Soil fertility management strategies in agroecosystem and implication on soil macrofauna diversity and populations

Abstract

Soil invertebrate fauna functions in decomposition of organic residues and thus nutrient release, soil structure and soil-water relations is well appreciated, however the scope for their manipulation to derive the potential benefits is little understood. A study was undertaken to assess how soil fertility management strategies within an agroforestry system affect soil biodiversity (macrofauna diversity and populations). The study was conducted on farm during the 1997 short rains (Oct 1997-Feb 1998) in western Kenya with the following treatments: (I) control without any input, (2) fertilizer at 120 kg N, ISO kg P and 100 kg K ha-I, (3) Tithonia diversifolia biomass at 5 t ha-I dry weight and (4) Senna spectabilis at 5 t ha-I dry weight. Riparian natural forest and a six-year grassland fallow were assessed and used as reference standards. Macrofauna diversity and populations were monitored in soil monoliths (25 x 25 x 30 cm) at the beginning of the season, 6 weeks after sowing maize and at maize harvest. Faunal diversity were assessed using Shannon-Wiener index of diversity (H'). Data were subjected to analyses of variance (ANOVA) in a split-plot design and treatment differences evaluated using least significance difference (LSD) at P=0.05. Macrofauna diversity and populations of most of the macrofauna groups were significantly higher under natural forest (H' = 2.31) than in all the other treatments (each H' = I).