Sunflower will respond to fertilization. Nitrogen, phosphate, and potash are important. The tables that follow list appropriate recommendations.
Nitrogen
We base nitrogen (N) fertilizer guidelines on the results of a soil NO3--N test or the consideration of expected yield, previous crop, and soil organic matter content. The soil NO3--N test is appropriate for western Minnesota (see Figure 1). With the soil nitrate test, we use the following calculation:
Nrec = (0.05) (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).
Table 1 summarizes these N credits.
Table 2 summarizes the N fertilizer guidelines for situations where the soil NO3--N test is not used.
Table 1 lists legume crops that might precede sunflower in a crop rotation. Use these credits for the Npc factor when you use the soil nitrate test.
* Add 20 lbs. of N per acre to the listed credits if the third or fourth cutting wasn’t harvested.
Table 1: Nitrogen credits
| Previous crop | First-year nitrogen credit |
|---|---|
| Soybean | 20 lbs. of N per acre |
| Edible beans, field peas | 10 lbs. of N per acre |
| Harvest sweetclover | 10 lbs. of N per acre |
| Harvested alfalfa*: 4 to 5 plants per square foot | 75 lbs. of N per acre |
| Harvested alfalfa*: 2 to 3 plants per square foot | 50 lbs. of N per acre |
| Harvested alfalfa*: 1 or fewer plants per square foot | 0 lbs. of N per acre |
| Harvested red clover per square foot | 35 lbs. of N per acre |
Table 2: Nitrogen fertilizer guidelines
| Crop grown last year | Organic matter level* | Expected yield: 1,400-1,900 lbs. per acre | Expected yield: 1,901-2,400 lbs. per acre | Expected yield: 2,401-2,900 lbs. per acre | Expected yield: 2,901-3,300 lbs. per acre | Expected yield: 3,300+ lbs. per acre |
|---|---|---|---|---|---|---|
| Alfalfa (4+ plants per square foot) | Low | 0 lbs. of N per acre | 0 lbs. of N per acre | 0 lbs. of N per acre | 0 lbs. of N per acre | 0 lbs. of N per acre |
| Alfalfa (4+ plants per square foot) | Medium and high | 0 lbs. of N per acre | 0 lbs. of N per acre | 0 lbs. of N per acre | 0 lbs. of N per acre | 0 lbs. of N per acre |
| Alfalfa (2 to 3 plants per square foot) | Low | 0 lbs. of N per acre | 20 lbs. of N per acre | 40 lbs. of N per acre | 60 lbs. of N per acre | 80 lbs. of N per acre |
| Alfalfa (2 to 3 plants per square foot) | Medium and high | 0 lbs. of N per acre | 0 lbs. of N per acre | 10 lbs. of N per acre | 30 lbs. of N per acre | 50 lbs. of N per acre |
| Soybeans | Low | 30 lbs. of N per acre | 50 lbs. of N per acre | 70 lbs. of N per acre | 90 lbs. of N per acre | 110 lbs. of N per acre |
| Alfalfa (1 or fewer plants per square foot) | Medium and high | 0 lbs. of N per acre | 20 lbs. of N per acre | 40 lbs. of N per acre | 60 lbs. of N per acre | 80 lbs. of N per acre |
| Group 1 crops (see below) | Low | 0 lbs. of N per acre | 15 lbs. of N per acre | 25 lbs. of N per acre | 45 lbs. of N per acre | 65 lbs. of N per acre |
| Group 1 crops (see below) | Medium and high | 0 lbs. of N per acre | 0 lbs. of N per acre | 0 lbs. of N per acre | 25 lbs. of N per acre | 45 lbs. of N per acre |
| Group 2 crops (see below) | Low | 70 lbs. of N per acre | 90 lbs. of N per acre | 110 lbs. of N per acre | 130 lbs. of N per acre | 150 lbs. of N per acre |
| Group 2 crops (see below) | Medium and high | 40 lbs. of N per acre | 60 lbs. of N per acre | 80 lbs. of N per acre | 100 lbs. of N per acre | 120 lbs. of N per acre |
*Low = less than 3.0%; medium and high = 3.0% or more.
Use these recommendations for sunflower production when the soil NO3--N test isn’t used.
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, potash and other nutrients
Table 3 summarizes phosphate recommendations for sunflower production in Minnesota. 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)
Table 3: Phosphate fertilizer suggestions
| Expected yield | P soil test: 0-5 parts per million (ppm) Bray and 0-3 ppm Olsen | P soil test: 6-10 ppm Bray and 4-7 ppm Olsen | P soil test: 11-15 ppm Bray and 8-11 ppm Olsen | P soil test: 16-20 ppm Bray and 12-15 ppm Olsen | P soil test: 21+ ppm Bray and 16+ ppm Olsen |
|---|---|---|---|---|---|
| 1,400-1,900 lbs. per acre | 55 lbs. of P2O5 per acre | 35 lbs. of P2O5 per acre | 15 lbs. of P2O5 per acre | 0 lbs. of P2O5 per acre | 0 lbs. of P2O5 per acre |
| 1,901-2,400 lbs. per acre | 65 lbs. of P2O5 per acre | 45 lbs. of P2O5 per acre | 20 lbs. of P2O5 per acre | 0 lbs. of P2O5 per acre | 0 lbs. of P2O5 per acre |
| 2,401-2,900 lbs. per acre | 75 lbs. of P2O5 per acre | 55 lbs. of P2O5 per acre | 25 lbs. of P2O5 per acre | 0 lbs. of P2O5 per acre | 0 lbs. of P2O5 per acre |
| 2,901-3,300 lbs. per acre | 85 lbs. of P2O5 per acre | 65 lbs. of P2O5 per acre | 25 lbs. of P2O5 per acre | 10 lbs. of P2O5 per acre | 0 lbs. of P2O5 per acre |
| 3,300+ lbs. per acre | 90 lbs. of P2O5 per acre | 70 lbs. of P2O5 per acre | 30 lbs. of P2O5 per acre | 10 lbs. of P2O5 per acre | 0 lbs. of P2O5 per acre |
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)
Table 4: Potash fertilizer suggestions for sunflower production in Minnesota
| Expected yield | K soil test: 0-40 ppm | K soil test: 41-80 ppm | K soil test: 81-120 ppm | K soil test: 121-160 ppm | K soil test: 161+ ppm |
|---|---|---|---|---|---|
| 1,400-1,900 lbs. per acre | 55 lbs. of K2O per acre | 40 lbs. of K2O per acre | 20 lbs. of K2O per acre | 15 lbs. of K2O per acre | 0 lbs. of K2O per acre |
| 1,901-2,400 lbs. per acre | 75 lbs. of K2O per acre | 50 lbs. of K2O per acre | 30 lbs. of K2O per acre | 15 lbs. of K2O per acre | 0 lbs. of K2O per acre |
| 2,401-2,900 lbs. per acre | 90 lbs. of K2O per acre | 65 lbs. of K2O per acre | 35 lbs. of K2O per acre | 20 lbs. of K2O per acre | 0 lbs. of K2O per acre |
| 2,901-3,300 lbs. per acre | 110 lbs. of K2O per acre | 75 lbs. of K2O per acre | 40 lbs. of K2O per acre | 25 lbs. of K2O per acre | 0 lbs. of K2O per acre |
| 3,300+ lbs. per acre | 115 lbs. of K2O per acre | 80 lbs. of K2O per acre | 45 lbs. of K2O per acre | 25 lbs. of K2O per acre | 0 lbs. of K2O per acre |
Research trials conducted in Minnesota have shown that other nutrients are not needed in a fertilizer program for sunflower production.
CAUTION! Do not apply more than 10 lb N + K2O per acre in contact with the seed. 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.
Reviewed in 2018