ISSUE #413

413 - Variable Rate N Application On Wheat After Beets Proves Successful


American Crystal Sugar Company has been promoting variable rate nitrogen application using satellite imagery of beet canopies since 1999. This program is based on the research of Dr. John Moraghan, North Dakota State University and Dr. Larry Smith, University of Minnesota, Northwest Research and Outreach Center, Crookston. Many growers adopted this program for the 2001 crop year. Nearly 50,000 acres were VRT spread using zone management, in all districts. However some grower skepticism surfaced concerning potential adverse effects of reduced N use on wheat yield, protein and test weight. This prompted the American Crystal Precision Farming Team to devise a plan to resolve the problem and provide answers to shareholder concerns.

Objectives of 2001 N Credit Study:

  • To determine if a variable rate application of nitrogen using beet top imagery adversely affects yield, protein or test weight in wheat following sugarbeets.
  • Maximize field uniformity in all crops.
  • Increase sugar content and lower loss to molasses in subsequent beet crops.
  • Lower on farm nitrogen costs.
  • Reduce lodging of small grains.
  • Increase on-farm profit.

What Was Done:

Wheat sampling was conducted on 24 fields throughout all 5 districts of the American Crystal Sugar Company growing region. Each agriculturist cooperated with a grower who used beet top imagery to variable rate apply nitrogen following sugarbeets. Prior to planting spring wheat, urea was applied variable rate according to management zones set up with the use of satellite images of the previous year's sugarbeet canopy. Nitrogen management zones were created based upon plant canopy density of the beet crop.

Sampling within these fields was conducted on three nitrogen management zones, 80, 40, and 0 lbs./acre N credit. GPS guidance was utilized to ensure that samples were taken from the correct zone. The samples were collected from each of the test fields when the standing grain reached physiological maturity. A total of 36 samples were taken from each field, 12 from each management zone, based on recommendations of Dr. J. Goos, North Dakota State University and Dr. J. Wiersma of the University of Minnesota, Northwest Research and Outreach Center, Crookston. All samples were collected from the field, placed in a heated aeration bin to be dried to the appropriate harvest moisture content. The samples were then thrashed using a test plot combine. Each sample was processed to determine bushels/acre, test weight, and protein percentage. All data was compiled and statistically analyzed to determine treatment differences.


For the Red River Valley summary (Table 1) zone C received the entire 150 lbs./acre of nitrogen, zone B received 110 to 120 lbs./acre, and zone A received 70 to 80 lbs./acre of nitrogen. Yield, test weight, and protein content were not significantly different between zones for the Red River Valley data summary. All three yield factors were remarkably similar indicating that the nitrogen credits assigned to zones A, B, and C were correct. Mineralization of nitrogen from beet tops occurred rapidly and supplied sufficient nitrogen to meet the wheat crop needs in the same manner in each zone.

Table 1. Red River Valley Wheat Yield and Quality (For 24 Fields Variable Rate Fertilized Based on Beet Top N Credits)

ZoneYield*Test Weight Protein*
A 56.2 a 59.7 a 12.9 a
B 55.1 a 59.6 a 12.8 a
C 55.9 a 59.5 a 12.7 a

*Numbers followed by the same letter do not differ Significantly at P = 0.05

Conclusion: This research indicates the N credit program is successful in giving the proper nitrogen credits to maintain a high yielding excellent quality wheat crop.

2001 Economic Impact to American Crystal Sugar Company Shareholders:

  • On farm fertilizer costs reduced by $500,000 ($10/A).
  • Environmental benefits of 2,000 tons less nitrogen applied.
  • Wheat yield and quality maintained.
  • Future beet crop quality improvements of .25 to .50% or more.

Contact your agriculturist to participate in this program for 2002. "Close the Gap" learning opportunities will discuss this project in much more detail.

Shareholders Dental Insurance Available

Last February, the Shareholders' Dental Plan was cancelled by North Dakota Dental Services, our dental insurance carrier. After careful review, we believe AFLAC will provide a viable insurance alternative for those of you who wish to purchase dental coverage. You should have recently received a letter summarizing the coverage and premiums along with a schedule of meeting dates. If you have any questions, please contact Jim Stengrim, District Sales Coordinator for AFLAC at 218-745-5766.