Nitrogen Economics: 2009 Update

Last year when I did this article, I used three wheat price scenarios $5, $10 and $15 per bushel. At that time I said that wheat has gone to $20 three times in the past — 1917, 1945 and 1973 — so perhaps we are due. It turned out I was right. There was a huge run up in price, but not for long. I heard about a few B-trains of wheat sold at $18 per bushel or better, but not much was sold at that price.

For this year, I will use $5, $7.50 and $10 per bushel as the price variables. The current Canadian Wheat Board PRO is about $6.80 for No. 1 CWRS 13.5 in our area. With no more daily price option, we are back to not knowing what the price of wheat is on any given day.

The following tables give nitrogen fertilizer economics for a wide range of moisture conditions. The data are based on actual field fertilizer experiments under dryland and various irrigation conditions in the Dark Brown Soil Zone. Rather than give a long winded harangue about the various moisture situations, I have described them in terms of the number of bushels of wheat you might expect to grow with that much soil moisture and rain.

All the data are for CWRS wheat on stubble with very low soil nitrogen and where legumes were not a part of the crop rotation.

All of these examples assume a nitrogen price of 50 per pound of actual N, which is a good guess at the time of writing (January 13.)

TABLE ANALYSIS

The first example (Table 1) is the situation in a 15-bushel year. There is little reserve soil moisture and you get only a few inches of rain. Of course with no yield increase, fertilizer is all red ink.

Table 1 confirms what I have always maintained — don’t pour fertilizer into dry ground!

If you are in the Brown Soil Zone and the moisture map puts you in the red, then best not get too aggressive with fertilizer.

Table 2 analyzes the situation for a bit better year, with 25-bushel yields. In a mediocre year, 50 pounds of actual nitrogen is lots — no matter what happens to wheat prices.

Table 3 takes us to a 40-bushel year. I have grown that or more on my dark brown soil at Dundurn in 2006, 2004 and 1999 and nearly that (37 bushels) in 2008. In 2002, with no soil moisture at seeding and about six inches of rain, I got 20 bushels per acre.

In a 40-bushel year, the rate to use is 75 pounds of nitrogen, no matter what the price of wheat. This situation probably covers a lot of the Dark Brown and Thin Black Soil Zones that have at least a few inches of available moisture in the soil at seeding time. Note that I say a few inches of available soil moisture. In a medium textured soil, one foot of moist soil equates to 1.5 inches of available soil water.

Finally, lets look at a bin buster — a 60-bushel crop (Table 4). In recent years an increasing number of farmers have actually sold that amount. For that bin buster year, there is almost no limit to the profit you make with nitrogen fertilizer. The yield has been tripled and is still going up at the higher N rates.

The only areas that are in a situation to expect that much are Manitoba, Eastern Saskatchewan and a few spots in Alberta. (See my soil stubble moisture map on page 14 of the February 16 Grainews.)

TO SUMMARIZE

In a year with prospects for a 15-bushel-per-acre wheat yield, forget about applying nitrogen fertilizer. There’s no payback.

In a 25-bushel year, use 50 pounds per acre of actual nitrogen, or less.

In a 40-bushel year, use 75 pounds per acre of actual nitrogen, or less.

And finally, in a bin-buster 60-bushel year, pork on the nitrogen. You’ll want to use 75 pounds per acre of actual nitrogen, or more.

Of course, when a good frost comes along on August 20 all these nice economic tables are thrown into a cocked hat!

FOOT NOTES

The chart data and the above recommendations are for a low organic matter soil in the Dark Brown Soil Zone with very low soil test nitrogen. In that situation, the main thing that will affect which table applies to you will be available soil moisture at seeding plus growing season rain. Growing season rain is anybody’s guess. Available soil moisture at seeding is a measurement you can make. If the soil is full of water at freeze up it will still be full at seeding time — except perhaps a bit of surface moisture that might evaporate if you seed too late. Do you know how much water is in your soil?

If you are in the Thick Black Soil Zone, if your soil test shows high residue nitrogen, if you have lots of organic matter, if you have manured soils, or if you seed wheat after a pulse crop, you’ll get different results than you see in these tables. Factor in these differences when making your estimates.

The tables do not consider protein premiums. In the mid ranges of yield, both yield and protein can go up at the same time — and the combined effect can be significant to the bottom line.

J. L. (Les) Henry is a former professor and extension specialist at the University of Saskatchewan.

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