Land degradation rating under different land use types

Abstract

Soil degradation is a major challenge to agricultural production and often leads to low crop yield in most parts of the world. Hence, a field study was carried out in the University of Ibadan to assess soil physical and chemical properties, and their level of degradation under different land use types. Six land use types consisting of fallow land (FL), arable land (AL), Oil palm plantation (OP), Residential land (RL), paddock (P) and valley bottom (VB) were identified and examined in this study. Disturbed and undisturbed soil samples were obtained from 0-3cm depth and analyzed for their chemical and physical properties using standard procedures. Soil colloidal fractions (organic matter, clay and silt) were integrated to estimate the soil structural stability index (S), while soil degradation rating (SDR) was determined from selected soil physical (Particle size distribution, bulk density and saturated hydraulic conductivity) and chemical (pH, organic carbon, total nitrogen and available phosphorus) properties. Data were analyzed using descriptive statistics and analysis of variance at α0.05. The land use types were slightly acidic with pH range of 5.7 (FL) to 6.9 (RL). Soil organic carbon differed significantly and was in the order: RL (29.8 g kg-1) > VB (20.0 g kg-1) > P(19.1 g kg-1) > FL (12.3 g kg-1) > OP (11.9 g kg-1) > AL (10.7 g kg-1). Significant differences were recorded for soil bulk density among the land use types. The VB had the lowest value (1.43 Mg m-3), followed by FL (1.52 Mg m-3), OP (1.64 Mg m-3), P (1.66 Mg m-3), RL (1.71 Mg m-3), and highest in AL (1.83 Mg m-3). The S also differed significantly among the land use types and was highest under VB (32.4), while AL had the lowest (3.1). On the average, AL, FL, OP, P and RL appeared to be moderately degraded, while VB was slightly degraded. The soil degradation rating mirrored the adverse effect of agricultural land use types, especially arable land, paddock and oil palm plantation on soil quality. Thus, soil conservation measures such as the use of organic fertilizers and organic mulch should be put in place in order to rehabilitate these land use types.