Phka Rumduol cultivar is one of the main rice cultivars in Battambang province of Cambodia. Lower rates of seedling establishment are observed when Phka Rumduol is directly sown in paddy fields under flooded conditions. In our previous report, lack of dissolved oxygen (DO) in flood water was considered to be the main cause of the low seedling establishment. In the present report, the relation between the DO quantity and establishment of seedlings was verified. When the number of seeds sown in the water in pots increased, the DO quantity in the water decreased and resulted in the lack of seedling establishment. When the pots were supplied with air, seedling establishment was improved, and hence the relationship between dissolved oxygen quantity and growth of Phka Rumduol cultivar was verified. The coleoptile grew in any quantity of DO, while the foliage leaf and roots did not grow with less than 2 mgl-1 of DO. The Phka Rumduol cultivar required more than 3 mgl-1 of DO for normal growth. Decrease in DO levels in paddy soil may be caused by microorganisms. When seeds treated with Kosaide and Kasmin Bordeaux mixture were sown into paddy soil under flooded conditions, the rates of seedling establishment for both treatments increased. Addition of Bordeaux mixture to the paddy soil inhibited the decrease of DO and Eh, suggesting that the Bordeaux mixture controlled the activity of microorganisms in the paddy soil. Hence improved seedling establishment can be expected when rice seedlings are treated with the Bordeaux mixture.
In May 2008, Cyclone Nargis struck the southern coast of Myanmar, causing extensive damage and severely affecting the livelihoods of the inhabitants of the Ayeyarwady Delta. This study compared data from different sources to examine the impact of the cyclone on rice production as well as the subsequent restoration process three years after the disaster. Official agriculture statistics from the government, reports by an international team (the Tripartite Core Group) led mainly by Association of Southeast Asian Nations, and results of field surveys by the author are presented here. Although the government’s statistics did not indicate a decrease in either the sown area or rice yields after Nargis, the other sources reported a marked decrease in rice production, particularly in rice yield (per area), in the monsoon season of 2008 (immediately after the disaster). Although rice yields in some of the affected areas had recovered by the monsoon cropping season of 2009, yields in some of the survey areas along the coast were still less than half that before Nargis in 2010. Assistance focused on the recovery of rice farming, as well as continuous monitoring of recovery level has been necessary, even after three years. The government played an important role in the recovery of the agriculture sector, particularly in ensuring the sown area in the monsoon cropping season of 2008. To better understand several of the irregular instances when no negative impact was observed on rice yield after the disaster, even in severely affected areas, further agro-ecological studies should be undertaken on the mechanisms of yield decrement and its restoration.