Yield Response of Transplanted Aman Rice (Oryza sativa L.) to Phosphorus Rates in Coastal Region of Southwestern Bangladesh

Abstract

Cropping in the southwestern (SW) coastal region of Bangladesh is completely different from that of other parts of the country. Only one crop, Transplanted (T.) Aman rice, is cultivated annually; thus, the prevailing cropping pattern is Fallow–Fallow–Transplanted Aman. Among the high-yielding rice varieties, BR23 is the most popular T. Aman rice in this area. However, farmers apply fertilizers, including phosphorus (P), to T. Aman only once a year. Since this cropping and fertilization practice has been followed for a long time, it is necessary to re-evaluate whether the current phosphorus fertilizer rate is optimum, insufficient, or excessive. The present field study was conducted in a typical coastal soil at Pankhali, Dacope, Khulna, a saline area of Agro-Ecological Zone (AEZ) 13, located approximately 30 km from Khulna city. The experiment consisted of six phosphorus rates: 0, 5, 7.5, 10, 12.5, and 15 kg P ha⁻¹, with three replications. The results showed that no significant grain yield benefit was obtained from phosphorus application rates ranging from 5 to 15 kg P ha⁻¹, although 10 kg P ha⁻¹ is the currently recommended rate. Approximately 90% of the maximum grain yield was produced in the treatment without added phosphorus, indicating that: (i) the field contained sufficient residual phosphorus to support the growth and yield of T. Aman rice; (ii) the current recommended phosphorus rate could be reduced to approximately 5 kg P ha⁻¹; and (iii) the residual phosphorus may support the growth and yield of a winter crop (if cultivated) or the following year's T. Aman.