Sunflower Response Under Strip Till
By Greg Endres
Strip till — also referred to as “zone till” in some circles — has generated increased interest among farmers in a number of areas around the Northern Plains and Great Plains. It is used in several crops, including corn, dry beans, sugarbeets — and sunflower.
To gain more information on sunflower’s response under a strip-till system, including fertilizer placement, researchers at North Dakota State University’s Carrington Research Extension Center conducted a four-year tillage study focusing on strip till. This study took place during the period of 2006-09. (The study was continued in 2010, but serious research plot damage from the sunflower midge negated its usefulness.)
Along with tillage system comparison all four years, fertilizer placement evaluations were added in 2008 and 2009. In those two years, the strip-till treatments included five to six gal/ac of 10-34-0 liquid fertilizer that was (1) deep-band applied (5-7” depth) in the fall prior to the sunflower planting, and (2) a 2x2 band and in-furrow application during planting.
This dryland 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 2-4” 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 (April) pass was conducted in 2006 and 2007. A Yetter strip-till unit on 30” rows was used. Set at depths between 3 to 7”, the unit produced tilled strips 8 to 12” in width.
A direct-seed treatment (in standing wheat stubble) was the third tillage system in this study.
A Clearfield® oil sunflower variety was planted in 30” rows in mid-May each year. Best management practices were employed during the sunflower production season, with the trials harvested by a plot combine during the period of mid-October to mid-November, depending on the year.
Averaged across the study’s four years, sunflower plant emergence, first flower and physiological maturity generally were similar across the three tillage treatments. Plant stand 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, it 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. When averaged across the combined four years, the fall strip-till yield was highest at 1,150 lbs/ac, followed by the direct-seed yield (1,070 lbs/ac) and conventional till (1,030 lbs/ac).
Sunflower plant development, seed yield and oil content levels were statistically similar during the 2008 and 2009 — the two years in which the impact of fertilizer placement in strip-till ’flowers was measured. Sunflower response was not expected, due to a high level (20 ppm – Olsen test) of soil phosphorus in 2008 and a medium level (9 ppm) in 2009.
For those farmers considering a transition from conventional to reduced tillage, this study suggests that sunflower seed yield and quality under a strip-till system will be at least similar to conventional till. So one can receive the benefits offered by strip till (e.g., 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.
Greg Endres is area agronomist with the North Dakota State University Extension Service at the Carrington Research Extension Center.
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