Manage Fertilizer Costs with Soil Testing and Planning

By Blake Jackson

Fertilizer prices are inherently volatile due to their energy-intensive production, reliance on global supply chains, and sourcing from regions with geopolitical risk.

According to Charles White, Professor of Soil Fertility, and Robert Meinen, Director of the Pennsylvania Nutrient Management Education Program at Penn State Extension, these price spikes should be expected, not viewed as unusual. Strategic fertility planning is essential to help farms remain resilient during sudden price increases.

A cornerstone of managing fertilizer costs is regular soil testing. Testing each field at least once every three years helps farmers identify which fields require immediate nutrients and which can temporarily forego applications.

During high-price periods, this allows limited fertility resources to be allocated strategically. Fields with soil test phosphorus (P) and potassium (K) in the optimum range-30-50 ppm P and 100-150 ppm K (or 200 ppm K for forages) can often maintain yields without additional fertilizer in the short term.

However, caution is advised near the lower end of the range, especially for potassium, which is less buffered than phosphorus. Building soil test levels toward the mid-range when prices are lower provides a buffer for future savings.

Farms with access to manure can reduce dependency on commercial fertilizers. Liquid manure applied through low-disturbance injection can replace a significant portion of nitrogen needs while reducing losses.

Prioritizing fields with low soil test levels for manure application maximizes nutrient use, while exporting excess phosphorus or potassium can generate revenue.

The Penn State Manure Economic Value Calculator helps determine the cost-effectiveness of manure relative to commercial fertilizer.

For example, importing poultry litter at $38 per ton instead of buying fertilizer saved $39 per acre while improving long-term soil health.

Diagnostic tools, such as Penn State’s nitrogen recommendation tool and the pre-sidedress soil nitrate test (PSNT), can help refine nitrogen applications, ensuring farms apply only what is necessary and avoid waste.

By adopting a soil test-driven, data-informed approach that combines targeted fertilizer use, effective manure management, and diagnostic tools, farms can manage fertilizer volatility, maintain profitability, and enhance long-term soil productivity.

FAQs

• Why do fertilizer prices fluctuate?

They are energy-intensive to produce and influenced by global supply chains and geopolitical risks.

• How often should I test my soil?

At least once every three years for each field.

• Can manure replace commercial fertilizers?

Yes, properly managed manure can reduce or replace nitrogen and other nutrients.

• What is the optimal soil test range for phosphorus?

30-50 ppm P on a Mehlich 3 extract.

• Does exporting excess manure have benefits?

Yes, it can generate revenue and reduce nutrient buildup on the farm.

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