Sunflowers can adapt to their environment and thrive better than other crops during less than perfect growing conditions due to their ability to utilize moisture and nutrients from the soil using their deep root system.
Water Utilization
Sunflowers often utilize water better than other crops during dry drought conditions due to their average rooting depth reaching down 4-5 feet into the soil and the plant’s ability to extract water out of the soil.
For example, sunflower and sorghum extract the same amount of water within 3.25 feet of soil, but between 3.25 to 6.5 feet, sunflower will extract 2 to 3 times the amount of water as sorghum. They can also extract more water from the soil than other crops such as corn and soybeans even though the other crops need more water during the growing season than sunflowers. They use 1.5 inches more water out the deeper soil than other crops. Since sunflowers can root down deeper than other crops under drier conditions they can fulfill water needs better than soybeans which require similar water use to sunflowers.
Timing of water availability is critical for sunflowers. Shortages during earlier vegetative stages, R4 through R7, do not affect sunflower yields as much as at later stages. The most critical water period, usually occurring during late July thru early September, is when water is typically least available.
Fertilizer Utilization
Due to the depth that sunflower roots can reach down into the soil, they are also able to utilize Nitrogen and other nutrients out of reach from other crops.
Nitrogen can be utilized from 2 to 4 feet down in the soil. Make sure to fertilize for a realistic yield based on geography, soil type and annual rainfall. Timings and methods vary from region to region based on different farming practices.
If a grower does decide their sunflowers do need a starter, the fertilizer should not be placed in the seed furrow. Nitrogen can have a negative affect on a sunflower crop’s yield if over fertilized.
North Dakota State University’s Nitrogen Calculator is a tool that growers can use when trying to determine the correct nitrogen use on their sunflower crop and can accessed on the NDSU website. The calculator uses updated nitrogen recommendations for phosphorus(P) and nitrogen (N) based on general productivity and not on a yield prediction model.
Additional sunflower fertilization resources:
National Sunflower Association Website
NDSU Fertilizing Sunflower Publication
High Plains Sunflower Production Handbook
