Abstract

Low use efficiencies of inorganic fertilizers coupled with their rising costs has diverted attention of farmers towards organic sources. A study was conducted in Yatta sub-county between October 2012 to February 2013 short rains and April-August 2013 long rainy seasons to evaluate how tillage, cropping and organic inputs influenced soil nutrient status. A randomized complete block design with a split-split plot arrangement replicated three times was used. The main plots were tillage practices (TP): Split-plots comprised the cropping systems (CS) while split-split plots were organic inputs, plus the control. The test crops were sorghum and sweet potatoes (Impomea batata) with Dolichos (Dolichos lablab) and chickpea (Cicer arietinum L.) added either as intercrops or in rotation. Soil was randomly sampled at 0 to 30 cm depth at the onset of the experiment and at maturity of test crop for NPK and % organic carbon (OC) analysis. Significant (P≤0.05) high level of K (1.91 Cmol/+kg), available P (51.45 ppm), total N (0.19%) and OC (2.19%), in combined TR, intercrop sorghum/chickpea with application of Minjingu rock phosphate (MRP)+ farmyard manure (FYM) during SRS of 2012 compared to the other treatment combinations was observed. Comparing different organic inputs, tillage practices and cropping systems combined tied ridges (TR), intercrop of sorghum/chickpea and MRP+FYM and FYM increased the soil nutrients status. Therefore, soil organic inputs such as MPR and FYM are viable alternatives to inorganic fertilizers for improving the soil nutrient status. The study therefore recommends incorporation of the organic inputs in combination with TR, as well as intercropping with legumes in their cropping systems to improve soil health and resilience.

Key words: Cropping systems, tillage practices, organic inputs, semi-arid, soil nutrients.