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Wider ‘seed spread’ boosts crop yield

New research shows farmers using row spacings over 10 inches can improve yield by using wider row widths. The results from a direct-seeding study entering its third year at the Alberta Agriculture, Food and Rural Development AgTech Centre in Lethbridge, back the thinking that yields increase with seedbed utilization, which is the percentage of seedbed used by the plant.

Row spacing is the distance between seed rows, typically eight to 12 inches. Row width, also known as seed spread, is the breadth of the seed row and typically ranges from one to five inches, depending on the seeder. Row width and row spacing both affect seedbed utilization, either independently or together. “Little research has been done on the interaction of row width and row spacing,” says Lawrence Papworth, an AgTech Centre Seeding and Tillage Project Engineer. “This research sheds some light on that interaction and how producers can optimize yield.”

Farmers in direct seeding systems often use wider row spacings to cut through crop residue, minimize soil disturbance and reduce operating costs such as fuel and repairs, says Papworth. “However, a row spacing study completed in 2000 at the AgTech Centre revealed that row spacing over 10 inches reduces yield considerably. We initiated the current study to determine if increasing row width would compensate for wider row spacings.”

The short answer is ‘yes,’ says Papworth, despite the fact drought conditions affected the study in 2001. “The results are good news for farmers using air drills with wide packers, which allow for a wider row width, because they can take advantage of wider row spacings without compromising too much yield.”

The study was conducted at six sites across the province, including Lethbridge, Provost, High River and Edmonton. Wheat, canola and barley were the crops used in the study. Row widths in the study were one, three and five inches, while the row spacings were eight, 10 and 12 inches. The seed was placed with Flexi-coil Stealth Single-shoot Spread tips and the fertilizer was placed with Morris Banding Coulters.

“Generally, the study showed that wider row width increases plant emergence and grain yield with all three row spacings,” says Papworth. “For example, at our Provost test site in 2001, the five-inch row width achieved the highest emergence, while the one-inch row width had the lowest.”

At the same test site in 2001, yields were significantly higher when a three-inch or five-inch row width was used over a one-inch row, he says. “This was the case at most of the test sites in both 2000 and 2001.”

However, the results from the row width study are not as strong as what was found in the row spacing study, completed in 2000. “We found a strong relationship between row spacing and production – narrower row spacing produced higher yields.”

In the row width study, the trend so far indicates increased row width will increase production, he says. “We still have another year to go, and because of the drought, we may add a fourth year to this study to ensure our results are solid.”

Nonetheless, both the row spacing and row width studies point to the importance of seedbed utilization (SBU), the percentage of the seedbed use by plants. “That percentage is a prime factor in how efficiently crops use soil, fertilizer and water resources.”

Percentage of seedbed used decreases as row width narrows and row spacing widens, explains Papworth. For example, a farmer who uses a nine-inch row spacing, with a row width of three inches, has achieved a seedbed utilization rate of 33 percent. “The higher that number, the more plants can efficiently use the resources of the seedbed.”

Yet, seedbed utilization must be tempered with other issues such as residue clearance, which encourages wider row spacing in the first place, he says. “While the notion of using as much as the seedbed as possible to achieve the best results is nothing new, our research, so far, supports the idea and that is a clear message we can send to farmers.”

The AgTech Centre is part of the AFFRD Agricultural Engineering Branch and has a mandate to support agricultural sustainability.

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