Impact of Improved Rice Variety on Productivity and Crop Diversity: A Case of Singye Gewog (Block) in Sarpang District of Southern Bhutan

The survey was conducted in 2019 to generate baseline information for rice yield and varietal diversity, involving 54 experienced rice farmers of Singye Gewog (block) under Sarpang Dzongkhag (district) in Southern Bhutan. A total of 9 varieties were found under cultivation, of which 2 and 7 were assessed to be improved varieties and landraces respectively. The mean yield of improved varieties was 1253.2 kg acre-1, whereas landraces yielded 777.1 kg acre-1 (P=.006). The chronological varietal diversity revealed that 47.05% of farmer-named varieties were either lost or replaced over 20 years. However, landrace such as Choti Mahsino was popular, covering 24.6% of the rice cultivated area. Further, taste, yield stability, and utility for festivals were the main reasons for perpetuating landraces’ cultivation. The study showed the positive impact of improved varieties on productivity while it has narrowed varietal diversity. On the flip side, the current research found that only one improved variety was adopted which shows a need to promote improved varieties, while the improvement of landraces should also be given priority.