Japonica rice is grown in the Central Valley of California primarily on dense clay soils under continuous flooding. Nitrogen is usually insufficient in these soils for optimum rice production, and nitrogen fertilization increases average yields about 40%. In some instances, nitrogen and phosphorus together are essential for optimum yields. Potash and other nutrient elements are usually adequate.

Rice Experiment Station personnel and farm advisors in Butte, Colusa, Glenn, San Joaquin, Sacramento, Sutler, Yolo and Yuba counties helped obtain data for this report.