Comparison of Various Plant Residues as Phosphate Rock Amendment on Savanna Soils of West Africa

Abstract

Phosphate rock (PR) is being considered as an important source for phosphorus (P) replenishment in sub-Saharan Africa soils. Field trials were conducted with two-season crops to compare the utilization of PR combined with or without plant residues by test crops. The plant residues studied include leaves of Dactyladenia barteri, Flemingia macrophylla, Gliricidia sepium, and Leucaena leucocephala, maize (Zea mays) stover, and rice (Oryza sativa) straw. The test plants were Crotalaria ochroleuca (legume cover crop) and maize (Zea mays) in sequential cropping systems. Where no plant residues were applied, apparent utilization efficiency (AUE) of PR was 1.0% in 1999 and 2.7% in 2001. The AUE of PR was improved in many cases with the addition of plant residues. The AUE of PR in all treatments with plant residues was on average 3.4% in 1999 and 6.2% in 2001 with a pronounced effect from Flemingia and Gliricidia. Negative values of AUE were observed in treatments with Leucaena and maize stover in 1999, and Dactyladenia in 2001. These results suggest that the choice of plant residues is an important step for using plant residues as PR amendment on the near-neutral and neutral soils of West Africa.