Erodibility in relation to water-dispersible clay for some soils of eastern Nigeria

Abstract

Water dispersible clay (WDC) can influence soil erosion by water. Therefore, in highly erodible soils such as the ones in eastern Nigeria, there is a need to monitor the clay dispersion characteristics to direct and modify soil conservation strategies. Twentyfive soil samples (0-20 cm in depth) varying in texture, chemical properties and mineralogy were collected from various locations in central eastern Nigeria. The objective was to determine the WDC of the soils and relate this to selected soil physical and chemical attributes. The soils were analysed for their total clay (TC), water-dispersible clay (WDC), clay dispersion ratio (CDR), dispersion ratio (DR), dithionite extractable iron (Fed), soil organic matter (SOM), exchangeable cations, exhangeable sodium percentage (ESP) and sodium adsorption ratio (SAR). Total clay contents of the soil varied from 80-560 g kg À1 . The USLE erodibility K ranges from 0Á02 to 0Á1 Mg h MJ À1 mm and WEPP K fall between 1Á2 Â 10 À6 -1Á7 Â 10 À6 kg s m À4 . The RUSLE erodibility K correlated significantly with CDR and DR (r ¼ 0Á44; 0Á39). Also, a positive significant correlation (r ¼ 0Á71) existed between WEPP K and RUSLE K. Soils with high clay dispersion ratio (CDR) are highly erodibile and positively correlates (p < 0Á51) with Fed, CEC and SOM. Also, DR positively correlates with Mg 2þ and SOM and negatively correlate with ESP and SAR. Principal component analysis showed that SAR, Na þ and percent base saturation play significant role in the clay dispersion of these soils. The implication of this result is that these elements may pose potential problem to these soils if not properly managed.

Physical indicators of soil erosion, aggregate stability and erodibility

“…Wakindiki et al (2009) asserted that the stability of microaggregates as opposed to their dispersion is important in keeping soil erosion in check. In another study, Igwe (2005) showed that soils which had high dispersible clay were highly prone to hardsetting and subsequently soil erosion. Earlier, Igwe et al (1995) studied the use of some soil aggregate indices to assess potential soil loss in soils of southeastern Nigeria.…”

“…The importance of microaggregates in the processes of infiltration, sealing and crust formation, runoff and soil erosion was also emphasized by Levy and Miller (1997). Some of the indices for microaggregate stability determination include, clay dispersion ratio (CDR), aggregated silt and clay (ASC) (Igwe et al 2009), water dispersible clay (WDC) (Igwe 2005) among others. Rhoton et al (2007) also showed that indices like WDC have been recognized as a key criterion for assessing the risk of surface sealing and crusting, and erosion of soil by water.…”

Effect of environmental pollution on susceptibility of sesquioxide-rich soils to water erosion

“…Soil aggregate stability in water has been described as one of the major factor controlling soils susceptibility to water erosion (Egashlra, Kaetsu, & Takuma, 1983;Igwe, 2005). However, this soil-water interaction is not only dependent of the chemical composition of the soil aggregate, but also on the chemical composition of the prevailing aqueous solution.…”

Effects of exchangeable Ca:Mg ratio on the dispersion of soils some southern Nigeria soils.

“…(Igwe and Udegbunam, 2008). Igwe (2005) remarked that the clay dispersion ratio and dispersible ratio were found to be good indices for predicting erodibility in some soils of southeastern Nigeria. In another study Igwe et al (1995) observed that DR and CDR correlated very significantly with erodibility in the Universal Soil Loss Equation (USLE) model.…”

“…Igwe (2005) remarked that pH, soil organic carbon, exchangeable Ca, exchangeable acidity, cation exchange capacity, sodium adsorption ratio, clay and silt contents of the soil are the soil factors that influence the water dispersible properties of the soils. The objective of this study was to determine the effect of exchangeable Ca and Mg on dispersion, chemical composition of soils from eight locations in Southern Nigeria.…”