Soil organic matter mobilization by root exudates

In order to study the different soil organic matter mobilisation by agraria n (Zen mais: cultivars Paolo and Sandek) and forest (Picea abies Karst. and Pinus sylvestris L.) root exudates, three different soils (Dystric Spodic Cambisol - S1, Haplic Luvisol - S2 and Calcaric Cambisol - S3) have been co nsidered. Treating the soils with water (control) or plant root exudates, s oil organic matter extracts were obtained. The extracts were characterised by hormone-like activities and gas chromatographic/mass spectrometric (GC/M S) measurements. Water extract and plant root exudates exhibited no hormone -like activity, while the other soil-extracts were endowed with a different hormone-like behaviour. GC/MS data indicated that in the acid soils (S1) S andek and Picea abies exudates showed a greater ability in extracting organ ic acid isomers (C14COOH, C15COOH and C17COOH), while in neutral soils (S3) all the exudates were active in separating organic acids. In intermediate conditions (S2), Picea abies and Pinus sylvestris exudates liberated C15COO H isomers, Paolo C11COOH isomers, while Sandek was not effective. The diffe rent role of plant root exudates in mobilising bio-molecules from the bulk of the soil is proposed. (C) 2000 Elsevier Science Ltd. All rights reserved .