Influence of Organic Based Technologies on Soil Nutrient Status in Semi-Arid Yatta Sub-County, Kenya

R. N. Onwonga, N. L. Namoi, J. J. Lelei


Declining soil fertility is the main cause of low and uncertain yields of sorghum and cassava traditional crops in arid and semi-arid areas of Kenya. Against this backdrop, this study investigated the effect of organic based technologies; application of organic fertilizers and integration of legumes in cassava and sorghum based cropping systems on soil chemical properties (Organic C, N, P and K). Field experiments were conducted in Katangi and Ikombe divisions of Yatta sub-County, Kenya during the short rain seasons (SRS) of 2010 and 2011 and long rain seasons (LRS) of 2011 and 2012. A randomised complete block design with a split plot arrangement was used. The main plots were three cropping systems: (i) intercropping (dolichos/cassava, dolichos/sorghum, pigeon pea/sorghum and pigeon pea/cassava); (ii) rotation (dolichos-cassava, dolichos-sorghum, pigeon pea-cassava and pigeon pea-sorghum); (iii) monocrop (cassava and sorghum). The split plots were organic fertilizers; Farm Yard manure (FYM), compost and control -no organic fertilizer added. Sorghum/dolichos+FYM had highest soil OC in LRS of 2011 at both sites and SRS of 2011 and 2010 at Katangi and Ikombe respectively. Cassava/dolichos+FYM had the highest soil OC in the SRS of 2011 and LRS of 2012 and 2011 at both sites. Sorghum/dolichos+FYM had highest soil N in LRS and SRS of 2011 in Katangi. Cassava-dolichos rotation accumulated highest soil N in SRS of 2010 and LRS of 2011 at both sites. Sorghum/dolichos intercrop accumulated higher soil P during the LRS of 2012 at both sites; and SRS of 2010 and LRS of 2011 in Katangi and Ikombe respectively. Cassava/dolichos intercrop produced higher soil P during the SRS of 2010 at both sites; and LRS of 2011 and SRS of 2011 in Katangi and Ikombe respectively. Higher soil K was observed under sorghum/dolichos intercrop in SRS of 2010 at both sites and LRS of 2011, SRS of 2011 and LRS of 2012 in Ikombe. Cassava/dolichos intercrop also had higher soil K during SRS of 2010, LRS of 2011 at both sites; LRS of 2012 at Katangi and SRS of 2011 at Ikombe. Application of FYM to sorghum/dolichos and cassava/pigeon pea intercrops is therefore a viable and sustainable trajectory to enhanced organic C and NPK levels in smallholder farming systems.

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Journal of Agricultural Science   ISSN 1916-9752 (Print)   ISSN 1916-9760 (Online)  E-mail:

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