Leave crusted-over canola be, and hope for the best

With a cycle of high moisture and then a few days of dry, soil crusting is an issue in canola fields in parts of eastern Saskatchewan in particular, according to the Canola Council of Canada.

Canola seedlings can’t penetrate the crust, and often curl back and die, the council said in its most recent Canola Watch publication.

No research has been conducted to show the best ways to break up crusting and free the crop. If a few plants have emerged, it may be best to leave them be, said the council.

Fields with plant counts as low as one to two per square foot evenly throughout the field are probably better to be left alone than reseeded as of this calendar date, the council says,

Very low plant counts can produce reasonable yields — as long as those plants are closely protected throughout the rest of the season and weed competition is kept in check.

Fields reseeded at this date have lower yield potential than a field seeded in mid-May, the council notes, and face a much higher risk of fall frost losses.

Soils with a higher percentage of clay will crust more in the weather conditions that encourage crusting, as clay tends to bind together much more than sand or loam soils. Clay soil granules are small enough to almost glue together with moisture and remain “cemented” when dry.

Loam and sandy soils have larger granules and therefore do not bind together as tightly.

Higher organic matter (OM) will amount to less crusting because OM, even though it acts as a binding agent for soil particles, only holds particles loosely.

Soils with high sodium and low calcium also have a higher tendency to crust.

Fields that are wet, then quickly dry due to wind and heat, are likely to crust.

Generally, soils in a moist state will not crust. In fact, the best cure for soil crusting is rain.

Tillage practices, however, can also play a role. Clay soils that are wet and then dry quickly can crust with any tillage practice. In general, fields with long-term no-till will have a lower risk of crusting because OM tends to be higher in a no-till situation.

Every tillage practice performed breaks down the stubble and OM, and therefore will increase the chances of soil crusting.

Packing during seeding is used to firm the soil around the seed. Increased packing pressure will compact the soil particles more ,and therefore can increase the chance of soil crusting. Reduce packing pressure in wet conditions, the council recommends.

Opener/packer combination is also a variable to watch. An opener that creates more soil disturbance can decrease the chances of soil crusting due to simple fracturing of the soil base. However, too much disturbance can also increase soil crusting by breaking down the soil base, which then has a higher chance compacting when packed.

There are no reliable solutions, the council says, other than to wait for rain. Some growers have reseeded the worst sections of fields.

A light harrowing might help, the council suggests, if nothing has come through. Do a couple passes, then assess whether canola seedlings are being ripped out of the ground. Harrowing too close to emergence can be harmful to a shallow-seeded crop such as canola, and may not be worth the risk.

Using a roller may be worse than harrowing when soils are wet below the crust, the council warns. Instead of cracking up the soil surface, a roller could turn the whole topsoil zone to concrete. — AGCanada.com Network

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