Nitrogen Nutrition for Sugar Beet
by John A. Lamb,
Nutrient Management Extension Specialist University of Minnesota, Department of Soil, Water, and Climate  10/08/2002

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Nitrogen Nutrition for Sugar Beet - Potassium Effects
John A. Lamb -

There was a question about how potassium affects nitrogen nutrition in sugar beet. Sugar beet takes potassium up as a K+ caution and nitrogen up as NO3-. Both of these nutrients can cause impurities which reduce the amount of extractable sucrose and slow the extraction process at the refinery. The majority of the soils in the SMBSC growing area are high in potassium with soil tests greater than 160 ppm. On these soils, there is no need to apply potash fertilizer. There has been some concern in the past about these high soil test levels and quality. There is not much in the way of management that can be done to reduce K levels without possible yield losses in other rotational crops. In 1985, two studies with potash treatments were conducted on sugar beet in the western growing area of SMBSC. At both locations the impurity index was not significantly affected by potassium. In the same study, nitrogen did significantly increase the impurities. At one site, the root yield was not increased by potassium fertilization, while at the other site the use of potash increased root yield 1.5 tons/acre. Sucrose concentrations were not affected by potash fertilizer at either site.

The use of potash on soils with high soil test potassium is not needed for sugar beet production. Fortunately, the use of potassium fertilizer at the normal application rates will not reduce sugar beet root quality.

If the soil potassium is excessive, it can interfere with ammonium-N uptake. This is of little concern in sugar beet production for two reasons: 1. the potassium concentrations in our soils are not even close to the concentrations needed to cause this problem and 2. sugar beet does not use much nitrogen in the ammonium form. If potassium concentration is low enough to warrant fertilizer application, the use of potassium is beneficial to nitrogen nutrition in the plant. Potassium in these conditions improves the efficiency of nitrogen use in the plant up to the point that the potassium needs of the plant are met. If you follow nitrogen and potassium soil test fertilizer recommendations, this is not a concern. Stay the course on nutrient management for growing a quality sugar beet crop.


 

How to get the most accurate N Fertilizer recommendation for sugar beet!!
John A. Lamb - Nutrient Management Extension Specialist
University of Minnesota, Department of Soil, Water, and Climate

Below are reminders on how to get the most accurate N fertilizer recommendation.

    1. Soil test after the soil temperature at 4 inches deep is less than 50 degrees.
    2. Take a soil sample to a depth of 4 feet. This is especially true if a field where the previous crop is corn, sweet corn, peas, and small grains. Also consider a 4 foot soil sample in fields with a history of manure application.
    3. Sample a field in areas of less than 20 acres in size. These 20 acres areas should be similar in soils, landscape, and previous management.
    4. Use the recommendation of 130 pounds N/acre and adjust it for soil test nitrate, recent manure applications, or legume history. If the nitrate-N levels are excessive in the 2 to 4 foot depth and the nitrate in the top two feet is less than 65 pounds then apply enough fertilizer N to bring the top 2 feet to 65 pounds. This is the only condition in which the 65 pound rule applies. If the there is small amounts of nitrate in the 2 to 4 foot depth, then ignore the 65 pound rule.
    5. Apply nitrogen fertilizer after the soil temperature at the 4 to 6 inches depth is continually below 50 degrees. This is normally around the third week of October in the SMBSC growing area.

RECOMMENDATIONS FOR NITROGEN IN SUGARBEETS
Mark Bredehoeft, Southern MN Sugar Coop
John A. Lamb - Nutrient Management Extension Specialist
University of Minnesota, Department of Soil, Water, and Climate

Fertility recommendations for sugar beets ask for 65 lbs. nitrogen to be maintained in the 0-2 ft. soil profile. This rule is important in cases where the nitrate-N in the 2 to 4 foot depth is large and there is little nitrate in the 2 to 4 ft depth. The situation is rare under normal production conditions. What happens is that because the nitrates are high in the 2 to 4 depth, 0 N is applied and there is less than 65 pounds in the 0 to 2 foot. Research at the Northwest Experiment Station indicates that no matter how much nitrate is in the 2 to 4 ft depth the beet plant needs 65 pounds in the 0 to 2 foot depth for vigorous early growth until the roots reach the deeper nitrogen. Normally the recommendation will supply enough N fertilizer with the nitrate in the 0 to 2 foot depth. Therefore, the rule is much more important in the case where the nitrogen in the 0-3 ft. soil profile is 115 lbs. or the 0-4ft. soil profile is 130 lbs. nitrogen In this case the recommended applied nitrogen would be 0. Therefore, nitrogen may need to be applied to maintain 65 lbs. nitrogen in the 0-2 ft. soil profile.  However, in the case in which the whole soil profile tested does not meet the recommended nitrogen needed and thus nitrogen is applied and in many cases the maintenance of 65 lbs. in the top two feet is already being met; then you do not have to add additional nitrogen beyond the recommended nitrogen of (0-3ft) 115 lbs. or (0-4ft.) 130 lbs.

We have been made aware of some recommendations being made in which the recommended nitrogen was being applied plus additional nitrogen to bring the 0-2 ft. soil profile to 65 lbs.. One needs to recognize that when nitrogen is applied to meet a specific recommendation, this is done to the 0-2 ft soil profile. This negates the need to add additional nitrogen to specifically meet the 65 lb. minimum in the 0-2 ft. soil profile. We have included some scenarios in the following examples.

Scenario 1

0-2 ft. 40 lbs. nitrogen
2-4 ft 40 lbs. nitrogen

Nitrogen available in the 0-4 ft. soil profile = 80 lbs.
recommended nitrogen to apply 50 lbs.

Do not need to bring 0-2 ft. soil profile to 65 lb. nitrogen minimum since 50 lbs. nitrogen will be applied plus there is 40 pounds of nitrate already there.

Scenario 2

0-2 ft. 40 lbs. nitrogen
2-4 ft 90 lbs. nitrogen

Nitrogen available in the 0-4 ft. soil profile = 130 lbs.
recommended nitrogen to apply 25 lbs. to bring the 0-2 ft. soil profile to the 65 lb. nitrogen minimum


Scenario 3

0-2 ft. 65 lbs. nitrogen
2-4 ft 65 lbs. nitrogen

Nitrogen available in the 0-4 ft. soil profile = 130 lbs.
recommended nitrogen to apply 0 lbs. since all nitrogen requirements are met.

If you have any questions please contact your Agriculturist.