The California rice cropping system: agronomic and natural resource issues for long-term sustainability

California rice is produced on approximately 200,000 ha mostly in the Sacramento Valley. The crop is planted in April/May and harvested in September/October. The growing season is characterized by a Mediterranean climate with negligible rainfall, high solar radiation, and relatively cold nighttime temperatures, thus yields may exceed 9 t ha(-1), 20% above the US average. California is a highly urbanized State with an affluent population demanding agricultural practices to be environmentally benign and food products to be safe for human health. This has contributed to a rigorous regulatory climate for plant protection chemicals thus increasing the cost of production. Likewise, the resource base is being challenged. Increased demand for clean potable water for urban expansion and the demand for environmental water compete with rice for limited supplies while raising cost. Production problems, such as straw management for cleaner air, weed resistance to herbicides, and the introduction of exotic pests also contribute to higher costs. The California rice industry is challenged by the increasing complexity of the rice production system to meet both the off-farm public demands and the on-farm need for higher productivity.