer use pattern Average quantity of Average Other farm inorganic fertilizer use rate of use (kg/ha) inputs (kg) (QFERT) (FERTRATE) Used tractor service No 21.2161 a 19.3560 a (2.59420) (2.06683) Yes 117.6300 b 49.6174 b (27.60893) (8.79023) t-value -7.907; p#0.01-3.617; p#0.01 Used herbicides No 21.8915 a 18.1976 a (3.05664) (1.98875) Yes 93.9083 b 57.8916 b (15.52054) (9.98499) t-value -6.290; p#0.01-5.301; p#0.01 Used insecticides No 17.7174 a 17.0429 a (2.34324) (1.95920) Yes 116.0664 b 60.5032 b (20.36689) (8.83196) t-value 10.093; p#0.01-6.530; p#0.01 Figures in parentheses are standard errors of means. a, b : Duncan test showing Average quantity and average rate of use within each other farm inputs grouping having different superscripts are significantly different was significantly different with respect to the quantity and rate of use of inorganic fertilizer. Herbicide and insecticides are other agro-chemical use apart from inorganic fertilizer on arable crop farms. Table 4 shows that farmers that used herbicide and insecticides utilized an average of 94 kg and 116 kg of inorganic fertilizer respectively. The rates of use were 58 and 61 kg/ha, respectively. This amount is high when compared with farmers that did not utilize herbicide and Table 5: Spatial distribution of farmers and inorganic fertilizer use pattern Geographical Average qqantity of Average rate Characteristics/ inorganic fertilizer of use(kg/ha) Use (Kg)(QFERT) (FERTRATE) Agrozone Rain forest 18.3745 20.2464 (2.30146) (2.76781) Savannah 36.3287 22.1826 (5.79001) (2.98496) t-value 2.851; p#0.0 10.476 Agrzone Abokuta 35.4700 b 34.2981 b (5.03134) (4.48081) Ijebu-Ode 8.1867 a 13.2231 a (2.06187) (3.66749) Ikenne 19.4249 ab 15.7217 a (4.47637) (4.23538) Ilaro 37.4719 b 16.6368 a (8.66940) (3.17800) F-value 4.597; p#0.01 6.436; p#0.01 Tarred Road Not Tarred 28.2927 15.5802 (6.86544) (3.55834) Tarred 27.2325 22.9483 (3.56942) (2.42070) t-value 0.137-1.535 Inorganic Fertilizer Depot Not Available 14.7202 14.6883 (2.74652) (2.38171) Available 48.7088 32.1678 (6.85816) (3.58541) t-value -5.321; p#0.01-4.218; p#0.01 a, b, ab : Duncan test showing Average quantity and average rate of use within each geographical variable, grouping having different superscripts are significantly different insecticide, whose average quantity and rate of inorganic fertilizer use were 22 and 18 kg. The rates of use were 18 and 17 kg/ha, respectively. This result shows that the use of herbicides and/or insecticide enhance the use of inorganic fertilizer. They go together as an improve technological package. The result of the t-test shows that both use of herbicides and insecticides were statistically significant with respect to the quantity and rate of use of inorganic fertilizer. Spatial distribution of farmers and inorganic fertilizer use pattern: It is believed that the socio-economic characteristics of a farmer go a long way to affect his farm performance and whether or not he will use certain inputs, such as inorganic fertilizer. This study investigated, beyond the socio-economic characteristics of farmers, the effects of farm and farmers spatial distribution on the quantity and rate of use of inorganic fertilizer. The spatial distribution of farmers and inorganic fertilizer use pattern in Ogun State is presented in Table 5. There are two main agro-ecological zones in the state, namely: Rain forest and Savannah zones. Results in Table 5 shows that farmers located in Rain forest zone used less quantity of inorganic fertilizer (18 kg) to those 29

Table 6: Farm characteristics and inorganic fertilizer use pattern Averageq quantity of Average inorganic fertilizer rate of use (kg/ha) Farm characteristics use (Kg) (QFERT) (FERTRATE) Farm size (ha) Below 1 12.5739 a 27.5921 a (1.62112) (3.74756) 1.0-<3.0 21.9252 a 14.9427 a (3.59450) (2.45003) 3.0 or more 71.4154 b 17.3753 a (13.43677) (3.29151) F-value 26.992; p#0.01 4.296 Farm fragmentation Non fragmented plot 38.3139 25.0460 (6.65588) (3.47099) Fragmented flots 20.1282 18.6047 (2.74587) (2.46583) t-value -2.835; p#0.01-1.556 Figures in parentheses are standard errors of mean in Savannah zone (36 kg). The rates of use in the two zones are almost the same. In the Rain forest, the use rate was 20 kg/ha while it was 22 kg/ha in Savannah zone. It is important to note, from the result of the t-test statistics that the agro-ecological location of a farmer only affects the quantity of inorganic fertilizer the farmer uses but has no effect on the rate of inorganic fertilizer use. This result, contrary to a priori expectation, revealed that farmers in the Rain forest zone had less access to inorganic fertilizer but had tendency for high rate of use if the inorganic fertilizer were available. The agricultural zone where farmers are located were also found to show significant differences in the quantity of inorganic fertilizer use and the rate of use by farmer. Farmers in Ilaro zone had the highest QFERT of 37 kg. This was closely followed by farmers in Abeokuta zone (35 kg). Farmers in Ijebu-zone and Ikenne zones used 8 and 19 kg of inorganic fertilizer, respectively. Abeokuta zone had the highest rate of inorganic fertilizer use of 34 kg/ha. The next to it was Ilaro and Ikenne zones with the rate of use of 17 and 16 kg/ha, respectively. Ijebu-Ode zone had the lowest rate of application of 13 kg/ha. Table 5 further reveals that farmers located in a community with untarred road used (28 kg) almost the same quantity of inorganic fertilizer with those located in a community with a tarred road (27 kg). Farmers located in a community with a tarred road had higher rate of use (23 kg/ha) when compared with those in a community with untarred road (16 kg/ha). The t-test statistics, however, shows that there were no significant differences between communities with tarred road and untarred road with respect to the quantity and rate of inorganic fertilizer use. The presence of inorganic fertilizer depot or sales point within a community where the farmers were located was also examined in Table 5. The mean quantity of inorganic fertilizer use in communities where inorganic fertilizer depot was not available was 15 kg. Their rate of use was about 15 kg/ha. Whereas farmers located in a community where there was inorganic fertilizer depot had mean inorganic fertilizer quantity use of 49 and 32 kg/ha, as the rate of use. The result of the t-test conducted shows that presence of inorganic fertilizer depot within a community made significant differences in the quantity and rate of inorganic fertilizer a farmer uses. Farm characteristics and inorganic fertilizer use pattern: The farm size of a farmer is believed to affect the quantity and the rate of use of inorganic fertilizer. Table 6 shows farm characteristics and inorganic fertilizer use pattern in arable crop production in the state. Farmers that cultivate below 1 ha of arable crop used 13 kg of inorganic fertilizer while those that cultivated between 1-3 ha used 22 kg. Farmers with 3 or more hectares used an average of 71 kg of inorganic fertilizer. This shows that quantity of inorganic fertilizer use will increase as the farm size increases. Conversely, farmers with less than 1 ha of arable crop farm had the highest rate of inorganic fertilizer use (28 kg/ha). Whereas, farmers with large farm size (3 or more ha) used inorganic fertilizer at the rate of 17 kg/ha. The reduction observed in the rate of inorganic fertilizer use, as farm size increases, suggests a cost constraint faced by large farms in inorganic fertilizer procurement, hence, resulting in low rate of use. ANOVA result shows that there were significant differences in farm sizes with respect to the quantity of inorganic fertilizer use but not significantly different in rate of use. The nature of the farm plot is also believed to affect the use of inorganic fertilizer. Table 6 also reveals that farmers with non-fragmented plot used more inorganic fertilizer (38 kg) and applied more inorganic fertilizer per hectare (25 kg/ha). This is unlike fragmented plot where the average quantity used was 20 kg and 21 kg/ha as the rate of use. This confirms the a priori expectation that non-fragmented plot enhances the use of inorganic fertilizer. The t-test statistics show that there were significant differences in the nature of the farm plot with respect to average quantity of inorganic fertilizer use but not with the rate of use. CONCLUSION AND RECOMMENDATION It can be concluded from the findings in the study that the quantity of inorganic fertilizer use and the rate of application are lower than the recommended standards thereby, limiting inorganic fertilizer users in the state to wholly benefit from the impacts of inorganic fertilizer on soil fertility and crop output. Since tractor services, herbicide and insecticide usage enhance the use of fertilizer by food crop farmers. It is recommended therefore, that agro-service centres and extension agents should provide and introduce tractor 30

hiring services, herbicide and insecticide along with fertilizer, as a technology package to farmers. REFERENCES Ahemba, T., 2009. Nigeria Inorganic Fertilizer Plant Restart after 10 Years. Retrieved from: http//www. Online Nigeria.com, (Accessed on: February 10, 2009). Environmental and Natural Resources Policy and Training Project (EPAT)/Winrock International, 1993. Agricultural Transformation in Africa. Proceedings of the Seminar on Agricultural Transformation in Africa. Harold, C., B. Larson and L. Scott, 1994. Inorganic fertilizer Consumption Remains Low in Africa and the Middle East. International Agriculture and Trade Reports, Situation and Outlook Series, USDA Economic Research Service, WRS-94-3, July, pp: 32-37. International Inorganic Fertilizer Development Center (IFDC), 1996. Africinorganic fertilizer Situation, IFDC November. Knepper, E.T., 2002. Factor Affecting the Use of Inorganic fertilizer by Small and medium-sized farming households in Zambia, 1997 to 2000. Unpublished M.Sc Thesis, Submitted to Department of Agriculture and Natural Resources, Michigan State University. Louis, P.L., 1997. Inorganic fertilizers and Raw Materials Supply Demand Balances. (Report at 65th IFA Annual Conference) Beijing: International Inorganic fertilizer Association. Ogun State Central Department of Statistics (CDS), 2008. Ogun State Statistics. Abeokuta: Ogun State Central Department of Statistics, Nigeria, pp: 2. Okoloko, O., 2006. African Green Revolution Paper Delivered at African Inorganic fertilizer Summit, (June 9-13, 2006), Abuja, Nigeria. Retrieved from: http://www.africainorganic.fertilizersummit.org (Accessed on: December 10, 2008). Otunaiya, A.O., 2010. Economics of fertilizer use among food crop farmers in OGUN state. Unpublished Ph. D Thesis, Submitted to the Department of Agricultural Economics and Farm Management, Olabisi Onabanjo University, Ago-Iwoye, Ogun state, Nigeria. Yanggen, D., K. Valerie, R. Thomas and N. Anwar, 1998. Incentives for Inorganic fertilizer Use in Sub-Saharan Africa: A Review of Empirical Evidence on Inorganic fertilizer Response and Profitability. MSU International Development Working Papers, Vol. 70. 31