What to do about crusting?

Rain after seeding can often cause top soil to crust, stopping the emergence of canola seedlings.

Canola seedlings can’t penetrate the crust, and often curl back and die. 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.

Fields with plant counts as low as two per square foot throughout the field are probably better left alone than reseeded, especially later in the seeding window. Very low plant counts can produce reasonable yields as long as growers protect them throughout the season and limit weed competition.

Conditions that cause crusting

Soil type

Soils with a higher percentage of clay will crust more, as clay tends to bind together much more than sand or loam soils. Clay soil granules are small enough to glue together with moisture and remain “cemented” when dry. Loam and sandy soils have larger granules that 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 or low calcium also have a higher tendency to crust.

Wet then dry

Crust-prone soil types that are wet then quickly dry due to wind and heat and 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

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. Every tillage practice performed breaks down the stubble and OM, which increases the chance of crusting.

Packing during seeding

Increased packing pressure will compact the soil particles and increase the chance of soil crusting. Reduce packing pressure in wet conditions.

Opener/packer combination

An opener with more soil disturbance can decrease the chance of crusting due to simple fracturing of the soil base. But it’s a balance. Too much disturbance breaks down the soil base and can increase crusting.

Solutions to crusting

We have no reliable research-driven solutions other than to wait for rain. Some growers have reseeded the worst sections of fields.

A light harrowing might help if no plants have poked through. Do a couple passes then assess whether canola seedlings are being ripped out of the ground. Harrowing too close to emergence can harm a shallow-seeded crop such as canola and may not be worth the risk.

A roller may be worse than harrowing when soils are wet below the crust. Instead of cracking up the soil surface, a roller could turn the whole topsoil zone to concrete.