カンボジアにおける灌漑導入が稲作の栽培と生産性に与える影響 --ポーサット州における隣接する地区の比較に基づく検討--

Abstract

Rice production in Cambodia has achieved rapid growth over the last 20 years. One of the major reasons for this is the development of irrigation facilities. This study conducted field investigations on rice production in the Krouch Saeuch irrigation area from the rainy season of 2013 to the dry season of 2015, and evaluated the effect of irrigation development on rice cultivation management and productivity in order to discuss future perspectives in rice production in Cambodia. Compared with the adjacent nonirrigated area, the irrigated area showed conspicuous expansion of aromatic cultivars in the rainy season and early-maturing high-yielding cultivars in the dry season within a few years after irrigation was provided. The expansion was focused on rice selling, suggesting that the focus of cultivation changed from self-sufficiency to commercial. The main planting method also changed from transplanting to broadcasting. Earlier planting became more common, and the use of fertilizers and agrochemicals was more prevalent in the irrigated than in the nonirrigated area. However, these changes did not necessarily lead to increased productivity. Instances of improper management, such as ineffective application of fertilizer, were sometimes observed. One of the major production constraints is lodging due to excessive growth of aromatic rice. The development of cultivation management is primarily recommended to eliminate this constraint. The development of irrigation canals changes the economic activities of farmers in addition to cultivation management. Accordingly, comprehensive assessment is necessary when new irrigation canals are planned.