Nitrogen Results Become More Significant

Skyrocketing price of N puts this nutrient at a premium.

Published on: Mar 24, 2008

Who would pay a $1,000 for a ton of anhydrous ammonia? The answer may surprise you. It may boil down to someone who didn’t get any locked in early, perhaps at no fault of their own. That price hasn’t been documented, but rumors put the current price in some areas of the country near that unbelievable level.

With N prices now going from super-high to ridiculously high, past N trials that indicate that moderate rates of N should be sufficient for maximum economic yield, even maximum agronomic yield in some cases, take on more significance. Unless you’ve already applied your N either last fall or already this spring, you could be surprised if you’re rethinking exactly how much to put on.

Several universities have issued their recommendations for ’08 N rates. Many are moving away from suggesting a specified amount of N per bushel of yield goal. Instead they’re leaning toward suggesting maximum agronomic yields if you’re after top yield, or maximum economic yield, if you’re trying to hit the point at which the next unit of N would likely return no extra net profit.

Purdue University, for example, puts the rate at 165 pounds per acre as an average statewide for maximum agronomic yield, and about 20 pounds less, or 145 pounds per acre, for maximum economic yield. That’s for corn after soybeans, and counts N applied in all forms, including starter fertilizer, added together. For continuous corn, most universities recommend adding somewhere between another 20 and 30 pounds per acre.

The Corn Illustrated trial sponsored by Farm Progress Companies last year arrived at similar conclusions. Dry weather on gravelly ground held down yield to about half normal, but the trend was still the same. In better years on the same ground, the numbers for most effective N rates have approached the 145 and 165 pound per acre ranges, respectively, for top economic and top agronomic yield, following soybeans.

Nitrogen in the Corn Illustrated plots in ’07 was applied both pre-plant and by sidedressing. The sidedressing application in the test was liquid 28% N. Some farmers who have used 28% N until this year, especially in no-till, are reporting they’re looking hard at pre-plant applications of anhydrous ammonia instead. The price difference between the two products is just too great not to ignore the better economic value of anhydrous ammonia, even at the extreme prices now surfacing. Prices for liquid nitrogen, in comparison to anhydrous ammonia, are also extremely high.

The Corn Illustrated plots won’t include a nitrogen test this year. However, it will include a comparison of pre-plant anhydrous ammonia vs. sidedressed anhydrous ammonia. In the past tests have shown that sidedressing is more efficient. If that’s in fact the case, improved efficiency would be more important now than ever before.