Hay preservative is insurance for the days the weather forecast turns against you. You've got a cutting down, a shower coming, and hay that's almost dry — preservative lets you bale it a few points wet and stack it without it heating, molding, or catching fire. But the product you choose and how you apply it makes the difference between cheap insurance and an expensive, baler-eating mess. Producers who've used both liquid acid and dry powder are blunt about which they'd do again.
Quick answer: Hay preservative lets you safely bale hay a few points above normal dry-hay moisture — roughly up to the mid-20s% — so a marginal day doesn't cost you the cutting. Buffered propionic acid (e.g., Crop Saver) and dry products like Silo King are the producer favorites because they won't corrode the baler the way raw, non-buffered acid does. Apply at the baler with a calibrated applicator — windrow spraying is uneven. Budget a few dollars a ton for product; automatic acid systems can run several thousand dollars. For hay wetter than preservative can handle, wrap it as baleage instead.
What preservative actually buys you
Preservative doesn't make wet hay into dry hay — it suppresses the mold and bacteria that cause heating and spoilage so you can bale a little wet and still store it. The use case producers describe is the classic marginal-weather save:
"So I am considering installing a Gandy style applicator on my small square baler for dry preservative. Not interested in liquid, been there, done that, not going down that road again. Just want a little insurance for less than optimum baling days when the weather forecast turns against me."
— joethefarmer75, Southern Indiana · AgTalk thread 1075026
The payoff that sells producers is being able to put borderline hay straight into the stack and not lie awake worrying about it:
"Can you put some 25%-30% hay in a stack right away with silo king and sleep that night?"
— farmer53, NW IL · AgTalk thread 1075026
"Did it last week!"
— olivetroad, Mid-Missouri · AgTalk thread 1075026
The big decision: buffered vs. non-buffered acid (and dry powder)
The most important choice isn't brand — it's whether the acid is buffered. Raw, non-buffered propionic acid is corrosive and will eat your baler where it contacts metal. The producer experience is consistent and a little scarred:
"I have use plain Propionic (non-buffered) with a 'manual' applicator, never again, but haven't had any problems with buffer (brand named Crop Saver) product, using an automatic system too. The manual, non-buffer product/system was 'expensive' to say the least."
— r82230, Thumb of Michigan · AgTalk thread 1075026
When another producer asked the obvious question — what does the acid do to the baler? — the answer was clean and short:
"Nothing, if it is buffered propionic acid."
— Gearclash, Sioux County, NWIA · AgTalk thread 1075026
The same producer who got burned by non-buffered acid is all-in on a buffered product through an automatic system:
"The old Johnny 24t was a rust bucket where the acid hit. Applying too much was a waste of product, while applying too little was a waste of hay. For me the automatic system (with a buffer product) more than paid for itself... Will not bale a bale without them."
— r82230, Thumb of Michigan · AgTalk thread 1075026
Dry products like Silo King are the other popular route, especially for operators who don't want to deal with acid at all — and the safety angle is real. One producer's switch was permanent after a single bad day:
"The day I got a mist of acid in my eyes is the last day I used acid. Started using Silo King and used it ever since. That was 17 years ago."
— Haygrower, Arthur IL · AgTalk thread 1075026
| Option | Pros | Cons |
|---|---|---|
| Buffered propionic acid (liquid) | Effective; won't corrode the baler; automatic systems meter precisely | System cost; handle product with care |
| Non-buffered propionic acid | Cheapest product | Corrodes metal; messy; harsh to handle — producers say "never again" |
| Dry powder (e.g., Silo King) | No corrosion; simple applicator; producer favorite for small squares | Even coverage depends on a good applicator |
Application: at the baler, calibrated — not on the windrow
However good the product, uneven application wastes it and leaves spoiled spots. The two failure modes producers describe are over- and under-applying with a cobbled-up manual rig:
"I had a cobbled up manual setup that I always seemed to get too much acid on. Did a good job on the hay but just too expensive and too much mess and hassle."
— joethefarmer75, Southern Indiana · AgTalk thread 1075026
Apply at the baler so product hits the hay as it forms the bale, calibrate to your moisture (more product for wetter hay), and — for a liquid system — expect a little paint to peel where nozzles drip on the pickup bands; it's cosmetic, not structural. If you're sizing an applicator, the practical tip from the thread is to spring for the bigger hopper so you're not refilling constantly: "spend the extra money and get the applicator with the larger hopper. You will not regret it." (olivetroad, Mid-Missouri).
What it costs — and where the line is
Dry preservative runs only a few dollars a ton, which is cheap against losing a cutting. The capital cost is in automatic liquid systems:
"10 years ago an automatic system ran $2000 to $2500 and I suspect today double that, plus I believe the preservative has doubled in price."
— joethefarmer75, Southern Indiana · AgTalk thread 1075026
That's why the math depends on volume: if you make a lot of hay on marginal days, a buffered automatic system pays for itself; if you only put up a few small squares, a dry-product applicator (or just wrapping the wet stuff) makes more sense. Preservative has a ceiling, though — it extends your moisture window a few points, it doesn't rescue genuinely wet hay. Past roughly the mid-20s%, you're in baleage territory: bale it wetter and wrap it so it ferments instead of molds. See baling moisture for net-wrapped bales and first-time baleage for that end of the range, and watch heating either way — hay bale heating and fire prevention.
Where XES fits
Preservative and net wrap solve the same problem at two ends of the moisture scale: preservative saves slightly-tough dry hay at the baler, and net wrap (over film, for baleage) saves the wet end by sealing the bale so it ferments. Whichever end you're working, the bale still has to hold its shape in storage to be worth saving. XES Extreme net wrap is DLG-tested (Report #7439) and UV-rated 12 months (tested to ISO 4892-2), so the hay you fought to put up stays tight and protected through storage. Compare widths and lengths on the net wrap product page.
The bottom line
Hay preservative buys you a few points of moisture and a few more baling days a year — real insurance when the forecast turns. Choose a buffered acid or a dry product like Silo King so you're not rusting out your baler, apply it at the baler with a calibrated applicator instead of spraying the windrow, and size the system to how much marginal hay you actually make. When the hay is wetter than preservative can handle, stop fighting it and wrap it as baleage. Either way, you keep the cutting instead of watching it heat in the stack.
Frequently asked questions
What moisture can you bale hay at with preservative?
Preservative typically lets you bale a few points above normal dry-hay moisture — into the low-to-mid 20s% depending on product, rate, and bale size — and stack it without heating or molding. Above that range you are better off wrapping the hay as baleage so it ferments rather than spoils.
Is buffered or non-buffered propionic acid better?
Buffered. Non-buffered propionic acid is corrosive and will eat metal on the baler, and producers who used it say "never again." Buffered propionic acid does no harm to the baler and is the preferred liquid preservative, applied through a metered system.
Does hay preservative damage the baler?
Raw non-buffered acid does — it rusts and corrodes where it contacts metal. Buffered acid and dry powders do not cause structural damage; with liquid systems you may see paint peel where nozzles drip on the pickup bands, which is cosmetic. Dry products like Silo King avoid corrosion entirely.
How much does hay preservative cost?
Dry preservative runs only a few dollars per ton of hay, which is inexpensive against the cost of losing a cutting. The bigger expense is an automatic liquid applicator system, which can run several thousand dollars, so the investment makes most sense for operations putting up a lot of hay on marginal days.
Preservative or baleage for tough hay?
Use preservative when hay is only a few points too wet to bale dry — it lets you bale and stack it safely. When hay is genuinely wet, wrap it as baleage so it ferments anaerobically instead of molding. Preservative extends your dry-hay window; baleage handles the wet end of the scale.
This guide is maintained by the XES Netting team — a bale net-wrap manufacturer. Every farmer quote in this post is verbatim with a thread link, so you can read the originals. Preservative products, rates, and moisture limits vary — follow the manufacturer's label, and handle acids with proper protective equipment.
Related guides
Featured photo: Baling Hay near Mayall's Coppice by Bob Embleton, licensed under CC BY-SA 2.0, via Wikimedia Commons.
