Use of models in assessing the impact of cropping system, land types and suitability on land degradation in Southwestern Nigeria

Two sites (Apomu and Alabata) measuring 10 ha and representing rainforest and savannah agroecological zones, respectively in South Western Nigeria were chosen to evaluate the influences of cropping system, suitability and land types on the degree of land degradation. Multiple linear step-wise forward elimination regression was use to measure the interrelationships of the land parameters measured. The result using the model Y = 0.99 – 0.21CS + 0.10LT + 0.36S showed that for Apomu, the cropping system contributed 30% to the degradation as indicated by bulk density. Organic matter, conductivity and land suitability contributed more than 15% in terms of bulk density and permeability while land type contributed 17.5 and 2% of the degradation due to permeability and organic matter respectively. At Alabata, the model that best describes the relationships is Y = 0.17 + 0.09CS + 0.23LT + 0.31S. Cropping system contributed 10 - 12% degradation while land type contributed between 6.5 – 17.3% due to organic matter content, ESP, exchangeable K and bulk density. Land degradation models were also developed for each nutrient based on the cropping system, suitability and topographic land types. Appropriate cropping systems such as alley cropping, organic farming, contour farming, and rotational cropping etc. are recommended for the defined soil / land types to minimise land degradation in the study area.