Fertilizing Hay Fields: A Soil-Test-First Guide to Lime, Potash & Nitrogen

By the XES Netting team — bale net-wrap manufacturer · Updated August 16, 2026 · ~13 min read

Hay is a mining operation. Every loaded wagon carries off nutrients the soil spent the season pulling up, and unlike grain or pasture, almost none of it cycles back — no stalks left standing, no manure dropped in the field. Skip the replacement and yields slide, stands thin, and your test numbers fall, usually a few years before anyone connects it to fertility. Yet plenty of ground gets nothing. One producer eyeing a load of free lime admitted his fields "had never been limed that I know of (15+ years)" (HayTalk).

This guide lays out hay-field fertility in the order that actually matters — soil test, lime, potassium, phosphorus, then nitrogen for grass — and then does the part most fertility articles skip: converting those numbers into pounds of actual product per acre. It draws on nutrient-management guides from Penn State, Virginia Cooperative Extension, Utah State, Iowa State, and Colorado State Extension, checked against what hay producers actually see in the field.

Start with a soil test, every time

A soil test costs a few dollars an acre and is the only way to know what your ground actually needs. Without one you are either wasting money on nutrients that are already sufficient or starving the one that is limiting yield — and you cannot tell which. The forum veterans say it more bluntly than any extension bulletin. When a grower asked about liming blind, the reply was immediate:

"Do you have a soil test? Go into this blind, and you will create yourself a world of hurt."

— TJH, HayTalk — Lime on hay ground

Pull a representative composite — 15 to 20 cores per field, zig-zagged across the area — and sample the same fields the same way every two to three years so you can watch trends. Colorado State Extension recommends 15 to 20 cores taken 8 inches deep, and says sampling every three years is sufficient for most established forage stands.

Depth matters more than most people realize, and it is lab-specific. An established hay field is not being plowed, so "plow depth" is the wrong instruction. For established grass hay, sample the top 6 to 8 inches. For alfalfa, some state labs — Utah State among them — calibrate their phosphorus recommendations to a 12-inch sample, and sending them a 6-inch core will give you a recommendation their tables were never built for. Ask your lab which depth its recommendations assume, then sample that depth every time so your numbers stay comparable year over year.

Test before establishing a new stand, because lime and phosphorus are far easier to work in before seeding than to fix afterward — something worth planning around when you are establishing an alfalfa stand. The report tells you pH, phosphorus, potassium, and usually organic matter and micronutrients; everything below depends on reading it first.

pH and lime: the master variable

Soil pH governs whether every other nutrient is actually available to the plant, so it comes first — but the target is crop-, soil- and lab-specific, not one national number. Published examples, to show the spread rather than to be copied:

• New Jersey (Rutgers): alfalfa is managed to a near-neutral target, in the 6.5–7.0 region on typical mineral soils.
• Pacific Northwest (Oregon State): alfalfa fertility guidance is written around regional soil conditions, where lime need and target pH differ substantially from the Northeast.
• Mid-Atlantic (Virginia Coop. Extension 452-703): cool-season grasses are managed at a lower target than alfalfa, and lime recommendations come off a buffer pH rather than the water pH alone.

Three things matter more than memorising a number. First, use the target your own lab sets for your crop on your soil — organic and high-organic-matter soils behave differently from mineral soils. Second, lime rate comes from buffer pH (sometimes called SMP or Adams-Evans depending on the lab), which measures the soil's reserve acidity; the water pH alone tells you the problem but not the dose. Third, check the liming material: its effective neutralizing value (ENV/ECC/RNV) determines how much you spread for the same pH change, and a dolomitic lime also supplies magnesium, which is worth choosing deliberately where soil magnesium is low or where grass tetany is a concern in the grazing herd.

The catch with lime is time: it can take 6 to 12 months — sometimes longer — to fully react and move pH, so it has to go on ahead of need, ideally worked in before a new seeding. Virginia Cooperative Extension goes further on established sod: surface-applied lime on a standing hay field changes pH mostly in the very top layer of soil, because there is no way to mix it into the root zone. That is the real argument for getting lime right at establishment. Trying to start alfalfa in sour ground is a losing battle, as one grower found when his soil test landed on the alfalfa field:

"I was hoping to plant alfalfa this fall until my soil test came back… the field for alfalfa had a ph of 5.6."

— OKrookie, HayTalk — 5.6 pH, will pelletized lime help?

At pH 5.6 that field needs lime and a season to react before alfalfa has a chance. Match the lime rate to your soil test's buffer recommendation, and remember not all liming materials are equal — a product's neutralizing value determines how much you spread to hit the same pH change. Where a large correction is called for, Virginia Extension suggests splitting it: apply half now and the remainder in six to 12 months.

Potassium: the big one for hay

If you remember one nutrient for hay, make it potassium. Hay crops are luxury consumers of K and remove enormous amounts of it — alfalfa hauls off roughly 50 to 60 pounds of K₂O per ton, and grass hay is in the same range at about 50 pounds per ton. Cut four or five tons an acre and you are removing 200–300+ pounds of K₂O every year. Potassium drives stand persistence, winter survival, and disease resistance; chronically short K is the quiet reason a lot of alfalfa stands thin out early — often misread as winterkill or age when it is really fertility, and a common reason growers end up trying to thicken a thin hay field.

Two practical cautions from people who fertilize hay for a living. First, timing: research favors fall application, though cash flow pulls many growers to spring. As one put it, "the best time for application is a fall application. I've always applied mine in the real early spring… because of pre-buy prices" (rjmoses, HayTalk). Either works. Set the rate from your soil test recommendation rather than from a removal figure.

Second, do not overdo it. Alfalfa will take up far more K than it needs — University of Wisconsin Extension calls this "luxury consumption", and it happens whenever soil or applied K is plentiful. Forage that tests high in potassium creates problems in the feed ration rather than in the field. High dietary potassium raises the dietary cation-anion difference — DCAD, which is calculated on a milliequivalent basis as [(%Na ÷ 0.023) + (%K ÷ 0.039)] − [(%Cl ÷ 0.0355) + (%S ÷ 0.016)] in mEq per 100 g of dry matter — which makes it harder to prevent milk fever in close-up dry cows, and high-K forage is likewise a factor in grass tetany risk in grazing beef cattle, where the potassium–magnesium–calcium balance of the whole diet is what matters. There is no single forage potassium percentage that is universally "too high": it depends on the animal class, the stage of production and what else is in the ration, and it is a call for the herd's nutritionist or veterinarian working from the total ration, not a number off a hay test alone. What matters to you in the field is simply that over-applying potash can make hay harder to sell into those markets. One grower ran straight into the commercial version of that:

"I only put down 20 pounds per acre. But was getting over 2.8%. Its high enough the daries wont buy my second cut anymore. Most of them just look at high k levels."

— hog987, HayTalk — Potassium in Alfalfa

His 2.8% figure is one buyer's purchasing rule, not a published safety threshold — but it shows how a fertility decision turns into a marketing one. The practical answer is to apply potash to your lab's recommendation rather than to a removal calculation, split larger amounts across the season instead of dumping them at once, and let soil and forage tests set the rate. If you sell into the dairy market, a forage test that reports potassium is worth having before you go looking for buyers.

Phosphorus: roots and stand life

Phosphorus is the quieter partner: hay removes far less of it than potassium, but it is critical for root development, seedling vigor, and long-term stand productivity. Published removal figures land in the 12 to 20 pounds of P₂O₅ per ton range depending on the state and the crop — Utah State's alfalfa table gives about 12 lb per ton, while Penn State and Iowa State put forage generally at 15 to 20 lb, and Virginia Extension puts tall-grass hay at 16 lb per ton. Those figures describe removal, not what to apply — take the phosphate rate from your soil test recommendation, which on a high-testing field may be nil.

Phosphorus barely moves in the soil, so the highest-payoff time to apply it is before seeding, worked into the root zone where new plants can reach it. On established stands, topdress to maintain the soil-test level your lab recommends. Keep phosphorus and potassium in balance rather than chasing one: research on alfalfa treats P and K as working together to build the taproot reserves that carry a stand through winter, so letting P slide while pouring on potash does not buy you a healthier stand.

Nitrogen: grass needs it, legumes don't

This is the split that confuses the most people, and it needs its qualifiers.

An established, effectively inoculated, well-nodulated pure alfalfa or clover stand normally needs no nitrogen fertiliser. Working Rhizobium nodules supply the crop, and applied N on such a stand is largely wasted and mostly feeds weeds. Three situations sit outside that rule:

• New seedings. Before nodulation is established the seedling has no fixation to draw on, and some states' establishment guidance includes a small starter nitrogen allowance. Follow your local establishment recommendation rather than assuming zero.
• Inoculation failure. Fixation depends on the right rhizobia actually being present and active — which is why seed is inoculated, why inoculant has a shelf life and dislikes heat, and why sour soil suppresses nodulation. If a stand is pale and poorly nodulated, dig roots and look for pink, active nodules before deciding the problem is fertility.
• Grass–legume mixed stands. Here nitrogen is a lever that changes the botanical composition: N favours the grass and shades out the legume, so a mixed stand is usually managed with little or no N, and the legume itself is the nitrogen source for the grass.

Grasses do not fix nitrogen and respond strongly to it — on pure grass hay, nitrogen is usually the single biggest yield lever.

There is no single national nitrogen rate for grass hay, and the published planning figures are explicitly scoped to a region and a system. Use them to see the shape of the decision, then take your number from your own Extension service:

The decision is really per cutting, not per season: set each application against the yield you realistically expect from the next cutting given your species, current soil moisture and the calendar. Split the application — a shot at green-up and more after each cutting — rather than front-loading it in spring, which wastes nitrogen and can lodge the crop.

Getting the nitrogen into the plant, not the air or the ditch

Rate is only half of it; a correctly calculated rate can still be largely lost. Mississippi State's guidance on urea-based fertilizers in forage production covers the main failure mode: surface-applied urea on a warm, moist soil surface hydrolyses and can lose a substantial share of its nitrogen to the air as ammonia before it ever reaches the roots. Practical mitigation is to time application ahead of rainfall or irrigation heavy enough to move the urea into the soil — and "enough" is a regional number:

• Mississippi State looks for more than 0.1 inch of rainfall within about 2 to 3 days of application in its forage urea guidance.
• Penn State works to a larger figure, on the order of 0.5 inch, for Pennsylvania conditions.

Take the threshold from your own Extension service rather than splitting the difference, and avoid applying ahead of a forecast heavy enough to produce runoff — the rain that incorporates urea and the rain that carries it off the field are not far apart. A urease-inhibitor-treated product is a useful tool when you cannot time the weather, but be clear about what it does: it extends the window before ammonia volatilization becomes serious. It does not stop runoff and it does not stop leaching.

• Do not spread on frozen or snow-covered ground, or on saturated soil — there is nowhere for the nutrient to go but off the field. The national USDA-NRCS Conservation Practice Standard 590 (Nutrient Management) requires that applications meet applicable state criteria; what actually governs your field is your current state Field Office Technical Guide, your nutrient management plan, and state law. Several states set specific setbacks and winter-application restrictions. Check yours before spreading.
• Keep applications back from waterways, wells and sinkholes, and watch for runoff risk when heavy rain is forecast.
• In a developing drought, cut the nitrogen rate. The yield you were fertilising for is not coming, and unused nitrogen in a stressed grass crop turns into a livestock problem — see K-State on nitrates in drought-stressed forages. If a heavily fertilised grass or small-grain crop goes through drought, test the forage for nitrate before feeding it.

On a grass-legume mix, go light on N: heavy nitrogen favors the grass and shades out the legume, gradually tipping a nice mixed stand toward pure grass. Match the rate to a realistic yield goal, not wishful thinking — our guide to hay yield per acre is a good sanity check before you set that number, and species matters too, since a tall fescue stand and a smooth brome stand do not respond to nitrogen the same way.

Sulfur, boron and the micros

Two secondary nutrients earn attention on hay ground, and both are diagnosis-first nutrients — there is no national rate worth copying.

Sulfur. Atmospheric sulfur deposition has fallen as power-plant emissions declined, so ground that used to get sulfur free in rainfall no longer does — noted by both Penn State and Virginia Extension. Response is most likely on sandy, low-organic-matter soils. But before applying, count your sulfur credits: manure and compost carry sulfur, and in many irrigated regions the irrigation water itself supplies a meaningful amount — enough that Western guidance often finds no response where Eastern guidance would predict one. Published rates are scoped examples, not prescriptions: Penn State suggests roughly 20–25 lb S/acre for legumes and 8–12 lb for grasses in Pennsylvania where deficiency is suspected; Utah State suggests 10–20 lb/acre in Utah when the soil test reads below about 8 ppm. Diagnose with a soil test plus, ideally, plant tissue analysis, since soil sulfate tests are notoriously variable.

Boron is the classic alfalfa micronutrient — deficiency shows as yellowed, stunted top growth — but the dose is small and the margin between enough and too much is narrow, so it is the last nutrient you ever want to guess at. University of Minnesota Extension describes it as a fine line between meeting the boron requirement and boron toxicity. Published state rates differ — Penn State's routine topdress rate is 2 lb of actual boron per acre in Pennsylvania; Virginia Extension goes to 2–4 lb where a soil test reads below 1 ppm in Virginia — which is itself the argument for taking the rate from your own lab rather than from an article. Note that rates are quoted as pounds of actual boron, not pounds of product; boron fertilisers vary widely in analysis and mixing that up is an easy way to overdose a field.

A grower on HayTalk gave the right instinct, and it is worth stating precisely where it stops:

"Do a soil test and specifically have it tested for Boron in addition to the others and it will tell you precisely what you need."

— Vol, HayTalk — Boron and potash on alfalfa

A soil test is the right first move, but it does not "tell you precisely what you need" for boron. Soil boron tests are poorly calibrated in many states and are best read alongside plant tissue analysis and local field-response data; your lab and agronomist interpret them together. Then:

• Apply only when a locally calibrated diagnosis calls for it, at the rate your lab specifies, expressed as actual boron.
• Get it spread uniformly. The application rate is a pound or two across an acre, so boron is normally blended into a carrier or applied in a uniform mix rather than spread neat — uneven spreading produces toxic streaks at the same average rate.
• Mind the companion and following crop. Boron carried over can injure a sensitive crop such as corn or soybeans in the next rotation, and on a grass–legume mix the grass tolerates less boron than the alfalfa does.

Do not buy a "complete" micronutrient blend on faith — on most hay ground the macros and pH are what limit yield, and a properly interpreted test will tell you if a micro is genuinely short.

Removal figures: what they do and don't tell you

Removal figures answer a different question from "what should I apply". They tell you how fast a field runs down if nothing goes back — which is why a hay field that has never been fertilised keeps testing lower. Use them for understanding, and use your lab's recommendation for the rate. The published figures below are typical values from Midwest and Mid-Atlantic Extension sources, on a dry-matter basis, and vary with species, maturity, soil and moisture basis:

Nutrient removed per ton	Alfalfa	Grass hay
Potassium (K₂O)	50–60 lb	~52 lb
Phosphorus (P₂O₅)	12–20 lb	~16 lb
Nitrogen (N)	fixes its own	40–50 lb*

*Grass nitrogen is supplied by the grower, and the planning figure is regional — Penn State publishes about 50 lb of actual N per ton of expected yield for Pennsylvania; Colorado State publishes 30–50 lb per ton for irrigated cool-season grass in Colorado. Sources for the removal figures: Utah State (alfalfa, dry-matter basis), Iowa State, Penn State and Virginia Coop. Extension 452-703 (tall-grass hay). These are bookkeeping values, not application rates. Your soil test and local lab recommendation set what you actually apply.

The shape of that table is worth noticing: hay removes considerably more potassium than phosphorus. That is why potassium is usually the nutrient that quietly runs down on hay ground, and why a stock blend with equal parts of each may or may not suit a given field — a question the section on blends works through against an actual recommendation.

How much fertilizer per acre? Work it in this order

Here is the step most fertility articles get backwards. Removal figures do not tell you what to apply. They explain why hay ground runs down — useful for understanding, useless as a prescription, because they take no account of what is already in your soil, what you have already applied, or what your crop actually responds to on your ground. The recommendation comes from your lab; removal is just bookkeeping behind it.

The order that produces a defensible number:

1. Start with your lab's crop-specific recommendation. Sample correctly, tell the lab the crop and a realistic yield goal, and use the rate it returns for your soil test level. This is the number to hit — not a removal calculation.
2. Subtract every credit you have. This is where most of the money is saved:
   • Manure or compost applied this year or recently, at its analysed nutrient content
   • Prior-crop and legume credits — nitrogen left by a legume in the rotation or by a terminated legume stand
   • Irrigation water, which in many regions supplies meaningful sulfur and sometimes nitrate

   Count each credit once, and do not subtract residual soil fertility. Your soil test level is already reflected in the recommendation itself — that is why a high-testing field gets a smaller number. Subtracting it again double-counts and will under-fertilise the crop.

3. Convert what is left into product. Pounds of nutrient still needed ÷ the decimal analysis on the bag = pounds of product per acre.

On soils testing high in phosphorus or potassium, the correct recommendation is frequently zero — and applying to "replace removal" anyway wastes money, and in the case of phosphorus can create a water-quality problem and may conflict with a nutrient management plan. Where you operate under a nutrient management plan, it is the plan and your state's current criteria that govern — and within them it is the recommendation, not a removal figure, that sets the rate.

Worked example, using illustrative numbers only — substitute your own lab's recommendation and your own credits:

Note the phosphorus row. A field with a high P test and a manure history can need no phosphate at all, even though the crop is removing it every year. That outcome is invisible if you budget from removal.

Turning pounds of nutrient into bags of fertilizer

Fertilizer is sold by analysis, not by nutrient. The three numbers on the bag are the percentage of N, P₂O₅ and K₂O by weight, so the conversion is simple division: pounds of nutrient still needed ÷ the decimal analysis on the bag = pounds of product per acre. The worked figures below continue the illustrative example above — the post-credit remainder of 140 lb N, 0 lb P₂O₅ and 130 lb K₂O. Substitute your own recommendation and credits.

Product	Supplies	To deliver	Product per acre
Urea (46-0-0)	46% N	140 lb N	~305 lb (split)
Muriate of potash (0-0-60)	60% K₂O	130 lb K₂O	~215 lb
Triple superphosphate (0-46-0)	46% P₂O₅	0 lb P₂O₅ in this example	none
DAP (18-46-0) where phosphate is recommended	18% N, 46% P₂O₅	per your recommendation	lb P₂O₅ ÷ 0.46 — then credit the N it carries

Two practical notes. If your recommendation does call for phosphate and you use DAP rather than triple super, subtract the nitrogen it carries from your urea plan — every 100 lb of 18-46-0 brings about 18 lb of N with it. And on alfalfa, prefer 0-46-0 over DAP precisely because you are not trying to add nitrogen to a legume.

Does a balanced blend like 19-19-19 fit your recommendation?

Often it will not, and it is worth checking rather than assuming either way. A balanced 19-19-19 (or 10-10-10) supplies N, P₂O₅ and K₂O in equal parts. Whether that fits depends entirely on the ratio of your remaining recommendation after credits — which is a number specific to your field, not a property of hay in general.

Take the worked example above, where 140 lb N, 0 lb P₂O₅ and 130 lb K₂O were still needed. Check the fit by dividing:

• Enough 19-19-19 to supply the 130 lb K₂O would be about 685 lb/acre (130 ÷ 0.19) — and would apply roughly 130 lb of P₂O₅ that the recommendation says is not needed at all.
• Sizing it to the phosphate instead is impossible here, because the phosphate requirement is zero.

On that field, straight materials fit and a balanced blend does not. On a different field the answer flips — a low-testing field that needs phosphate, potash and nitrogen in roughly similar amounts may be served perfectly well by a balanced blend, and buying one product can be cheaper and simpler than three.

So the method, rather than the verdict: work out your remaining recommendation first, then divide it by the analysis of each product you are considering, and see which comes closest without over-applying anything. Many retailers will custom-blend to a soil-test recommendation for little or no premium, which usually beats forcing a stock blend to fit. Price the options per pound of the nutrient you actually need, not per ton of product.

Take your lab's recommendation, subtract your credits, convert the remainder to product, and that is your fertilizer budget. Knowing what your hay tests for protein and energy makes those decisions sharper — see our guide to reading a hay test — and quality you grow is quality you can price, which we cover in how to price hay.

Frequently asked questions

How much fertilizer do I need per acre for hay?

Work it in three steps rather than from a removal figure. Start with your soil testing lab's crop-specific recommendation for your yield goal. Subtract your credits — manure or compost, legume and prior-crop credits, and nutrients in irrigation water — counting each once. Do not subtract residual soil fertility, because the recommendation already reflects your soil test level. Then divide what is left by the decimal analysis on the bag to get pounds of product per acre. On ground testing high in phosphorus or potassium the correct amount is often zero, which is a result you never see if you budget from crop removal.

How much potash per acre for hay?

Take the rate from your soil test recommendation, not from a removal figure. Hay removes a lot of potassium — Extension sources put grass hay near 52 lb of K2O per ton and alfalfa at 50 to 60 lb — which is why potassium runs down on hay ground, but a field already testing high may need little or none. Once you have the recommendation and have subtracted any manure credit, divide by 0.60 to convert pounds of K2O into pounds of 0-0-60. Split larger amounts across the season rather than applying them at once.

How much nitrogen does grass hay need?

It depends on your region, species and moisture, so take the rate from your own Extension service. As scoped examples, Penn State publishes about 50 pounds of actual nitrogen per ton of expected yield for Pennsylvania, and Colorado State publishes 30 to 50 pounds per ton for irrigated cool-season grass in Colorado; dryland and warm-season systems are managed differently again, and grass-legume mixtures usually get little or none. Set each application against the yield you realistically expect from the next cutting, split rather than front-loaded, and reduce the rate in a developing drought.

Is 19-19-19 a good fertilizer for hay fields?

It depends on the ratio of your remaining recommendation after credits, which is specific to your field. Where a soil test shows adequate phosphorus, a balanced blend forces you to buy phosphate you do not need in order to reach your potassium target, and straight materials fit better. Where a low-testing field needs nitrogen, phosphate and potash in broadly similar amounts, a balanced blend can be a perfectly sensible and cheaper purchase. Work out the remaining recommendation first, divide it by the analysis of each product, and see which fits without over-applying anything.

Do I need to fertilize alfalfa with nitrogen?

An established, effectively inoculated, well-nodulated pure alfalfa stand normally needs none — it fixes its own nitrogen, and applied N is largely wasted and mostly feeds weeds. The exceptions matter: new seedings follow local establishment guidance, which in some states includes a small starter allowance before nodulation is working; a stand whose inoculation failed is not fixing anything, so dig roots and look for pink active nodules before assuming fertility is the problem; and in a grass-legume mixture nitrogen shifts the stand toward grass, so it is usually kept low deliberately.

Why is potassium so important for alfalfa?

Alfalfa removes more potassium than any other nutrient, in the region of 50 to 60 pounds of K2O per ton, and potassium drives stand persistence, winter survival and disease resistance. Chronically short potassium is a leading cause of stands thinning out early. Avoid over-applying, though: alfalfa takes up more potassium than it needs, and high-potassium forage raises the dietary cation-anion difference, which complicates milk fever prevention in close-up dry cows and factors into grass tetany risk in grazing beef cattle. There is no single forage potassium percentage that is universally too high — that is a whole-ration judgement for a nutritionist or veterinarian — but it can make hay harder to sell into dairy markets.

Should I lime before or after planting alfalfa?

Before, ideally well ahead of seeding. Lime can take 6 to 12 months to fully react and raise pH, and it is far easier to work into the root zone before establishment than to fix a sour stand afterward, since surface-applied lime on established sod mostly changes the top inch or two of soil. Use the pH target your own lab sets for alfalfa on your soil, and size the rate from the buffer pH rather than the water pH. Check the material's effective neutralizing value too, and consider dolomitic lime where soil magnesium is low.

Do I need to fertilize grass hay every year?

Nitrogen, usually yes, because grasses cannot fix it and it is removed every cutting. Phosphorus, potassium and lime are a different question — those are applied to soil-test recommendation, and a field testing high may need none for several years. Test every two to three years so you can see the trend, and let the recommendation rather than the calendar decide.

The bottom line

Productive hay ground is a balance sheet, but the entry that matters is your lab's recommendation, not a removal table. Test first and sample to the depth your lab calibrates to. Fix pH to the target your lab sets for your crop, using buffer pH to size the lime. Then take the recommendation, subtract your manure, prior-crop and irrigation credits — counting each once, and not double-subtracting soil test level, which the recommendation already reflects — accepting that on a high-testing field the right answer may be zero — and convert only the remainder into product at the analysis on the bag. Put nitrogen where grass needs it, at a rate scoped to your region and to the next cutting, and get it into the soil rather than the air. Do that instead of spreading the same thing every spring out of habit, and you keep stands thick, yields up and quality high without buying nutrients the ground already has.

Fertility is only one of the levers, of course: weed control, variety choice, and cutting at the right stage all move quality as much as a fertilizer bill does — and cutting timing is why first, second and third cutting test so differently off the same field.

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Sources: Penn State Extension, "Soil Fertility Management for Forage Crops: Maintenance" (extension.psu.edu, accessed August 16, 2026); Virginia Cooperative Extension, "Liming and Fertilization of Cool-Season Forage Crops," Soil Test Note No. 3, publication 452-703 (pubs.ext.vt.edu, accessed August 16, 2026); Utah State University Extension, "Alfalfa Nutrient Management Guide" (extension.usu.edu, accessed August 16, 2026); Iowa State University Extension, "Forage Fertilization Considerations" (crops.extension.iastate.edu, accessed August 16, 2026); Colorado State University Extension, "Fertilizing Cool-Season Grasses and Grass-Legume Mixtures" (extension.colostate.edu, accessed August 16, 2026); University of Wisconsin Extension, "Potassium in Forages" (cropsandsoils.extension.wisc.edu, accessed August 16, 2026); University of Minnesota Extension, "Boron for Minnesota Soils" (extension.umn.edu, accessed August 16, 2026); Rutgers NJAES, alfalfa soil fertility fact sheet FS1295 (njaes.rutgers.edu, accessed August 16, 2026); Oregon State University Extension, "Alfalfa Soil Fertility and Fertilization Requirements," BEEF119 (extension.oregonstate.edu, accessed August 16, 2026); Mississippi State University Extension, "Urea-Based Fertilizers for Forage Production" (extension.msstate.edu, accessed August 16, 2026); Kansas State University Agronomy eUpdate, "Nitrates in Drought-Stressed Forages," August 2026 (agronomy.k-state.edu, accessed August 16, 2026); Penn State Extension, "Grass Tetany: A Disease of Many Challenges" (extension.psu.edu, accessed August 16, 2026); USDA Natural Resources Conservation Service, Conservation Practice Standard 590, Nutrient Management (nrcs.usda.gov, accessed August 16, 2026); HayTalk.com forum threads "Lime on hay ground" (#37121), "5.6 pH—Will Pelletized Lime Help?" (#13675), "Potassium in Alfalfa" (#24374), and "Advice on when to apply boron and potash to alfalfa" (#19415), accessed August 16, 2026. Scope note: every numeric rate on this page is labelled with the state or region that published it, because fertility recommendations are calibrated locally and do not transfer between regions. Nutrient-removal figures are bookkeeping values that vary with species, maturity, soil and moisture basis — they are not application rates. Product quantities shown are arithmetic conversions from the guaranteed analysis on the bag. Confirm every rate against your own current soil test and your local Extension service or soil testing laboratory before applying; where you operate under a nutrient management plan, that plan governs.

Featured photo: Spreading fertilizer by Russel Wills, licensed under CC BY-SA 2.0, via Wikimedia Commons / Geograph.