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Irrigation

Safflower can be irrigated and yields are highest in many locations in the state when irrigation is used, even on deep, permeable soils. But caution is always required. Any condition created by irrigation or rainfall, which initiates and promotes infection by Phytophthora will result in significant yield loss. Irrigation guidelines are focused on the ways to reduce the likelihood of an outbreak of Phytophthora. The deep, vigorous root system of safflower allows the crop to use moisture stored in the subsoil, making it desirable to pre-irrigate, filling a deep soil profile with water. If winter rainfall is adequate, or water is available in the soil profile that was missed by shallower-rooted crops, irrigation may be avoided altogether. Deep rooting by safflower also can allow the grower to minimize the number of irrigations required during the cropping season and reduce the possibility of root-rot injury.

Irrigation practice must vary with soil conditions affecting water penetration, drainage, water storage, and root development. If a soil is sandy or shallow but drains readily, safflower requires the same irrigation as other crops growing at the same time. Deeper soils with high water storage capacity permit longer intervals between irrigations provided the subsoil is moist in an uninterrupted column. Root rot will be less likely to occur under these conditions. On soils with poor internal drainage, careful, early irrigation is possible, but late season irrigation is risky. Raised beds are necessary if safflower is to be irrigated because this reduces the danger of root rot.

There is a wide range of soil conditions between the extremes of coarse and fine soil textures, where surface and sprinkler irrigation of safflower can be effective. A balance between supplying adequate water and avoiding injury from excess must be achieved. Some general guidelines for irrigation have been developed over time, but they must be modified by the grower's own experience.

Irrigation Guidelines:

1. Pre-irrigate whenever possible, filling the soil profile completely. Pre-irrigation should raise the soil to field capacity to a depth of at least 6 feet and preferably to 10 feet (2 to 3.1 m).

2. Provide complete surface drainage.

3. Keep irrigations short, especially during hot weather. In general, it is better to avoid irrigating during hot weather.

4. Irrigate before the appearance of drought symptoms. The drying of lower leaves ("firing") can indicate moisture stress. Drought and plant water stress are correlated with increased disease occurrence.

5. Minimize the number of irrigations needed after planting by storing water in the soil prior to planting (rainfall, pre-irrigation).

6. Use beds with furrow or sprinkler irrigation.

7. Do not plant safflower on soils with slow internal drainage if it will be necessary to irrigate during warm weather. Typically, these are clay soils, stratified soils, and all soils with clay pans or other hardpans.

One special characteristic of safflower deserves mention. Safflower is well adapted to the use of water from saturated soil horizons within rooting depth. It does very well with subirrigation alone under conditions where most other summer crops would require supplemental irrigation. The highest yields of safflower in California often come from areas with shallow water tables, such as the Delta region and the Tulare Lake Basin. In the Tulare Lake Bed area, growers estimate average safflower water use as approximately 26 to 28 inches (660 to 710 mm). Up to 60% of this water is applied in a single irrigation, and the remainder (8 to 12 inches; 200 to 300 mm) is derived from the soil.

Safflower Contents | Weeds [10]

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Modified: 11 Jun 1999 Comments to webmaster@agric.ucdavis.edu