Conceptual Models for Erosion Induced Productivity Decline in Tropical Ultisols.

Abstract: We propose some conceptual models on erosion – induced productivity decline on the ultisols of southeastern Nigeria. Data used were generated from experiments conducted over a 3 year period with maize and cassava as test crops on naturally eroded and artificially desurfaced plots. The mechanism of productivity decline would appear to be strongly tied to organic matter dynamics, which influences several other soil parameters, such as aggregate stability, available nutrient pools, aluminium toxicity and nutrient imbalance. In desurfaced plots, the sudden drastic loss of microbial populations and activities, necessary for decomposition and nutrient recycling, the loss of the nutrients pools concentrated on the top 2 cm of soil are critical factors in rapid yield declines. An understanding of the mechanisms at work in tropical, low-input based farming systems will help develop accurate models for predicting yield declines induced by erosion.