Soil microarthropod populations under natural and planted fallows in southwestern Nigeria

Microarthropods, such as soil mites (Acari) and springtails (Collembola), w ith body width between 0.08 mm and 0.5 mm play important roles in soil fert ility maintenance through their regulatory activities in decomposition and nutrient turnover. Observations were made at IITA, Ibadan, southwestern Nig eria to evaluate the effects of natural regrowth of vegetation - mainly the shrub Chromolaena odorata - and three planted woody fallow species (Acacia leptocarpa, Senna siamea, and Leucaena leucocephala) on soil microarthropo ds in a degraded Alfisol. Populations of soil microarthropods were higher i n the rainy season than the dry season, and populations were greater under natural fallow than for continuous cropping with maize (Zea mays) and cassa va (Manihot esculenta). Populations of soil microarthropods were comparable under leucaena and natural fallow, but populations in the rainy season wer e 38% higher under senna than natural fallow and 36% higher under acacia th an natural fallow. Regression analysis indicated that soil microarthropod p opulation under fallow species was positively correlated with the lignin co ntents of leaf litter.