Biotechnologie, Agronomie, Société et Environnement (Jan 1998)
Description du système racinaire de trois espèces fourragères en zone soudano-sahélienne : Andropogon gayanus, Vigna unguiculata et Stylosanthes hamata
Abstract
Description of root systems of three fodder crops in the Soudano-Sahelian area: Andropogon gayanus, Vigna unguiculata and Stylosanthes hamata. Root systems of fodder crops (Andropogon gayanus, Vigna unguiculata and Stylosanthes hamata) were studied at two Research Stations in Mali in 1992, using soil monoliths. In this method, roots are studied throughout the soil profile in cubical compartments of 1 dm3. Root biomass production of A. gayanus planted in 1951 was 4 t.ha-1 against 5 t.ha-1 when planted in 1991. Above-ground biomass was 12 and 8 t.ha-1, respectively. The majority (90%) of the root biomass was concentrated in the upper 60 cm of the soil profile even if the root depth reached 180 cm. Root biomass decreased with depth following a negative exponential curve, but root length density decreased to a lesser extent, resulting in increasing specific root length (root length per unit of root biomass) with depth. Root biomass of V. unguiculata was 1,118 kg.ha-1 without phosphorus fertilization and 2,922 kg.ha-1 with Pfertilization. The effect of Pon above ground biomass was negligible, and no reduction of specific root length with depth was observed. Root biomass production by S. hamata hardly responded to P fertilization: 3,596 kg.ha-1 without P and 4,161 kg.ha-1 with non-limiting P-supply; above-ground biomass was 8,360 and 10,680 kg.ha-1 respectively. Root length density was relatively high for the whole root profile and specific root length increased from 35 m.g-1 for the 0–20 cm layer to 100 m.g-1 for the 130–140 cm layer, allowing S. hamata to use water and nutrients efficiently throughout the whole profile.
