Classification and Evaluation of Soils for Maize Cultivation in Western Part Akoko Southwest Local Government Area of Ondo State, Nigeria

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1 A publication of the School of Agriculture Technology, The Federal University of Technology Akure, Nigeria. Applied Tropical Agriculture Classification and Evaluation of Soils for Maize Cultivation in Western Part Akoko Southwest Local Government Area of Ondo State, Nigeria 1 Adesemuyi Department 1, E.A., of Soil B.S. Science Ewulo 2 and * & Meteorology, Ojeniyi 2, S.O. Michael Okpara University of Agriculture, Umudike, Nigeria. 2 Department of Crop, Soil and Pest Management, Federal University of Technology, Akure, Nigeria, bsewulo@yahoo.co.uk. *Corresponding author: ABSTRACT Soil varies both laterally and vertically over landscape and therefore requires proper inventory of its attributes for classification and optimal utilization. In order to examine the attributes of soils in selected locations in western parts of Akoko Southwest Local Government Area of Ondo state and evaluate its potential for maize cultivation, six pedons were established at Ose-Oba (Pedon 1), Ago-Ajayi (Pedon 2), Oyinmo (Pedon 3), Agbanimu (Pedon 4), Araromi (Pedon 5) and Ago-Fulani (Pedon 6). Morphological descriptions of the pedons were carried out and horizons sampled for chemical analysis. Pedons were characterize and classified according to USDA soil Taxonomy and FAO/UNESCO system of soil classification. The suitability of the study area for maize cultivation was evaluated with non-parametric and parametric square-root methods. The results of morphological and physical analyses revealed deep ( cm) and well drained soils with increase in clay content with depth (argillic). Surface soil textures were sandy loam underlain by sandy clay loam. Topsoil reaction varied from slightly acidic to neutral (ph: ). Percentage organic carbon and total nitrogen were low. The soil were acidic with low base saturation (<50% by NH4OAc), a requirement for classifying the soil in the order Ultisols following USDA system of soil taxonomy. The appropriate correlation in FAO/UNESCO system of classification is Acrisol. All pedons were kandic in nature with ustic moisture regime. Parametric evaluation showed that sites with Pedons 1, 5, and 6 are not currently suitable for maize cultivation, Pedon 4 site is marginally suitable while sites with Pedons 2 and 3 are moderately suitable for agriculture. However, potentially, Pedons 5 and 6 are marginally suitable for agriculture. The soil requires varying level of fertility management practices targeted at alleviating its identified constraint to maize productivity. Key words: soil classification, taxonomy, fertility, agriculture, pedon INTRODUCTION The importance of any soil management system lies in the extent to which it can sustain agricultural production without adverse effect on soil, water and environment. Thus, soil management and conservation may not be effective unless the soil is reliably characterized, classified and interpreted with regard to specific crop growth requirements. This cannot be overemphasized particularly in this era of constant threats of misuse of soil resources that result in serious degradation, soil erosion and other environmental hazards (Akamigbo, 2010). It is therefore, important to understand the characteristics of soils in an area, which is very important and crucial for their productive and sustainable management for the betterment of lives of the inhabitants (Oluwatosin et al., 2006). Decisions on land-use are now based on comprehensive analysis of the potential and productivity of resources such as climate, soil, topography, hydrology, etc. Land evaluation is very important in this direction as it provides information on the potentials and constraints for a defined land-use type with respect to crop performance as affected by the physical environment. In agricultural production, the interest of the farmer lies mainly on how profitable it is to grow a particular crop and what amendments are necessary to optimize the productivity of the soil for the specified crop (Fasina and Adeyanju, 2006). Maize, as a major source of calories, is not only for humans consumptions but also for animals feeds in Nigeria and other parts of the world, which has resulted to more soil being opened up for large scale production to meet the high demand (Udoh and Ogunkunle, 2012). Therefore, one of the strategies to achieve food security in a sustainable environment is to study soil resources in details through soil characterization and land evaluation for various land utilization types (Esu, 2004). However, in the low activity clay soils where this study was conducted, lands have been utilized intensively for different purposes thereby resulting in their degradation and imbalanced ecosystem in a landscape. The study was therefore, conducted to characterize, classify and assess the suitability of selected basement complex soils of the western part of Akoko Southwest Local Government Area in Ondo State for maize production. 10

2 MATERIALS AND METHODS The study area The study was conducted in the Western part of Akoko Southwest Local Government Area of Ondo State. Soils of the area were formed predominantly from Precambrian Basement Complex, which forms parts of the African crystalline shield (Alabo, 1985). The western part of Akoko Southwest Local Government Area where the study was carried out is located o o o between latitudes 07 18? and 07 29? N and longitudes 05 32? o and 05 43? E with altitude that ranged from 228 m to 321 meters above sea level. The terrain of the study area nearly level plain to gently undulating. The climate of the area is humid tropical, with wet and dry seasons. Rainfall is bimodal, with mean annual rainfall ranging between mm while mean annual temperature is between 21 and 320C. Mean relative humidity is generally high (about 80%), reaching the peak between May and October. The natural rainforest vegetation that previously characterized the study area is gradually receding to derived savannah due to human activities. The vegetation contains some important hardwood species such as Melicia exelsa, Antaris Africana, e.t.c. The major agricultural tree crops cultivated in the area include Theobroma cacao, Cola spp and Elaeis guineensis. Traditional subsistence arable crops like Zea mays, Dioscorea spp. and Manihot spp. are cultivated in the study area. FIELD STUDY Six pedons were established in the following locations: Ose-Oba (Pedon 1), Ago-Ajayi (Pedon 2), Oyinmo (Pedon 3), Agbanimu (Pedon 3), Araromi (Pedon 5) and Ago-Fulani (Pedon 6) (Fig.1). The dimensions of the pedons were 1.5m wide x 1.5m long x 1.8m deep. The pedon locations were geo-referenced with Global Positioning System (GPS). Horizons were naturally designated and morphological description carried out on the field in moist condition using Munsell Soil Colour Charts. A sample was collected from each of the designated horizon, making a total of four samples per pedon. They were packed into polythene bags, neatly labeled and taken to the laboratory for physical and chemical analysis. LABORATORY STUDIES The Soil samples were air-dried, gently ground in a mortar and sieved with a 2mm sieve. Particle size distribution was determined by hydrometer method (Gee and Or 2002). Soil ph was determined using a glass electrode in 1:2 soil:water ratio (Thomas, 1996). Soil organic carbon (O.C) was determined using Walkley and Black method and Organic matter estimated by multiplying with a factor of as was done by Nelson and Sommers (1996). Total Nitrogen was determined by Kjeldahl digestion procedure (Bremmer, 1996). Available phosphorus was determined using the Bray 1 Method and exchangeable acidity by KCl extraction method (Mclean, 1965). Exchangeable Bases (Ca, Mg, Na and K) were extracted by leaching with 1N NH4OAC (ph 7.0). Ca and Mg were determined by atomic absorption spectrophotometer and Na and K by flame emission spectrophotometer. Cation exchange capacity (CEC) was determined by ammonium saturation method. Percent base saturation, effective cat ion exchange capacity (ECEC) and Silt/Clay ratio were calculated. SOIL CLASSIFICATION AND LAND EVALUATION Data obtained from the field and laboratory analyses were used to classify the soil into its appropriate order and suborder following the guideline in USDA Soil Taxonomy (Soil Survey Staff, 2010) and FAO system of classification (FAO, 2006). The suitability of the study area for maize cultivation was evaluated by conventional (non-parametric) and the parametric square methods as was done by Udoh and Ogunkunle (2012). For nonparametric evaluation, pedons morphology and chemical attributes were matched with established maize cultivation requirements, resulting in their being allocated to suitability classes. The suitability class is that indicated by the most limiting characteristics of the pedon (Udoh and Ogunkunle, 2012). For the parametric square method, each limiting characteristic was rated. The index of productivity (IP) for each pedon was calculated using the equation: Udoh and Ogunkunle, (2012) is that exchangeable K, available P and total N are not part of the fertility (f) group in the calculation of IPp. This is because these soil properties can be easily altered. However, these properties were considered in calculating the IPc. RESULTS AND DISCUSSION Morphological and physical properties of the soil Table 1 shows pedons morphological properties and particlesize distribution. The soils were deep (>120 cm) and well drained. Colour matrix of the epipedons ranged from grayish brown (10YR5/2) to brown (7.5YR5/3). Epipedon with similar hue of 10YR has also been observed granitic derived soil in Ado-Ekiti (Fasina, et. al., 2007). Okusami et al. (1997) on the other hand reported 5 amd 7.5YR hue for soils in southwest Nigeria. The epipedons were moderate, medium and crumb in structure and friable consistence. The endopedons ranged between strong brown (7.5YR4/6) and yellowish brown (10YR5/4) and from moderate, medium, blocky structure to structureless (incoherent) at various pedal depths with firm consistence. The position of pedons 1, 2, 4 and 5 on the landscape was nearly level plain (0 2%) while pedons 3 and 6 occurred on gently undulating slope (2 4%). Figure 1: Pedon Location in the Western part of Akoko southwest Local Government Area of Ondo State Where: IP= Index of Productivity (%), A = Overall lowest characteristic rating and B, C, D, F are the lowest characteristic ratings for each land quality group. The potential index of productivity (IPp) and the current or actual index of productivity (IPc) were calculated for each pedon using the established class scores. In each pedon, only one member of each of the five land quality groups (climate (c), topography (t), soil properties (s), wetness (w) and fertility (f)) were used in the calculation because there were strong correlations among members of the same group (Ogunkunle, 1993). The basic difference between IPp and IPc, according to The particle-size distribution showed that all the pedons had high percentage sand that ranges between 67-71% in the topsoil and 50-71% in subsoil, low percentage silt (10 22% in topsoil and 8 24% in the subsoil) and low to moderate percentage clay (11 18% in topsoil and 10 42% in subsoil) in all the pedons (Table 1). Clay content increased down the profile in all the pedons while sand content decreased with soil depth (Table 1). Silt fraction did not show any definite pattern of distribution. Soils with more than 15% clay have been reported to be dispersive (levy et al., 1993: Shainberg et al., 1992). The higher clay content observed in the sub-surface horizons in the pedons can be as a result of illuviation processes (Ojanuga, 1975 and Malagwi, et al., 2000). The silt/clay ratio is between , , , , , and in pedons 1, 2. 3, 4, 5 and 6 respectively. Silt/clay ratio indicates the degree of pedogenic weathering in soil (Sombroek and Zonneveld, 1971). The silt/clay ratio values in pedon 2 is less than 0.75 and indicates old age of the soil (Sombroek and Zonneveld, 1971), 11 12

3 Pedon 1, 4, 5 and 6 have values greater than 0.75 but not more than 1.5, indicating moderate pedogenic weathering (Sombroek and Zonneveld, 1971). Pedon 3 have values above 1.5 indicating recent pedogenic process (Sombroek and Zonneveld, 1971). Silt/clay ratios are generally less at the subsoil horizon indicating more intense weathering at the zone. A similar silt/clay ratio trend was observed by Ayodele et al., (2012) in arable lands in the Guinea savanna area of Nigeria. Quesada et al., (2011) report indicates Ultisol as more strongly weathered than Alfisol. Soil chemical properties The results in Table 2 show that soil ph ranged from , indicating moderately acid to neutral acid reaction. These values fluctuate irregularly with depth. Chude et al., (2011), reported similar ph range to be suitable for crop production. This is because plant nutrient elements are readily available at ph range. and World Reference Base for all pedon is Acrisols (FAO, 2006). Similar works carried out in Ado Ekiti by Fasina et al (2007), and in Akoko North West Local Government Area by Ewulo (2012) revealed Ultsol in addition to Alfisol. Okusanmi et al, (1997) also reported Ultisol in southwest Nigeria. Land suitability evaluation Table 3 shows land-use requirements for maize cultivation as established in literature. Table 4 (suitability class scores of soils of the study area for maize cultivation) was generated from the matching of soil morphological and chemical properties of the study area (Table 1 and 2) with the land use requirement of maize (Table 3). It also shows the summary of suitability classes under potential and actual (current) evaluation with parametric and non-parametric methods. The percentage organic carbon was low to moderate, ranging from 0.31% to 1.95%. The value decreased with soil depth in all the pedons probably, due to the concentration of plant and animal residues on the soil surface (Jenny, 2008). The low value of organic carbon could be attributed to high rate of decomposition/mineralization of organic matter because of intense cultivation and seasonal bush burning, which is a common practice in the area. The soil available phosphorus was low and decreased irregularly with soil depth in all the pedons except in pedon 4 where it was high. Relatively low amounts of available phosphorus and exchangeable bases were present in all the soils except pedon 4, which had high amount of available P and exchangeable K. The cation exchange capacity (CEC) values of the soils were generally low ( cmolkg-1).this may be attributed to their low clay content and type, and perhaps low organic matter. Nnaji, et al., (2002) opined that low CEC of a soil could be because of high rainfall intensity, clay type and content as well as previous land-use. Soil classification All the pedons showed consistently increasing clay with soil depth and are therefore argillic. They are characterized by low base saturation <50% by CEC determined at ph 7.0 (NH4OAc), which is part of the basis for classifying them as Ultisol (Soil Survey Staff, 2010). The prevalent Ustic moisture regime in the soils classified them into the suborder Ustults (Soil Survey Staff, 2010).. All the pedons had low CEC, indicating low-activity clay and are therefore classified as Kandiustults with reference to Soil Survey Staff (2010). The appropriate correlation in FAO/UNESCO Soil Map of the World Legend Source: Sys et al., (1991); Mongkolsawat et al., (1999). Key: C-Clay, CL=Clay Loam, L=Loam, SiCL= Silty Clay Loam, SL= Sandy Loam, SCL = Sand Clay Loam, SC= Sandy Clay, LS=Loamy Sand 13 14

4 Parametric evaluation The potential suitability of the soils under parametric method as calculated with the index of productivity for each pedon (Ogunkunle, 1993; Ogunkunle, 2012) (Table 4), showed that pedons 2 and 3 (33% of the soils) are moderately suitable (S2), pedons 4, 5 and 6 (50%) are marginally suitable (S3) while pedon 1 (17%) is not suitable (N1) for maize cultivation. However, in the actual (current) suitability, pedons 2 and 3 (33% of the soils) are moderately suitable (S2), pedon 4 (17%) are marginal (S3) while pedons 1, 5 and 6 (50%) are not suitable (N1) for maize cultivation. The use of similar index by Senjobi and Ogunkunle (2010) on Ultisol and Alfisol in South Western Nigeria showed pedons that were marginally suitable (S3) for maize. Non-parametric evaluation The potential assessment of the soils under non-parametric method following the method of Udoh and Ogunkunle, (2012), indicated that about 67% of the soils (pedons 2, 3, 4 and 6) are marginally suitable for maize production (S3) due to limitations imposed by the soil CEC (9.30, 7.28, 8.12 and 8.16cmol/kg respectively) and organic C in pedon 4 and 6 (0.79, 0.82% respectively) ((Table 2) when compared with land requirement for maize as outlined by Sys et al., (1991) (Table 3), while pedons 1 and 5 (33%) are considered not suitable (N1) due to limitation imposed by the soil organic C (0.31 and 0.71% respectively). However, the actual (current) suitability placed 50% of soils (pedons 2, 3 and 4) as marginally suitable (S3) due to limitations imposed by the soil P, K and CEC (Table 2 and 3) while the remaining 50% (pedons 1, 5 and 6) are non suitable (N1) for maize cultivation due to limitations imposed by soil P, N and organic C for pedon 1 (3.5cmol/kg, 0.07 and 0.31% respectively), P, K and organic C for pedon 5 (4.36mg/kg, 0.14cmol/kg and 0.71% respectively) and P and K for pedon 6 (2.88mg/kg and 0.13cmol/kg respectively). The major limitation to maize cultivation in the soil is fertility status (f), which is consistent with the report of Oluwatosin et al (2007) in his evaluation of Idoffa soils within Yewa North Local Government Area of Ogun state in southwest Nigeria for arable crop. Senjobi and Ogunkunle (2010) also reported a similar finding. Major limitation to land suitability for maize. The ratings (Table 4) showed that three of five the land qualities climate (rainfall, temperature and humidity), wetness (drainage), topography (slope), were optimum for maize cultivation in the study areas. In addition, under physical characteristic and fertility, soil depth and soil ph respectively were optimum for maize cultivation in the study area (Table 3). However, the sandy loam texture of the soils has rendered the whole area sub-optimal for optimum maize performance. It has been noted that for optimum maize productivity, clay loam or loamy textured is required (Sys et al., 1991). Another land quality that hinders the optimum production of maize in the study area was soil fertility, which has rendered some parts of the area marginal and others unsuitable for maize cultivation. In order to increase the productivity of the land for maize cultivation, good management techniques that will enhance nutrient retention in the soil should be adopted. 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