Cultural Weed Control

Time of Seeding

A common practice used by no-till farmers is early seeding of spring crops before weeds emerge. This can mean that a spring glyphosate application may not be necessary. Of course, this is only possible if winter annuals and perennial weeds such as quackgrass and foxtail barley have been taken care of. Early seeding means the crop being grown must be able to germinate and develop in the cooler soil conditions. Usually, early seeding is restricted to cereal grains such as wheat and barley and occasionally to flax, field peas and lentils.

The firm, moist zero till seed-bed allows shallow seeding and ensures quick emergence for maximum crop competition.

Variety Selection

A variety which germinates and emerges quickly and then grows rapidly to cover the ground is important in reducing weed competition. This is especially important when growing crops like canola as there are broadleaf weeds such as lamb's quarters and shepherd's purse which can not be controlled with any of the post-emergence herbicides presently available.

Optimum Placement of Seed and Fertilizer

Shallow zero till seeding into a moist seed-bed encourages quick emergence. Packing directly on the row (compared to the random packing of a harrow or harrow-packer operation) improves seed germination but does not stimulate germination of weed seeds between the rows.

With on-row packing only, the area between the rows often has a covering of loose soil. As this layer quickly dries out, it is an environment that discourages weed seed germination. This effect is more evident with hoe type openers with their greater soil throwing action.

"Post-emergent crop care reduces pesticide use because we treat only problems which exist - not problems we think are going to exist. "

Scott Halley Bisbee, North Dakota

Side banded or seed placed fertilizer can also improve a crop's competitiveness. Weeds isolated between the row and away from the fertilizer band are much less vigourous than the crop growing close to the fertilizer band.

The object of zero tillage is to minimize soil disturbance with seeding and fertilizer placement operations. The combination of low soil disturbance with high residue levels discourages growth and reduces populations of annual weeds such as green foxtail (pigeon grass).

Field Border Sanitation

Be careful not to bring weeds into the field from the border. This is particularly true with some grassy species such as smooth brome grass. Mowing headlands in mid-summer prevents heads from being cut and spread further into the field by the swather or combine.

Control by sanitation is important since brome grass control requires as much as 2.0 litres/acre of 356 g/L cone. (2.0 U.S. quarts/acre of 3 lb. cone.) of glyphosate. Spraying field perimeters at this rate may occasionally be necessary but spraying into the actual grass headland should be avoided as grasses that are controlled will only be replaced by other weeds such as Canada thistle.

Selection and Rotation of Crops

Crop selection and rotation considerations are more critical in a no till crop system since tillage and soil incorporated herbicide options are not available.

When choosing a crop to be grown on a particular field, it is important to know the control options for potential weed problems. A good knowledge of field weed history and a practical knowledge of available post-emergent herbicides is essential. Sometimes there are no post-emergent weed control options. For example, zero tilling field peas into a field with a wild buckwheat problem could be risky and should be avoided.

Crop selection must also be considered in relation to perennial weed problems. For example, selective herbicides are available to control or suppress quackgrass in broadleaf crops but not in cereals. In-crop control of Canada thistle with Lontrel (or Stinger) and Curtail is also possible in many crops. Selecting the right crop can mean addressing a weed problem that you were unable to address the previous fall or earlier in the growing season. Avoid situations where perennial weeds are left uncontrolled. On heavy or persistent perennial weed areas, choose a cropping sequence which will place maximum pressure on the weed through crop competition and chemical control measures.

Rotation from a cereal to a broadleaf crop (and the reverse) allows for effective control of volunteer cereals or broadleafs.