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Fertilizing your wheat crop

Richard Snell
Barton County Extension Agent

Just when we were talking about the glory days of agriculture, things are headed the wrong way. Grain prices are getting cheaper and the input costs of seed, fertilizer, fuel and herbicides are going up.

It was like somebody decided farmers were finally making some good profits and we just couldn’t have that. Granted that’s sounds like a conspiracy and I doubt there is one, but it sure seems like it.

The question is, what can we do about it? Well, we have to be as efficient as we can with those inputs to start with and today I want to focus on fertilizer and soil fertility.

First, even with the higher costs of crop inputs, it still pays to fertilize. How much, obviously depends on what the expected price per bushel is of the wheat and how much yield increase you might get with that extra 5-10 pounds of fertilizer. In these uncertain times, soil testing is critical. It may have been alright to shoot in the dark when nutrients were 10-20 cents per pound. But today, looking at 60-90 cents per pound, you had better put them where they belong and in the right amount. We need to be good environmental stewards and not put excessive amounts on, but right now I think the economics are helping that along.

Some years, when it is has been dry and yields low, we have a lot of nutrients left in the soil or after a large crop, we may have very little left. Take the guess work out and soil test! Normally I try to get our local growers to put their yield goal at around 50 bushels per acre. I ask them to determine what their five year average is and then what is the very best yield per acre they have ever had on that field. From those two values I come up with a yield goal. For some that may be 40 and for some 60.

For your total nitrogen need, I figure it takes 1.5 pound per bushel on continuous crop. On no-till, I add 5 pounds after wheat, 10 pounds after corn and maybe 15 pounds after sorghum. I also add more nitrogen if you plan to graze it. So often, with a 50 bushel yield goal, we could be looking as high as 90 pounds of actual nitrogen on dryland wheat. As you go west, you would lower that. For irrigated, you would increase that. You also might increase that for sandy soil because they really respond to fertilizer because there isn’t much organic matter to hold things together.

On summer fallow, if you don’t have a nitrogen profile test, I usually figure only one pound of nitrogen per bushel of yield goal. So you may only be looking at 50 pounds per acre.

Assuming there isn’t much nitrogen to start with and many times there will be. In theory, the first 10 pounds of actual nitrogen you apply may gain you 10 bushels per acre additional yield. The next ten pounds only eight and so on. This may be a year, where, by the time you get to 60 pounds of nitrogen on dryland, the added bushels may not offset the costs of fertilizer, if wheat is only $6 per bushel. The economics are changing almost on a daily basis.

How should you put your fertilizer on? Research done by Carlisle Thompson at Hays years ago suggests that on silt loam and clay soils you are just as well off, if not better off, to put all your fertilizer down pre-plant or at planting time. I like the old dual application method of putting phosphorus and nitrogen on together. This does not work for everyone. If you are no-tilling, I like putting nitrogen on with a coulter before planting. Dribble banding or applying it with the drill is alright too, but you are very limited in how much you can put on with the seed and most drills are set-up for the 2″ X 2″ placement.

Over the years, my observations tell me that the people who have been most successful, put all or most of their fertilizer on early. Now let me qualify that. In sandy soils, you have to put on split applications of nitrogen or you will most likely get it leached out through the winter. You may need 2-3 applications say once with one-third at or before planting, one-third in December, January or very early February. Then the final third in mid-March. I am not a believer in putting most of it on real late. Most of that goes into protein and not yield.

On clean tilled ground, you can apply nitrogen as a broadcast or banded, injected or surface applied. It will get there. In no-till or heavy residue, you should get that nitrogen below the soil surface or it will get tied up in the stubble and not available for that crop this year.

Potassium, phosphorus or lime should go down early, before or at planting time.

By the way, if you are going to apply a herbicide over the top anyway, then it’s fine to top dress nitrogen, I am just trying to save you some field trips.


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