An Assessment Of Fallows As A Natural Strategy To Restore Erosion Degraded Lands

Abstract

The Ultisols of Southeastern Nigeria, which cover more than 70% of the total land area, are the main agricultural soils of the area. And this vital resource – base is being reduced drastically by erosion. The rehabilitation and restoration of these lands remains a major challenge to land users. The effectiveness of a short term, 5 year, natural fallow as a practical, affordable strategy to restore the fertility status of degraded ultisols was evaluated. Three levels of eroded lands were identified and delineated using the guidelines recommended by USDA'S Soil Conservation Service (1989) and Soil Survey (1993) manuals,.A- horizon depth was the primary criteria used to identify slightly eroded plots (S), moderately eroded plots (M) and severely eroded plots ( Sv) with reference to the non eroded plateau land (NE). The following physical factors were evaluated as physical fertility recovery indicators: saturated hydraulic conductivity (Ks); available water capacity (AWC); bulk density (BD); mean weight diameter (MWD) and total aggregation (TA). Status of chemical fertility improvement was evaluated by the following indicators: soil reaction, CEC, BS, exchangeable cations, Nutrient Imbalance and the weights and distribution of organic matter and total nitrogen in the effective rooting zone. Of the physical fertility indicators only total aggregation (over 80%) recovery, and MWD showed appreciable improvements similar to the levels of the non eroded plots. Chemical fertility recovery was as low as 30% in the severely eroded field for most of these soil factors: Soil organic carbon, total nitrogen, basic cations, and nutrient ratios. Available phosphorus and pH were not affected by the five year fallow.

In summary after 5 years of natural fallow, both physical and chemical fertility improvement indicators were abysmally low in all the degraded lands. Therefore, short term natural fallows will not appear to be feasible options to restore the fertility status of degraded ultisols. Erosion-induced loss in productive capacity of these soils requires alternative management strategies.


International Journal of Agriculture and Rural Development Vol. 9 2007: pp. 22-29