The rock-phosphate solubilizing capacity ofPueraria javanica as affected by soil pH,superphosphate priming effect and symbiotic N2 fixation

Summary WhenPueraria javanica was grown on acid soil in a pot experiment, the legume’s acidifying effect, originating from an uptake pattern in which on an equivalence basis more nutritive cations than-anions were absorbed, was sufficient to mobilize rock phosphate even when added as very insoluble material. In neutral soil, a small quantity of triple superphosphate proved necessary to set into motion a chain of reactions in which the priming action of the TSP enables nodulation to take place followed, in order, by N₂ fixation, soil acidification and rock phosphate mobilization. More attention should be paid in tropical regions to mixed farming systems in which leguminous crops, like Pueraria, produce fodder for livestock whose faeces and urine, when properly collected, can be used for the manufacturing of biogas, after which the residues can serve as manure to food crops. Even when they prove unsuitable for beneficiation, many rock phosphates found in African and Latin American countries can be made useful as fertilizer for leguminous fodder crops.