How Much Fertilizer Per Acre? Rates by Crop

The amount of fertilizer per acre depends on the crop, soil test results, yield goal, and previous crop history. Without a soil test, you are guessing, and guessing usually means wasting money or leaving yield on the table. A basic soil test costs $15-$30 and pays for itself many times over.

For corn targeting 180 bushels per acre, a general starting point is 180-200 lbs of nitrogen (N), 50-80 lbs of P2O5, and 40-60 lbs of K2O per acre. Nitrogen is the primary driver of corn yield, and the rule of thumb is 1.0-1.2 lbs of N per bushel of expected yield. Split applications, with some N at planting and the rest as sidedress at V6-V8, improve efficiency by 10-15% compared to a single preplant application.

Wheat requires 60-120 lbs of N per acre depending on yield goal and variety. Soft red winter wheat typically needs 80-100 lbs N for a 60-70 bushel goal. Hard red winter wheat may need 100-120 lbs N for milling quality protein. Topdress nitrogen in early spring when wheat breaks dormancy.

Soybeans generally do not need nitrogen fertilizer because they fix their own through Rhizobium bacteria. However, they are heavy users of phosphorus (40-60 lbs P2O5 per acre) and potassium (80-120 lbs K2O per acre), especially at high yield levels above 50 bushels per acre.

To convert nutrient recommendations to actual product, divide the nutrient pounds by the analysis percentage. For example, if you need 150 lbs of N and are using urea (46-0-0), divide 150 by 0.46 to get 326 lbs of urea per acre. For DAP (18-46-0), 100 lbs of product supplies 18 lbs N and 46 lbs P2O5.

Soil pH affects nutrient availability more than any other factor. At a pH below 6.0, phosphorus and several micronutrients become locked up regardless of how much fertilizer you apply. Always correct pH with lime before investing heavily in fertilizer. The most expensive fertilizer in the world cannot overcome poor soil pH.

Manure and compost provide significant nutrients but require testing to know exact content. Dairy manure typically supplies 10-15 lbs N, 5-8 lbs P2O5, and 10-15 lbs K2O per ton. Credit these nutrients against your fertilizer recommendation to avoid over-application, particularly of phosphorus.