FERTILIZER BLEND OPTIMIZER · RUNS IN YOUR BROWSER · NOTHING UPLOADED

What is the cheapest fertilizer program that still hits your nutrient targets?

List the products you can buy with a price per ton and their grade, enter the pounds per acre of N, P2O5, K2O and S your crop needs, and a linear-programming solver finds the lowest-cost pounds of each product per acre. It totals the field cost and tons to buy, prices one more pound of each nutrient, shows the price at which an unused product would start to pay, and compares the result with the obvious one-product-per-nutrient plan.

The starter list uses standard grades and example prices: edit every price to your dealer's quote. The crop presets are rounded rules of thumb, so set the targets from your soil test and extension recommendation. New to this? Read how to calculate the cheapest fertilizer blend, with a worked example.

1. Products

2. Field and targets

Add your products and targets, then click Find the cheapest program.

How it works

Model: choose pounds x of each product per acre to minimise the sum of price times pounds, subject to each nutrient you set a target for being delivered at or above the target (and below your overshoot limit, if you set one), and each product staying under its maximum. Multi-nutrient products such as DAP, MAP and ammonium sulfate are credited for everything they carry. That is a linear program, solved with a two-phase simplex that cannot cycle.

Cost of one more pound: it raises one target by 10 lb per acre, re-solves and divides the extra cost by 10. When a product would pay: it lowers an unused product's price by bisection until the cheapest blend starts to use it. The obvious plan: for each nutrient, the single product with the lowest price per pound of that nutrient, either bought on its own for every nutrient or crediting what earlier purchases carried (phosphate, potash, sulfur, then nitrogen).

Not modelled: your soil test, crop stage and rate response, application method and timing, nitrogen loss and stabilizers, seed-placed salt and burn limits, lime and pH, micronutrients, delivery, freight and application cost, bag, tote or bulk minimums, and local nutrient rules. The crop presets are rounded rules of thumb, not recommendations. Unverified against real farm programs: checked against exhaustive vertex enumeration on small product lists, against random blends, and by an independent feasibility check on every result.

Common questions

How do I find the cheapest fertilizer program that still hits my N, P and K rates?

List every product you can buy with its price per ton and grade, enter the pounds per acre of N, P2O5, K2O and S you want, and the optimizer finds the pounds of each product per acre with the lowest cost that meets every target. Products that carry more than one nutrient, such as DAP, MAP and ammonium sulfate, are credited for everything they supply. It solves a linear program, the classic least-cost blend problem.

Are the crop rates accurate?

No. The presets are rounded rules of thumb for a typical field and are labelled approximate. Fertilizer rates depend on your soil test, yield goal, previous crop, manure, irrigation and local rules. Use your soil test and your extension service's recommendation to set the targets, then use this tool to price the cheapest way to meet them.

What does the cost of one more pound of a nutrient mean?

For each nutrient the optimizer raises the target by 10 pounds per acre, re-solves, and divides the extra cost by 10. That is what the next pound really costs you given the whole product list, which can differ a lot from the price on the invoice because the phosphate product also carries nitrogen.

What does 'a product would enter the blend below this price' mean?

For each product the optimizer left out, it lowers that product's price until the cheapest blend starts to use it. That is the quote you should ask for, or the point at which an offer becomes worth taking.

How is the savings figure calculated?

The obvious plan buys, for each nutrient, the single product with the lowest price per pound of that nutrient. One version buys every nutrient on its own with no credit for what else the product carries; the other credits those nutrients as it goes, in the order phosphate, potash, sulfur, nitrogen. The savings are the cost of that plan minus the optimum. Neither version looks at application cost, timing or crop safety.

Is this agronomic advice?

No. It does arithmetic on the numbers you give it. It does not look at your soil, crop stage, application method, salt or burn risk, nitrogen loss, micronutrients, lime or local nutrient rules. Use a certified crop advisor, your soil test and your extension service before you change a fertility program.

Are my field and prices uploaded or stored?

No. Everything runs in your browser, nothing is sent to a server, there are no accounts, and nothing is saved when you close the page. Download the plan as a CSV to keep it.