ISSUE #359

359  - SPRING NITROGEN APPLICATIONS

2-11-1999

The wet fall and a desire to delay fertilizer purchases from fall to spring pose potential problems for growers. Some fields require as much as 100 pounds of actual N per acre. What rate of nitrogen is safe to apply immediately prior to planting beets this spring?

Application of urea and anhydrous ammonia both have risk when spring applied. Growers need to be careful not to reduce sugarbeet seed germination and emergence with spring-applied nitrogen. Excessive rates of nitrogen applied too close to the seed may seriously reduce plant population. There should be few problems if nitrogen is applied as urea, liquids, or ammonium – nitrate at broadcast rates of 75 pounds of actual nitrogen or less per acre. Be sure to incorporate the spring nitrogen applications to prevent loss of nitrogen.

Greatest risk with application of urea may be with air-seeder use. For example an air seeder applying 90 lbs. of nitrogen per acre in 5 1/2-inch bands on 11-inch shank spacings is very risky. Why? Because the effective nitrogen application rate is actually 180 lbs. per acre. The rate per acre in the 5 1/2" band has to be doubled to get a 90 lb. per acre broadcast rate. Remember, additional potassium applied in the spring increases the chance of injury to germinating seed also. Research results at Crookston in 1993 by Allan Cattanach showed serious stand loss on a wheatville loam soil from spring applied nitrogen, table 1.

Table 1. Effect of spring applied shallow incorporated nitrogen on stand establishment.

N Rate/Acre (lbs)Stand Reduction (%)
100 12
200 30

Conditions that increase the likelihood of stand loss include:

  • A dry seedbed
  • Nitrogen rates over 75 lbs./acre
  • Coarse textured soils
  • 1-2" deep fertilizer incorporation
  • Planting immediately after application
  • Calcareous soils with free lime at the surface

Take Special Care with Spring Anhydrous Ammonia

The low cost of anhydrous ammonia makes it an attractive source of nitrogen to use. Be aware of increased risk with spring anhydrous use. If applying spring anhydrous ammonia follow these recommendations.

  • Delay seeding for 5-7 days to reduce risk.
  • Apply anhydrous at least 5 to 6 inches deep.
  • Use narrow injection shank spacings to reduce effects of nitrogen.
  • Apply anhydrous at an angle to planned row direction.
  • Be sure soil seals up well behind injection shanks.
  • Apply only 50-60 lbs. N/acre.

Greatest risks with anhydrous ammonia are associated with low-organic matter; dry, coarse textured soils calcareous at the surface.

NEVER apply nitrogen to sugarbeets without a soil test. Following soil test recommendations will ensure a high yield, high quality crop and protect the environment from unneeded nitrogen.

Reduce nitrogen use after beets.

REMEMBER you can reduce nitrogen use on crops following beets where green tops were present at beet harvest. Extensive research by Dr. Larry Smith and Dr. John Moraghan at the NWES at Crookston, MN and on grower fields document this. Reduce nitrogen on crops after beets by 50-70 lbs./acre where beets had heavy green tops. Areas of beet fields with yellow-green tops can contribute 20 lbs./acre or more nitrogen to subsequent crops. Satellite images of beet canopy growth in 1998 fields can pin point how to make these fertilizer adjustments.

Fields with yellow canopy growth indicating proper nitrogen depletion by harvest, would receive no nitrogen credits.