. The potential for the development of paddy rice on tidal swamp land is relatively high, however, rice yield on this land is low due to low soil fertility, especially because of low phosphorus (P) and low organic matter in the soil. The experiment was conducted in the tidal swampland at Sungai Solok Village, Pelalawan Regency, Riau Province with the objectives of developing P fertilizer in combination with organic matter recommendation. The treatments were arranged in a split plot design with three replications, where rice straw compost was the main plot, and P fertilizer as the subplot. The main plot was P fertilizer rates: 30; 60; 90; 120 kg P2O5/ha in the form of TSP. The sub-plot was organic matter (O) in the form of rice straw compost at rates: 1.0 ; 2.0 ; 3.0 t ha-1. Observations consisted of (i) soil chemical properties including soil pH, organic C, available P, excangeable Ca, Mg, K, and Na, and cation exchange capacity (CEC), measured before fertilization and (ii) crop yield. The results showed that the soil was very acid with low levels of organic C and available P, while the total N was moderate, and basic cation contents and CEC were low. The rate of rice straw compost, P fertilizer and interaction of the two affected the productivity of rice in the tidal swampland. The highest productivity (5.73±0.49 t ha-1) was produced from the treatment of 2.0 t ha-1 composted rice straw in combination with 60 kg P2O5 ha-1.