Now that crops have emerged, it may be a good time to evaluate whether one-pass seeding and fertilizing
operations have damaged seedlings.
Cynthia Grant, a soil scientist at the Agriculture Canada Research Centre in Brandon, says while side-banding fertilizer is generally an effective and safe method of application, it is important to evaluate the risks involved in individual fields.
For producers who encounter seedling damage, Grant has suggestions on how to fine-tune their one-pass system:
- Increase the separation between the seed and fertilizer band.
- Use a less damaging fertilizer.
- Use a controlled-release fertilizer or urease inhibitor.
- Reduce fertilizer rate at seeding.
- Consider an alternate method of fertilizer application.
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High concentrations of fertilizer that come into contact with seedlings can cause damage.
Nitrogen fertilizers pose a greater risk than phosphate. Damage can occur either by an osmotic effect, where the fertilizer salt draws water away from the seedling, or by a direct ammonia toxicity, when an ammonia-producing form of fertilizer is used.
Damage will show up as delayed or uneven crop emergence, reduced crop vigor, stand thinning, and yellowing or browning of leaf tips.
This can lead to increased weed competition, higher dockage, delayed crop maturity, risk of frost damage, down grading and lower yield.
Symptoms can be assessed by comparing suspect stands to areas of the field without seed-placed fertilizer.
Another way is to determine if stands are denser in areas of the field with heavier texture or higher organic matter because the same rate of fertilizer will cause less injury on these soils.
Because of the problems associated with fertilizer-seed contact, many producers have bought seeders with the ability to side-band fertilizer.
However, recent studies by Agriculture Canada have shown that seedling damage can also occur if the fertilizer rate is too high or if the separation between the seed and fertilizer band is not wide enough.
Seed-to-fertilizer separation may fail because of opener wear, changes in soil conditions that affect soil movement during seeding, speed of field operations, varying topography, or because the planned separation is insufficient.
Many opener systems are designed to place the fertilizer about five centimetres from the seed row. While this is enough in many cases, extra caution must be taken when side-banding is combined with wide row spacing. When row spacing is increased to 30 cm from the traditional 15 to 23 cm seed-bed use decreases and the concentration of fertilizer in each row increases. This will reduce the amount of fertilizer that can safely be seed-placed or side-banded.
Other factors can increase seedling damage:
- Dry and windy conditions in the two weeks after seeding.
- Growth of sensitive crops, such as canola or flax.
- Use of urea or urea-based fertilizers.
- Use of high fertilizer rates.
- High-pH carbonated soils.
Trials are under way to evaluate the use of controlled-release (polymer-coated) urea and the urease inhibitor Agrotain in wheat and canola.
