Soil respiration curves as soil fertility indicators in perennial central Amazonian plantations treated with charcoal, and mineral or organic fertilisers Christoph Steiner 1 *, Murilo Rodrigues de Arruda 2 , Wenceslau G. Teixeira 2 and Wolfgang Zech 1 1 Institute of Soil Science and Soil Geography, University of Bayreuth, Bayreuth, Germany. 2 Embrapa Amazonia Ocidental, Manaus, Brazil. *To whom correspondence should be addressed: Biorefining and Carbon Cycling Program, Driftmier Engineering Center, University of Georgia, Athens, GA 30602, USA (csteiner@engr.uga.edu) Abstract We assessed substrate-induced respiration and soil chemical properties in order to study the influence of charcoal, nitrogen and phosphorus fertilisation on two different perennial crops in a confounded factorial design on a highly weathered Amazonian upland soil. Each plantation tested three different factors in three different levels making up 27 (3 3 ) treatment combinations. Whereas the banana plantation received mineral fertilisation in addition to charcoal applications (3 rd factor), the guarana (Paullinia cupana) plantation was fertilised organically using chicken manure and bone meal as the corresponding factors. Charcoal increased pH, total nitrogen, availability of sodium, zinc, manganese, copper and soil humidity, and decreased aluminium availability and acidity in the mineral-fertilised plantation only. This caused a significant increase in basal respiration and microbial effi- ciency in terms of carbon dioxide release per microbial carbon in the soil. The microbial biomass, efficiency and population growth after substrate addition was significantly increased with increasing levels of organic fertiliser amendments. We conclude that charcoal is a valu- able component especially in inorganic-fertilised agricultural systems. Copyright © 2008 John Wiley & Sons, Ltd Key words: banana, biochar, Ferralsol, guarana, slash and char, soil respiration, Terra Preta Introduction Without continuous fertilisation, the extremely nutrient-poor Amazonian upland soils show no potential for agriculture beyond a tree-year lifespan of the forest litter mat, once biological nutrient cycles are interrupted by slash-and-burn (Tiessen et al. 1994). Slash-and-burn agri- culture is a common practice in the tropics (Giardina et al. 2000; Goldammer 1993) and is Tropical Science Trop. Sci. (2008) Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/ts.216