Abstract
The current study investigated how the presence of tamarinds and manure affect (1) soil chemical properties; (2) C and N mineralization; (3) microbial biomass indices (C, N, and fungal ergosterol); (4) microbial residues, that is, amino sugars; and (5) the germination of sorghum seeds in soils of the littoral zone in southwestern Madagascar. Soil pH was lower under than outside the tamarind canopy, whereas SOC, total N content, and the cation exchange capacity were roughly three times higher than in the uncovered situation. Under the tamarind canopy, basal respiration was increased nearly threefold, whereas net N mineralization remained unaffected. However, net N mineralization was increased by 74% in the manure treatment, especially under the tamarind canopy. Tamarind did not inhibit the germination of sorghum seeds. Contents of microbial biomass C and N, and especially fungal ergosterol, were also higher under the tamarind canopy. Muramic acid, galactosamine, and glucosamine were increased threefold under the tamarind canopy. The mean fungal C to bacterial C ratio was 0.67 and remained unaffected by any treatment. The presence of manure increased the contribution of microbial residue C to SOC from 28% to 41% and of microbial biomass N to total N from 3.5% to 5.6%, especially under the tamarind canopy.
