Organic matter and biofunctioning in tropical sandy soils and implications for its management

E Blanchart (1) , A Albrecht (1) , M Bernoux (1) , A Brauman (1) , C L Chotte (1) , C Feller (1) , F Ganry (2) , E Hien (2) , Raphaël J. Manlay (3) , D Masse (4) , S Sall (5) , C Villenave (6)

1 Laboratoire Biologie et Organisation des Sols Tropicaux
2 UPR Recyclage et risque - Recyclage et risque
3 ENGREF - Ecole Nationale du Génie Rural, des Eaux et des Forêts
4 Laboratoire d'Ecologie
5 LPAO-SF - Laboratoire de Physique de l'Atmosphère et de l'Océan Siméon Fongang
6 IRD [Sénégal] - Institut de recherche pour le développement

Tropical sandy soils (or upper sandy horizons of tropical soils) have diverse physical and chemical constraints: poor structural stability (making soils sensitive to crusting, and compaction), poor nutrient holding capacity and low cation exchange capacity. In these soils, in which the clay content is low (3 to 15% by mass), organic matter is the main determinant of fertility, nutrient storage, aggregate stability, microbial and enzymatic activities. However, cultural practices or land uses aimed at increasing organic matter stocks have a minor impact if compared with the potential storage of organic matter in clayey soils. Nevertheless, this stock increase is possible in sandy soils and is mainly linked with the increase of the " vegetal debris " functional pool. Like organic matter, the abundance, activity, and diversity of soil biota are largely dependent upon land management. In these soils, biotic interactions such as termites-microorganisms or nematodes-microorganisms modify nutrient fluxes, N mineralization being higher in soil-feeding termite mounds or in the presence of bacterial feeding nematodes. Moreover, the management of organic residues represents a means to control the activity of soil microorganisms and the structure of nematode and other fauna populations. An adequate management of organic matter (through fallows, improved fallows, pastures, external organic inputs) through its consequences on soil biofunctioning, largely determines the agronomic (plant production) and environmental (carbon sequestration) potentials of sandy soils. In the present paper, we provide information on the biofunctioning in sandy soils, i.e., interactions existing between organic matter, biological activities (termites, earthworms, nematodes, microorganisms) and physical soil properties, in natural and cropped ecosystems. Data mainly originate from experiments and measurements from West (Senegal, Burkina Faso, Ivory Coast) and East (Kenya) Africa.

Mots clés: soil microorganisms; soil fauna; crop management; soil carbon fractions

Domaines: Science des sols

E Blanchart, A Albrecht, M Bernoux, A Brauman, C L Chotte, et al.. Organic matter and biofunctioning in tropical sandy soils and implications for its management. Management of Tropical Sandy Soils for Sustainable Agriculture. A holistic approach for sustainable development of problem soils in the tropics, Nov 2005, Khon Kaen, Thailand. pp.224-241. ⟨hal-01420428⟩