Monday, November 13, 2006 - 1:30 PM

Classification of Legume Cover Crops Based on their Potentials to Solubilize and Absorb P from Phosphate Rock Under Field Conditions in the Humid Forest Agroecology of West Africa.

Sylvester Oikeh1, Kanwar Sahrawat2, Eklou Somado3, Amadou Toure3, Sitapha Diatta3, and Kayode Sanni3. (1) WARDA, Africa Rice Center (WARDA), B.P. 2031, Cotonou, 01BP2031, BENIN REPUBLIC, (2) ICRISAT, ICRISAT, Patancheru 502324, Andhra Pradesh, 502324, INDIA, (3) Africa Rice Center (WARDA), B.P. 2031, Cotonou, 01 BP 2031, BENIN REPUBLIC

Phosphate rock (Rock-P) is an affordable source of P to ameliorate P deficiency common in the acid humid forest agroecology of West Africa. But its solubility is low. Some legumes have been reported to enhance Rock-P solubilization in acid soil conditions encountered in the area. This study evaluated the potentials of 16 legume cover crops to solubilize and absorb P from Rock-P applied at 100 kg P ha-1 under field conditions in Côte d’Ivore. The results of Principal Component analysis (PCA) suggest that the most important traits for the classification of the legume cover crops were biomass at 28, 56, and 84 days after sowing (DAS) and N-uptake at 28 and 84 DAS. Other important traits were canopy height at 56 and 84 DAS, root mass density and P-uptake at 28 DAS. Hierarchical Cluster analysis (HCA) showed 5 distinct clusters. The first cluster consisted of eight cover crops (Aeschynomene histrix, Eupatorium odoratum, Crotalaria micans, Vigna radiate, Sesbania pachycarpa, Crotalaria sp. Cameroun, Mucuna cochinchinensis, and Dolichos lablab) characterized by low biomass at 28 DAS, but with moderate to high P-uptake 56 and 84 DAS, thus possess moderate potential to solubilize Rock-P. The dendrogram indicated two isolated cover crops distinctively clustered III (Cajanus cajan) and IV (Canavalia ensiformis). The cluster III was distinguished by low biomass at 28 and 56 DAS, and low P-uptake at 56 DAS, while cluster IV had high biomass and N- uptake at 28, 56, and 84 DAS, high root mass densities and P-uptake at 56 and 84 DAS, and high canopy height at 28 DAS. Results indicated that cluster IV cover crop tended to have greater potential to contribute C, N and P to local production systems when grown with Rock-P. Key words: Legume cover-crops; PCA; P-deficiency; Phosphate rock; P-uptake efficiency; West Africa