Fertilizer trials with safflower in sacramento valley
These tests, and other field observations, indicate that moisture is a key consideration in selecting a fertilizer program for safflower in the Valley. For dry-land soils or soils with low sub-surface moisture levels, 20 to 60 lbs per acre of N appear to be sufficient. Excess N may reduce yields. Greater amounts of N may be utilized when safflower is grown under irrigation, or on soils with a high water table, or on deep soils filled with moisture. The effect of the previous crop is important here: when safflower follows rice or sorghum, up to 150 lbs per acre of N are generally adequate. However, when it follows a nitrogen-fixing crop such as alfalfa or vetch, smaller amounts may be sufficient. No reduction in safflower yield has been observed from excess N under highmoisture conditions. Because safflower may not be irrigated, fertilizers should be placed in the moist root zone, at least 4 inches deep. If a nitrogen fertilizer is broadcast, at least 1 inch of rain or its equivalent in irrigation is needed to move it into the root zone. Spring applications are preferable to fall applications. In a dry spring, aqua or anhydrous ammonia placed at a depth of from 4 to 8 inches can be expected to be more effective than broadcast dry materials. If dry materials are to be used, applications early in the spring are desirable to take advantage of spring rains.