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Extension > Agriculture > Nutrient Management > Nutrient/Lime Guidelines > Fertilizer Recommendations for Agronomic Crops in Minnesota > Buckwheat

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Fertilizer Recommendations for Agronomic Crops in Minnesota

Buckwheat

Daniel E. Kaiser, Extension Soil Scientist; John A. Lamb, Extension Soil Scientist; and Roger Eliason, Director, University of Minnesota Soil Testing Laboratory

Revised 2011

Nitrogen

subsoil map

Figure 1. The fall soil nitrate test should be used for nitrogen recommendations in the counties that are shaded.

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 (see Figure 1). When the soil NO3--N test is used, the fertilizer N guidelines are calculated as follows:

Nrec = (0.0458) (EY) - STN(0-24 in. - NPc

Where:

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).
These N credits are summarized in Table 1.

The N fertilizer guidelines for production situations where the soil NO3--N test is not used are listed in Table 2.

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.

Table 1. Nitrogen credits for various legume crops that might precede barley in a crop rotation. Use these credits for the "Npc" factor in situations where the soil nitrate test is used.

Previous Crop 1st Year Nitrogen Credit
  lb. N/acre
  Soybean 20
  Edible  beans, field peas 10
  Harvest sweetclover 10
  Harvested alfalfa*  
    4 to 5 plants/ft2 75
    2 to 3 plants/ft2 50
    1 or fewer plants/ft2 0
  Harvested red clover 35

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

Table 2. Nitrogen guidelines for buckwheat in situations when the soil NO3--N test is not used.

  Expected Yield (bu./acre)
Crop Grown Last Year Organic Matter Level* 1200-1450 1451-1700 1701-1950 1951-2200
  Alfalfa (4+ plants/ft2) Low Med and high

0
0

0
0
0
0
0
0
  Soybeans Alfalfa (1 or less plants/ft2) Low Med and high 0
0
10
0
20
0
30
0
  Edible beans, field peas Low Med and high 20
0
30
10
40
20
50
30
  Group 1 Crops Low Med and high 0
0
0
0
0
0
0
0
  Group 2 Crops Low Med and high 40
20
50
30
60
40
70
50

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

Therefore, all sources of N are equal if properly applied.

Crops in Group 1:

Alsike clover, birdsfoot trefoil, grass/legume hay, grass legume pasture, fallow, and 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, and wheat.

Phosphate and Potash

The guidelines for the use of phosphate and potash are summarized in Tables 3 and 4.

These fertilizers, when needed, should be broadcast and incorporated before planting. Special sources of phosphate and potash are not needed for buckwheat production. All commonly sold sources for each nutrient are equal.

There is no research which suggests 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.

Table 3. Phosphate fertilizer guidelines for buckwheat production.

    Phosphorus (P) Soil Test, ppm *
Expected
Yield
Bray: 0-5 6-10 11-15 16-20 21 +
Olsen: 0-3 4-7 8-11 12-15 16 +
1200-1450   35 20 15 0 0
1451-1700   40 25 15 0 0
1701-1950   45 30 20 0 0
1951-2200   50 35 20 0 0

* 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)

Table 4. Potash fertilizer guidelines for buckwheat production.

Expected
Yield
Potassium (K) Soil Test, ppm *
0-40 40-80 80-120 120-160 160 +
lb./acre — K2O to apply (lb.acre) —
1200-1450 45 35 20 0 0
1451-1700 55 40 25 0 0
1701-1950 60 45 25 10 0
1951-2200 70 50 30 10 0

* Use the following equation if a potash guideline for a specific expected yield.

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

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