Growing Sweet Potatoes – Crop Nutrition 101

Soil Requirements for Sweet Potato Cultivation

Sweet potatoes perform best in light, sandy loam or silt loam soils with good surface and internal drainage. Soil structure significantly affects root shape and market quality: 

• Ideal pH: 5.8 to 6.0 (tolerant between 5.5–6.8) 

• Soil type: Sandy loams or leveled, slightly sloped fields 

• Avoid: Poorly drained, heavy clay soils that can cause malformed roots 

Maintaining proper soil pH and structure is essential. Use acidifying fertilizers (e.g., Nova products) or lime to correct pH outside the optimal range. Success in sweet potato production depends on proper field selection, tailored fertility programs, and efficient nutrient uptake—particularly potassium, which is required in higher quantities than nitrogen or phosphorus. 

Sweet Potato Nutrient Needs

A well-balanced fertility plan ensures healthy plant growth without sacrificing tuber development. Sweet potatoes are relatively low-input crops in terms of nitrogen and phosphorus, but they demand high potassium levels, especially in sandy soils with low cation exchange capacity. 

Primary Nutrients

• Potassium (K)
  Critical for cell elongation, drought resistance, water regulation, and tuber quality. Sweet potatoes remove large amounts of potassium at harvest, requiring replenishment. Yield responses to K are common. 

Recommendation: Use sulfate-based potassium sources like Polysulphate, which also supplies calcium, magnesium, and sulfur in plant-available forms.  An effective, multi-nutrient source, offering season-long availability; it can also replace gypsum for calcium enrichment while providing broader nutritional support. 

• Phosphorus (P)
  Important during early root development, particularly in weathered soils where phosphorus availability is limited. Over-application is often unnecessary in moderately fertile soils. 

• Nitrogen (N)
  Required for vine growth, but excess nitrogen can reduce yields by promoting excessive foliage instead of tuber formation. Split N applications and avoid high rates early in the season. 

Recommendation: applying a biostimulant or enhanced nutrient fertilizer like BIOZ, X-tra with Agrolution pHlow or Polysulphate as an early season program can improve nutrient uptake.  

Secondary Nutrients & Micronutrients

• Magnesium, Calcium, Iron: Contribute to photosynthesis, cell strength, and enzymatic activity 

• Sulfur: Aids in protein synthesis and supports root growth 

• Micronutrients: Boron, manganese, zinc, molybdenum, and copper may be required depending on soil tests 

Recommendation: Supplementing micronutrients—through targeted foliar applications and fertigation when soil supply is limited or uptake is restricted can help prevent deficiencies before they start. Nova and X-tra foliars provide highly compatible, economical options for mid-season foliar application. 

Fertility Management Best Practices

• Conduct soil testing before planting to determine baseline nutrient levels and pH 

• Apply balanced pre-plant fertilizers (broadcast or banded) based on soil test results 

• Use in-furrow side-dressings or fertigation once vining begins for sustained nutrient supply 

• Avoid over-fertilizing with nitrogen early in the season 

• Target sandy soils with low fertility for fertilization focus—these show the most yield response 

• Consider tissue testing, but know that incorporating mid-season foliars into fertility planning can help prevent deficiencies before they start.  

Common Fertility Challenges in Sweet Potato Production

• Low soil fertility in sandy or eroded fields 

• High potassium removal at harvest 

• Nutrient imbalances from improper fertilizer timing 

• Economic constraints tied to fertilizer input costs 

• Abiotic stress (e.g., drought, salinity, extreme temperatures) 

• Biotic threats such as weevils and root diseases

Recommended Products 

ICL solutions help meet the unique nutritional needs of sweet potato crops while improving fertilizer efficiency and reducing input costs. 

• Polysulphate® – A versatile, naturally sourced fertilizer delivering S, K, Mg, and Ca in granular sulfate form for season-long release. Low-salt, low-chloride, OMRI-approved, and neutral pH. 

• Nova FLOW (5-10-20 +9Mg)- Micronutrient foliar for mid-season nutrition that is highly compatible with most crop protection and fertilizer programs. This highly soluble foliar alternative to magnesium nitrate contains N-P-K, plus magnesium, sulfur, and boron to provide balanced nutrition during reproductive phases.

• BIOZ® Diamond 10-0-1 – Enhanced nutrient fertilizer that improves uptake by feeding microbes with molasses and yeast extract, proven in trials to improve nutrient uptake and lead to increase yields. 

• X-Tra – Advanced liquid micronutrients with amino acids, fulvic acids, and plant extracts for enhanced nutrient uptake and availability.

• CHALLENGE 8-32-5 – High-phosphorus liquid fertilizer with humic and lignosulfonic acids to boost root growth, nutrient uptake, and crop quality.

Regional Considerations 

Commercial sweet potato production is most successful in the southeastern United States, where acidic soils, warm temperatures, long growing seasons, and well-drained conditions provide optimal growing conditions. North Carolina and Louisiana lead in production due to their favorable climate, soil type, and long-standing agricultural expertise. In northern and Midwestern regions, shorter seasons and cooler temperatures can limit yields. However, with adjusted planting times, proper variety selection, and diligent field management, sweet potatoes can still be grown successfully in these areas. 

Contact an ICL expert for region-specific recommendations based on your soil conditions and production goals.