Agronomic practices affect soil phosphorus(P)availability,P uptake by plants,and subsequently the efficiency of P use.A field experiment was carried out to investigate the effects of various agronomic practices(straw incorporation,paddy water management,nitrogen(N)fertilizer dose,manure application,and biochar addition)on soil P availability(e.g.,soil total P(STP),soil available P(SAP),soil microbial biomass P(SMBP),and rice P uptake as well as P use efficiency(PUE))over four cropping seasons in a rice-rice cropping system,in subtropical central China.Compared to the non-straw treatment(control,using full dose of chemical N fertilizer),straw incorporation increased SAP and SMBP by 9.3％-18.5％and 15.5％-35.4％,respectively;substituting half the chemical N fertilizer dose with pig manure and the biochar application increased STP,SAP,and SMBP by 10.5％-48.3％,30.2％-236.0％,and 19.8％-72.4％,respectively,mainly owing to increased soil P and organic carbon inputs;adding a half dose of N and no N input(reduced N treatments)increased STP and SAP by 2.6％-7.5％and 19.8％-33.7％,respectively,due to decreased soil P outputs.Thus,soil P availability was greatly affected by soil P input and use.The continuous flooding water regime without straw addition significantly decreased SMBP by 11.4％compared to corresponding treatments under a mid-season drainage water regime.Total P uptake by rice grains and straws at the harvest stage increased under straw incorporation and under pig manure application,but decreased under the reduced N treatments and under biochar application at a rate of 48t ha-1,compared to the control.Rice P uptake was significantly positively correlated with rice biomass,and both were positively correlated with N fertilizer application rates,SAP,SMBP,and STP.Phosphorus use efficiency generally increased under straw incorporation but decreased under the reduced N treatments and under the manure application(with excessive P input),compared to the control.These results showed that straw incorporation can be used to increase soil P availability and PUE while decreasing the use of chemical P fertilizers.When substituting chemical fertilizers with pig manure,excess P inputs should be avoided in order to reduce P accumulation in the soil as well as the environmental risks from non-point source pollution.