The present invention relates to a fertilizer composition comprising nitrogen and phosphorus, wherein nitrogen is provided by basic L-amino acid(s) complexed to polyphosphate(s). The complex may be precipitated with multivalent metal ion(s) to provide a solid phase fertilizer composition. The basic L-amino acid is advantageously L-arginine and/or L-lysine. The fertilizer composition is capable of providing controlled release of nitrogen during prolonged periods of time.