Types of Fertilizers Recommended for South Dakota Crops

Understanding South Dakota soils and climate

South Dakota has a wide range of soils and climatic zones, from the glacial soils and humid plains in the east to drier, loess and shale-derived soils in the west. Soil texture, organic matter, drainage, and seasonal precipitation patterns strongly influence nutrient availability and fertilizer choices. Cool springs, variable summer rainfall, and occasional droughts make fertilizer timing and source critical to crop performance and nutrient-use efficiency.
Soil pH in many South Dakota fields ranges from slightly acidic to neutral, but localized acidity and low organic matter occur. Typical yield goals for major crops (corn, soybeans, winter wheat, alfalfa, sunflowers) differ and should drive fertility planning. A sound fertility program begins with representative soil tests taken at the same time each year and interpreted against realistic yield goals.

Primary nutrients and recommended fertilizer types

Nitrogen (N)

Nitrogen is the most yield-limiting nutrient for row crops in South Dakota, especially corn. Common commercial N sources and their characteristics:

• Anhydrous ammonia (82-0-0): high analysis, economical per lb N, best applied with injection and timely incorporation to minimize volatilization and denitrification losses.
• Urea (46-0-0): versatile and widely available; surface-applied urea is vulnerable to volatilization unless incorporated or treated with urease inhibitors (NBPT).
• UAN liquids (28-0-0, 32-0-0): flexible for in-season sidedress applications, foliar or starter use; mixes with ammonium polyphosphate or herbicides require compatibility checks.
• Ammonium sulfate (21-0-0 plus ~24% S): supplies both N and sulfur; useful where S is deficient or where acidifying N is acceptable.
• Stabilized N (urease or nitrification inhibitors, e.g., NBPT, DCD, nitrapyrin): reduce losses from volatilization and denitrification, enabling fall application in some cases and improving late-season N availability.

Typical N rate guidance (broad ranges; refine by soil test and yield goal):

• Corn: 120-220 lb N/acre depending on yield potential, soil organic matter, and manure history.
• Winter wheat: 50-120 lb N/acre split between preplant and tiller/green-up applications.
• Sunflower and sorghum: 60-130 lb N/acre depending on expected yield.
• Soybean and alfalfa: soybeans generally require minimal to no commercial N; alfalfa is a legume that fixes N but benefits from P, K, and S.

Use split applications (starter plus sidedress) in areas with leaching or denitrification risk. Calibrate rates using a yield-based economic optimum approach (EONR) and consider late-season tissue testing or chlorophyll sensors.

Phosphorus (P)

Phosphorus is immobile in soil and critical for early root development. Recommended P sources:

• Monoammonium phosphate (MAP, 11-52-0) and diammonium phosphate (DAP, 18-46-0): high-analysis granular or starter fertilizers; DAP has higher ammonium content and raises pH locally.
• Ammonium polyphosphate (10-34-0): commonly used as a liquid starter or in-furrow application; excellent for early-season uptake.
• Triple superphosphate and other blends: used for banding or corrective applications when needed.

Best practices: band or place P near the seed (starter rates) for young plants; avoid deep placement in low-testing soils. Maintain soil-test P at agronomic levels based on crop type and replacement guidelines rather than high build-up levels that lower return on investment.

Potassium (K)

Potassium is important for drought resistance, winter hardiness, and grain quality. Common K sources:

• Muriate of potash (MOP, 0-0-60): potassium chloride, economical and commonly used in South Dakota where chloride is not harmful.
• Sulfate of potash (SOP, 0-0-50 plus sulfur): used where chloride-sensitive crops or soils require a non-chloride K source.

Apply K based on soil-test recommendations and crop removal. In sandy or low-K soils increase rates and consider split applications or banding to place K near roots.

Sulfur (S)

Sulfur deficiencies are more common as atmospheric deposition has declined. Common S sources:

• Ammonium sulfate: supplies both N and S, acidifying effect.
• Elemental sulfur: slow-release, requires microbial oxidation; useful when long-term S build-up is desired.
• Sulfate of potash and gypsum (calcium sulfate): supply S in sulfate form for immediate plant availability.

Consider applying S where soil-test sulfate is low or crops demonstrate S deficiency symptoms. Oilseed crops (canola, sunflower) and high-yield corn may show S response.

Secondary nutrients and micronutrients

Secondary nutrients (calcium, magnesium) and micronutrients (zinc, manganese, iron, boron, copper, molybdenum) are needed at low rates but can limit yield on deficient soils.

• Lime (calcium carbonate) raises pH and supplies calcium; important where pH is below crop-specific targets.
• Gypsum (calcium sulfate) supplies calcium and sulfur without raising pH; useful on sodic or subsoil issues.
• Zinc sulfate or chelated zinc: often recommended for high pH or low available zinc soils; common response in young corn and soybeans in parts of South Dakota.
• Boron: critical for alfalfa and sunflower at low rates; overapplication is toxic–follow soil or tissue test guidance.

Use banding or foliar micronutrient applications when soil tests, previous crops, or tissue analysis indicate deficiency.

Fertilizer strategies by crop

Corn

Corn is the most N-responsive crop in South Dakota. Recommended approach:

• Base fertility on soil tests and yield goals. Establish an N rate that reflects expected yield and soil N supply.
• Use a starter application (10-20 lb N plus 10-30 lb P2O5/acre) placed with the seed or in a 2×2 band to jump-start early growth, especially in cool soils.
• Consider split N: apply 30-50% as starter/preplant and the remainder as sidedress V6-V8 depending on season and rainfall.
• Choose N source based on timing: anhydrous ammonia or fall-applied fertilizer with nitrification inhibitors in well-drained fields; UAN for in-season sidedress; NBPT-treated urea if surface-applied.
• Monitor for sulfur or zinc deficiencies and correct with soil or foliar applications when indicated.

Soybeans

Soybeans typically require little to no commercial N because of biological fixation; attention should be on P, K, S, and pH.

• Ensure adequate P and K based on soil tests; band starter P can improve early vigor in cool soils.
• Maintain soil pH in an optimum range for rhizobia activity (near pH 6.5-7.0).
• In fields with low residual P or K, apply corrective rates prior to or at planting as banded starter or broadcast with incorporation.

Winter wheat

Winter wheat responds to timely N and P applications:

• Apply starter P at planting if soil-P is low. A modest preplant N application plus a spring topdress N at green-up or tillering provides most yield response.
• Split N applications reduce risk from late-season leaching and allow adjustment of rates with seasonal conditions.

Alfalfa and forage crops

Alfalfa is sensitive to pH and potassium:

• Lime acidic soils to recommended pH for alfalfa (around 6.5-7.0).
• Maintain K at higher soil-test levels than for annual crops because alfalfa removes large amounts of K per ton of forage.
• Boron at low rates may be required in some fields; test before application.

Sunflower and specialty crops

Sunflowers and other oilseed crops need balanced fertility:

• Provide moderate N and ensure adequate P, K, and S for oil synthesis and stand establishment.
• Avoid excess N late in the season that delays maturity and increases lodging.

Application methods and timing

• Banding: concentrates nutrients near the seed or in-furrow; increases efficiency of P and starter nutrients but must avoid seed-placed salt injury with high rates.
• Broadcast and incorporate: effective for P and K build-up; incorporate to reduce volatilization with urea.
• Surface-applied UAN/urea: use urease inhibitors for urea; incorporate or apply before rainfall when possible.
• Sidedress: best for in-season N top-ups based on crop condition and rainfall forecasts.
• Foliar applications: used for quick correction of micronutrient deficiencies; not a substitute for balanced soil fertility.

Timing keys: apply P and K preplant or as starter; split N applications where possible; avoid fall-applied N on poorly drained or sandy soils unless stabilized and risk is low.

Environmental considerations and nutrient stewardship (4R principles)

Four principles guide responsible fertilizer use: right source, right rate, right time, right place.

• Right source: match fertilizer chemistry to crop needs and field conditions (e.g., ammonium-based N where denitrification risk is high).
• Right rate: base rates on soil tests, realistic yield goals, and nutrient-removal estimates. Consider manure nutrient credits.
• Right time: apply major N during crop uptake window and avoid vulnerable periods for leaching or denitrification. Use split applications.
• Right place: place nutrients to maximize uptake and reduce loss (banding for P, subsurface application for anhydrous ammonia).

Additional environmental practices: cover crops to capture residual N, buffer strips near water bodies, avoid broadcasting without incorporation on frozen or saturated soils, and calibrate equipment to minimize overlap and over-application.

Practical takeaways and a field-ready checklist

• Start with a recent, representative soil test and define yield goals before selecting fertilizer types and rates.
• Use banded starter P and modest seed-row N for early growth in cool soils; follow with in-season N sidedress for corn based on crop condition and weather.
• Choose N sources to match timing and risk: anhydrous ammonia and stabilized fall-applied products where appropriate; UAN for sidedress; NBPT-treated urea if surface-applied without incorporation.
• Maintain soil pH with lime where necessary; alfalfa, soybeans, and many forages are pH-sensitive and benefit from a higher target pH.
• Monitor sulfur and micronutrients–apply where soil tests or tissue tests indicate deficiencies rather than routine blanket applications.
• Adopt 4R stewardship: match source, rate, time, and place to field-specific conditions to maximize efficiency and minimize environmental loss.
• Integrate manure and organic nutrient sources into fertilizer plans by crediting available nutrients from manure tests.
• Use variable-rate technology, remote sensing, and in-season N tests (e.g., chlorophyll meters, remote sensing indices) to refine applications and reduce waste.
• Keep records of fertilizer application rates, sources, timing, and yields to improve future decisions.

Checklist before planting season:

• Verify recent soil test results and map field variability.
• Confirm pH targets and lime needs; prioritize lime on fields with legumes or sensitive crops.
• Select fertilizer source based on expected timing of application and risk of losses.
• Plan split N applications for corn and wheat; schedule sidedress windows.
• Check calibration of spreaders and applicators; ensure safe handling and storage.
• Consider inhibitors or stabilized products for fields with high denitrification or leaching risk.

Conclusion

Selecting the right types of fertilizers for South Dakota crops requires integrating soil test data, crop-specific nutrient demands, timing of rainfall and fieldwork, and environmental risk. No single fertilizer or practice fits every field. Emphasize soil testing, balanced nutrient programs (N, P, K, S, micronutrients), 4R stewardship, and split or in-season adjustments. With careful product selection and timing–banding where appropriate, using stabilized N sources when needed, and addressing pH and sulfur–growers can improve nutrient-use efficiency, protect water quality, and increase crop profitability across the diverse soils and climates of South Dakota.