CHARACTERISTICS AND CLASSIFICATION OF SOILS AS INFLUENCED BY PARENT MATERIALS IN SOUTH-EASTERN NIGERIA

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1 CHARACTERISTICS AND CLASSIFICATION OF SOILS AS INFLUENCED BY PARENT MATERIALS IN SOUTH-EASTERN NIGERIA ABSTRACT Udoh *, B. T. and Akpan, U. S. Department of Soil Science and Land Resources Management, University of Uyo, Uyo, Akwa Ibom State, Nigeria *Corresponding author: Phone: ; The objectives of this study were to characterize and classify soils influenced by parent materials in south-eastern Nigeria. Four parent materials were selected, namely, beach ridge sands (BRS), coastal plain sands (CPS), sandstone (SS) and alluvial deposits (ALD). For the BRS, CPS and SS, toposequences (two for each parent material) were used as study sites and profile pits were studied at the crest, middle slope and valley bottom. For the ALD, soils were identified through auger borings and modal profiles were sited in areas typical of each soil unit. In all, 24 profile pits (six for each parent material) were studied. The result showed that there were three soil orders in the landscape studied, and they occurred as follows: (i) Entisols/Arenosols (37.5%), Inceptisols/ Cambisols (12.5%) and Ultisols/Acrisols (50%). All the soils derived from CPS and ALD were Ultisols (Typic Kandiudults from CPS and Aeric Endoaquults from ALD). On the other hand, all the soils derived from SS and three (of the six) pedons from BRS were Entisols (Typic Udipsamments and Typic Psammaquents) while three BRS pedons were Inceptisols (Typic Dystrudepts and Aeric Endoaquepts). This result shows definite association of certain soil types with a particular parent material. Therefore carrying out soil mapping on the basis of known parent materials would cut costs and produce rapid results with high reliability for agricultural land use planning in the area of study. Keywords: Parent material, soil types, humid tropical climate, soil mapping, INTRODUCTION Parent material is the initial material from which the soil is formed. It is the framework on which the other soil forming factors operate to form soils, hence can be regarded as providing the body of the soil (Ibanga, 2006). Parent materials influence soil formation by their different rates of weathering, the nutrients they contain for plants use and the dominant particle size they contain (Esu, 2005). Such attributes as the texture of the soil, water retention and release, chemical and mineralogical characteristics, and hence the fertility status of the soil, are highly influenced by the nature of the parent material. Therefore, the type of soil formed under a particular set of environmental conditions is a function of the parent material and time (Ajiboye and Ogunwale, 2010). In Akwa Ibom State, the major parent materials from which most soils have developed include the coastal plain sands (CPS), sandstone (SS), alluvial deposits (ALD) and beach ridge sands (BRS) (Petters et al; 1989; Ibia and Udo, 2009). The characteristics of these soils are largely determined by these original materials and influenced by climate, topography and the general agricultural land use pattern and management. Classifying soils occupying any particular agro-ecological zone into defined types would bring about proper recommendation for utilitarian purposes and also aid the transfer of technology to areas of similar soil types. This will bring about general agricultural development. However, soil survey and classification though very useful in agricultural land use planning, is expensive. A good knowledge of a definite relationship between a particular parent material and certain soil types in the landscape, would guide in efficient, quick and accurate soil mapping. This will reduce the cost of soil survey and produce rapid results (soil maps) with high reliability for agricultural land use planning in the area of study. Therefore, the aim of this study was to assess the influence of parent materials on the types of soil found in the landscape of Akwa Ibom State under the humid tropical climate. This is with a view to contributing to better understanding and classification of these soils for proper management for improved and sustainable agricultural productivity. MATERIALS AND METHODS Study area Akwa Ibom State is located in Southeastern Nigeria. It lies within latitudes 4 30' and 5 30' N and longitudes 7 30' and 8 20' E. The climate is humid tropical, annual rainfall ranges from more than 3000 mm along the coast to about 2250 mm at the extreme north, with 1 3 dry months in the year. Mean annual temperature varies between 26 and 28 C, while mean relative humidity is 80%. The original natural vegetation which comprised lowland rainforest, mangrove forest and coastal vegetation, has given way to a mosaic farmland/ oil palm forest, riparian forest and oil palm forest (Petters et al., 1989, Udoh, 2009) Field work Four parent materials from which most soils in the state are derived were selected for the study. The parent materials were, coastal plain sands (CPS), beach ridge sands (BRS), sand stone (SS) and alluvial deposits (ALD). NJAFE VOL. 11 No. 3,

2 For the CPS, BRS and SS, toposequences (two for each parent material), were used as study sites. In each site profile pits were studied (one each) at the crest, middle slope and valley bottom. For the ALD, soils were identified through auger borings and modal profiles were prepared in areas typical of each soil unit. In all 24 profile pits (six for each parent material) were described and sampled according to the FAO (1990) guidelines. The samples collected were processed for laboratory analysis. Laboratory analysis Laboratory analyses of soil samples were carried out using appropriate standard procedures (IITA, 1979; Udo and Ogunwale, 1986, Udo et al., 2009). The following parameters were analysed for: particle size distribution, soil reaction (ph), electrical conductivity, organic carbon, total nitrogen, available phosphorus, exchangeable bases, exchangeable acidity, among others. Also, using appropriate formula/methods, the following were determined: effective cation exchange capacity (ECEC) and based saturation (BS). Soil classification From the result of the soil analyses of the 24 pedons from the four parent materials were classified, following the USDA Soil Taxonomy (Soil Survey Staff, 2006) into orders, suborders, great groups and subgroups, and correlated with FAO/UNESCO Legend / World Reference Base (FAO/WRB, 2006). RESULTS AND DISCUSSION Characteristics and classification of soils derived from different parent materials Some characteristics of soils derived from the following parent materials; coastal plain sands (CPS), beach ridge sands (BRS), sandstone (SS) and alluvial deposits (ALD) are shown in Tables 1, 2, 3 and 4 respectively. Also, the classification of the 24 pedons (six pedons from each parent material) are presented in Table 5. Soils derived from coastal plain sands (CPS) Soils derived from CPS were characterized by high sand content, ranging from 618 to 884 g kg -1 (Table 1). Generally, the sand content decreased with depth. Silt content was generally very low and irregularly distributed within the profile. Compared with sand fraction, clay content was relatively low ranging from gkg -1 and characteristically increased with profile depth. There was clear evidence of clay movement down the profile resulting in the formation of argillic (Bt) horizons in all the six pedons (CPS A1, CPS A2, CPS A3, CPS B1, CPS B2, CPS B3) derived from CPS (Table 1). Also base saturation ranged from very low (5%) to medium values (77%). These results have confirmed earlier observations that soils derived from CPS are characteristically coarse textured, highly weathered and low in base status due to intense leaching of basic cations as a result of the inherent high rainfall in the area (Petters et. al., 1989, Udoh, 2003, Udoh et al., 2007). Classification of the six CPS pedons by the Soil Taxonomy (Soil Survey Staff, 2006) shows that, with argillic horizons and low base status all the pedons belong to the order Ultisols or Acrisols (WRB/FAO, 2006). They all qualified as Udults at the suborder category, being under Udic moisture regime. As a result of their very deep profiles and relatively minimal decrease in clay content down the profile (Soil Survey Staff, 1999), all the CPS pedons qualified as Kandiudults at the Great Group category. All except pedon CPS A3, classified as Typic Kandiudults at the subgroup level while CPS-A3 was placed under Arenic Kandiudult because of its high sand content (Table 1). Soils derived from the beach ridge sands (BRS) In Table 2 are some characteristics of soils derived from the BRS parent material. The pedons (BRS A1, BRS A2, BRS A3, BRS B1, BRS B2, BRS B3) all had very high sand contents in all the horizons, ranging from 953 to 833 g kg -1. As expected clay content was very low in all the horizons, ranging from 110 to 46 g kg -1. However, pedons BRS A1, BRS A2, and BRS A3, were relatively better developed than pedons BRS B1, BRS B2, and BRS B3. Hence, whereas some horizons of A1, A2 and A3 pedons had loamy sand textures, all the horizons of B1, B2 and B3 had sand texture (Table 2).The above observation shows that soils derived from the BRS are relatively young and characteristically coarse textured. Previous workers (Geodata, 1979, Tahal, 1982 and Petters et al., 1989) have had similar results. In terms of soil classification, pedons BRS A1, A2 and A3, with little diagnostic features (Cambic horizon), all qualified as Inceptisols soil order (Soil Survey Staff, 2006) or Cambisols (WRB/FAO, 2006) (Table 5). On the other hand, pedons BRS B1, B2 and B3, with very minimal profile development, all qualified as Entisols or Arenosols (Soil Survey Staff, 2006; WRB/FAO, 2006). Two Entisols (BRS-A2 and A3) under poorly drained (Aquic) moisture regime, but with relatively high chroma qualified as Aeric Endoaquept at the subgroup category. Also one Entisol (BRS B3), under similar moisture regime as above, but with very high sand content, qualified as Typic Psammaquent. On the other hand the freely drained Inceptisol (BRS A1), with its acidic nature, the soil was classified as Typic Dystrudept at the subgroup category, while the Entisols (BRS B1 and B2) under the same (Udic), moisture regime, but with high sand content both qualified as Typic Udipsamment at the subgroup category. 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3 Table 1: Some Characteristics of Pedons derived from coastal plain sands (CPS) parent material design depth (cm) Sand Silt Clay *Textural g kg- 1 class Org. M (g kg -1 ) ECEC (cmol kg -1 ) CPS A1 Ap LS Bt SL Bt SCL Bt SCL B SCL C SCL CPS A2 Ap SL Bt SCL Bt SCL Bt SCL C SCL CPS A3 Ap LS Bt LS Bt SL B LS C SL C SCL CPS B1 Ap S AB Ls Bt SCL B SCL C SCL CPS B2 Ap LS Bt SCL Ab LS Bt SCL C LS CPS B2 Ap SCL Ab S Bt SCL B SCL Bt SCL C SCL * SL = sandy loam; SCL sandy clay Loam; S = sand; LS = loamy sand Base sat (%) Soils derived from sandstone (SS) From Tables 3 and 5, soil profile characteristics and taxonomy showed that soils derived from SS parent material were similar to soils derived from the BRS except that they were more uniform than BRS soils. With very high sand content in all the horizons (ranging from 710 to 930 gkg -1 ), minimal profile development and almost no evidence of formation of diagnostic horizons, all the pedons were classified as Entisols (Soil Survey, Staff, 2006) or Arenosols (WRB/FAO, 2006). All the freely drained Entisols (SS-A1, A2, A3, B1, and B2) qualified as Typic Udipsamment because of their high sand content, while the poorly drained pedon (SS-B3) qualified as Typic Psammaquent. Soils derived from alluvial deposits (ALD) From the result of particle size analysis in Table 4, it is evident that soils derived from the ALD parent material were considerably different from those of CPS, BRS and SS parent materials. They all had high clay content in the various horizons of their profiles (ranging from 268 g kg -1 in the Ap horizon to 588 g kg -1 in the Bt horizon. The textural class ranged from sandy clay loam to sandy clay or clay. All the profiles from the ALD parent material are well developed with clear evidence of argillic (Bt) horizon formation. With argillic horizons, but low CEC, all the pedons derived from ALD were classfieid as Ultisols soil order (Soil Survey Staff, 2006) or Acrisols (WRB/FAO., 2006). They are all under the influence of high water table resulting in reducing (or gleyic) conditions in some parts of profile. Therefore they all classified as Aquult NJAFE VOL. 11 No. 3,

4 and Endoaquult at the suborder and great group categories, respectively. All the pedons were placed under Aeric Endoaquults at the subgroup category (Soil Survey Staff, 2006) which correlated with Gleyic Acrisol (WRB/FAO, 2006). Table 2: Some characteristics of pedons derived from beach ridge sands (BRS) parent material design depth (cm) Sand Silt Clay Textural g kg- 1 ) class Org. M (g kg -1 ) ECEC (cmol kg -1 ) BRS A1 Ap S B S B LS B S C LS BRS A2 Ap S B S B LS B LS BRS A3 Ap S Ap Ls BA S B LS B LS B S BRS B1 Ap S BA S B S B S C S BRS B2 Ap S BA S B S B S C S BRS B3 Ap S BA S B S B S Base sat (%) Soil classification (parent material soil relationship) From the above results, the influence of parent material on soil properties, soil types and classification is clearly revealed in the study area. Soils developed from coastal plain sands (CPS) are well developed, with argillic (B t ) horizons. They belong to the Ultisols soil Order (or Acrisols). They are upland soils and mostly (83.3%) Typic Kandiadults and to a lesser extent (16.7%) Arenic Kandiudults. Soils derived from beach ridge sand (BRS) and those derived from sandstone (SS) parent materials are relatively less developed. Of the six pedons from the BRS, 50% are Entisols (Arenosols) while 50% are Inceptisols (Cambisols). On the other hand all (100%) of the soils derived from sandstone are Entisols (Arenosols). However, unlike the CPS soils which are generally upland soils, 50% of the BRS soils are upland soils (Typic Dystrudept and Typic Udipsamment), while 50% are lowland or wetland soils (Aeric Endoaquept and Typic Psammaquent). On the other hand most (83.3%) of the SS pedons which are all Entisols are upland soils (Typic Udipsamment) while few (16.7%) are wetland soils (Typic Psammaquent). Finally, soils derived from alluvial deposits (ALD) parent material are all well developed. They have high clay content in all their profiles which makes these soils to be special in nature. They are all Ultisols (Acrisols) which occur in the wetland environment (Aeric Endoaquults/Gleyic Acrisols). The above results are in agreement with earlier findings that the type of soil formed under a particular set of environmental conditions is a function of the parent material and time (Ajiboye and Ogunwale, 2010). Also parent material is regarded as providing the body of NJAFE VOL. 11 No. 3,

5 the soil, while the texture of the soil, water retention and release, chemical and mineralogical characteristics are highly influenced by the nature of the parent material (Esu, 2005, Ibanga, 2006). Also Tahal (1982), Petters et al. (1989) FMANR, (1990) and Ibia and Udo (2009) have observed that the characteristics of soils in the study area (Akwa Ibom State), Southeastern Nigeria, are largely determined by their parent materials, and influenced by climate, topography and the general agricultural land use pattern and management. Table 3: Some characteristics of pedons derived from sandstone (SS) parent material Sand Silt Clay Textural Org. M ECEC Base sat design depth (cm) gkg- 1 ) class (gkg -1 ) (cmol kg -1 ) (%) SS A1 Ap S AB S B LS B LS C LS SS A2 Ap LS Ap LS AB LS B LS B LS C LS SS A3 Ap S AB S B S B S C S SS B1 Ap S AB LS B LS B LS C LS SS B2 Ap LS B LS B LS C LS C LS SS B3 Ap LS B LS B LS B LS CONCLUSION The result of this study has shown that soils derived from different parent materials possess different characteristics and belong to different soil classes. Furthermore, this result has revealed that carrying out soil survey, classification and mapping along the lines of different parent materials will be effective in separating soils requiring different management for optimum returns. In an area with predominantly low-income farmers and other land users, this method is highly recommended because it will reduce the cost of soil survey and produce rapid result soil maps, with high predictive power for agricultural and general land use planning. Table 4: Some characteristics of pedons derived from alluvial deposits (ALD) parent material NJAFE VOL. 11 No. 3,

6 Sand Silt Clay Textural Org. M ECEC Base sat design depth (cm) g kg- 1 class (g kg -1 ) (cmol kg -1 ) (%) ALD A1 Ap SC Bt C Bt C BC SC C C ALD A2 Ap SC Bt C Bt C C C ALD A3 Ap SCL Bt C Bt C BC C C C ALD B1 Ap SCL Bt C BC C C SC ALD B2 Ap SCL Bt SC BC C ALD B3 Ap SCL Bt SCL Bt SCL C SCL SCL = sandy clam loam; C = clay; SC = sandy clay REFERENCES Ajiboye, G. A. and Ogunwale, J. A Characteristics and Classification of soils developed over talc at Ejiba, Kogi State, Nigeria. Nigeria Journal of Soil Science 20 (1):1-14. Esu, I. E Characterization, Classification and Management Problems of the Major Soil Orders in Nigeria. 26 th Inaugural Lecture, University of Calabar, Calabar, Nigeria, 66pp. FAO, Guideline for Soil Descriptions. 3 rd Ed. FAO, Rome. FMANR (Federal Ministry of Agriculture and Natural Resources) Literature Review on Soil Fertility Investigations in Nigeria. (Enwezor, W. O., Ochiri, A. C., Opuwaribo, E. E. and Udo, E. J. (eds). Bobma Publishers, Ibadan. pp Geodata Limited, Inventory of Natural Site Conditions for the Cross River Basin Development Authority, Calabar. Ibanga, I. J Soil Studies: The Pedological Approach Maesot Printing and Computers, Calabar, Nigeria, 144pp. Ibia, T. O. and Udo, E. J Guide to Fertilizer Use for Crops in Akwa Ibom State, Nigeria, Sibon Books Limited, Lagos, 103pp. IITA (International Institute of Tropical Agriculture) Selected methods for Soils and Plant Analysis. IITA Manual Series 1. IITA, Ibadan, Nigeria. 70pp. IUSS Working Group WRB World Reference Base for Soil Resources First updated World Soil Resources Reports No. 103, FAO, Rome. Petters, S. W., Usoro, E. J., Udo, E. J., Obot, U. W. and Okpon, S. N Akwa Ibom State: Physical Background, Soils and Land Use and Ecological Problems (Technical Report of the Task Force on Soils and Land Use Survey. Government Printer, Uyo. 602 pp. Soil Survey Staff Keys to Soil Taxonomy. USDA NRCS, Washington D. C. 332pp. Soil Survey Staff Soil Taxonomy, a basic system of soil classification for making and interpreting soils surveys: USDA Agric. Handbook No Second edition U.S. Govt. Printing Office, Washington, D. C. 869pp. NJAFE VOL. 11 No. 3,

7 Tahal Consultants, Qua Iboe River Basin Pre-feasibility Study Vol. 1 Main Report Cross River Basin Development Authority, Calabar. Udo, E. J. and Ogunwole, J. O., Laboratory Manual for the Analysis of Soil, Plant and Water Samples, Department of Agronomy, Univ. of Ibadan, Nigeria. Udo, E. J., Ibia, T. O., Ogunwale, J. O. Ano A. O. and Esu, I. E Manual of Soil, Plant and Water Analyses. Sibon Books Ltd., Lagos. 183 pp. Udoh, B. T, Ogunkunle, A. O. And Ibia, T. O Soil-landscape relationship in a law-lying topography in Akwa Ibom State, Nigeria. Nigeria Journal of Agriculture, Food and Environment 4 (1-4): Udoh, B. T An Evaluation of the Soil Map of Akwa Ibom State for Agricultural Land Use. Ph.D. Thesis, Department of Agronomy, University of Ibadan, Ibadan. 302pp. Udoh, B. T Mapping Unit Complexities and high variation of soil properties in a semi-detailed soil map produced for agricultural land use planning in South Eastern Nigeria. Journal of Sustainable Tropical Agricultural Research 31: Table 5: Classification of soils in the study area Pedon USDA WRB (FAO) Order Subgroup Coastal Plain Sands (CPS) Parent Material CPS A1 Ultisols Typic Kandiudult Haplic Acrisol (Chromic) CPS A2 Ultisols Typic Kandiudult Haplic Acrisol (Chromic) CPS A3 Ultisols Typic Kandiudult Haplic Acrisol (Arenic) CPS B1 Ultisols Typic Kandiudult Haplic Acrisol (Chromic) CPS B2 Ultisols Typic Kandiudult Haplic Acrisol (Chromic) CPS B3 Ultisols Typic Kandiudult Haplic Acrisol (Epieutric) Beach Ridge Sands (BRS) Parent Material BRS A1 Inceptisols Typic Dystrudept Haplic Cambisol (Eutric) BRS A2 Inceptisols Aeric Endoaquept Endogleyic Cambisol (Eutric) BRS A3 Inceptisols Aeric Endoaquept Endogleyic Cambisol (Eutric) BRS B1 Entisols Typic Udipsamment Haplic Arenosol (Eutric) BRS B2 Entisols Typic Udipsamment Haplic Arenosol (Eutric) BRS B3 Entisols Typic Psammaquent Endogleyic Arenosol (Eutric) Sandstone (SS) Parent Material SS A1 Entisols Typic Udipsamment Haplic Arenosol (Eutric) SS A2 Entisols Typic Udipsamment Haplic Arenosol (Eutric) SS A3 Entisols Typic Udipsamment Haplic Arenosol (Eutric) SS B1 Entisols Typic Udipsamment Haplic Arenosol (Eutric) SS B2 Entisols Typic Udipsamment Haplic Arenosol (Eutric) SS B3 Entisols Typic Psammaquent Haplic Arenosol (Eutric) Alluvial Deposit (ALD) Parent Material ALD A1 Ultisols Aeric Endoaquult Gleyic Acrisol (Clayic) ALD A2 Ultisols Aeric Endoaquult Gleyic Acrisol (Clayic) ALD A3 Ultisols Aeric Endoaquult Gleyic Acrisol (Clayic) ALD B1 Ultisols Aeric Endoaquult Gleyic Acrisol (Clayic) ALD B2 Ultisols Aeric Endoaquult Gleyic Acrisol (Clayic) ALD B3 Ultisols Aeric Endoaquult Gleyic Acrisol (Chromic) NJAFE VOL. 11 No. 3,