Characterizing sites for the design and restoration of Kalacha irrigation scheme, Chalbi district, Kenya: Socio-economic and biophysical considerations

E. M. Muya¹*, K. Gitau¹, S. Obanyi¹, M. Ngutu², S. Kuria², H. Sharfi², D. G. Dub², H. Bulle², D. M. Miano³, J. Muriethi³, G. Keya³, I. V. Sijali¹, S. Mamo², P. M. Maingi¹, M. Okoti² and Eng. M. J. Omedi⁴ and A. Esilaba³

¹National Agricultural Laboratories, P. O. Box 14733, Nairobi, Kenya.

²KARI-Marsabit, P. O. Box 147, Marsabit, Nairobi, Kenya.

³Kenya Agricultural Research Institute, P. O. Box 57811, Nairobi, Kenya.

⁴Ministry of Water and Irrigation, P. O. Box 29703, Nairobi, Kenya.

*Corresponding author. E-mail: edwardmuya@yahoo.com. 

Accepted 9 June, 2010

 Abstract

Site characterization was carried out in Kalacha irrigation scheme for the design and restoration of the scheme. Detailed soil survey was carried at the scale of 1:2,000, through systematic observations, where the soils were described in terms of depth, texture, structure and consistence. Based on these characteristics, four soil units were identified and designated as block A, B, C and D, covering 23, 18, 17 and 42% of the scheme, respectively. In each unit, representative soil profiles were identified, characterized in terms of soil physical and chemical properties, and classified according to FAO-UNESCO system of classification. The soils in block A, B, C and D were classified as Petric Calcisols, Salic Fluvisols, Calcic Solonetz and Calcaric Fluvisols, respectively. The aggregate stability of the topsoils for Block A, B, C, and D was found to be 40, 10, 2 and 4%; while the water uptake capacity was 218, 158, 76 and 86 mm, respectively. The highest level of nutrients was found in Block A, followed by Block B, while block C and D had relatively lower levels. The most limiting factors were found to be high salinity, high sodicity, low aggregate stability and high soil pH, hence low nutrient availability.

Key words: Irrigation layout and design, soil quality, irrigation blocks.