Sweet corn is an important processing crop grown in Minnesota and ranks second in acreage for processing in the US. While acreage of sweet corn is less than dent corn in the state, fertilizer guidelines for sweet corn are different.
Lime needs
Managing soil pH can be important for crops to ensure high availability of some nutrients. Lime is suggested for sweet corn in situations where soil water pH in the top six inches is less than 6.0. Lime suggestions are based on the location where the crop will be grown in the state and buffer pH values.
Nitrogen guidelines
Nitrogen is one of the most limiting nutrients for sweet corn production. Current nitrogen guidelines are based on the crop grown the previous year, soil organic matter level, and the expected yield of the sweet corn crop grown.
Nitrogen can be applied as a single application in most situations in Minnesota where sweet corn is grown on medium or fine-textured soils. For irrigated sandy soils, split N applications are recommended with 10 to 20 lbs. N per acre applied as a starter at or just before planting. The remainder of the suggested N should be applied in one or two split applications at the 4- to 6-leaf stage and the 10- to 12-leaf stage.
Nitrogen guidelines for sweet corn
| Crop grown last year | Organic matter level* | Yield goal: Less than 6 tons/acre | Yield goal: 6–7 tons/acre | Yield goal: 8–9 tons/acre | Yield goal: 10+ tons/acre |
|---|---|---|---|---|---|
| Alfalfa (4+ plants/ft2) | Low | 10 lbs. N/acre | 30 lbs. N/acre | 50 lbs. N/acre | 70 lbs. N/acre |
| Alfalfa (4+ plants/ft2) | Medium/High | 0 | 0 | 40 | 60 |
| Soybeans or field peas | Low | 100 | 120 | 140 | 160 |
| Soybeans or field peas | Medium/High | 70 | 90 | 110 | 130 |
| Group 1 Crops | Low | 90 | 110 | 130 | 150 |
| Group 1 Crops | Medium/High | 60 | 80 | 100 | 120 |
| Group 2 Crops | Low | 130 | 150 | 170 | 190 |
| Group 2 Crops | Medium/High | 100 | 120 | 150 | 160 |
| Organic soil** | 20 | 50 | 70 | 70 |
Nitrogen recommendations in pounds per acre (lbs./acre) for sweet corn by previous crop and soil organic matter content (OM). *Low = less than 3.0%; Medium/High = 3.0% or more. **Organic soil = more than 19% O.M.
Crops in Group 1: Alsike clover, birdsfoot trefoil, grass/legume hay, grass/legume pasture, fallow, red clover.
Crops in Group 2: Alfalfa (0-1 plants/ft.2), barley, buckwheat, canola, corn, flax, grass hay, grass pasture, oat, potato, rye, sorghum-sudan, sugarbeet, sunflower, sweet corn, triticale, vegetables, wheat.
A soil nitrate test is available for sweet corn. It can be taken in the fall for areas west of Highway 71 and in the spring before fertilizer application for central and southeastern Minnesota. The soil nitrate test is only calibrated for soil samples collected at a two-foot sampling depth. The amount of nitrate measured in the two-foot sample can be subtracted from the amount of N in the table below.
Because sweet corn is harvested earlier in the season and at an immature stare relative to dent corn, about one-half of the nitrogen taken up is still in the stover, which also has a low carbon-to-nitrogen ratio. Use a cover crop such as oats or winter rye to reduce nitrogen losses following harvest.
Nitrogen suggestions for sweet corn when a two-foot soil nitrate sample is used
| Expected yield | Soil Nitrate N plus Fertilizer N |
|---|---|
| Less than 6 tons/acre | 70 lbs. N/acre |
| 6–7 | 130 |
| 8–9 | 165 |
| 10 or more | 200 |
Phosphate and potash guidelines
Suggestions for phosphate and potash are adjusted based on how the nutrients are applied. Rates of both nutrients can be reduced with band applications. Rate reductions with banded application are at the discretion of the grower. Rate reductions are greater for Very Low and Low soil tests.
Broadcast and band phosphate fertilizer guidelines
| Expected yield Bray-P1 Expected yield Olsen |
Broadcast/Row Broadcast/Row |
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 |
|---|---|---|---|---|---|---|
| Less than 6 tons/acre | Broadcast | 70 lbs./acre | 40 lbs./acre | 30 lbs./acre | 10 lbs./acre | 0 lbs./acre |
| Less than 6 | Band | 40 | 25 | 20 | 10–15 | 10–15 |
| 6–7 | Broadcast | 80 | 50 | 30 | 10 | 0 |
| 6–7 | Band | 40 | 30 | 20 | 10–15 | 10–15 |
| 8–9 | Broadcast | 90 | 60 | 40 | 10 | 0 |
| 8–9 | Band | 40 | 35 | 25 | 10–15 | 10–15 |
| 10 or more | Broadcast | 100 | 70 | 40 | 20 | 0 |
| 10 or more | Band | 40 | 40 | 25 | 10–15 | 10–15 |
Broadcast and band phosphate fertilizer guidelines (lbs. of P2O5 suggested to apply per acre) for sweet corn production are 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 broadcast phosphate guideline for a specific soil test and a specific expected yield is desired:
- P2O5rec = [11.98 – (0.5627) (Bray P, ppm)] (Expected Yield)
- P2O5rec = [11.63 – (0.7034) (Olsen P, ppm)] (Expected Yield)
Potash fertilizer guidelines
| Expected yield (tons/acre) | Broadcast/Row | 0–40 ppm | 41–80 ppm | 81–120 ppm | 121–160 ppm | 161+ ppm |
|---|---|---|---|---|---|---|
| Less than 6 tons/acre | Broadcast | 120 lbs./acre | 60 lbs./acre | 40 lbs./acre | 40 lbs./acre | 0 lbs./acre |
| Less than 6 | Band | 40 | 30 | 10–15 | 10–15 | 10–15 |
| 6–7 | Broadcast | 140 | 80 | 40 | 40 | 0 |
| 6–7 | Band | 40 | 30 | 10–15 | 10–15 | 10–15 |
| 8–9 | Broadcast | 160 | 100 | 60 | 40 | 0 |
| 8–9 | Band | 40 | 40 | 25 | 10–15 | 10–15 |
| 10 or more | Broadcast | 180 | 120 | 80 | 60 | 0 |
| 10 or more | Band | 40 | 40 | 30 | 25 | 10–15 |
Potassium recommendations (lbs. K2O per acre) for sweet corn production are based on K soil test results. Use the following equation if a broadcast potash guideline for a specific soil test and a specific expected yield is desired:
- K2O rec = [20.21 – (0.1133) (Soil test K, ppm)] (Expected yield)
Using a banded fertilizer with the planter
A banded fertilizer applied 2 inches below and to the side of the seed at planting is sometimes used to boost early-season growth. Banding fertilizer directly on the seed can present a significant risk for reducing plant emergence. The rate of fertilizer that can be applied in a band directly on the seed at planting (popup) varies by fertilizer source and soil texture and has not been evaluated in Minnesota for sweet corn production, but evidence suggests that stand may be reduced when popup rates for dent corn are used for sweet corn.
Phosphorus is the main nutrient likely to enhance early plant growth and selecting a starter high in phosphorus and low in nitrogen and potassium can greatly reduce the risk of seedling damage. Research has shown that increased early plant growth is largely cosmetic in Medium to High P testing soils and will likely not increase yield.
CAUTION: Do not apply urea, ammonium thiosulfate (12-0-0-26), potassium thiosulfate, or fertilizer containing boron in contact with the seed.
Other nutrients
Research has not found a need for calcium and magnesium applications to sweet corn in Minnesota. The need for calcium and magnesium can usually be met by using dolomitic lime to adjust soil pH. There may be a few rare situations where the magnesium soil test is low. For those situations follow the guidelines in the table below.
Questions on the application of sulfur have surfaced recently due to responses seen in dent corn fields. Sulfur responses in dent corn are more likely in situations with low organic matter and high leaching potential but have also occurred in poorly drained, high organic matter fields, especially in high crop residue situations. Application of sulfur may be warranted for sweet corn under some circumstances at the rate of 10 to 25 lbs. S per acre. If groundwater is used for irrigation, up to half the sulfur requirements and all the magnesium requirements can be supplied with the irrigation water in most years.
Magnesium recommendations for sweet corn
| Magnesium soil test | Relative level | Broadcast | Row |
|---|---|---|---|
| 0–49 ppm | Low | 100 lbs./acre | 20 lbs./acre |
| 50–99 | Medium | 50 | 10 |
| 100+ | High | 0 | 0 |
The only micronutrient likely deficient in sweet corn production is zinc. The zinc guidelines table summarizes the amount of zinc suggested in a band or broadcast application based on a 0- to 6-inch soil sample. Do not apply zinc directly to the seed.
Zinc guidelines for sweet corn
| Zinc soil test* | Band | Broadcast |
|---|---|---|
| 0.0–0.5 ppm | 2 lbs./acre | 10 lbs./acre |
| 0.6–1.0 | 1 | 5 |
| 1.1 + | 0 | 0 |
* Zinc extracted by the DTPA procedure.
There is no evidence that the application of boron, copper, or manganese will increase the yield of sweet corn in Minnesota grown on mineral soils. When grown on organic soils with a pH greater than 5.7, manganese should be monitored for possible deficiency. If manganese deficiency has been identified in previous years, broadcast applications of 4 to 6 lbs. Mn/A are suggested when soil pH is greater than 5.7. Foliar applications of 0,2-0.3 Mn/A can be applied if deficiencies occur during the growing season.
Reviewed in 2022