Manioc peel and charcoal: a potential organic amendment for sustainable soil fertility in the tropics

Abstract

In tropical areas, where crop production is limited by low soil quality, the development of techniques improving soil fertility without damage to the environment is a priority. In French Guiana, we used subsistance farmer plots on poor acidic soils to test the effect of different organic amendments, bitter manioc peel (M), sawdust (Sw) and charcoal (Ch), on soil nutrient content, earthworm abundance and yard-long bean (Vigna unguiculata sesquipedalis) production. The peregrine Pontoscolex corethrurus was the only earthworm species found. Pod production and plant growth were lowest in unamended soil. The application of a mixture of manioc peel and charcoal (M+Ch) improved legume production as compared with other organic mixtures. It combined favourable effects of manioc peel and charcoal. Manioc peel improved soil fertility through its low C:N ratio and its high P content, while charcoal decreased soil acidity and exchangeable Al and increased Ca and Mg availability, thus alleviating possible toxic effects of Al on plant growth. The M+Ch treatment was favourable to P. corethrurus, the juvenile population of which reaching a size comparable to that of the nearby uncultivated soil. The application of a mixture of manioc peel and charcoal, by improving crop production and soil fertility and enhancing earthworm activity, could be a potentially efficient organic manure for legume production in tropical areas where manioc is cultivated under slash-and-burn shifting agriculture.

Harmful or useful? A case study of the exotic peregrine earthworm morphospecies Pontoscolex corethrurus

“…Although it seems to favour soils with high pH, Marichal et al (2012) found a positive relationship between mortality and pH in soil sampled in Eastern Brazilian Amazonian soils with high pH values (7.41 and 7.96). Juveniles seem more sensitive to pH than adults; Topoliantz et al (2005) found that treatments increasing pH, such as charcoal addition, promoted juvenile activity (i.e., casting).…”

Black (pyrogenic) carbon: a synthesis of current knowledge and uncertainties with special consideration of boreal regions

“…Apart from these specific studies of boreal and temperate forest soils, charcoal amendment has been associated with general improvement and sustainability of soil fertility in fire-prone native grassland sites in the North American Great Plains (Glaser and Amelung, 2003), and from charcoal amendment of tropical soils (Glaser et al, 2000Topoliantz et al, 2005). While studies thus far support a positive influence of charcoal on boreal forest soils, more extensive studies are required to test its substantive consequences in the field, and especially to disentangle the direct effects of charcoal from those mainly resulting from postfire effects on soil temperature and moisture, and on plant succession.…”

Impact of Biochar on Earthworm Populations: A Review

“…Limited studies were available reporting earthworm populations in agricultural systems receiving biochar-like substances or biochar; these studies included [74,75]. Topoliantz et al [74] observed a difference in earthworm abundance for combined charcoal + other organic amendments, compared to a natural fallow field.…”