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KSU Study Explores Sunflower & Strip-Till

Wednesday, February 15, 2006
filed under: Minimum Till/No-Till

No one questions the value of no-till sunflower production when it comes to moisture conservation and soil erosion control. But how does no-till compare to strip-till in terms of sunflower yield and root growth (which obviously, in turn, affects yield)?

Those were the key questions being asked by researchers at the Kansas State University's Northwest Research & Extension Center, Colby, when they initiated a two-year study comparing the two production systems on a field one-half mile east of Quinter, Kan. (Gove County), in 2004 and 2005.

The 2004 season's research site had been under no-till for five years, while the nearby 2005 study site had been in no-till the previous four years. Crop residue was wheat. The sunflower planted at both locations was a Clearfield oil-type variety.

Four systems were compared in the study, with 75 pounds of nitrogen applied to each treatment. Those systems - and their N application details - were as follows:

1) Fall Strip-Till - 50 lbs of N applied as UAN, plus 25 lbs applied as urea 2x2 at planting.

2) Winter Strip-Till - 50 lbs N applied as anhydrous, plus 25 lbs as urea 2x2 at planting.

3) Spring Strip-Till - 50 lbs N applied as UAN, plus 25 lbs as urea 2x2 at planting.

4) No-Till - 75 lbs of N applied as urea 2x2 at planting.

At the end of the growing season, plots were harvested and sunflower plant roots from the spring strip-till treatment and the no-till treatment were randomly selected and extracted. The roots were washed and air dried to assess taproot and lateral root mass, as well as to visually observe root straightness (an indicator of soil compaction or lack thereof).

When yield data for both years were combined, there turned out to be a significant advantage to the winter strip-till and spring strip-till treatments versus no-till. The fall strip-till and no-till yields were virtually identical, however. Average yields were as follows across the


1) Winter Strip-Till - 2,225 lbs/ac

2) Spring Strip-Till - 2,218 lbs

3) No-Till - 2,008 lbs

4) Fall Strip-Till - 1,984 lbs

One reason for the better yields in winter and spring strip-till, the researchers suggest, was their higher plant populations at harvest compared to the no-till and fall strip-till plots. Another important factor was root development. "Roots examined from both years from the spring-applied strip-till treatment had straight roots with more lateral and secondary root growth than those extracted from the no-till treatment," they reported.

"Although the field had been in no-till prior to the study, root growth was still impeded - which in turn likely affected yield."

In addition to the above tests, in 2005 the KSU researchers also compared strip-till sunflower to the tillage practices utilized by the cooperating farmers on fields located throughout northwestern Kansas. There were three comparisons (two locations each) evaluated. The first site was irrigated confections, while the other five were, respectively, dryland confections, dryland oils, irrigated oils, dryland oils and double-crop irrigated oils.

The three tillage system comparisons were as follows:

1) Sunflower was planted into no-till wheat stubble by the farmer, while tillage was used to prepare the ground for wheat planting. That was contrasted with a strip-till pass conducted in the spring. At least half the required fertilizer was applied during the strip-till pass, with the remainder applied at planting.

2) Here, the farmer was exclusively no-till. The spring strip-tilled acreage was treated similarly to the previous example.

3) The farmer employed a reduced-tillage system, using sweeps or a field cultivator to prepare the seedbed. Again, the strip-till acres were prepared similarly to the two preceding examples.

Although harvested yields were higher with the strip-till system at all six sites, the difference was not statistically significant at five of the sites. The only exception was at the double-crop/irrigated oils location, where there was a severe soil compaction problem.

The KSU-Colby group believes a strip-till system for sunflower production offers at least four potential benefits. First, the drying and warming of the soil in the spring can aid seedling emergence and survival. Second, the majority of the field (the inter-row areas) remains in a no-till state, thereby conserving moisture and protecting against soil erosion. Third, restrictive soil layers are fractured by the strip-till implement shanks, thus improving plant access to water and nutrients and likewise benefiting root development. And fourth, fertilizer is placed several inches below the seed, thus providing the taproot with a readily available supply of nutrients.

But strip-till is not without risk, they add. Most of that risk is related to soil conditions. If too dry when strip-tilling, the result can be large clods, a poor seedbed, and ground too rough for uniform herbicide application. If the field is too wet during strip-till pass, hardpans may not be sufficiently fractured; and, in fact, soil compaction could actually increase. Also, the soil may not fill back in properly behind the fertilizer knife, and any ensuing hard rains could cause depressions within the strip-tilled zones. -Don Lilleboe

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