Site Specific Nutrient Management (SSNM) is a plant need based approach for optimally applying nutrients to lowland rice to achieve high yield and increased profitability. In SSNM approach fertilizer P and K requirements are determined through omission plot technique, which enables the determination of P and K rates sufficient to overcome their deficiencies as well as maintain P and K fertility of soil. We evaluated omission plot technique under SSNM approach in 98 farmers' fields in wet (Aman) and in 31 farmers' fields in dry (Boro) seasons during 2000 to 2003 in southwestern Bangladesh to optimize P and K fertilization in lowland rice. Omission plot technique has enabled the identification of locations where the rice yields and profitability can be increased by applying P and K at optimal rates and times along with other nutrients. The average fertilizer P rates calculated through omission plot technique were lower by 5 to 23 kg P ha¹ than average fertilizer P rates used by farmers across villages and seasons. The calculated average fertilizer K rates were higher by 7 to 52 kg K ha¹ than the average fertilizer K rates used by farmers across all villages and seasons except 2 villages in wet season. Improved management of P and K in lowland rice through omission plot technique along with optimal use of other nutrients consistently increased profit for rice cultivation across villages and seasons.