Soil Invertebrate Macrofauna Composition within Agroforestry and Forested Ecosystems and their Role in Litter Decomposition in Embu, Kenya

Abstract

Adequate food to meet the needs of an ever-increasing population is a major challenge for most developing countries, especially in the tropics. Despite this, few new technical packages capable of increasing net returns without deteriorating the environment have been developed. Crop yields in Embu, Kenya are poor due to declining soil fertility prompted by continuous cropping and application of fertilizers in non-sufficient quantities by farmers. Studies have shown that soil biota provides the means and regulates the transformation of organically bound nutrients into plantavailable forms through mineralization. An experiment was conducted to investigate soil macrofauna composition within agroforestry and forested ecosystems and their role in litter decomposition. This was anticipated to address poor crop yields in the study region. The study was conducted during the long and the short rains of the year 2000 on-station at Embu in an ongoing hedgerow intercropping experiment. Two types of Standard PVC litterbags with mesh size 7 mm and 1mm, were used. The 7 mm mesh size allowed macrofauna to enter while the 1 mm excluded the macrofauna. Two types of litter: Calliandra calothyrsus (low quality) and Leucaena leucocephala (high quality), were placed in the litterbags in duplicate in selected treatments of the Embu trials and were sampled at 1, 2, 4, 8, and 16 weeks. Decomposition rate constants (k) were estimated using a non-linear module in the EXCEL spreadsheet upon fitting first order exponential equations. Results from the study depicted that different management practice and/or land use affect soil macrofauna in varied manner. Soil invertebrate macrofauna enhanced the rate of decomposition of C. calothyrsus and L. leucocephala litter.