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Clemson Ag Service Lab - Soil Testing

This free web app was developed to provide N, P, and K fertilizer recommendations for agricultural, turf, silvicultural, and home/garden producers based on Clemson Extension recommendations.

This calculator requires entry of soil test P₂O₅ and K₂O levels from a lab report. Fertilizer recommendations based on soil test results are scientifically supported and result in economic and environmentally sound fertility management. Clemson recommends testing soil every year on land that is intensively managed. To learn how to submit a soil sample to the Clemson Agricultural Service Laboratory, please click here.

Reports from the Clemson Ag Service Lab provide phosphorus and potassium fertilizer recommendations in alignment with those presented here. This web app allows you to update those recommendations, for instance, using a different crop code. Nitrogen (N), phosphorus (P₂O₅), and potassium (K₂O) fertilizer recommendations are calculated as functions of soil fertility test level, soil type, crop type, and (in some cases) yield goals. References for these fertilizer recommendations can be found at the bottom of the web app for more information.

This calculator does not assess secondary or micronutrients at this time, although comments for Clemson recommendations are provided, which address these nutrients. One benefit of this web app is the ability to integrate with our other online tools. NPK fertilizer recommendations can be output in several different rate units and recommendations can be pushed to our Fertilizer Blend Calculator for optimizing fertilizer rates and costs.

Be sure to visit our other free fertility-related web apps and calculators from Clemson Precision Ag, including: Lime Rate Calculator, Soil Acidification Calculator, Drip Fertigation Calculator, Pivot Fertigation Calculator, and Liquid Fertilizer Solution Calculator.

(...click for less)

This web app was developed to provide N, P, and K fertilizer recommendations for agricultural, turf, silvicultural, and home/garden producers based on Clemson Extension recommendations. (...click for more)

References:

• Clemson Ag Service Lab. Fertility recommendations and nutrient management: Agronomy. Clemson University. Retrieved from https://www.clemson.edu/public/regulatory/ag-srvc-lab/soil-testing/pdf/agronomic_crops.pdf.
• Clemson Ag Service Lab. Fertility recommendations and nutrient management: Crop codes. Clemson University. Retrieved from https://www.clemson.edu/public/regulatory/ag-srvc-lab/soil-testing/pdf/cropcodes121907.pdf.
• Clemson Ag Service Lab. Fertility recommendations and nutrient management: Flowers, shrubs, and trees. Clemson University. Retrieved from https://www.clemson.edu/public/regulatory/ag-srvc-lab/soil-testing/pdf/flowers-shrubs-trees.pdf.
• Clemson Ag Service Lab. Fertility recommendations and nutrient management: Fruits. Clemson University. Retrieved from https://www.clemson.edu/public/regulatory/ag-srvc-lab/soil-testing/pdf/fruits.pdf.
• Clemson Ag Service Lab. Fertility recommendations and nutrient management: Home owner, golf green. Clemson University. Retrieved from https://www.clemson.edu/public/regulatory/ag-srvc-lab/soil-testing/pdf/turf.pdf.
• Clemson Ag Service Lab. Fertility recommendations and nutrient management: Major nutrients. Clemson University. Retrieved from https://www.clemson.edu/public/regulatory/ag-srvc-lab/soil-testing/pdf/plant-nutrient-levels.pdf.
• Clemson Ag Service Lab. Fertility recommendations and nutrient management: Small area (Square footage). Clemson University. Retrieved from https://www.clemson.edu/public/regulatory/ag-srvc-lab/soil-testing/pdf/sq-foot-recommendations.pdf.
• Clemson Ag Service Lab. Fertility recommendations and nutrient management: Soil test rating system. Clemson University. Retrieved from https://www.clemson.edu/public/regulatory/ag-srvc-lab/soil-testing/pdf/rating-system.pdf.
• Clemson Ag Service Lab. Fertility recommendations and nutrient management: Subsoil. Clemson University. Retrieved from https://www.clemson.edu/public/regulatory/ag-srvc-lab/soil-testing/pdf/subsoil.pdf.
• Clemson Ag Service Lab. Fertility recommendations and nutrient management: Vegetables. Clemson University. Retrieved from https://www.clemson.edu/public/regulatory/ag-srvc-lab/soil-testing/pdf/vegetables.pdf.
• Clemson Ag Service Lab. Fertility recommendations and nutrient management: Wildlife. Clemson University. Retrieved from https://www.clemson.edu/public/regulatory/ag-srvc-lab/soil-testing/pdf/wildlife.pdf.

APA Citation:
Kirk, Kendall R., Alford, Shannon R., Croft, Jonathan, and Davis, Charles (2022). NPK Recommendation Calculator. Clemson University Cooperative Extension. Retrieved from https://www.clemson.edu/extension/agronomy/PrecisionAgriculture/calculators/

(c) 2022 Clemson University Cooperative Extension

The authors are grateful for the many individuals that helped to review this tool during its development. Thank you to Dan Anco, Justin Ballew, Matt Burns, Brian Callahan, Jay Crouch, Matt Fischer, Ben Fogle, Rob Last, Fleming McMaster, Chris Ray, Scott Sell, Bryan Smith, Zack Snipes, and James Thomas.

Disclaimer: This calculator is brought to you as a free service by Clemson University Cooperative Extension. The accuracy of the calculator is not guaranteed. User assumes all risks and liabilities from its use.

We are dedicated to making this a valuable tool for you. If you have suggestions for improvements, please contact us by email.