[01] Samwel Nyakach, Department of Agricultural Engineering, Egerton University, Njoro, Kenya. [02] Seth F. O. Owido, Department of Crops, Horticulture and Soils, Egerton University, Njoro, Kenya. [03] Japheth O. Onyando, Department of Agricultural Engineering, Egerton University, Njoro, Kenya.

Black cotton soils which are classified as Vertisols cover approximately 200 million hectares of land in the arid and semi arid tropics. In these environments they are considered the most suitable soils for agriculture because of their high water holding capacity. However, this water holding ability has been found to be deceptive since not all the water is readily available for crop use. In addition, the soils present a range of management challenges that limit their suitability for agricultural production. The soils are easily eroded, have poor infiltration rates coupled with very slow hydraulic conductivities which limit both irrigation and drainage, and a highly varied consistency. Various management technologies for the soils have been developed resulting into varying degrees of productivity and sustainability. This study evaluated the effect incorporating organic matter into the soil prior to firing at definite temperatures and for given durations of time. Based on factorial experimental design, analysis of variance (ANOVA) was done using the SAS studio. Results indicated that the mean bulk density decreased by 20% when 10% (by weight) of rice husk was added. The mean bulk density changed from 1.29 g/cm³ before firing to 1.12 g/cm³ on firing and further to 0.99 g/cm³ upon size reduction. The Pearson correlation coefficient was -0.019 for time of firing and increased marginally to 0.076 after size reduction. The time of firing had the least effect on bulk density. However, for saturated hydraulic conductivity, the temperature, time and percent black cotton soil all had a significant effect with Pearson’s correlation analysis giving coefficients of 0.77, 0.22 and -0.43 respectively. The mean saturated hydraulic conductivity for the aggregates was 0.0045 cm/s which compares closely to that of Loamy Sand as estimated as 0.0041 cm/s by the RETention Curve (RETC) model.

Vertisols, Bulk Density, Hydraulic Conductivity, Temperature, Time

[01] Chalker-Scott, L. (2009). The Myth of Soil Amendments Part II. http://www.theinformedgardener.com. Accessed on 24/6/2013. [02] Chow, V. T., Maidment, D. R. and Mays, L. W. (2012). Applied Hydrology. Tata Mc Graw Hill. New Delhi, India. 572pp. [03] Da Costa, V. P. F. X. (1973). Characterization and Interpretation of the Soils of the Kano Plains for Irrigation Agriculture. MSc. Thesis. University of East Africa. [04] DeBano, L. F. (1990). The Effect of Fire on Soil Properties. Paper presented at the Symposium on Management and Productivity of Western-Montane Forest Soils, Boise, ID, April 10-12, 1990. [05] Eswaran, H. and Cook, T. (1988). Classification and Management-related Properties of Vertisols IN Management of Vertisols in Sub Saharan Africa. Proceeding of a Conference held at ILCA, Addis Ababa, Ethiopia. [06] Freebairn, D. M., Lock, R. J. and Silburn, D. M. (1996) Soil Erosion and Soil Conservation in Vertisols IN Vertisols and Technologies for their Management. Elsevier, Canada pp 306-363. [07] Gheorge, R., Adia, G., Dorin, T., and Radu, B. (2013) Engineering Properties of Vertisols. Soil Forming factors and Processes from the Temperate zone, 12 (1): 59-67. [08] Grunwald, S. (2003). Vertisols. University of Florida. http://soils.ifas.ufl.edu. Accessed on 29/7/2013. [09] ISRIC – World Soil Information. (2007). Vertisols. www.isric.org. Accessed on 7/8/2013. [10] Kutilek, M. and Nielsen, D. R. (1994). Soil Hydrology. Catena Verlag, Germany. 370pp. [11] Mehta, K. S., Sonecha, R. J., Daxini, P. D., Ratanpara, P. B. and Gaikward, K. S. (2014) Analysis of stabilization of Black cotton Soils and Stabilization using Lime. International Journal of Engineering Research and Applications 4 (5): 25-32. [12] Millan, R. (1973). Problem of the Natural Environment on the Kano Plains of Western Kenya IN Cahiers d’etudes Africaines, 13 (50): 181-192. [13] Ozsoy, G. and Aksoy, E. (2007). Characterization, Classification and Agricultural Usage of Vertisols Developed on Neogen Age Calcarous Marl Parent Materials. Journal of Biological and Environmental Science, 1: 5-10. [14] Swindale, L. D. (1988). Developing, Testing and Transferring Improved Vertisol Technology. The Indian Experience IN Management of Vertisols in Sub Saharan Africa. Proceeding of a Conference held at ILCA, Addis Ababa, Ethiopia. [15] Virmani, S. M. (1988). Agroclimatology of the Vertisol and Vertic Soil Areas of Africa IN Management of Vertisols in Sub Saharan Africa. Proceeding of a Conference held at ILCA, Addis Ababa, Ethiopia. [16] Virmani, S. M., Sahrawat, K. L. and Burford, K. L. (1982). Physical and Chemical Properties of Vertisols and Their Management.