Management of plant residues and its effects on decomposition and soil macrofauna in central Amazonian agroecosystems

SHIFT project ENV 52

Within the research program SHIFT (financial support by BMBF, Bonn and CNPq, Brasilia) a project executed by the State Museum of Natural History Karlsruhe and the EMBRAPA Amazônia Ocidental investigated the structure and function of soil macrofauna communities in Amazonian agroecosystems and the reaction of the fauna to experimental management measures like slash-and-burn, slash-and-mulch, slash-and-stockpile, intercropping of legumes for mulch production and the use of pesticides. In 8 different plantation types the soil fauna was sampled and the most important physical and chemical soil variables, which are supposed to contribute to soil fertility, were measured. These data formed the background for an evaluation of the effects of different mulch treatments on soil fauna and soil fertility. The crop species determines the soil fauna through its residues (litter quantity and quality) and by influencing habitat characteristics like microclimate or bulk density. Results show that soil fauna, and consequently soil fertility and the sustainability of the agroecosystem, can be managed by selecting and combining crop species, by alley cropping of shrubby legumes and mulching and by fire-free land preparation. Laboratory experiments and the study of soil profiles with special regard to biogenic structures have shown that specific soil fauna taxa have specific effects on soil structure, distribution of soil organic matter and nutrients and soil fertility. Ecotoxicological studies showed that tropical conditions influence tests and are relevant for a risk assessment of pesticides in the tropics. First tests under specific tropical conditions were successfully developed.