An overview of soil erosion modelling

Soil erosion is one of the most important environmental issues in natural and synthetic territories. It can lead to loss of fertility, slope instability, soil truncation; etc. which causes irreversible effects on the poorly renewable soil resource. Therefore, understanding the key parameters and factors to model soil erosion will enable the conservation of soil system goods, services and resources, and will avoid the damage outside of fields caused by transported and accumulated sediments and water. In view of this, a review was carried out on previous studies to examine the concept of soil erosion and review various soil models widely used in literature. It was found that several models are used for soil assessment and prediction and these models are classified into physical (e.g. WEPP), conceptual (SEDNET) and empirical (USLE). The Universal Soil Loss Equation (USLE) and its modifications were found to be the most commonly used soil erosion models due to its simplicity, ease of use and the ability to integrate the various ecosystem parameters successfully. Furthermore, it was found that one of the major limitations associated with the use of models is lack of data for validation especially in large areas where obtaining ground data is not feasible. Although some researchers have suggested the use of correlation between modeled erosion results with factors such as land cover and management factor and soil erodibility factor as well as results of land use change analyses as alternatives for validation purpose. Others correlate the predicted soil erosion results with that of sediment yield. Some validated their soil erosion data with results of land use change analyses, slope length and slope steepness factor, land cover and management factor and soil erodibility factor. However, there is still ambiguity in the knowledge of our understanding as to which soil erosion prediction model to use. Keywords: soil erosion, model, validation, USLE, RUSL

Models for predicting pore space indices of an irrigated lowland rice soil in a Sudan Savanna of Nigeria

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A review of the influence of irrigation water on the selected physical and chemical properties of wetland soils of northern Nigeria

Wetlands are soils subjected to excessive wetness, to the extent that the wet conditions influence the possible land uses. To some  extent, irrigation water is rampantly being applied on these wetlands without observing and considered the possible short and long-term effects on the soil. This paper provides a review on the influence of irrigation water on the physical and chemical properties of wetland soils. It is evident that most of these wetlands are of high importance to food security and sustainability which are however, influenced by the application of irrigation water. However, it has been reported that decrease in soil pH as a result of continuous build-up of salts due to poor soil management, fertilizer application and poor irrigation water quality has adversely affected the soil surface. The presence of exchangeable Ca, Mg and Na as carbonates influence hydroxyl ions over hydrogen ions in the soil solution therefore making the soil alkaline. The continuous intensive cropping without addition of organic matter and crop residues has rendered theirrigated areas low of organic carbon when compared to non-irrigated areas. Moreover, due to poor seasonal drainage taking place in wetlands, the rate of OM decomposition and mineralization reduces in the soils. Nonetheless, the influence of irrigation water on the physical and chemical properties of the wetlands differs among wetlands, and even within the same wetlands. In conclusion, most of the wetlands were neither saline nor sodic but if not properly manage, could lead to build-up of exchangeable bases. Keywords: Wetland soils, physico-chemical properties, calcium carbonates, organic carbon, crop residues and irrigation wate