Ag PhD Crop Removal Calculator — Estimate Nutrient Removal by Crop

Quickly calculate nitrogen, phosphorus, potassium, and sulfur removal for corn, soybeans, wheat, and alfalfa using trusted Ag PhD removal rates. Plan your fertilizer replacement strategy with instant, step‑by‑step results.

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Ag PhD Crop Removal Calculator

Select a crop and enter your harvested yield to see how many pounds of N, P₂O₅, K₂O, and S are removed per acre.

bu/acre
Select a crop and enter yield, then click Calculate Removal.

Crop Nutrient Removal Formula Explained

Nutrient removal by a harvested crop is a simple multiplication of yield and the nutrient concentration in the harvested portion. The formula used in this calculator is:

Nutrient Removal (lbs/acre) = Yield (bu/acre or tons/acre) × Removal Rate (lbs/unit)

Variable Definitions

  • Yield — The harvested amount per acre, measured in bushels for grain crops (corn, soybeans, wheat) or tons for hay (alfalfa).
  • Removal Rate — The pounds of nutrient removed per bushel (or per ton) of harvested crop. These rates are based on Ag PhD’s published crop removal data.
  • N — Nitrogen (elemental N) removed.
  • P₂O₅ — Phosphate removed, expressed as phosphorus pentoxide equivalent.
  • K₂O — Potash removed, expressed as potassium oxide equivalent.
  • S — Sulfur removed.

Rates are crop‑specific and represent the average nutrient content of the harvested grain or hay. They do not include nutrients returned through crop residue.

How to Calculate Crop Nutrient Removal

Follow these steps to estimate nutrient removal using Ag PhD rates:

  1. Choose your crop — Select corn, soybeans, wheat, or alfalfa from the dropdown. The calculator automatically loads the correct removal rates per unit of yield.
  2. Enter the harvested yield — Type the yield in bushels per acre (grain) or tons per acre (alfalfa). Use your actual scale tickets or yield monitor data.
  3. Click Calculate Removal — The tool multiplies yield by each nutrient’s removal rate to show lbs/acre of N, P₂O₅, K₂O, and S.
  4. Interpret the results — Use the total removal values to plan fertilizer applications that replace what the crop removed, while considering soil test levels and other nutrient credits.

Crop Removal Calculation Examples

Example 1: Corn Grain at 200 bu/acre

Yield: 200 bu/acre. Corn removal rates: N 0.75, P₂O₅ 0.35, K₂O 0.25, S 0.08 lbs/bu.

N removal = 200 × 0.75 = 150 lbs N/acre
P₂O₅ removal = 200 × 0.35 = 70 lbs P₂O₅/acre
K₂O removal = 200 × 0.25 = 50 lbs K₂O/acre
S removal = 200 × 0.08 = 16 lbs S/acre

Example 2: Soybeans at 60 bu/acre

Yield: 60 bu/acre. Soybean rates: N 3.8, P₂O₅ 0.8, K₂O 1.4, S 0.18 lbs/bu.

N removal = 60 × 3.8 = 228 lbs N/acre
P₂O₅ removal = 60 × 0.8 = 48 lbs P₂O₅/acre
K₂O removal = 60 × 1.4 = 84 lbs K₂O/acre
S removal = 60 × 0.18 = 10.8 lbs S/acre

Example 3: Alfalfa Hay at 5 tons/acre

Yield: 5 tons/acre. Alfalfa rates: N 40, P₂O₅ 10, K₂O 50, S 5 lbs/ton.

N removal = 5 × 40 = 200 lbs N/acre
P₂O₅ removal = 5 × 10 = 50 lbs P₂O₅/acre
K₂O removal = 5 × 50 = 250 lbs K₂O/acre
S removal = 5 × 5 = 25 lbs S/acre

Real‑World Uses of Crop Removal Data

  • Fertilizer replacement planning: Determine how much N, P, K, and S must be applied to maintain soil test levels after harvest.
  • Variable‑rate prescriptions: Use removal maps to create zone‑based fertilizer applications that match nutrient export.
  • Rental agreement negotiations: Quantify nutrient value removed by a tenant to fairly adjust land lease terms.
  • Manure application planning: Compare manure nutrient content against crop removal to avoid over‑application.
  • Soil test interpretation: Combine removal estimates with soil test results to set realistic yield goals and fertility budgets.
  • Whole‑farm nutrient balance: Track nutrient inputs vs. removal across rotations to meet environmental regulations.

People Also Ask

Crop nutrient removal is the amount of nitrogen (N), phosphorus (P₂O₅), potassium (K₂O), and sulfur (S) that is taken up by a harvested crop and removed from the field. It does not include nutrients returned through crop residue.
Crop removal is calculated by multiplying the harvested yield by the crop’s nutrient removal rate per unit of yield. For example, corn grain removes about 0.75 lb N per bushel, so 200 bu/acre removes 150 lb N/acre.
Ag PhD lists removal rates for major crops: corn grain (0.75 N, 0.35 P₂O₅, 0.25 K₂O, 0.08 S lb/bu); soybeans (3.8 N, 0.8 P₂O₅, 1.4 K₂O, 0.18 S lb/bu); wheat (1.2 N, 0.6 P₂O₅, 0.3 K₂O, 0.1 S lb/bu); alfalfa hay (40 N, 10 P₂O₅, 50 K₂O, 5 S lb/ton).
Understanding nutrient removal helps farmers and agronomists determine how much fertilizer is needed to replace nutrients lost through harvest. It is essential for maintaining soil fertility, avoiding nutrient depletion, and planning cost‑effective fertilizer programs.
Not exactly. Crop removal indicates nutrients leaving the field, but fertilizer recommendations also consider soil test levels, nutrient availability, previous crop credits, and application efficiency. Crop removal is a starting point for building a balanced fertility plan.

Frequently Asked Questions

The calculator covers four major commodity crops: corn (grain), soybeans, wheat, and alfalfa (hay). Removal rates are drawn directly from Ag PhD’s published crop removal guidelines.
Rates are for the harvested portion only – grain for corn, soybeans, and wheat; hay for alfalfa. Nutrients remaining in stover, stalks, or roots are not included because those are typically left in the field.
Yes, the formula is linear, so it scales with any realistic yield. However, for exceptionally high yields, nutrient removal per bushel can vary slightly; the Ag PhD rates represent long‑term averages that remain reliable for planning.
Subtract your crop removal from your soil test nutrient levels to see if the soil is being depleted or built up. Most university recommendations combine removal estimates with soil test results to suggest a maintenance plus build‑up approach.
Alfalfa hay is a high‑biomass crop that accumulates large amounts of potassium in the plant tissue. Each ton of hay can remove 40–60 lbs of K₂O, making potassium management critical for maintaining alfalfa stands.
Silage corn removes significantly more nutrients because the whole plant is harvested. This calculator currently uses grain‑only rates; for silage, typical removal is about 7.5 lbs N, 3.5 lbs P₂O₅, 8 lbs K₂O, and 1 lb S per ton of silage at 65% moisture.

Crop Nutrient Removal Glossary

Nutrient Removal

The total amount of N, P₂O₅, K₂O, and S carried away in harvested grain or hay, expressed in pounds per acre.

Removal Rate

Pounds of nutrient removed per unit of yield (bushel or ton). Rates are based on average nutrient concentration of the harvested product.

Bushel (bu)

A volume measurement for grain. One bushel of corn weighs 56 lbs, soybeans 60 lbs, and wheat 60 lbs.

P₂O₅ (Phosphate)

The oxide form used to express phosphorus fertilizer recommendations. Actual phosphorus content is about 44% of P₂O₅.

K₂O (Potash)

The oxide form used to express potassium fertilizer recommendations. Actual potassium content is about 83% of K₂O.

Maintenance Fertilization

Applying nutrients at a rate equal to crop removal to keep soil test levels stable over time.

Soil Test

A laboratory analysis that measures plant‑available nutrient levels in the soil, used together with removal data to build fertility plans.

Crop Residue

Plant material left in the field after harvest (stalks, leaves, roots). Nutrients in residue are not considered removed and can become available for future crops.

Editorial Review & Methodology

This Ag PhD crop removal calculator was built and reviewed by the NumbrWiz Editorial Team. Nutrient removal rates are sourced from publicly available Ag PhD crop removal tables and cross‑checked against university extension publications (e.g., Iowa State University PM 1688, University of Illinois Crop Removal Rates).

  • Rate verification: Rates were confirmed against multiple land‑grant university and industry sources to ensure they reflect common Midwestern removal averages.
  • Calculation accuracy: The simple multiplication formula is tested with zero‑yield, fractional yields, and extreme values to ensure linearity and no rounding errors.
  • Practical applicability: Designed for corn‑soybean‑wheat‑alfalfa rotations common in North America; rates may need adjustment for specialty crops or double‑crop systems.

Transparency note: All calculations run locally in your browser. No yield data is ever stored or transmitted. Removal figures are for planning purposes; always consult a certified crop advisor and use soil tests for final fertilizer decisions.

Page last reviewed: May 2026 · NumbrWiz Editorial Team