EFFECT OF CHARCOAL POWDER AND SAWDUST ON NUTRIENT AVAILABILITY IN A DEGRADED AMAZONIAN OXISOL Newton Paulo Souza Falc

1. EFFECT OF CHARCOAL POWDER AND SAWDUST ON NUTRIENT AVAILABILITY IN A DEGRADED AMAZONIAN OXISOLNewton Paulo Souza Falcão (1), Nicholas Brian Comerford (2)(1) INPA, AM. Brazil (2) University of Florida. Gainesville. USA. 1, OBJECTIVES a) investigate the effect of charcoal, sawdust and organic compost on the chemical properties of a representative, low fertility, Amazonian soil in an attempt to reproduce the fertility of Dark Earth soils; b) study the potential of charcoal to increase the uptake efficiency of phosphate fertilizer and decrease the nitrogen and potassium loss by leaching; and (3) study the potential of charcoal, sawdust and organic compost to increase corn and bean biomass/grain production. 2. RESULTS AND DISCUSSION a) Sawdust decreased exchangeable Al, while charcoal increased exchangeable K. P was unaffected by sawdust or charcoal due to P fertilization close to time of sampling; b) pH increased with addition of both sawdust and charcoal, but increases were small c) At a given level of fertilization, sawdust and charcoal increase grain yield. Charcoal was superior, providing increased grain yield per unit charcoal added. This metric increased with each subsequent harvest;

2. d) A similar situation exists for dry biomass but to a lesser extent and only for the first 2 harvests e) The fact that grain and biomass yield increased with each unit of charcoal added to the soil suggests that either this material has a fertilizer effect (bioavailable nutrients contained within) or the presence of charcoal increased the fertilizer efficiency. Given the large influence on growth. The latter explanation is considered more reasonable; f) Sawdust was effective at reducing Al, and is expected to be useful for alleviation Al toxicity symptoms in some agronomic plants. It is interesting that charcoal had no measurable influence on exchangeable Al; g) The small increase in soil pH is attributable to the fact that the soil was sampled two harvests following application, allowing for soluble salts to leach out of the system; h) Charcoal increased exchangeable K in the soil, yet at the highest rate of charcoal addition only 3 to 4 kg K per ha were measureable in an exchangeable form. It is estimated that total K added at the highest charcoal rate was 1250 kg.