Why measure sowing depth
Plants sown at significantly deeper levels will tend to be less vigorous and in many situations will have less leaf development. This is because the seedling uses much of its stored energy for growing through the soil so seedlings will be less vigorous upon reaching the surface when they can begin photosynthesis.
Factors that may influence depth of sowing and crop emergence include:
- use of pre-emergent soil applied herbicides such as trifluralin or systemic seed dressing fungicides,
- soil characteristics such as surface crusting or sands that are ‘non-wetting’,
- type of machinery, tine width, covering devices and how they are used,
- soil type and conditions at sowing (moisture, stubble and plant residues)
- It may be of interest to measure the depth of sowing achieved for different soil types within the paddock.
Narrow sowing points tend to give better seed placement, and in turn help to reduce uneven coverage of sown seed between rows. Slower sowing will assist in providing greater accuracy in seed placement.
Measuring sowing depth
What to do:
While carrying out the seedling counts:
- Gently remove ten seedlings from the soil, taking care to leave the sown seed attached to the plant
- Measure from the base of the seed to the part of the plant where it has emerged through the soil surface
Work out the average sowing depth and compare your result to the recommended depths shown in the table below.
|Crop type||Seed depth (mm)||Crop type||Seed depth (mm)|
|Wheat||20 - 50||Canola||5 - 15|
|Oats||20 - 50||Lupins||10 - 25|
|Triticale||20 - 50||Faba beans||25|
* These depths will vary according to soil types and soil moisture, but generally you should not be sowing deeper than the depths shown.
Rule of thumb: Optimum sowing depths for different plant species vary according to soil type, rainfall and soil conditions at sowing. However as a rule of thumb, the seeding depth should be about five times the size of the seed.