EFFECT OF SELECTED INSECTICIDE ON WHITEFLY (Bemisia tabaci) INFESTING BRINJAL PLANTS 313 Morphological and Physical Characteristics of Soils Developed on a Toposequence Derived from Coarse-grained Pegmatites in a Tropical Region, Delta State, Nigeria Egbuchua, C. N. Department of Agronomy, Delta State University, Asaba Campus, Asaba, Delta State, Nigeria Abstract A study was conducted to evaluate the morphological and physical characteristics of a soil devel- oped on a toposequence using fire slope positions. Modal profile pits were dug in each of the slope positions and characterized. Soil samples were collected from each of the pedogenetic horizons and analyzed routinely for particle size distribution of bulk/particle densities and total porosity. Results showed that the landscape had a relative elevation of 0-24. 25 m with a slope gradient value from the crest to valley bottom as: 1.68, 1.55, 1.46, 1.42 and 1.22%. Soil colour from the crest to the valley bottom varied significantly from dominant 5YR to 7.5 YR and 10YR respec- tively. Soil depth, structure, consistence and rootlets varied significantly (P ≤ 0.05) across slope position. Bulk and particle densities value were higher in the crest and upper-slope positions with mean values of 1.20 gcm -3 and 2.35 gcm -3 . There were no significant variations (P > 0.05) in parti- cle size distribution across slope position. Keywords: Morphological, physical characteristics, toposequence, coarse-grained, pegmatites, tropical re- gion Introduction 1 Many topical soils are derived from coarse grained pegmatites whose parent materials are resistant to weathering, and the fine earth fractions usually made up of coarse sand and are rarely clayey. These soils are known to be rich in feldspars and quartz primary min- erals and, they are neither stable nor resis- tance to human induced activities (Akinbola et al., 2010). The physical, morphological, chemical and mineralogical properties which are fundamentally related to their geological background, parent materials and the inten- sity of the different soil forming factors and processes varied considerably. Most African soils are characterized by roll- ing landscape and soil properties are differ- Corresponding author’s Email address: egbuchuacn@gmail.com ent due to the factor of topography which plays a vital role in bringing about changes in soil properties as one moves from inter fluves/crest position down to the valley bot- tom. These changes in soil properties led to the concept of CATENA (Milne, 1935) or Toposequence (King et al., 1983). In other words, where related soils differ in their characteristics due to the influence of topog- raphy, such a sequence of soils is known as a Toposequence. According to Juo and Moorman (1981), Toposequence refers to a succession of sites from crest to a valley bot- tom, which contains a range of soil profiles that are representative of the landscape and soils. The topographical features of a land- scape are vital in understanding soil forming processes and modification of soil profile development. Consequently, understanding the roles of topography in a landscape will help in assessing productive values of soils and most importantly, in developing strate- gies for its conservation. The influence of Asian Journal of Agriculture and Rural Development journal homepage: http://aessweb.com/journal-detail.php?id=5005 mailto:egbuchuacn@gmail.com Asian Journal of Agriculture and Rural Development, 4(5)2014: 313-323 314 soil morphological and physical properties on plant growth cannot be under-estimated. Since most tropical soils are on a rolling ter- rain, agricultural crop production activities are bound to be affected negatively thereby resulting to low productivity. It is therefore the objective of this study to evaluate the morphological and physical properties of these soils and their management implica- tions. Materials and methods Description of the study area The study was conducted in Anwai-Asaba in Delta State, Nigeria. Anwai is located be- tween latitude 06° 14¹N and longitude 06° 99¹E of the equator and lies significantly in a tropical rainforest zone with over 1,565mm of rainfall per annum. The rainfall character- istics are bimodal in nature with peaks in July and September. The mean annual tem- perature ranges between 27° – 28.6°C with an annual relative humidity of about 65.7%. The geology is made up of coarse grained pegmatites derived from a basement com- plex that gave rise to coarse-textured soils that are more acid than base (Egbuchua, 2012). The landscape is generally undulating with pockets of rolling features scattered all over the places. Land use is typically based on rain-fed agriculture and crops commonly cultivated include roots and tuber crops, ce- reals, pulses and different varieties of vege- tables. An isohyperthermic temperature re- gime and an udic soil moisture regime typify the general area. Field work A topographic survey of the study area was carried out using Dumpy level and soil char- acteristics described in accordance with the guidelines provided by Young, (1976), for topographic survey description and interpre- tations. Based on the guidelines, five slope positions were created. These were crest, upper-slope, middle-slope, lower-slope and valley bottom positions (Fig 1). Fig 1: A cross section of the study area showing the various slope positions In each of the slope positions, a transect was selected and two profile pits dug to the re- quired depth where possible. The profile pits were carefully examined; delineated and de- scribed using the guidelines as contained in the soil survey manual (Soil survey staff, 2006). From each of the pedogenetic hori- zons, soil samples were collected, formally processed by air-drying, grinding and siev- ing through a 2 mm mesh and labelled prop- erly for laboratory analysis. Laboratory analysis The particle size distribution of the soil samples were analysed by hydrometer method as described by Gee and Bauder, (1986), and the textures were finally deter- mined using the USDA textural triangle. Bulk density was determined by core- method using a metal sampler as described by Blake and Hartge, (1986). Particle den- sity was determined by the pycometer method (Blake and Hartge, 1986). Total po- rosity was calculated using the formular: Tp = I – B d x 10 P d Where, Tp = Total porosity Upper-slope Middle-slope Lower-slope Valley bottom 2000 m Horizontal distance Relative Elevation 24.2 m Asian Journal of Agriculture and Rural Development, 4(5)2014: 313-323 315 B d = Bulk density P d = Particle density Statistical analysis Descriptive statistics such as mean, standard deviation and coefficient of variation were used according to the procedure outlined by Steel and Torrie (1980). Results and discussion Topographic features The results of the topographic survey showed a relative elevation of 0 - 24.25m (Fig 1). This is an indication that the study area was a plain of low relief (Young, 1976). Slope gradients as determined from the crest, to the valley bottom positions were 1.46, 1.68, 1.28, 1.42 and 1.55% respec- tively (Table 1). The slope gradient could be said emphatically to be very gentle at all po- sitions. Table 1: Topographic characteristics of the study area Landscape posi- tion Gradient (%) Distance from absolute crest at mid position (m) Relative elevation at mid position (m) Crest 1.68 222.34 22.30 Upper slope 1.55 1425.47 19.47 Middle slope 1.46 1223.2 14.27 Lower slope 1.42 548.2 8.21 Valley bottom 1.22 53.46 3.17 Morphological characteristics The morphological features (Table 2) were found to vary along toposequence. The soil colours differed from the crest, upper and middle-slope positions and are characterized by a Hue of 5YR yellowish red. The lower and valley bottom slope positions have 7.5 YR and 10 YR reddish, yellow and grayish colour sequence as evidence of water satura- tion at some period of the year thereby signi- fying poor drainage conditions. The ob- served change in soil colour along the to- posequence was as a result of the influence of topography on micro-climate. In times of rainfall, the crest and upper slope positions receive atmospheric precipitation only, while the lower and valley bottom slopes re- ceive both precipitation and run off from the crest and upper slope positions. This phe- nomenon saturates the lower and valley bot- tom slope positions with water for an ex- tended period than the crest and upper slopes. The implication of this, is the red- dish, yellowish and greyish colour sequence in the lower slopes depicting mottling as ob- served in the study. Soil depth or thickness of solum Soil depth increased progressively along the slope positions. The crest and upper-slopes were deep up to 140 cm. The lower and val- ley bottom slopes were shallow (60-80 cm depth) because of high water table. The shal- low depth observed in the lower/valley bot- tom slope positions could be attributed to water erosion effects along the slope as some materials could be eroded from the crest and upper slopes downward thereby decreasing the thickness of the solum. The implication is that land use will therefore vary between the lower/valley bottom and upper slope positions. The available mois- ture in the lower/valley bottom positions will therefore, guarantee dry season farming in them. The structure was found to improve down-slope. The crest, upper-slope and middle-slope positions were weakly struc- tured due to the impact of run-off, while the lower slope/valley bottom positions were strongly structured, firm, sticky and plastic due to increased clay and organic mattercon- tents. Asian Journal of Agriculture and Rural Development, 4(5)2014: 313-323 316 Table 2: Morphological descriptions of the soils Pedon 1 Horizon design Soil depth (cm) Colour (moist) Mottling Structure Consistence Inclusions Rootlets Boundary A Ap B Bti C 0-15 15-45 45-75 75-115 115-140 5YR 2/3 5YR 4/8 5YR 5/8 7.5YR 5/8 7.5YR 4/8 - - - - - 1, c, gr 1, c, gr I, c, sbk I, c, abk I, c, abk Lo, fr Lo, fr Lo, fr Lo, fr Lo, fr - - - - - 1 1 1 - - cs cs cs d d Pedon 2 A Ap B Bti C 0-15 15-45 45-75 75-115 115-140 5YR 2/3 5YR 2/3 5YR 5/8 5YR 5/8 7.5YR 5/8 - - - - - 1, c, gr 1, c, gr I, c, gr I, c, gr I, c, gr Lo, fr Lo, fr Lo, fr Lo, fr Lo, fr - - - - - 1 1 1 - - cs cs cs d d (Upper Slope Position) Pedon 3 A Ap B Bti C 0-25 25-60 60-75 75-95 95-140 5YR 2/3 5YR 2/3 2.5YR 7/6 2.5YR 7/6 2.5YR 7/6 - - - - - 1, c, gr 1, c, gr I, c, gr I, c, gr I, c, gr Lo, fr Lo, fr Lo, fr Lo, fr Lo, fr - - - - - 1 1 1 1 - gs gs cs cs d Pedon 4 A Ap B Bti C 0-25 25-60 60-75 75-95 90-140 5YR 2/3 5YR 2/3 2.5YR 7/6 2.5YR 7/6 2.5YR 7/6 - - - - - 1, c, gr 1, c, gr I, c, gr I, c, gr I, c, gr Lo, fr Lo, fr Lo, fr Lo, fr Lo, fr - - - - - 1 1 1 1 - gs gs cs cs d (Middle Slope Position) Pedon 5 A Ap B Bti C 0-25 25-45 45-65 65-85 85-120 7.5YR 4/3 7.5YR 4/3 7.5YR 6/8 7.5YR 6/8 7.5YR 5/8 - - - - - 1, c, gr 1, c, gr I, c, gr I, c, gr I, c, gr Lo, fr ns Lo, fr ns Lo, fr ns Lo, fr ns Lo, fr ns - - - - - 2 2 2 - - gw gw gs gs gs Pedon 6 Asian Journal of Agriculture and Rural Development, 4(5)2014: 313-323 317 A Ap B Bti C 0-25 25-45 45-65 65-85 85-120 7.5YR 4/2 7.5YR 4/2 5YR 5/8 5YR 5/8 7.5YR 5/8 - - - - - 1, c, gr 1, c, gr I, c, gr I, c, gr I, c, gr Lo, fr ns Lo, fr ns Lo, fr ns Lo, fr ns Lo, fr ns - - - - - 2 2 2 - - gw gw gs gs gs (Lower Slope Position) Pedon 7 A Ap B Bti C 0-15 15-35 35-45 45-60 60-80 5YR 5/8 5YR 5/8 7.5YR 4/8 7.5YR 4/8 7.5YR 5/8 - - - - 7.5YR 5/8 1, c, 1, c, 2, sbk 2, abk 2, abk sh, sst sh, sst sh, sst sh, sst sh, sst - - Fe conc Fe conc Fe conc 3 3 3 F F gw gw ds gs gs Pedon 8 A Ap B Bti C 0-15 15-35 35-45 45-60 60-80 5YR 5/8 5YR 5/8 7.5YR 5/8 5YR 5/4 5YR 5/8 - - - - 7.5YR 5/8 1, c 1, c 1, sbk 2, abk 2, abk sh, sst sh, sst sh, sst sh, sst sh, sst - - Fe conc Fe conc Fe conc 3 3 3 F F gw gw ds ds gs (Valley Bottom Position) Pedon 9 A Ap B Bti C 0-15 15-30 30-45 45-60 60-75 7.5YR 4/6 7.5YR 4/6 7.5YR 4/1 7.5YR 6/8 7.5YR 6/8 - - - 7.5YR 5/8 7.5YR 5/8 2, sbk 2, sbk 2, sbk 3, sbk 3, sbk fm, spl fm, spl fm, spl fm, spl fm, spl - - Fe Mn conc Fe Mn conc Fe Mn conc M M 2 2 2 cs cs gw gw gw Pedon 10 A Ap B Bti C 0-15 15-30 30-45 45-60 60-75 7.5YR 6/2 7.5YR 6/2 7.5YR 6/2 7.5YR 6/8 7.5YR 6/8 - - - 7.5YR 5/8 7.5YR 5/8 2, sbk 2, sbk 2, sbk 3, sbk 3, sbk fm, spl fm, spl fm, spl fm, spl fm, spl - - Fe Mn conc Fe Mn conc Fe Mn conc M M 2 2 2 cs cs gw gw gw Symbols as interpreted in the USDA – SCS (1998) Special publications on soil profile description Structure: 1 = weak, 2= moderate, 3 = strong, c= coarse, gr = gravelly, sbk = sub angular block, abk = angular blocky Consistence: Lo= loose, fr = friable, sh=slightly hard, h=hard, pl=plastic, st = sticky, sl st = slightly sticky Inclusions: Fe = Iron concretion, Mn = Manganese concretion Rootlets: 1 = common, 2 = few, 3 = many, m = many Boundary: cs = clear smooth, d = diffuse, gs = gradual smooth, gw = gradual wavy, ds = diffuse smooth, gv = gradual wavy Asian Journal of Agriculture and Rural Development, 4(5)2014: 313-323 318 The consistence also improved down-slope. At the upper slope positions, the consistence was loose, friable, non plastic and non- sticky due to erosion influence. At the lower slope position the consistence was however more compact, plastic, firm and sticky. Rootlets were common, with few roots at the upper-slope position, to many, fine and me- dium in the lower slope position. The dis- tinctness and outline of horizons within the horizons ranged from clear smooth to dif- fused at the crest and upper slope positions to gradual smooth at the middle slope and dominantly gradual and wavy at the lower/valley bottom slopes. Particle size distribution The data for the particle size distribution is shown in (Table 3) while the weighted means, standard deviation and coefficient of variations for the crest/upper-slope, middle- slope and lower slope/valley bottom posi- tions are shown in (Table 4), respectively. In the crest, upper-slope and middle-slope positions, sand seemed to be the dominant soil fraction at the surface horizon and tend to decrease with depth. The cumulative weighted mean values for the crest/upper- slope positions were 56.84% with a coeffi- cient of variation of 21.49%. The middle- slope position had a mean value of 67.52% and a coefficient of variation of 63.06%. The lower and valley bottom-slopes had a mean value of 38.82% sand and a coefficient of variation of 13.87% (Table 4). The percentage clay content on the other hand, increased downward from the crest to middle slope positions while the lower and valley bottom slopes showed a contrasting trend in clay accumulation and an increasing trend in sand accumulation. The differences in clay accumulation along the toposequence could have resulted from lateral transloca- tion of clay which were removed in suspen- sion from the upper slopes due to surface wash and deposited in the lower slopes. The decrease and irregular accumulation of clay with depth and progressive increase as ob- served in some of the topographic positions could be due to differences in parent mate- rial or lithologic discontinuity. Another ob- served feature was the presence of gravelly concretions in the lower horizons in the crest upper-slope and middle-slope positions. Ac- cording to Idoga and Malgwi (2006), these minerals are mainly iron oxide nodules or dimitritus of lateritic ironstone and quartz which have been deposited to form the par- ent materials of the area. Bulk density The mean bulk density for the crest/upper slopes, middle-slope and lower/valley bot- tom slopes were 1.20 gcm -3 , 0.79 gcm -3 and 0.47 gcm -3 and coefficient of variations of 19.30%, 11.47% and 14.65% in that order respectively (Table 4). Generally, in all the topographic positions, the bulk density was found to increase with depth of profiles. This could be attributed to decrease in or- ganic matter accumulation with depth, less root penetration and compaction caused by the weight of the overlying layers (Brady and Weil, 2007). Particle density The mean values of particle density (Table 4), ranged from 2.35 gcm -3 with a coefficient of variation of 4.22% for the crest/upper slope position; 2.20 gcm -3 and a coefficient of variation of 8.49% for the middle-slope position and 1.19 gcm -3 and a coefficient of variation of 6.53% for the lower/valley bot- tom slope positions. The particle density has an inverse relationship with bulk density as it decreases with depth of profile. This could be vividly explained by the higher content of organic matter in the soil surface which weighs much less than an equal volume of mineral solids. Therefore, its presence in large quantity in the soil will lower the soil’s particle density as reported by Brady and Weil (2007). The data obtained from this study was an indication that particle density of most mineral soils does not very much. Asian Journal of Agriculture and Rural Development, 4(5)2014: 313-323 319 Table 3: Some physical properties of the soils Horizon de- sign Soil depth (cm) Gravel Sand Silt % Clay Silt/clay ratio Bulk density gcm -3 Particle density gcm -3 Total porosity % Text class Crest Position Pedon 1 A Ap B Bti C 0-15 15-45 45-75 75-115 115-140 - - - - 58 52.26 50.23 46.24 34.32 40.18 28.28 28.28 19.74 18.24 15.36 19.46 21.49 34.02 47.44 44.46 1.45 1.32 0.58 0.38 0.35 0.95 0.98 1.35 1.46 1.55 2.54 2.52 2.32 2.25 2.18 63 61 42 35 29 SL SCL CL C SC Pedon 2 A Ap B Bti C 0-15 15-45 45-75 75-115 115-140 - - - - 60 54.27 52.25 48.37 42.75 43.18 22.14 21.37 19.31 19.31 20.13 23.59 26.38 32.32 37.94 36.69 0.94 0.81 0.60 0.51 0.54 0.98 1.03 1.17 1.35 1.45 2.52 2.49 2.42 2.36 2.24 61 59 52 43 35 SCL CL CL SCL SCL Upper slope position Pedon 3 A Ap B Bti C 0-25 25-60 60-75 75-95 95-140 - - - - 62 72.34 69.21 65.34 62.10 59.38 22.74 20.85 19.75 19.20 17.35 5.92 9.94 14.91 18.70 23.27 3.67 2.09 1.32 1.03 0.75 0.86 0.95 1.13 1.24 1.54 2.39 2.35 2.30 2.27 2.22 64 60 51 45 31 LS SL LS SL SCL Pedon 4 A Ap B Bti C 0-20 20-45 45-75 75-90 90-140 - - - - 64 75.45 72.10 69.85 65.25 63.75 13.45 11.75 10.24 10.75 10.10 11.10 16.15 19.91 24.0 26.15 1.21 0.73 0.51 0.45 0.39 0.91 0.98 1.24 1.34 1.47 2.42 2.38 2.32 2.28 2.23 62 59 47 41 34 LS LS SL SCL SCL Middle Slope Position Pedon 5 A Ap B Bti C 0-25 25-45 45-65 65-85 85-120 - - - - 54 72.35 70.28 67.34 62.14 62.05 17.35 15.45 12.75 12.05 11.74 10.30 14.27 19.91 25.81 26.21 1.68 1.08 0.64 0.47 0.45 0.68 0.73 0.81 0.85 0.93 2.36 2.34 2.27 2.21 1.87 71 69 64 62 50 SL SL SL CL CL Asian Journal of Agriculture and Rural Development, 4(5)2014: 313-323 320 Pedon 6 A Ap B Bti C 0-25 25-45 45-65 65-85 85-120 - - - - 60 73.25 71.28 69.11 65.24 63.14 19.24 16.34 14.35 14.15 13.28 7.51 12.38 18.54 20.61 23.58 2.56 1.32 0.77 0.69 0.56 0.67 0.72 0.78 0.85 0.90 2.34 2.30 2.24 2.18 1.85 71 69 65 61 51 SL SL SL SCL SCL Lower slope position Pedon 7 A Ap B Bti C 0-15 15-35 35-45 45-60 60-80 - - - - - 36.15 38.0 40.45 42.34 44.17 29.15 31.10 32.60 34.10 36.10 34.70 30.90 26.95 23.56 19.73 0.84 1.01 1.21 1.45 1.83 0.43 0.47 0.53 0.58 0.61 1.35 1.25 1.20 1.15 1.12 68 62 56 50 46 CL CL CL CL CL Pedon 8 A Ap B Bti C 0-15 15-35 35-45 45-60 60-80 - - - - - 37.30 38.12 42.35 42.95 45.10 26.34 28.25 32.0 35.24 36.31 36.36 33.63 25.65 21.81 18.59 0.72 0.84 1.25 1.62 1.95 0.74 0.49 0.51 0.53 0.59 1.36 1.27 1.19 1.15 1.10 65 61 57 54 46 CL CL CL CL C Valley Bottom Position Pedon 9 A Ap B Bti C 0-15 15-30 30-45 45-60 60-75 - - - - - 28.35 30.15 35.45 42.28 45.30 31.34 35.24 32.14 32.13 38.35 40.31 34.61 32.41 25.11 16.35 0.78 1.02 0.99 1.28 2.35 0.37 0.38 0.41 0.43 0.45 1.25 1.21 1.18 1.12 1.10 70 69 65 62 59 CL CL CL CL C Pedon 10 A Ap B Bti C 0-15 15-30 30-45 45-60 60-75 - - - - - 31.20 33.10 35.35 41.20 47.12 34.12 36.35 42.14 38.35 35.37 34.68 30.55 22.51 20.45 17.51 0.98 1.19 1.87 1.88 2.02 0.39 0.41 0.45 0.48 0.50 1.23 1.20 1.17 1.12 1.09 68 66 62 57 54 CC SCG L L C Asian Journal of Agriculture and Rural Development, 4(5)2014: 313-323 321 Table 4: Mean, standard deviation and coefficient of variation (CV %) of slope positions in the study area Slope position Soil properties Sd CV% Crest/upper slope Sand Silt Clay Silt/clay ratio B d P d Tp 56.84 18.36 24.67 0.83 1.20 2.35 48.45 12.22 5.23 11.21 0.45 0.23 1.11 11.81 21.49 28.41 45.43 54.25 19.30 4.22 24.37 Middle slope Sand Silt Clay Silt/clay ratio B d P d Tp 67.52 14.47 17.91 10.22 0.79 2.20 63.30 4.26 2.26 6.54 0.67 0.09 0.19 7.62 63.06 15.59 36.52 65.68 11.47 8.49 12.83 Lower slope/valley bottom Sand Silt Clay Silt/clay ratio B d P d Tp 38.82 32.12 27.19 1.35 0.47 1.19 59.85 5.38 3.42 6.41 0.48 0.07 0.08 7.28 13.87 10.66 23.58 35.77 14.65 6.53 12.16 Keys: x = mean, sd = Standard deviation; CV% = Coefficient of variation. Pd = Particle density, Bd = Bulk density, Tp = Total porosity This is because quartz, feldspars and colloi- dal silicate clays make up the major portions of mineral soils and impart their intrinsic characteristics of stability to the soil (Brady and Weil, 2007). Total porosity The crest/upper slopes have lower total po- rosity with mean values of 48.45%, while the lower/valley bottom slopes have mean total porosity of 59.85% (Table 4). Total po- rosity was found to decrease with depth of profile and it is closely related to organic matter content, clay accumulation and the activities of earthworms and other macro- animals in the soil system. Total porosity has also an inverse relationship with bulk density. Silt/clay ratios The silt/clay ratio which is used to study the degree of pedogenetic weathering in soils Sombroek and Zonneveld (1971) showed that the crest/upper slope and lower/valley bottom slope positions had mean silt/clay ra- tios of 0.83 and 1.35 indicating moderate pedogenetic weathering processes. The mid- dle-slope with a mean silt/clay ratio of 10.22 was an indication of recent pedogenetic process. According to Sombroek and Zonneveld (1971), any value of silt/clay ratio less than 0.75 indicates old age of the surface deposits while values between 0.75 and 1.5 indicate moderate pedogenetic weathering processes. Higher values (>1.5) indicate recent pe- dogenetic processes. The findings in this study to some extent collaborate with earlier works on toposequence in the tropics by Juo and Moorman (1981), Essoka et al. (2006) and Idoga et al. (2006) respectively who af- firmed some variations in soil properties on toposequence. Asian Journal of Agriculture and Rural Development, 4(5)2014: 313-323 322 Conclusion The study was carried out to evaluate the morphological and physical characteristics of soils on a toposequence. The results showed the landscape as a plain of low relief with very gentle slope. The morphological properties showed variations in soil colour in relation to slope positions with a domi- nant 5YR at the crest and 7.5YR and 10YR in the lower slope positions. Soil depth, structure, consistence, and rootlets varied across slopes. The texture especially the clay fraction was not statistically significant across slopes, while the silt/clay ratio re- vealed moderate pedogenetic weathering processes for the crest/upper slope and lower valley bottom positions. The middle slope position indicated recent pedogenetic proc- esses. Bulk, particle densities and total po- rosity were not statistically influenced (P > 0.01) across slope positions. The general re- sults showed the role of topography in as- sessing the productive value of soils and the need to develop strategies for its conserva- tions. Because of the nature of rainfall with its attendant erosion effects, the crest, upper slope and middle slope positions should re- main under vegetative cover. The establish- ment of vetiver grass stripes across slope po- sitions will help to stabilize the soil and in effect, check erosion. The lower slope and valley bottom position can be cultivated with field crops under strict soil conserva- tion practices. References Akinbola, G. E., Ojo U. A., & Adigun, M. O. (2010). Variability of properties of some pedons on basement complex of south western Nigeria, Proceedings of the 34 th annual conference of the soil science society of Nigeria. March 22 nd -26 th , 2010 Ibadan, Nigeria. Blake, G. R., & Hartge, K. H. (1986). Bulk density. In: Klute (eds). Methods of soil analysis, Part 1: Physical and mineralogical methods. 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(ed.) Characteristics of soils in relation to their classification and management for crop production. Clarendon press Oxford pp. 10 - 29. Soil Survey Staff (2006). Keys to Soil Tax- onomy. USDA soil conservation ser- vice (10 th edition) N.R.C.S/Washington, D.C. Sombroek, W. G., & Zonneveld, I. S. (1971). Ancient dune fields and fluviatile deposits, Soil survey paper No. 5 soil survey institute Wageningen. The Netherlands. pp. 109. Steel, R. R., & Torrie, J. H. (1980). Princi- ples and procedures of statistics with special reference to biological sci- ence, McGraw Hill Book Co. Inc. New York, 481p. Young, A. (1976). Tropical soils and soil Survey, Cambridge University press, Cambridge.