Biochar: pyrogenic carbon for agricultural use: a critical review.

O biocarvão (biomassa carbonizada para uso agrícola) tem sido usado como condicionador do solo em todo o mundo, e essa tecnologia é de especial interesse para o Brasil, uma vez que tanto a ?inspiração?, que veio das Terras Pretas de Índios da Amazônia, como o fato de o Brasil ser o maior produtor mundial de carvão vegetal, com a geração de importante quantidade de resíduos na forma de finos de carvão e diversas biomassas residuais, principalmente da agroindústria, como bagaço de cana, resíduos das indústrias de madeira, papel e celulose, biocombustíveis, lodo de esgoto etc. Na última década, diversos estudos com biocarvão têm sido realizados e atualmente uma vasta literatura e excelentes revisões estão disponíveis. Objetivou-se aqui não fazer uma revisão bibliográfica exaustiva, mas sim uma revisão crítica para apontar alguns destaques na pesquisa sobre biochar. Para isso, foram selecionados alguns temaschave considerados críticos e relevantes e fez-se um ?condensado? da literatura pertinente, mais para orientar as pesquisas e tendências do que um mero olhar para o passad

Field validation of DNDC and SWAP models for temperature and water content of loamy and sandy loam Spodosols

The objectives of the research were to: fulfil the preliminary assessment of the sensitivity of the soil, water, atmosphere, and plant and denitrification and decomposition models to variations of climate variables based on the existing soil database; validate the soil, water, atmosphere, and plant and denitrification and decomposition modelled outcomes against measured records for soil temperature and water content. The statistical analyses were conducted by the sensitivity analysis, Nash-Sutcliffe efficiency coefficients and root mean square error using measured and modelled variables during three growing seasons. Results of sensitivity analysis demonstrated that: soil temperatures predicted by the soil, water, atmosphere, and plant model showed a more reliable sensitivity to the variations of input air temperatures; soil water content predicted by the denitrification and decomposition model had a better reliability in the sensitivity to daily precipitation changes. The root mean square errors and Nash-Sutcliffe efficiency coefficients demonstrated that: the soil, water, atmosphere, and plant model had a better efficiency in predicting seasonal dynamics of soil temperatures than the denitrification and decomposition model; and among two studied models, the denitrification and decomposition model showed a better capability in predicting the seasonal dynamics of soil water content

Changes in soil conditions after application of biochar

Abstract Biochar is a carbonized, stable product obtained by pyrolysis. Due to its structure, chemical composition and characteristics biochar can change soil properties over a long period. To study the effect of woody biochar on loamy sand Spodosol, a small-scale field experiment was conducted. Following treatments were used in the experiment: soil-control, soil with biochar at a rate of 5 t ha−1, soil with nitrogen fertilizer at a rate of 90 kgN ha−1 and soil with combined application of biochar and N fertilizer. Application of biochar increased water-holding capacity of the soil in the range of plant-available water by 7%, in average, increased soil moisture 1.13-1.19 times, reduced the soil bulk density by 5% and led to a short-term increase in soil pH.</jats:p

Earthworm activity as a determinant for N2O emission from crop residue

Earthworm activity may have an effect on nitrous oxide (N2O) emissions from crop residue. However, the importance of this effect and its main controlling variables are largely unknown. The main objective of this study was to determine under which conditions and to what extent earthworm activity impacts N2O emissions from grass residue. For this purpose we initiated a 90-day (experiment I) and a 50-day (experiment II) laboratory mesocosm experiment using a Typic Fluvaquent pasture soil with silt loam texture. In all treatments, residue was applied, and emissions of NO and carbon dioxide (CO2) were measured. In experiment I the residue was applied on top of the soil surface and we tested (a) the effects of the anecic earthworm species Aporrectodea longa (Ude) vs. the epigeic species Lumbricus rubellus (Hoffmeister) and (b) interactions between earthworm activity and bulk density (1.06 vs. 1.61 g cm(-3)). In experiment II we tested the effect of L. rubellus after residue was artificially incorporated in the soil. In experiment 1, N2O emissions in the presence of earthworms significantly increased from 55.7 to 789.1 mu g N2O-N kg(-1) soil (L. rubellus; p <0.001) or to 227.2 mu g N2O-N kg(-1) soil (A. longa, p <0.05). This effect was not dependent on bulk density. However, if the residue was incorporated into the soil (experiment II) the earthworm effect disappeared and emissions were higher (1064.2 mu g N2O-N kg(-1) soil). At the end of the experiment and after removal of earthworms, a drying/wetting and freezing/thawing cycle resulted in significantly higher emissions of NO and CO2 from soil with prior presence of L. rubellus. Soil with prior presence of L. rubellus also had higher potential denitrification. We conclude that the main effect of earthworm activity on N2O emissions is through mixing residue into the soil, switching residue decomposition from an aerobic and low denitrification pathway to one with significant denitrification and NO production. Furthermore, A. longa activity resulted in more stable soil organic matter than L. rubellus. (c) 2007 Elsevier Ltd. All rights reserved