N rates improved
On Dec. 1, the new North Dakota spring wheat and durum nitrogen rate recommendations were unveiled. The new rates are the product of North Dakota research since 1970. Archived data represents about half of the data, and field research from 2005-2008 represents the other half of over 100 site-years of N rate studies.
The state is divided into three recommendations — eastern North Dakota, western North Dakota and the Langdon Region. Fields and parts of fields (in fields managed using site-specific technologies) are categorized as low, medium or high in productivity. The recommendations discourage growers from yield prediction. Growers are required to look at their yield history to choose a productivity category.
The grower chooses the expected wheat price and the N cost from the table, which results in an N rate. The table rate will not always result in maximum yield, but it will provide maximum grower profit.
Soil test nitrate is then subtracted along with previous crop N credits. Data analysis showed that plots in long-term no-till required less N than conventional-till plots. Therefore, there is a credit of 50 pounds of N per acre for long-term no-till. Due to extra N required during the first five no-till years, a 20-pound-per-acre addition is included in short-term no-till fields.
Although organic matter up to 5.9% was important in defining relative productivity within a field, there was no need for an organic matter N credit. For fields with 6% organic matter or greater, there is a credit of 50 pounds of N per acre for each full percentage point of organic matter greater than 5%.
The grower is left with an N rate. However, this N rate is not final. There are other considerations before a final decision is made: the protein characteristics of the intended variety, less-than-optimal N application methods, excessive straw from the previous season, soils with denitrification issues, grower experiences and common sense.
An easy method of determining rate is through the new North Dakota Nitrogen Wheat Calculator, available online at www.soilsci.ndsu.nodak.edu/
wheat/index.html. Growers can go through the process in less than a minute. They can also use the new Spring Wheat and Durum Fertility circular SF-712, available from NDSU Extension offices.
The new recommendations are heavily research-based and economics-based, with logical considerations for tillage system, previous crop and residual soil nitrates. The growers are also being credited for common sense in making any additional adjustments to the preliminary value.
Use of these recommendations should help avoid the protein disasters experienced by many growers in 2009.
Franzen is an NDSU Extension soils specialist.
This article published in the March, 2010 edition of DAKOTA FARMER.