Fertilizing sunflower in Minnesota

Quick facts

Sunflower is highly responsive to nitrogen (N).
Nitrogen rates should be adjusted for the type of sunflower grown.
Suggested nitrogen fertilizer rates are no longer based on yield goals minus N fertilizer credits, as recent data has not shown a link between the yield of sunflower and N fertilizer requirements.

Recommended N fertilizer rates

Recommended rates of nitrogen (N) should be based on the value of the sunflower seed in price per harvested pound and the unit price per pound of N applied.

The suggested rate of N also varies based on the type of sunflower grown.

Nitrogen suggestions for oilseed sunflower are given in Table SF-1.
Suggestions for confection sunflower production are given in Table SF-2.
Guidelines are based on suggestions for sunflower grown under conventional tillage for Eastern North Dakota, which has similar climate and soils as Northwest Minnesota.
Suggested first and second year N credits are listed in Tables SF-3 and SF-4.

The N rates suggested in Tables SF-1 and SF-2 include all known sources of N including the amount of Nitrate-N in a two-foot soil sample and any N credits from previous crops. We suggest sampling for Nitrate-N. Samples can be collected in the fall after the previous crop has been harvested.

For more specific recommendations, North Dakota State University has an interactive sunflower N calculator.

Nitrogen application rate tables

Total known available N for oilseed sunflower

Table SF-1. Total known available N (lb./acre) for oilseed sunflower in situations based on N cost and sunflower harvest price. Total known available N includes soil test N to 2 feet, previous crop credit and fertilizer amendment N rate.

* Chart adapted from NDSU Extension Publication SF713.

Sunflower seed price per pound harvested	N use @$.20/lb	N use @$.30/lb	N use @$.40/lb	N use @$.50/lb	N use @$.60/lb	N use @$.70/lb	N use @$.80/lb	N use @$.90/lb	N use @$1/lb
$0.09/lb	150 lb	135 lb	124 lb	111 lb	96 lb	84 lb	72 lb	59 lb	47 lb
$0.12	150	145	135	125	116	106	96	87	78
$0.15	150	150	143	135	127	119	112	104	96
$0.18	150	150	148	141	135	128	126	115	109
$0.21	150	150	150	146	141	135	129	124	118
$0.24	150	150	150	150	145	140	135	130	125
$0.27	150	150	150	150	148	144	139	135	131
$0.30	150	150	150	150	150	147	143	139	135
$0.33	150	150	150	150	150	150	150	150	138
$0.36	150	150	150	150	150	150	150	150	142
$0.39	150	150	150	150	150	150	150	150	144
$0.42	150	150	150	150	150	150	150	150	146
$0.45	150	150	150	150	150	150	150	150	148
$0.48	150	150	150	150	150	150	150	150	150
$0.51	150	150	150	150	150	150	150	150	150
$0.55	150	150	150	150	150	150	150	150	150
$0.60	150	150	150	150	150	150	150	150	150

Total known available N for confection sunflower

Table SF-2. Total known available N (lb./acre) for confection sunflower in situations based on N cost and sunflower harvest price. Total known available N includes soil test N to 2 feet, previous crop credit and fertilizer amendment N rate.

*Chart adapted from NDSU Extension Publication SF713.

Sunflower seed price per pound harvested	N use @$.20/lb	N use @$.30/lb	N use @$.40/lb	N use @$.50/lb	N use @$.60/lb	N use @$.70/lb	N use @$.80/lb	N use @$.90/lb	N use @$1/lb
$0.09/lb	160 lb	107 lb	43 lb	0 lb	0 lb	0 lb	0 lb	0 lb	0 lb
$0.12	160	155	107	59	11	0	0	0	0
$0.15	160	160	145	107	69	30	0	0	0
$0.18	160	160	160	139	107	75	43	11	0
$0.21	160	160	160	160	134	107	79	52	25
$0.24	160	160	160	160	155	131	107	83	59
$0.27	160	160	160	160	160	149	128	107	86
$0.30	160	160	160	160	160	160	145	126	107
$0.33	160	160	160	160	160	160	160	142	139
$0.36	160	160	160	160	160	160	160	155	151
$0.39	160	160	160	160	160	160	160	160	160
$0.42	160	160	160	160	160	160	160	160	160
$0.45	160	160	160	160	160	160	160	160	160
$0.48	160	160	160	160	160	160	160	160	160
$0.51	160	160	160	160	160	160	160	160	160
$0.55	160	160	160	160	160	160	160	160	160
$0.60	160	160	160	160	160	160	160	160	160

Nitrogen credits

Table SF-3. Suggested nitrogen credits for various crops that might precede sunflower in a crop rotation. Use these credits when the soil nitrate test is used.

*For harvested alfalfa, if the third or fourth cutting was not harvested, add 20 pounds N per acre to the N credits listed.

Previous crop	1st 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
Sugarbeet
Yellow leaves at harvest	0
Light-green leaves at harvest	15-30
Dark-green leaves at harvest	60-80

Table SF-4. Suggested nitrogen credits when sunflower is grown 2 years after a legume crop.

Previous legume crop	2nd 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, potash and other nutrients

Phosphate

Table SF-5. Phosphate fertilizer guidelines (pounds of P₂O₅ suggested to apply per acre) for sunflower 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 you want a phosphate guideline for a specific soil test and a specific expected yield:

P₂O₅ rec = [0.0225 - (0.0011) (Bray P in ppm)] (Expected yield)
P₂O₅ rec = [0.0225 - (0.0014) (Olsen P in ppm)] (Expected yield)

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
1400-1900 lb./acre	55 lb./acre	35 lb./acre	15 lb./acre	0 lb./acre	0 lb./acre
1901-2400 lb./acre	65	45	20	0	0
2401-2900 lb./acre	75	55	25	0	0
2901-3300 lb./acre	85	65	25	10	0
3300+ lb./acre	90	70	30	10	0

Potash

Table SF-6. Potash fertilizer guidelines (pounds of K₂O suggested to apply per acre) for sunflower production based on the ammonium acetate potassium test reported in parts per million (ppm).

Use the following equation if you want a potash guideline for a specific soil test and a specific expected yield:

K₂O rec = [0.0410 - (0.00027) (Soil test K in ppm)] (Expected yield)

CAUTION: Do not apply more than 10 pounds N + K₂O per acre in contact with the seed for medium to fine textured soils. Starter fertilizer placed on the seed is not suggested for sandy textured soils.

Expected Yield	0-40 ppm	41-80 ppm	81-120 ppm	121-160 ppm	161+ ppm
1400-1900 lb./acre	55 lb./acre	40 lb./acre	20 lb./acre	10 lb./acre	0 lb./acre
1901-2400 lb./acre	75	50	30	15	0
2401-2900 lb./acre	90	65	35	20	0
2901-3300 lb./acre	110	75	40	25	0
3301+ lb./acre	115	80	45	25	0

Other nutrients

Research trials conducted in Minnesota have shown that most secondary macronutrients and micronutrients are not needed in a fertilizer program for sunflower production.

The need for sulfur (S) for sunflower has not been evaluated in Minnesota. The likelihood of sulfur deficiency on soils high in clay content (loam soils or heavier) is low if soil organic matter content is 2-3% or greater in the top six inches. The likelihood of an S deficiency is greater for sandy textured soils low in organic matter. If a sulfur deficiency is anticipated, an application of 10 pounds of S in the sulfate form at or before planting or post emergence before the R1 growth stage may be required. We suggest you apply a sulfate or thiosulfate form.

Do not place ammonium thiosulfate (12-0-0-26) in direct contact with the seed. Do not place fertilizers containing boron in direct contact with the seed.

Sources

NDSU Fertilizing Sunflower Guide: https://www.ndsu.edu/agriculture/sites/default/files/2022-08/sf713.pdf

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

Reviewed in 2023