Why aerobic rice?
There are three main driving forces for aerobic rice:
- The increasing realization that not all “uplands” are “unfavorable”, in the sense that certain uplands may possess soils with good water-holding capacity and high fertility, that they are not always sloping land, that rainfall may be sufficient for a “decent’ crop growth, and that sometimes investments can be made to improve the quality of the uplands. An example of the latter is the terracing of slopes in the hilly and mountainous regions in Yunnan, China, and in North Vietnam. Aerobic rice is seen as a relatively high-yielding production system that optimally exploits the resources available. Other examples of “favorable” uplands are the flat Cerrado region in Brazil, and the North China Plain where aerobic rice is introduced in typical high-yielding upland cropping systems (such as maize, cotton, soybean).
- The increasing awareness that many areas in the so-called “rainfed lowlands” don’t receive enough water to keep the rice fields predominantly flooded. Rainfed lowlands are often characterized by slightly undulating topography with differences in elevation of a few meters across a toposequence of a few hundred meters only. Because of this topography, however, fields at the top of a toposequence often have deep groundwater tables, more coarse-textured soils, and more runoff and seepage losses. The soils in these fields are often dominantly aerobic and hence an ideal target domain for the system of aerobic rice.
- The increasing water scarcity in irrigated lowlands. The causes for water scarcity are diverse and location-specific, but include decreasing resources (e.g., falling groundwater tables, silting of reservoirs), decreasing quality (e.g., chemical pollution, salinization), malfunctioning of irrigation systems, and increased competition from other sectors such as urban and industrial users. In extreme cases, water scarcity can be so severe that farmers can not maintain flooded conditions in their fields for even a small part of the growing season, and rice fields are not ponded and saturated with water anymore. However, irrigation water availability is still sufficient for supplementary irrigation to keep the soil water content around field capacity. Under such conditions, lowland rice can not be grown anymore, and aerobic rice becomes a suitable alternative along with upland crops (diversification).