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Organic fertilization, a critical agronomic practice for improving nutrient availability and crop growth, may increase the risk of phosphorus (P) loss. To investigate the effect of organic fertilization on P availability, crop growth and P loss, a paddy field experiment was conducted in the saline-alkaline paddy soil. We designed four treatments: CK (no fertilizer), NPK (mineral fertilizer), and NPKC1 and NPKC2 (mineral fertilizer with low and high levels of organic fertilizer, respectively); the amounts of N, P2O5, and K2O were equal in the NPK, NPKC1, and NPKC2 treatments. Compared with the NPK treatment, organic fertilization enhanced the content of total, organic, and available P in the topsoil. Moreover, organic fertilization significantly improved both the growth and P removal of crops. The content of oxalate Fe, Al, and dissolved organic carbon, the main carriers of P loss, in the soil was the highest in the NPKC2 treatment. The soil P saturation ratio (PSR) in the NPKC2 treatment was 0.25, exceeding the threshold PSR for P loss of 0.16. Therefore, organic fertilizer application could improve P availability and crop growth; however, high-level organic fertilization increases the risk of P loss in coastal saline-alkaline paddy soils. [ABSTRACT FROM AUTHOR]