By Harry Brook
When fertilizer prices are high, there are many fertilizer products and micro products that are touted as giving something for nothing. Stop for a minute and ask if these claims make sense. There are many calculators that give you the amount of macronutrients you are removing for every bushel of grain or oilseed as well as straw. Growing and shipping crops, whether they are annual or perennial, is exporting nutrients. Where they come from is up to you.
I’ve said it before, your organic matter is a bank account of nutrients. The higher the organic matter, the more you can skimp on fertilizer yet still get a good yielding crop. The organic matter acts as a buffer to provide the nutrients needed when under-fertilizing. You can’t do that for too long without lower organic matter and the soil’s ability to cover the shortfall. In low organic soils (<2% OM) continued mining of the organic matter can lead to soil structural issues. You get puddling and crusting of the soil surface, impeding the crop’s ability to emerge from the soil.
Due to our drought last year, there should be leftover fertilizer in our soil and it is important you know what is available this spring to minimize fertilizer costs. Soil sampling to 24 inches (60 cm) should be warranted to see what you have.
About 10 years ago, the federal government removed the requirement that a fertilizer had to be effective to be registered. They simplified the system and now fertilizers only need to prove they are safe to be registered and sold. On that basis you could sell dihydrogen oxide (water) as a fertilizer and make a number of weird (but true) claims.
A growing crop uses a lot of nitrogen, less phosphorus, some sulfur and a lot of potash. If these are not supplied by the fertilizer or the soil, they will be deficient. It depends on weather and moisture conditions. Under wet conditions, more nutrients are released from the organic matter into the soil solution. The vast majority of nutrients are absorbed into the plant by the time the plant flowers. Maturing and filling of seed involves a redistribution of nutrients within the plant and late foliar applications of nutrients will not affect yields.
Special formulations of “seed primers” and other miniscule amounts of micronutrients rarely provide a yield boost. The Canola Council conducted fertilizer studies recently for several years at many diverse sites on the prairies. They used all sorts of “special” fertilizers and additives and tested them for benefits. The only profitable addition that consistently provided a yield response, in their trials, was an addition of 20% more nitrogen.
If some type of “new” fertilizer comes out and you want to give it a try, measure the results. Put some strip trials on a field and record them. Don’t just do it once, but several times. In any trial, there is always a 5% chance you may get a response from random factors, which is why you need to do it several times and possibly, over two or three years. Prove to yourself whether or not this product is worth the money. It is a well-known fact that selling the “special” fertilizers has a much higher retail margin than selling nitrogen, phosphorus, potash and sulfur.
It pays to be skeptical and test the value of any fertilizer that is not a macronutrient. Use your soil test as a guide. As a farmer, you are in the business of extracting nutrients and exporting them as crop. Don’t bankrupt your soil nutrient account but keep it healthy.