Abstract: Background and Objective: Soil available boron can be the limiting factor for rice production in rainfed lowland condition. This study aimed to identify the external boron requirement of the rainfed lowland rice varieties. Materials and Methods: A field experiment was conducted during June-October, 2016 at Purkot, Tanahun, Nepal to assess the performance of rice varieties grown under rainfed condition. Using split plot design, three replicates of four rice varieties (Sukkhadhan-2, Sukkhadhan-4, DRR-44 and Ciherang sub-1) under four levels of soil boron (B) application (0, 1, 2 and 3 kg ha–1) were cultivated. Results: We found that the significant effects of B application among rice varieties on yield and its associated traits; the genotypic differences, however, varied. On average, B application at the upper level -as compared to the control of no B application- increased the plant height, effective tiller numbers and effective grain numbers by 7, 3 and 5%, respectively. Similarly, it increased grain yield and straw yield by 38% and 12%, respectively. While, Sukkhadhan-2 appeared to be the highest grain yielding variety, the straw yield was the premier for Ciherang sub-1. Such B induced grain yield increment corresponded to the decline in unfilled grains proportion (43%)-the highest for Sukkhadhan-2. B also induced the 1000 grains weight (12%) and harvest index (15%). Conclusion: Hence, not only the genetic makeup but also the soil B application controls rice production under rainfed condition.