RESEARCHER: Dr. Stephen Kaffka, UC Davis, 2021
KEY TAKE-A-WAYS
• Safflower crops planted in winter in the San Joaquin Valley were efficient with respect to water use, comparable in feed quality to cereal silages made from small grains like wheat and were able to remove a large amount of nitrogen from soil.
• Safflower can play an important role on dairy farms as feed for growing heifers and dry cows when harvested at a vegetative stage in early spring, following a November planting.
BACKGROUND, OBJECTIVES, FINDINGS AND OUTCOMES
Safflower is a deep-rooted plant that recovers water and nutrients from deeper in the soil profile than any other annual crop. This was the second year of research funded by CDRF on the use of safflower as winter forage for dairy cows. The first year of research took place on the UC Davis campus and found many benefits of safflower, including greater water use efficiency and a large amount of forage dry matter biomass. The second year of research was conducted on two cooperator dairy farms in the San Joaquin Valley (SJV) and addressed a broader set of objectives including evaluating forage yield and feed quality of fall-planted safflower under different planting and harvesting dates; quantifying safflower crop water use in winter; and, quantifying the capacity of safflower to recover nitrogen and water deep in the soil profile.
The researchers identified trade-offs among length of safflower growing season, crop quality, soil water depletion and nutrient uptake. Safflower yield was similar on each dairy farm despite differences in planting and harvesting dates. However, the quality of safflower at each site changed throughout the growing season. As yield increased, safflower crops declined in metabolizable energy and crude protein, and also in nitrate content. By harvest, nitrate content reached levels that were safe for feed and declined further after ensiling.
Another notable trade-off was between level of soil water depletion and harvest date. By harvest in early April, safflower had begun to deplete soil moisture up to 6 feet in the profile. A later harvest time could also increase soil water depletion. In the first year of research, a portion of the UC Davis field, which was allowed to flower until late May, soil water depletion reached 9 feet. However, there was a corresponding decrease in forage quality. One possible solution for increasing forage quality with a later harvest date could be mowing safflower when it is at a higher height.
Soil samples collected at SJV farms indicated that plant-available nitrogen increased with depth, demonstrating a need for deeper rooted crops like safflower to be able to recover nitrogen that could otherwise leach to groundwater. In this study, safflower crops recovered from 250 to 300 lbs. of nitrogen per acre depending on the length of season and soil fertility levels. This compares favorably with published values for nitrogen recovery from cereal silages (approximately 180 to 200 lbs. of nitrogen per acre) produced in the SJV. Safflower grown in rotation with other cereal crops offers the chance to utilize resources more completely.
Based on these promising results for safflower as winter forage, the researchers worked with three professional commercial dairy nutrition consultants to determine how they might utilize safflower as a new feed ingredient in diet formulations for dairy cattle. The consultants considered safflower silage to be a highly acceptable feed ingredient for replacement heifers.
Safflower was efficient with respect to water use, comparable in feed quality to cereal silages made from small grains like wheat and removed a large amount of soil nitrogen. In addition, safflower silage conserved well and was stable to oxygen after pile opening. Safflower can play an important role on dairy farms as feed for growing heifers and dry cows when harvested at a vegetative stage in early spring, following a November planting.