Soil Phosphorus Management in Organic Cropping Systems: From Current Practices to Avenues for a More Efficient Use of P Resources
Christine A. Watson
BORDEAUX SCIENCES AGRO-INRA, UMR1220 TCEM Transfert Sol-Plante et Cycle des Éléments Minéraux dans les Ecosystèmes Cultivés, 33175, CS 40201, Gradignan Cedex, France.
Phosphorus (P) is a major nutrient for all living organisms and a key production factor in agriculture. In crop production, it is usually supplied to soils through fertilisers or recycled manure and compost. Organic production guidelines ban the use of highly soluble, manufactured P fertilisers and, thus, recommend recycling P from livestock manure and compost. In this chapter, after an overview of P dynamics in soils, we explore the consequences of such guidelines in terms of field- and farm-gate P budget, soil P availability and crop productivity. Moreover, we propose some avenues for the more effective use of P resources, ranging from rhizosphere-based processes (e.g., soil microorganism manipulation), genotype selection and cropping practices (e.g., intercropping), to farming system design (e.g., a combination of crops and animals at the farm scale). Finally, the potential benefits of these options are compared with respect to soil P status, field- and farm-P budgets.
Keywords:Farm inflow and outflow; Farm-gate budget; Field budget; Genotype; Mixed farm;
Phosphorus; Rhizosphere; Roots; Stockless farm.