1. Phosphorus adsorption, rice dry matter yield, and P use efficiency as influenced by phosphorus fertilizer rates in rainfed lowland soils in Togo
The study focused on improving phosphorus (P) fertilizer recommendation in rainfed lowland rice soils in Togo. Phosphorus adsorption was conducted on four soils to determine their P adsorption characteristics and standard phosphorus requirement (SPR). The adsorption maximum ranged from 143 to 200 mg P/kg. The amount of P adsorbed range from 62.70 to 74.85 mg P/kg. Greenhouse experiment was conducted to determine rice response to phosphorus rates based on the SPR values, and to assess rice P uptake and use efficiency. Five phosphorus rates, Control: 0 mg P kg−1, P recommended rate (RR): 5 mg P kg−1, 4 × RR: 20 mg P kg−1, 50% SPR and 100% SPR were used. Results indicated no significant difference between the Control treatment and the P recommended rate (RR), and between the 50% SPR and the 100% SPR with reference to shoot dry matter yield. P uptake and P use efficiency were significantly and positively influenced by the various P fertilizer rates. From the study, the blanket P recommended rate is inappropriate, however, site-specific P fertilizer rate of 50% SPR may be recommended to improve rainfed lowland rice yields in Togo.