Why doesn't Ontario follow U.S. fertilizer rates?

Monday, October 7, 2013

Research in the Tri-States of Ohio, Michigan and Indiana has led to changes in their fertilizer recommendations for different soils. Rather than duplicating this, Ontario would better spend its research dollars on its own problems

by PAT LYNCH

Some growers base their fertilizer rates on what a crop removes. Some base it on what they did in other years. And some base it on soil tests.

For those who base fertilizer use rates on soil tests, questions have been raised in the past three to five years – specifically, how come soil test levels are dropping so much, especially when applying what the standard recommendations suggest.

Researchers in the northern Tri-States of Ohio, Michigan and Indiana have spent years looking at this question and have changed how they make their recommendations. Their phosphorus (P) recommendations change as yield potential changes. Current Ontario recommendations do not separate P recommended rates for different yield levels. The accompanying table shows that, for a soil test of 15-30 parts per million, Ontario recommendations are 20 pounds per acre while the tri-states recommend 70-90 pounds per acre. The Tri-states' recommendation changes with yield potential. They recommend 20 pounds per acre more P at 180 bushels an acre than at 120 bushels. Their potassium (K) recommendations are also different than ours. They have found that, for the same soil test levels, less K is available on heavier soils. For years, some folks in Ontario looked at K soil test levels, especially on heavier soils, and said that not all of those nutrients are available. Now there is research from the Tri-States to validate this.

In the Tri-States, more fertilizer (K) is recommended on heavy soils than on loams with the same soil test level. The heavier soils have a higher Cation Exchange Capacity (CEC). They base their K recommendations on the CEC of a soil and yield. On a soil with an extractable K of 100 parts per million, Ontario recommends 50 pounds per acre while the Tri-states recommend 45-120 pounds. (See table.)

A logical question is whether Ontario will start research to develop P and K recommendations based on yield levels and soil CEC. Hopefully not. It will take years, numerous locations and hundreds of thousands of research dollars to come to the same conclusion as exists in bordering states. That research money would be better spent on Ontario crop problems.

The pesticide industry has gone to registrations in different countries at the same time. Seed companies use research data from bordering states. We can do the same thing with fertility recommendations. If the outcome of the War of 1812 had been different, we would already have these Tri-State fertilizer recommendations in Ontario.

The examples I used are specific. You can view all the recommendations if you google 'Tri-State Fertilizer Recommendations'. In this report, you will see formulas that use CEC and yield goals for specific soils and crops. The recommended rates also take into account whether you want to maintain or raise soil test levels.  

The report was a collaboration of numerous researchers. The authors are M.L. Vitosh from Michigan State University, J. W. Johnson from Ohio State University, and D. B. Mengel from Purdue University. All well-respected public researchers. BF

Consulting agronomist Pat Lynch, CCA (ON,) formerly worked with the Ontario agriculture ministry and with Cargill.