Characterization, Classification And Suitability Of Selected Soils Of Amasiri, Ebonyi State: A Geographical Information System Approach

ABSTRACT 

The study was carried out between October – November 2008 and aimed at applying Geographical Information System (GIS) approach in characterizing, classifying and making suitability recommendations of soils in Ohia Nekechi within Amasiri area, Afikpo north, Ebonyi State. This study site was identified in a farmland consisting of a toposequence some meters away from Okposi road, Amasiri. A transect was cut across the toposequence revealing its North facing and the South facing slopes as well as the three major crops commonly grown in the farmland; cassava, rice and yam. Three pedons were sunk on each side of the toposequence (North facing and South facing slopes) each representing the crest, midslope and footslope physiographic positions. Pedons were aligned along the transect at an inter-pedon distance of about 50m. Soil samples were collected from each of the pedons according to their horizonations while surface sampling was carried out on each of the crop based farmland. Samples collected were air-dried, crushed and sieved using 2-mm sieve and further subjected to physical, chemical analysis considering some selected parameters. Data generated from the analysis were subjected to coefficient of variation (CV) as well as analysis of variance (ANOVA) for the crop based soils and relationship among soil properties were estimated using correlation coefficient and test of levels of significance. Variations in soil parameters were as follow; percent sand was higher at the footslope (77.3, 80.5%), followed by crest (75.7, 76.8%) and then by midslope(73.8, 75.4%) of both NFS and SFS respectively at all physiographic positions. Percent organic matter was highest at the cassava plot (2.75%) when comparing the crop based soils and the surface horizons of the profiles. At the toposequence however, organic matter was higher at the surface of midslope(2.41%) at the NFS while at the surface of crest(1.28%) at the SFS. However, organic matter decreased down the profiles at all positions. Soil acidity ranged from strongly to moderately acidic (4.4-5.2). Exchangeable Ca2+ and Mg2+ were higher than Na+ and K+ in all physiographic positions. Percent base saturation decreased down the profile and increased down the slope in all the positions while Al3+ saturation was almost a direct opposite to percent base saturation except at the SF midslope where Percent Al3+ saturation was higher than that at the crest. There was a low variation in the particle size fractions especially sand in all physiographic positions, moderate to high variation in organic matter while base saturation varied highly in all physiographic positions except at the footslopes where it indicated moderate variation. Soil pH VS OM, pH VS Avail. P, OM VS Avail P, indicated significant positive correlation (p=0.01 and p=0.05) while OM showed a negative and insignificant correlation with ECEC at the crest of NF and SF slopes. At the NF midslope, there was positive and significant (p=0.001, p=0.01 and p=0.05) correlation between soil parameters considered. However, at this physiographic position OM indicated negative and insignificant correlation with ECEC. At the SF midslope, OM had positive and significant (p=0.001) correlation with total N and Avail. P, while p=0.05 with ECEC. The NF footslope recorded non significant correlations with soil parameters while at the SF footslope, total N correlated significantly (p=0.05) positively with pH and (p=0.01) with OM, OM was p=0.05 with Avail. P. The crop bases soils indicated significant (p=0.01 and p=0.05) variations. The GPS was used to determine the geographical coordinates and also in generating data used to determine the Digital Elevation Modeling (DEM) of the study area. The DEM revealed both gentle and steep sloppy surfaces in the area but the place seems to have more steep slopes. This otherwise explains the reason why the place could be regarded as a place with rough terrain. The valley bottoms as shown by the DEM could be said to be suitable for rice and other crops which tolerate aquic conditions due to its submerged state. The toposequence can be suitable for cassava and yam which does not require much water condition while other geologic feature at the site such as rocks have been subjected to quarrying. The soils fall within Class II soils since they have some limitations that reduce the choice of plants or require moderate conservation practices while non agricultural activity such as quarrying was also evident. The DEM also reveals the pathway of Cross river which flows through valleys and most of the roads (both secondary and main roads) pass through valleys. Soils were classified as typic kandiudults (Plinthic Acrisol) at pedons A, D and E while in pedons B and F as typic kandiudalfs (Albic Luvisol) and Pedon C was classified as typic Kandiaqualfs (Gleyic Luvisols).