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Fertilizing buckwheat in Minnesota

Nitrogen guidelines

Nitrogen (N) fertilization is an important management practice for optimum production of buckwheat. Nitrogen fertilizer guidelines can be based either on the results of the soil NO3--N test or the consideration of the combination of expected yield, previous crop, and soil organic matter content. The soil NO3--N test is appropriate for western Minnesota. When the soil NO3--N test is used, the fertilizer N guidelines are calculated as follows:

Nitrogen fertilizer formula

Suggested N in lb/acre = (0.0458) (EY) - STN(0-24 in.) - Npc

Nitrogen formula variables

  • EY = expected yield (lb./acre)
  • STN = nitrate-nitrogen (NO3--N) measured to a depth of 24 in. (lb./acre)
  • Npc = amount of N supplied by the previous legume crop (lb./acre)

For most production situations, the N fertilizers should be broadcast and incorporated before planting. The N fertilizer can be applied in either dry or liquid form. There is no research to document that one form is superior to the other.

Nitrogen guidelines for buckwheat* in pounds per acre

Crop grown last year Organic matter level** 1200-1450 lb/acre 1451-1700 lb/acre 1701-1950 lb/acre 1951-2200 lb/acre
Alfalfa (4+ plants/ft2) Low 0 lb N/acre 0 lb N/acre 0 lb N/acre 0 lb N/acre
Alfalfa (4+ plants/ft2) Medium/High 0 0 0 0
Soybeans or alfalfa (1 or less plants/ft2) Low 0 10 20 30
Soybeans or alfalfa (1 or less plants/ft2) Medium/High 0 0 0 0
Edible beans, field peas Low 20 30 40 50
Edible beans, field peas Medium/High 0 10 20 30
Group 1 Crops Low 0 0 0 0
Group 1 Crops Medium/High 0 0 0 0
Group 2 Crops Low 40 50 60 70
Group 2 Crops Medium/High 20 30 40 50

*in situations when the soil NO3--N test is not used based on expected yield of the crop.

**low = less than 3.0%; medium and high = 3.0% or more

  • Crops in group 1: Alsike clover, birdsfoot trefoil, grass/legume hay, grass legume pasture, fallow, red clover.
  • Crops in group 2: Barley, buckwheat, canola, corn, grass hay, grass pasture, oat, potato, rye, sorghum-sudan, sugar beet, sunflower, sweet corn, triticale, wheat.

Suggested nitrogen credits for crops that might precede wheat in a crop rotation*

Previous crop First year N credit (lb N/acre)
Soybean 20
Edible beans, field peas 10
Harvested sweet clover 10
Harvested alfalfa** or non-harvested sweet clover
4-5 plants/ft2 75
2-3 plants/ft2 50
1-2 plants/ft2 25
1 or fewer plants/ft2 0
Harvested red clover 35
Sugar beet
Yellow leaves at harvest 0
Light-green leaves at harvest 15-30
Dark-green leaves at harvest 60-80

*Use these credits when the soil nitrate test is used.

**If 3rd or 4th cutting was not harvested, add 20 lb. N/acre to the N credits listed.

Suggested nitrogen credits when wheat is grown 2 years after a legume crop

Previous legume crop Second year N credit (lb N/acre)
Alfalfa (4+ plants/ft2) 35
Non-harvested sweet clover 35
Alfalfa (2-3 plants/ft2) 25
Birdsfoot trefoil 25
Red clover 20

Phosphate and potash guidelines

These fertilizers, when needed, should be broadcast and incorporated before planting. Special sources of phosphate and potash are not needed for buckwheat production. Phosphorus guidelines are given for the Bray-P1 and Olsen soil test methods. The Olsen soil test should be used in situations where soil pH is greater than 7.4.

Recommendations suggest pounds of actual nutrient needed to be applied and do not reflect pounds of product that should be applied.

Pounds of product to apply needs to be calculated based on the amount of nutrient suggested divided by the percentage of P2O5 or K2O per pound in the material to be applied.

All commonly sold sources for each nutrient are equal. There is no research suggesting that nutrients other than N, P and K are needed in a fertilizer program for buckwheat production in Minnesota.

CAUTION: Do not apply any fertilizer in contact with buckwheat seed at planting.

Phosphate fertilizer guidelines*

Expected Yield Bray-P1
Expected Yield Olsen
0-5 ppm
0-3 ppm
6-10 ppm
4-7 ppm
11-15 ppm
8-11 ppm
16-20 ppm
12-15 ppm
21+ ppm
16+ ppm
1200-1450 lb/acre 35 lb/acre 20 lb/acre 15 lb/acre 0 lb/acre 0 lb/acre
1200-1450 lb/acre 35 20 15 0 0
1451-1700 lb/acre 40 25 15 0 0
1701-1950 lb/acre 45 30 20 0 0
1951-2200 lb/acre 50 35 20 0 0

*Pounds of P2O5 suggested to apply per acre for buckwheat production based on either the Bray-P1 or Olsen soil methods test reported in parts per million (ppm). Use one of the following equations if a phosphate guideline for a specific soil test and a specific expected yield is desired:

  • P2O5 rec = [0.0275 - (0.0014) (Bray P, ppm)] (Expected Yield)
  • P2O5 rec = [0.0275 - (0.0017) (Olsen P, ppm)] (Expected Yield)

Potash fertilizer guidelines*

Expected Yield 0-40 ppm 40-80 ppm 80-120 ppm 120-160 ppm 160+ ppm
1200-1450 lb/acre 45 lb/acre 35 lb/acre 20 lb/acre 0 lb/acre 0 lb/acre
1451-1700 lb/acre 55 40 25 0 0
1701-1950 lb/acre 60 45 25 10 0
1951-2200 lb/acre 70 50 30 10 0

*Pounds of K2O suggested to apply per acre for buckwheat production based on the ammonium acetate potassium test reported in parts per million (ppm). Use the following equation if a potash guideline for a specific soil test and a specific expected yield is desired.

  • K2O rec = [0.0358 - (0.023) (Soil Test K, ppm)] (Expected Yield)

Authors: Daniel E. Kaiser, Extension nutrient management specialist, and Keith Piotrowski, director of the soil testing laboratory

Reviewed in 2023

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