When does top-dress fertilizer make sense?

Click here for more information on products, rates and timing for best results from a fertilizer top-dress. This article has just been updated.

If you’re on the fence about a top-dress application, consider applying a rate high enough to make a difference — such as 30 pounds of nitrogen or 20 pound of sulphur — to part of a field. Mark the location and compare yields for treated and untreated areas. Increasing greening does not necessarily translate into increased yield, so a simple observation of crop colour is not enough to determine the value of the top dress. If you do see a yield difference, the best solution may be to increase fertilizer rates at seeding.

Seed-place ammonium phosphate only

The bottom line for seed-placed fertilizer in canola:
1. Apply plant available sources of nutrients.
2. Place a modest rate of P in the seedrow. At rates over 20 lb./ac., the salt component in MAP, for example, can start to set back seedling survival.
3. Place N and S in a band away from the seed.

Buyer beware with novel fertilizer products

If a grower decides to try something new, find a uniform field, try one product at a time and leave an untreated check, ensuring both treated and untreated areas are accurately measured for final yield and grade so a true economic comparison can be made. In reality, some products may provide a good payoff for the price, but that payoff may only materialize one year in 4. A few years of trials may be required to get a true picture of the economics before making a final decision. Check out these strip trial tips for more insights on how to get the best possible information from your own on farm research.

N does bad things when S is missing

When fields are sulphur deficient, canola that receives only nitrogen fertilizer (front left in photo) can yield less than canola that receives no fertilizer at all (right in photo). Canola plants need sulphur to produce three key amino acids: methionine, cysteine and cystine. Without the S to build these amino acids, N creates toxic amides in the plant that greatly inhibit seed set.

“Hidden hunger” with P deficient soils

A 50-bushel crop can remove more than 50 pounds of P205 per acre. Growers using only seed-placed phosphate at a rate of 15 pounds per acre can slowly deplete the soil of phosphate. That can start to affect yield potential on the field over time. These plants, demonstrated at CanoLAB, were seeded the same day in a greenhouse and fed hydroponically to demonstrate extreme P deficiency. The potting mix has no nutrient value. The large plant received required levels of P. The tiny plants in front received no P.

Agriculture labs

Here is a list of labs that service canola growers in Canada. Labs are organized under the following headings: Soil nutrient analysis, Plant tissue nutrient analysis, Seed quality tests, Disease diagnostic on plant tissue, Soil analysis for clubroot, Herbicide resistant test for weeds, Herbicide carryover in soil, and Pesticide residue in plant tissue

Taking a good soil sample

Not a regular soil sampler? If you’re interested in starting, this is as good a time as any to start. The more you test, the more you can learn from the numbers. Benchmark samples collected from the same places for years will tell you more than a random sample done once. To see trends, you need several years. You can also learn to identify sample results that don’t seem right.

Fall soil tests: Now or before freeze up?

If you want to use soil test results to see whether this year’s crop had enough nutrients, sampling now would be the better option. To plan for next year, soil samples taken closer to freeze up are a more accurate estimate of levels next spring.

Safe rates of seed-placed nitrogen

Safe rates of seed placed fertilizer depend on seedbed moisture conditions, soil type, row-width utilization, and nitrogen source. For example, the safe rate of seed-placed nitrogen is only 10 pounds of actual nitrogen per acre when using a 1” knife on 9” spacing and seeding into moist, medium soils.