Sunflower growers who use conventional tillage and switch to strip-till can expect yields and quality that will be at least similar, according to a 4-year North Dakota State University (NDSU) study.
"When averaged across the combined 4 years, the fall strip-till yield was highest at 1,150 pounds per acre, followed by the direct-seed yield (1,070 pounds per acre) and conventional till (1,030 pounds per acre)," says Greg Endres, an NDSU agronomist. "Farmers can receive the benefits offered by strip-till — savings in fuel, moisture and time — without sacrificing yield or quality," says Endres.
"The study also indicated that a sunflower response to placement of liquid-phosphorus fertilizer is not likely when soil phosphorus levels are medium or high."
Researchers at NDSU's Carrington Research Extension Center conducted the 4-year tillage study from 2006 through 2009. (The study continued in 2010, but serious plot damage from the sunflower midge negated its usefulness.)
Along with a tillage-system comparison all 4 years, fertilizer-placement evaluations were added in 2008 and 2009.
In those 2 years, the strip-till treatments included 5 to 6 gallons per acre of 10-34-0 liquid fertilizer that was deep-banded 5 to 7 inches deep in the fall, prior to the sunflower planting, and a 2-by-2-inch band and in-furrow application during planting.
The dryland cropping study was carried out on a well-drained loam soil. Spring wheat was the preceding crop. The conventional-till plots were tilled to a depth of 2 to 4 inches in the fall and again in the spring prior to planting. These plots also received in-season cultivations.
The strip-till treatments were established in October-November each fall. Also, a spring pass was conducted in April 2006 and 2007. A Yetter strip-till unit on 30-inch row spacings was used.
Set at depths between 3 and 7 inches, the strip-till rig produced tilled strips 8 to 12 inches wide. A direct-seed treatment (in standing wheat stubble) was the third tillage system in this study.
Averaged across the 4 years of the study, the sunflower plant emergence, first flower and physiological maturity generally were similar across the 3 tillage treatments. Plant stands tended to be highest with strip-till when averaged across all of the study years.
When fall and spring strip-till were compared (2006 and 2007), seed yield was statistically similar. However, the yield tended to be higher with spring strip-till. Seed yield and oil content were statistically similar among the three tillage systems (conventional, direct seeded and strip-till) each year of the study.
Sunflower plant development, seed yield and oil content levels were statistically similar during 2008 and 2009 — the 2 years in which the impact of fertilizer placement in strip-till sunflowers was measured.
Sunflower response was not expected, due to a high level of soil phosphorus in 2008 (20 ppm) and a medium level (9 ppm) in 2009.
"For farmers considering a transition from conventional to reduced tillage, the results of the study suggests that sunflower seed yield and quality under a strip-till system will be at least similar to conventional till," Endres says. "Farmers can receive the benefits offered by strip-till — such as savings in fuel, moisture and time — without sacrificing yield or quality."
The study also indicated that a sunflower response to placement of liquid phosphorus fertilizer is not likely when soil phosphorus levels are medium or high.