System shift in rice: Processes and pathways of change in rice-based production systems of Southeast Asia

Predicting future production trends and associated land use and management practices requires an understanding of past changes in productivity and of pathways of evolving system configurations. We argue that rice systems' evolution reflects a process of adaptation to changing availabilities of production resources and the adoption of technological innovations and that differs by marginality/favorability of sites. Understanding past change trends and their determinants can help avoiding undesirable future developments and guide policy decisions for a sustained supply of rice. We aimed to assess agronomic system change and practices, to quantify pathways of change and to identify likely drivers of but also possible risks or opportunities associated with observed patterns of agronomic system transformation in six representative lowland rice production environments in Asia. We implemented a diachronic analysis (years 2000 vs. 2018) of rice production practices and yield attributes in 1024 households. We documented changes between 2000 and 2018 in lowland rice-based systems in six rice-growing environments in the Philippines, Myanmar and Cambodia, differentiating marginal and favorable sites in irrigated and in rainfed environments. Farmers' household attributes, resource endowment, rice yields, and key constraints differed among sites. We observed relatively low annual yield in marginal (2.2–3.0 t/ ha) than favorable (3.3–8.9 t/ ha) sites depending on countries and seasons. The farmers adopted intensification related agronomic practices has increased significantly between 2000 and 2018, especially in dry season (i.e., improved seeds by 28%, mechanical tillage by 52%, direct seeding by 21%, combined harvester by 62%). The marginality of climatic and edaphic conditions, the systems' evolutionary state in 2000, and differential pressures (policy environment), opportunities (technological change) and household attributes (resource endowment) determined the observed transition pathways across study sites. The trends towards maximizing land use intensity (double or multiple cropping), converging in the emergence of high-input and highly mechanized (laborsaving) in irrigated, and diversified rotations in rainfed rice production systems may help to elucidate agricultural research needs and potentially predict the requirements for future sustainable intensification of rice-based systems. Additionally, we argue for a continued need for further mechanization of rice establishment, especially shifting from transplanting to direct seeding during dry and wet seasons, and of the rice harvest, especially during wet season under fully irrigated environments.