What leaves the field when you bale stalks, chop silage or sell hay
Sigurd Lindquist, Certified Crop Adviser (CCA), Chetek, Wisconsin
Every ton of stalks, straw, silage or hay you haul off takes phosphate and potash with it. Here is how much, by crop, and what it costs to buy it back at fertilizer prices Kansas co-ops posted through the latest read. Potash is most of the bill.
Pounds from UW Extension A2809, Table 4.2. Stalks, straw and hay are per ton of dry matter. Nitrogen and sulfur are left out: A2809 gives no N or S removal per ton, and we print only what we have read in a published table.
- N a lb loading
- P₂O₅ a lb loading
- K₂O a lb loading
Where these prices come from and the math
Every price comes from the one list behind fertilizer prices: the middle cash price Kansas farm co-ops post on their own websites, read each weekday, each with its co-ops and date. Nothing here is typed in by hand. Phosphate is priced from the cheapest product on the list that carries P, after the nitrogen in it is credited at the cheapest straight N price. Potash is potash. Nitrogen is only shown for that credit.
- Loading the price list.
Your dealer’s price will differ, and Kansas is not everywhere. Put your own pounds and prices through the same math.
Calculator
Pick what you are hauling off and put in your yield. For bales, put in your bale weight and moisture and the sale price if you sell them. It shows the pounds of P₂O₅ and K₂O leaving, and what they cost to put back per ton, per bale, per acre and for the field.
The calculator needs JavaScript. The table below gives the pounds without it.
Removal by crop
Pounds of P₂O₅ and K₂O in one unit of what is harvested, and what that costs to put back at the prices above. Bales are counted by the dry ton; the next column is a ton as baled at 15% moisture (0.85 dry ton).
| Crop | lb P₂O₅ | lb K₂O | P and K cost to replace | Per ton as baled, 15% | A2809 yield range an acre |
|---|---|---|---|---|---|
| Corn | |||||
| Corn stalks (stover) per dry ton | 4.6 | 32 | 1 to 5 ton DM | ||
| Corn silage per ton at 65% moisture | 3.6 | 8.3 | 10 to 40 ton | ||
| Corn grain per bu at 15.5% | 0.38 | 0.29 | 70 to 290 bu | ||
| Soybeans | |||||
| Soybean stubble (straw) per dry ton | 5.4 | 19 | 2 to 4 ton DM | ||
| Soybean grain per bu at 13% | 0.8 | 1.4 | 15 to 105 bu | ||
| Small grains | |||||
| Wheat straw per dry ton | 6 | 28 | 1.5 to 3.5 ton DM | ||
| Wheat grain per bu at 13.5% | 0.5 | 0.35 | 20 to 120 bu | ||
| Oat straw per dry ton | 9.4 | 47 | 1 to 3 ton DM | ||
| Oat grain per bu at 14% | 0.29 | 0.19 | 30 to 120 bu | ||
| Barley straw per dry ton | 10 | 32 | 1 to 3 ton DM | ||
| Barley grain per bu at 14.5% | 0.4 | 0.35 | 25 to 100 bu | ||
| Small grain silage per dry ton | 11 | 44 | 2 to 3.5 ton DM | ||
| Hay | |||||
| Alfalfa hay per dry ton | 13 | 60 | 2.6 to 9.5 ton DM | ||
| Red clover hay per dry ton | 13 | 60 | 1 to 6.5 ton DM | ||
| Grass hay per dry ton | 15 | 55 | 0.5 to 8 ton DM | ||
| Mixed hay, over 30% legume per dry ton | 13 | 60 | 0.5 to 5 ton DM | ||
| Mixed hay, 30% legume or less per dry ton | 13 | 51 | 0.5 to 5 ton DM | ||
Source: UW Extension A2809, Nutrient Application Guidelines for Field, Vegetable, and Fruit Crops in Wisconsin (Laboski and Peters), Table 4.2, crop removal in lb per unit of yield. The copy UW posted in March 2026 and the 2022 county copy have the same numbers for every crop here. Grain is per bushel at the moisture A2809 reports it. Mixed hay uses A2809’s legume-grass lines, which it lists under pasture.
What is not on this page yet
- Nitrogen and sulfur. A2809 gives no N or S removal per ton. They go on once a published table (Iowa State PM 1688, the Tri-State guide or Penn State’s Agronomy Guide) is saved and read. Even then, N in stalks and straw is mostly tied up in the residue, so it will be shown on its own line, not in the replacement total.
- Earlage and high-moisture corn. Not in A2809. Not shown until a source gives them.
- Other sources side by side. Removal numbers differ a little from guide to guide. When a second source is read, its range goes here next to A2809’s.
Reading it right
- This is replacement cost, not a price for your bales. What a bale sells for depends on your market. This shows the fertilizer side of the trade so you know what you are giving away.
- Weigh some bales. A2809 counts by the dry ton. Bale weight and moisture move the per-bale number more than anything else here.
- Soil test level matters. On ground testing high in K, the potash leaving may not need to go back right away. On ground at or below optimum it does.
- Stalks are more than P and K. Residue also holds soil, feeds organic matter and catches snow. Those are real but are not priced here.
Questions
How much P and K is in a ton of corn stalks?
UW Extension A2809 puts corn stover at 4.6 lb of P₂O₅ and 32 lb of K₂O per ton of dry matter (Table 4.2). A ton of bales at 15% moisture is 0.85 dry ton, so about 3.9 lb of P₂O₅ and 27 lb of K₂O. At 3 dry tons an acre that is about 14 lb of P₂O₅ and 96 lb of K₂O leaving each acre. Potash is most of the dollar value.
What is the fertilizer value of a bale of corn stalks?
Multiply the dry tons in the bale by 4.6 lb of P₂O₅ and 32 lb of K₂O, then by the price of a pound of each. A 1,000 lb bale at 15% moisture is 850 lb of dry matter, 0.425 dry ton: about 2 lb of P₂O₅ and 13.6 lb of K₂O. The calculator on this page prices it at today's posted co-op prices and shows the date. Weigh a few of your own bales; weight and moisture move the answer more than anything else.
Why is nitrogen not counted?
The source for these pounds, UW Extension A2809, gives P₂O₅ and K₂O removal for every crop but no N or S removal per ton. We do not fill in a number we have not read in a published table. Nitrogen in stalks and straw is also mostly tied up in residue and is not there for next year's crop the way a pound of fertilizer N is, so P and K are the honest replacement cost.
How much P and K does corn silage take off?
A2809 lists corn silage at 3.6 lb of P₂O₅ and 8.3 lb of K₂O per ton at 65% moisture. A 20 ton crop takes about 72 lb of P₂O₅ and 166 lb of K₂O an acre, more than twice the potash that 180 bushels of grain take (52 lb), because the stalks and leaves leave too.
How much do soybeans, wheat and hay remove?
Per A2809 Table 4.2: soybeans 0.8 lb P₂O₅ and 1.4 lb K₂O a bushel; wheat 0.5 and 0.35 a bushel, wheat straw 6 and 28 per dry ton; oat straw 9.4 and 47; alfalfa 13 and 60 per dry ton; grass hay 15 and 55 per dry ton.
Where do the fertilizer prices come from?
From the same list as the fertilizer prices page: the middle cash price that Kansas farm co-ops post on their own websites, read each weekday, with the co-ops and the date on every price. Phosphate is the cheapest P product on that list after its nitrogen is credited, potash is potash, and the nitrogen credit uses the cheapest straight N product. Your dealer's price will differ; the math is shown so you can redo it.
Related
Book values are averages. A forage test of your own hay or stalks beats the book. Questions or a number that looks wrong: contact me. Sig