Soil sampling now will save time in spring and early planning of your fertilizer programs gives you the chance to take advantage of lower fertilizer prices that may occur, says a provincial crop specialist.
But soil samples need to be representative of the field, said Mark Cutts.
“For example, if there are small areas of poorly drained low spots in a field, these areas should not be included in the sample collection,” he said. “The non-representative areas can be sampled separately to determine their fertility status.”
Sampling at the appropriate depths is also important to ensure meaningful nutrient information is obtained. Recommended sampling depths are zero-15 centimetres, 15-30 centimetres, and 30-60 centimetres.
“The zero-15 centimetres depth will capture crop-available soil phosphorus and potassium,” said Cutts. “However, for mobile nutrients such as nitrate nitrogen and sulphate, sampling to a depth of 60 centimetres will provide a more reliable measure of the amount present in the soil profile.”
The most common approach for applying fall fertilizer is to band nitrogen either as urea (46-0-0) or anhydrous ammonia (82-0-0).
“Since nitrogen makes up the biggest volume of applied fertilizer, a fall application will enhance efficiencies during spring seeding,” said Cutts.
Fall nitrogen fertilizer applications can be made once soil temperatures are below 10 C. Applying urea or anhydrous ammonia fertilizer at cooler soil temperatures will help maintain nitrogen in the ammonium (NH4+) form.
“The ammonium form of nitrogen is preferred as it will be protected from losses that can occur from denitrification or leaching,” said Cutts.
For nutrients such as phosphorus and potassium, which are typically seed placed, there is no real advantage to applying these fertilizer products in the fall.