The highest average rice yield was from irrigated ecosystem, followed by deep water, rainfed lowland, and upland ecosystems.
Current national policy is ambitious regarding irrigation development, and this drive will likely be strengthened by losses in rainfed cropping.
To evaluate uncertainties related to the simple irrigation adjustment factor, data on harvested area and crop produced by irrigation and rainfed categories at the grid cell are needed.
To examine differences between the irrigated and rainfed yields by crops, now consider Figure 11, which shows differences between the irrigated and rainfed yields for six crop categories for the major crop producer countries of USA, EU, China, and India.
Habitat cover shifts as a result of climate change include a net increase of open water (2 21%), as well as a reduction of rainfed habitats by 2 5% and seasonally flooded habitats by 5 11%.
Yields for cereals produced with irrigation exceeded rainfed yields by 115percentt in developing countries collectively and by 150percentt in sub-Saharan Africa and West Asia/North Africa in 1995.
A challenge recognized by breeders in the 1970s was the need to improve yields in the rainfed lowlands by introduction of submergence tolerance to high yielding varieties (Mackill et al. 1996).
As a result, in high population areas the landscape became dominated by fields planted to rainfed upland crops, wetland rice terraces, fallow vegetation, and patches of secondary forest.
We addressed this issue within the Lebna watershed (210 km² size, located on the Cap Bon Peninsula in Tunisia), which is typified by a hilly topography, rainfed mixed farming (cereals, fodder, legumes, spices) and livestock (cattle, sheep and goat), and strong farmland fragmentation.
