California Agriculture

California state legislation passed in 1991 mandated a phased reduction of rice straw burning in the Central Valley, to reduce air pollution. In 1993, UC Davis scientists launched an 8-year research project on the long-term effects of various alternative means of managing rice straw. Burning, incorporation into the soil, rolling, and baling and removing the straw were compared, with and without winter flooding. None of the various practices reduced grain yields on our experimental plots, but there was an increase in weeds when straw was incorporated, and in particular when the fields were not winter flooded. However, when straw is incorporated, nutrients are returned to the soil and less nitrogen fertilizer can be applied, resulting in lower production costs and less potential for water pollution. In addition, waterfowl on the Pacific Flyway benefit significantly from the wetlands created when fields are flooded during the winter.