Impact of Fertilizer Nitrogen Prices on Spring Wheat Fertilization
(Prairie Provinces and Northern Great Plains States)
By Adrian Johnston, Scott Murrell, and Grant Jackson1
Spring wheat is the dominant crop grown across the northern Great Plains states and the Prairie Provinces. It is used primarily for the production of leavened bread, with its high grain protein critical to baking quality.
Fertilizer nitrogen (N) prices are impacted by natural gas prices, given that it represents a significant portion of the production cost of fertilizer N. Periodically, the price of natural gas rises with demand, increasing the price of fertilizer N. This brings up the question: How does the price of fertilizer N influence the decision on the optimum rate of N applied to a spring wheat crop?
A data set developed by the Montana State University Experiment Station in Conrad, Montana, was selected to help evaluate N price impacts on optimum N rate decisions. During the period 1986 to 1996, a series of fertilizer N rate response trials were conducted in northern Montana. The goal was to determine the optimum N rates required to produce spring wheat with 14% protein. The trials were divided into groups, with results from the “dry trials” yielding less than 36 bu/A (14 locations), and “medium trials” yielding between 36 to 56 bu/A. The optimum N rate derived in these production functions includes both soil residual nitrate-N to 36 in. plus fertilizer N applied, fertilizer N price, and wheat price.
The impact of yield potential (dry vs. medium sites) had a major impact on the optimum N rate selected, especially at low wheat prices (Table 1). It is obvious that when yield potential is low, and wheat price is low, increasing N prices have a major impact on optimum N rate. Rising wheat prices reduce the difference in optimum N between the sites varying in yield potential, and narrows the range in the optimum N rate as N prices rise. For example, with wheat at $4.00/bu, and increase in N price from $0.20/lb to $0.30/lb (50%), optimum N rate was reduced by 24 lb N/A (19%) at the dry sites, and 11 lb N/A (8%) at the medium sites.
Remember to use all of the available tools when making N management decisions in semiarid environments. These include:
A regionally developed soil analysis method to provide a good estimate of soil residual nitrate-N levels.
Understand the N requirements to grow high protein spring wheat. These range from 2.5 to 3.3 lb N/bu, with 14% protein wheat requiring the higher N rates.
In drought areas, select those fields with high residual nitrate-N levels to grow high N demanding crops, like spring wheat. This will minimize the fertilizer N required to optimize return.
Ensure that where high N rates are used, this N supply is properly balanced with adequate phosphorus (P) and sulfur to ensure optimum N-use efficiency. A survey of soil labs on the northern Great Plains indicated that at least 70% of all soil samples would respond to fertilizer P addition.
Source: Jackson, G. 1998. Predicting spring wheat yield and protein response to nitrogen. Fertilizer Facts number 17. Montana State University Extension Service, Bozeman, MT.
1Dr. Johnston is PPI Western Canada Regional Director, e-mail: ajohnston@ppi-ppic.org.
Dr. Murrell is PPI Northcentral Regional Director, email: smurrell@ppi-far.org.
Dr. Jackson is a Professor at Montana State University.
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