Effect of Land Use on Soil Degradation and Soil Productivity Decline on Alfisols and Ultisols in Ogun State in South Western, Nigeria

摘要

One of the critical factors influencing land degradation is land use. However, the extent to which land use influences land degradation has not been fully ascertained in the southwestern part of Nigeria (i.e. particularly in Ogun State). Thus, this study was designed to assess the extent to which land use influences crop productivity in Ogun State. Two major soil types identified at the site were Alfisols and Ultisols. Within these, three land use types (LUT) were identified: arable crop - Land Use 1, cash crop production - Land Use 2, and non-agricultural use a?? Land Use 3. Th ese were evaluated for three commonly cultivated crops in the area, namely: maize, cassava and oil palm, using the FAO framework for Land Sustainability Evaluation (LSE). Soil degradation levels were assessed under three LUTs using parametric approach. Descriptive statistics and rank ordered correlation were used for the data analysis. The results of the LSE showed that all the pedons were marginally suitable (S3) for maize, 60 % were of moderate (S 2) and 40 % of marginal (S 3) suitability for cassava respectively. However, for oil palm, 47 % of the lands were classified as being marginally suitable (S 3) while 53 % were not suitable (N). The major limitations identified were sub-optimal, poor soil (i.e. texture(s) and fertility), poor drainage/ wetness (w), steep topography (t), and sub-optimal climate (c) (i.e. annual rainfall, mean annual temperature and length of growing season). Parametric assessment revealed that chemical degradation was moderate within LUT 2, but ranged between slight to none in LUTs 1 and 3 respectively. Land uses 2 and 3 were slightly degraded physically, while 1 was moderate. Land use was found to be significantly (P 0.01) correlated with land degradation (r = 0.47**) at all sites. The degradation level ranked from moderate to high due to inappropriate land uses. Thus, it is recommended that in all LUTs must be a careful choice of appropriate use of land in order to reduce degradation.