Silage Bunker Covers: 610g PVC vs 400g TPO — How to Choose the Right Bunker Tarp for 2026

Why Your Silage Bunker Cover Makes or Breaks the Season

You’ve spent all summer planting, harvesting, and packing your silage. The bunker is sealed. The plastic is on.

Then three months later you open it and find mold along the edges, crust on top, and a bottom layer that’s gone black. The loss isn’t just the feed — it’s the milk yield and weight gain you were counting on.

A good silage bunker cover is the single most important investment you make after the harvest itself. It keeps oxygen out, locks in lactic acid fermentation, and stops rain and UV from degrading your feed before the cows ever see it.

But here’s the problem most farmers run into: they buy the cheapest tarp they can find, and it fails by January. Or they overspend on a spec that’s heavier than they actually need.

In this guide, we break down the two materials Lonsun Tex supplies for bunker silage applications every season — 610g PVC and 400g TPO — so you can pick the right one the first time.

What Is a Silage Bunker Cover?

A bunker silo is a long, rectangular pit or above-ground stack where you ferment chopped forage — corn silage, haylage, alfalfa, or grass. Once it’s packed tight, you cover it immediately to exclude oxygen.

The cover does three jobs:

1. Oxygen barrier — keeps air out so anaerobic fermentation continues and mold can’t grow.

2. Weather protection — sheds rain and snow so water doesn’t seep into the feed face.

3. UV resistance — slows down plastic degradation from sunlight so the cover lasts the full feeding season.

Thin 6-mil polyethylene sheeting is the cheap option, but it tears easily, lets rodents through, and rarely makes it through a full winter. A reinforced fabric cover — whether PVC or TPO — is a reusable, puncture-resistant upgrade that pays for itself in fewer spoiled piles.

Option 1: 610g PVC Silage Bunker Covers

Best for: Large operations, long feeding seasons, rough sites

Our 610g PVC agricultural fabric is the workhorse of bunker covers. It’s the same weight class we supply for grain piles, bulk commodity storage, and heavy-duty farm tarps.

What Makes 610g PVC Stand Out

1. Heavy-duty waterproof seal

At 610g per square meter, this is a thick, reinforced fabric with a high-tenacity polyester scrim inside. It forms a complete waterproof and airtight seal over the bunker — no seepage, no wicking along the edges. Rain runs off instead of pooling and finding weak spots.

2. Tear and puncture resistance

You’re driving a front-end loader on and off the pile. Birds land on it. Rodents chew at the edges. Snow piles up on top. The reinforced scrim in 610g PVC handles all of it without tearing. It’s the same fabric we sell for truck side curtains and flatbed tarps, so it’s built for outdoor abuse.

3. UV stabilization built in

The PVC coating is treated against UV degradation, so it doesn’t get brittle and crack after a summer in the sun. On a southern bunker that’s exposed year-round, this matters — a cheap tarp will turn chalky and split within months.

4. Reusable across multiple seasons

This isn’t single-use plastic. When you open a bunker, you can fold the cover, clean it, and store it for next season. Most customers get 3–5 years out of a 610g PVC cover with reasonable care.

5. Custom sizes, cut to your bunker

Every bunker is a different length and width. We fabricate covers to your exact dimensions, with reinforced hems and D-rings or grommets every meter for anchoring with sandbags, tires, or weighted chains.

When to Choose 610g PVC

– You’re feeding a bunker over 6+ months (long winter feeding season)

– You have rough terrain, rodent pressure, or heavy snow load

– You want a reusable cover that lasts multiple seasons

– Your operation is large (100+ head of cattle, or multiple bunkers)

– You prioritize durability over lightweight handling

Option 2: 400g TPO Silage Bunker Covers

Best for: Smaller farms, short-season feeding, eco-conscious operations

TPO (thermoplastic polyolefin) is a PVC-free, recyclable fabric that’s been gaining ground in agricultural and food-contact applications. Our 400g TPO is a newer offering we’ve been refining for customers who want a lighter, more eco-friendly cover.

What Makes 400g TPO Different

1. 100% recyclable and PVC-free

Unlike PVC, which contains plasticizers (phthalates) that can leach over time, TPO is a polyolefin-based material with no PVC. It’s food-grade certified and fully recyclable at end of life. For dairies and livestock operations marketing to organic or grass-fed buyers, this is a real differentiator.

2. Lighter and easier to handle

At 400g, TPO is roughly 35% lighter than 610g PVC. That matters when you’re unfolding a 30-meter cover by hand on a hot harvest day. It’s easier to roll, easier to drape over the pile, and two people can handle it without a tractor.

3. Food-grade and non-toxic

TPO doesn’t contain the chemical softeners you find in PVC. For a bunker that sits directly on silage — feed that goes into the milk supply — some farmers prefer the cleaner material profile.

4. Good UV and weather resistance

Don’t let the lower weight fool you. TPO has excellent inherent UV resistance and weatherability. It won’t get brittle, chalky, or leach plasticizers the way older PVC films can. It performs well in direct sun without needing heavy coatings.

5. Anti-dumping safe

For US importers, TPO avoids the anti-dumping duties and tariff complexity that have tangled PVC fabric imports in recent years. We’ve written about this in detail in our TPO anti-dumping guide, but the short version: TPO is a cleaner customs classification.

When to Choose 400g TPO

– You’re feeding the bunker in under 4–5 months (shorter season)

– You want a lighter cover that’s easier for a small crew to handle

– Your farm markets organic, grass-fed, or sustainability-focused products

– You’re a smaller operation (family farm, 20–80 head)

– You want a PVC-free, recyclable material for environmental or regulatory reasons

– You’re importing into the US and want to avoid PVC tariff complications

Side-by-Side Comparison

How to Make the Right Choice

Ask yourself these four questions:

1. How long is your feeding season?

If you open the bunker in November and finish it by March — a 4–5 month window — 400g TPO will do the job and save you money up front. If you’re feeding from October all the way through May, go with 610g PVC. The longer the cover has to sit, the more durability you need.

2. How rough is your site?

Rodents, deer walking on the pile, heavy snow loads, gravel edges, tractors driving over the cover — all of these point to 610g PVC. If your bunker is on a clean, concrete pad in a mild climate with no rodent pressure, TPO is fine.

3. Who’s handling the cover?

If you have a crew and a tractor to deploy and remove the cover, the weight of PVC isn’t an issue. If it’s you and one farmhand on a Saturday, the lighter TPO cover will make harvest day a lot easier.

4. Does your farm market matter?

Organic certification, grass-fed labels, or sustainability claims — TPO’s PVC-free, food-grade profile aligns better with those stories. If you’re selling commodity milk or beef, the extra cost and handling of PVC may be justified purely on durability.

Common Questions

Do I really need a reinforced fabric cover instead of 6-mil plastic?

If your bunker sits for more than a few weeks, yes. Thin polyethylene tears on rocks, lets rodents through, and UV-degrades within months. A reinforced fabric cover saves feed you’d otherwise lose to mold and spoilage — usually paying for itself in one season.

Can I reuse a silage cover the next season?

Yes. Both 610g PVC and 400g TPO are designed for reuse. Fold them clean, rinse off any silage juice, and store them off the ground away from direct sun. PVC covers typically last 3–5 years; TPO covers 2–3 years depending on UV exposure.

How do I anchor the cover?

Sandbags, old tires, or weighted chains along all edges. We fabricate every cover with reinforced hems and webbing loops or D-rings every meter, so you can tie it down properly. Don’t rely on just laying tires on top — the wind will get underneath.

What size do I need?

Measure the length and width of your packed bunker, then add 1 meter on each side for overhang and anchoring. Tell us your dimensions and we’ll cut the cover to fit.

Ready to Order?

At Lonsun Tex, we’ve been manufacturing agricultural and industrial fabrics for over 15 years. We supply both 610g PVC grain and bunker covers and 400g TPO eco-fabric in custom sizes, with reinforced hems, UV treatment, and factory-direct pricing.

Whether you run a 500-head dairy in Wisconsin or a small organic alfalfa operation in Oregon, we’ll help you pick the right weight and size — and ship it to your port.

Get a quote for your bunker cover →

Lonsun Tex — Agricultural fabric manufacturer. PVC bunker covers, TPO eco-fabrics, grain storage tarps, and custom agricultural membranes, factory-direct from China since 2008.