Cereals: Tillage

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Pub 811: Agronomy Guide > Cereals > Tillage

Excerpt from Agronomy Guide for Field Crops
Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

• Tillage Options
• No-Till Seeding
  • Table 4-1. Winter Wheat Yield Response to Tillage Systems
  • Table 4-2. Corn Row Syndrome
• Conventional Tillage
  • Frost Seeding of Spring Cereals
  • Table 4-3. Yield Response to Fertilizer Rate
  • Table 4-4. Frost Seeding vs. Seeding Into Dry Soil of Spring Cereals
• Aerial Seeding Winter Wheat
• Broadcast Seeding

Tillage Options

Cereal crops do not respond significantly to tillage. Research comparing the yield response of winter wheat to various tillage options demonstrated no yield advantage among moldboard plowing, minimum tillage and no-till systems Table 4-1, Winter Wheat Yield Response to Tillage Systems. While yields are not affected greatly by tillage systems, good seed-to-soil contact and soil moisture for germination are essential.

The selection of a tillage system will impact other components in the system. The tillage method chosen must fit with factors such as fertility, insect pressure, disease incidence and weed control for producing high-yielding, profitable crops. Risks associated with more intensive tillage in winter crops include greater frost-heaving potential and increased risk of snow mould. Erosion is a concern with tillage in all crops.

There are several options for seeding cereals that include:

• no-till seeding
• conventional tillage
• frost seeding
• aerial seeding of winter cereals
• broadcast seeding

No-Till Seeding

Most winter wheat is grown using a no-till system. No-till yields are often equal to yields obtained with conventional tillage. No-till drills can follow the combine in the same field, which advances seeding date, therefore increasing yields. No-till planted winter cereals are better able to resist frost heaving, as the plant anchors itself in firmer soil.

¹ Average yields vary because comparisons come from a range of sites.

The success of a no-till system requires consideration of fertilizer management, drill capability and weed control. No-till cereals show more response to seed-placed starter fertilizer, especially phosphorus, compared to conventional tilled crops.

No-till crops grown without starter fertilizer often develop "corn row syndrome" symptoms. Wheat plants growing over old corn rows will be significantly taller and more vigorous than plants growing between the rows. This is primarily due to higher phosphorus availability from the corn starter fertilizer band, even though the corn crop was grown 2 or 3 years prior to the wheat crop. Fields receiving 58 kg/ha of supplemental P₂O₅ (100 lb/acre MAP) overcame the variability in wheat growth. The addition of low rates of P with a liquid starter reduced the corn row effect but did not eliminate it. (Table 4-2, Corn Row Syndrome, and Plate 23. Winter wheat is one of the most responsive crops to phosphorus fertilization. This is shown in Table 4-3, Yield Response to Fertilizer Rate, which summarizes 4 years of comparisons on fields with a large range of fertility levels.

Plate 23. Corn row syndrome of winter wheat is caused by fertilizer or pesticide carryover in the rows of previous crops.

Seed-to-soil contact is critical for moisture uptake. No-till drills must be able to cut through residue and penetrate into hard soil to accurately place seed. Adding seed-firming wheels or plastic "hockey stick" seed firmers will help press the seed into the bottom of the seed trench, which will help increase seed-to-soil contact and improve seed depth uniformity.

Weed control is critical in no-till systems. A burndown before planting ensures control of dandelions and other winter annual weeds and should be a standard practice. See OMAFRA Publication 75, Guide to Weed Control, for burndown recommendations. To reduce disease incidence, use a fungicide seed treatment. For further information on seed treatments, see the OMAFRA Publication 812, Field Crop Protection Guide.

In dry soils, the addition or use of tillage coulters may show some benefit in a no-till system. Slight loosening of dry, hard soils allows for better, more rapid root development and growth. In a wet fall season, light tillage may speed soil drying and allow for planting in better conditions. These limited tillage methods should be used when soil conditions dictate.

Conventional Tillage

Cereals have been grown for generations using the plow, disc and cultivator for seedbed preparation. Many spring cereals are still grown using conventional tillage. While this system works well, erosion concerns, fuel costs, labour costs and limited yield response to tillage continue to shift acres into reduced tillage. The guidelines regarding seed-to-soil contact, planting into moisture and seeding depth accuracy are consistent with the no-till section. The tillage operations replace the herbicide burndown.

Frost Seeding of Spring Cereals

Seeding spring cereals into frost can significantly advance seeding dates and increase yields.

"Frost seeding" refers to no-till seeding cereals into a light frost in early spring. After the snow has melted, and the frost is out of the ground, there are often several cold nights with below-zero temperatures. Seeding into this light frost is possible, as the frost will support the tractor and avoid compaction or rutting. It is not essential to close the seed trench when frost seeding, as the soil will naturally fall in and cover the seed as the frost comes out of the ground. Simply set no-till equipment to make a shallow (2.5-cm or 1-in.) seed trench and firm the seed into the bottom of the trench.

The window of opportunity for this method of seeding is short. Do not attempt this method of seeding when air temperatures drop below -8°C. The ground will be frozen hard enough to damage the no-till equipment, and seed will be left on the soil surface with poor results. Best results are generally as the frost is just beginning to firm the soil, about -3 to -4°C, often near midnight. It is critical to stop as soon as frost begins to soften in the morning sun, as thawed soil will stick and plug equipment in as little as 15 m (50 ft.) of travel.

While this narrow window of opportunity may not occur every year, the increase in yield from early planting using this technique can be as much as 25%. Table 4-4, Frost Seeding vs. Seeding Into Dry Soil of Spring Cereals, shows the yield and quality advantage of frost seeding. Frost seeding of winter cereals in the late fall or early winter has also been successful. However, in these situations it is critical that seed placement is at least 2.5 cm (1 in.) deep, and that yield expectations are realistic.

Aerial Seeding Winter Wheat

Aerial seeding is most successful when seed is flown on before 10% of the soybean leaves have dropped. Soybean leaves will cover seed and help retain moisture for wheat germination.

Results from aerial seeding have been variable. The seed is extremely vulnerable to slug damage. Slugs feed on the germ of the kernel, which can severely thin or destroy the stand, particularly on headlands. The seed will appear to still be on the surface, as if waiting to germinate, but on closer examination, the damage to the kernel becomes evident. Reseeding of headlands after soybean harvest can help overcome this problem.

The shallow root system that develops from aerial-seeded wheat is more prone to heaving injury and wind damage Depth of Seeding. In the spring, wheat plants will be attached to the soil by only one hair root. If this hair root breaks as plants twist with the wind, the plant dies.

¹ Each treatment represents an average of three different populations; 0.8, 1.2 and 1.6 million seeds/acre for oat and 1.2, 1.6 and 2.0 millions seeds/acre for spring wheat.

With these inherent risks, yields from aerial-seeded wheat are often 10% lower than from drilled wheat, (limited on-farm trial data). Therefore, aerial seeding is not a standard practice. Where aerial seeding is attempted, increase the seeding rate to 5.0 million seeds/ha (2 million seeds/acre) to compensate for stand loss.

Broadcast Seeding

Broadcast seeding can greatly speed the planting process. It is important to get good seed-to-soil contact and a uniform seeding rate across the width of the spread pattern and between passes of the spreader.

Using airflow units is an effective way to achieve the uniform spread pattern. Till fields at a shallow depth (7.5-cm or 3-in.) twice, at right angles, then pack the crop to help prevent streaking in the seeding pattern and improve seed-to-soil contact.

This method produces an inconsistent seeding depth. Variable maturity and a 5%-10% reduction in yield are often the result. Increasing seeding rates by 10% will help compensate for the potential variability of broadcast seeding.