The controversy over the distance between shanks on an air seeder or air drill for seed-row spacing is still with us after 15 years of direct seeding.
Eric Oliver’s approach is that row spacing is important only when using narrow openers with low seedbed use, such as a knife or disc. The conservation agronomist with the Saskatchewan Soil Conservation Association said the issue is moot if higher seedbed use is achieved using openers such as a spreader tip, paired row, spoon, mini-sweep or even a full sweep because the negative impacts associated with row spacing generally occur only when narrow seed rows are used.
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“If, as Oliver contends, the issue is moot, we have to wonder why we keep hearing about it,” said Peter Gamache, Reduced Tillage Linkages team leader in Edmonton. “Part of the reason might be the conflicting results from research. Studies can be found to support wide and narrow spacing. The different results are often a result of different factors being tested. SBU (seedbed use), the width of the seed row relative to shank spacing, opener type, climatic conditions and crops are some factors that may impact the results.”
Changes in row spacing and width do not always correlate directly to crop emergence and yield. Yield and maturity are influenced by weather, soil moisture and fertility. Crops respond to growing conditions by adjusting growth: tillers, branches and maturity.
Work in Saskatchewan indicates that wider row spacings have performed as well or better than narrower in black, grey and dark brown soil. Research in Swift Current, Sask., in the brown soil zone points to an advantage of narrower 20 to 22.5 centimetre spacing compared to 30 cm spacing. The AgTech Centre’s work in Alberta indicates that more seedbed use is better. However, that is not the same issue as shank spacing. A wide shank spacing can still have high seedbed use, depending on the opener. Most drills now come with either 22.5 or 30 cm spacing.
Farmers may want to consider these questions:
- What soil types do they have: clay, loam or sand? Soil types affect opener performance and growing conditions.
- Do they have the tractor power to pull the shank width-openers they want to use? Wider row spacing and a narrower opener likely means less horsepower. It also means less soil disturbance and better residue clearance at seeding.
- What is the typical amount of stubble and residue produced in an average year? Will the crops canopy over with a given row spacing? Wider spacing is a good option, especially in black and grey soil where more residue is produced. Crops also tend to canopy sooner in high moisture areas. Narrow may be better in the drier brown soil zones because crops tend to canopy slower. However, moisture loss is a risk if seedbed use is high.
- How will fertilizer be applied? Are the logistics in place to handle everything at once? Shank spacing cannot be divorced from row width. It is more of a concern in single-shoot systems where fertilizer may need to be applied separately. If producers are double shooting, the amount of fertilizer is not usually an issue as related to seed safety.
- Will the crop be swathed or straight cut? Wider shank spacing with low seedbed use may result in less stubble to hold the crop off the ground and may be a problem when swathing short crops caused by low fertility or drought.
