With the increasing use of sprinkler irrigation on vegetables and other intensively grown crops, has come a need to evaluate herbicide effects. Herbicidal activity is often stepped up under sprinkler irrigation. The degree of crop selectivity may be increased, or decreased, depending upon the herbicide, the soil, the weed species, and the vegetable crop. Sprinkler irrigation advantages have been demonstrated, particularly in areas with saline soils or drainage problems. However, along with increased stands and vigor generally associated with sprinkling, comes an increase in weed populations. And as the cost of hand weeding rises, chemical herbicides become more desirable to the grower. The early use of sprinklers to help germinate the crop and activate the herbicide, even though furrow irrigation is used subsequently, is another promising approach in growing vegetables and other row crops. These observations of recent field tests and commercial applications of herbicides to control weeds under sprinkler irrigation are not to be considered recommendations for use of the herbicides mentioned. For recommendations, refer to University of California Weed Control Recommendations, 1969, or contact local farm advisors.

Cooperation was given by H. Sciaroni and W. Humphrey, Farm Advisors in San Mateo and Orange counties; and H. Johnson, Vegetable Crops Specialist and Bob Hildebrandt, Lab Assistant, U.C., Riverside. The Thompson-Hayward Chemical Company, Eli Lilly Chemical Company, Diamond-Shamrock Chemical Company, Upjohn Chemical Company, Shell Chemical Company, Stauffer Chemical Company, Geigy Chemical Company, and the Rohm & Haas Chemical Company provided partial financial assistance for this project.