Impact of Iron and Aluminum on the Aggregate Stability of Some Latosols in Central and Southern Liberia (West Africa)

Abstract

Problem: Latosols of Liberia are marked by intense surface leaching, strong acidity, low soil organic matter (SOM) content, and low nutrients status, caused by low aggregate stability, which are limiting factors to crop production.
 Aim: to evaluate the effect of soil organic carbon (SOC) different forms of Fe and Al on the aggregate stability of latosols.
 Methodology: Composite surface (0-20 cm depth) samples of four latosols at different localities in Liberia (Lat1, Phebe; Lat2, Felela; Lat3, Salala; Lat4, Todee) were collected and analyzed for aggregate stability parameters and factors by standard laboratory methods.
 Results: the studied soils are sandy clayey, very acidic and poor in SOC. The cation exchange capacity (CEC) ranges from 10.28 to 14.80 mmol.kg−1. Dominant forms of Al and Fe are free Fe (Fed) and Al [1], followed by amorphous Fe (Feo) and Al (Alo) and chelated Fe (Fep) and Al (Alp). The highest levels of water dispersible clay (WDC) and clay dispersible index (CDI) in Lat1 and Lat2 implied that these two soils are less stable compared to Lat3 and Lat4. The Fe and Al in all forms seem to contribute to soil aggregate stability. The SOC, although very low, also contributes to soil aggregate stability. SOC correlated positively with WDC, CDI and ASC, indicating the impact of SOC both as an aggregating agent and as a dispersing agent, in contrast to previous studies.
 Conclusion: The study reveals that Fe, Al and SOC are cementing materials which impact the aggregate stability in Latosols.