The Dry Matter Sweet Spot: Why 30% DM is Key to Better Silage on Irish Farms

When it comes to making high-quality grass silage, one of the most important measures is your dry matter (DM) percentage. Getting this figure right can mean the difference between well-fermented, nutritious silage and a clamp full of disappointment.

In this edition of the Silage Sessions video series, Ryan Duffy from Precision Microbes dives into why 30% dry matter is the “sweet spot” — and how to consistently hit it, even in the face of Irish weather challenges.

What is Dry Matter (DM) in Silage?

Dry matter is simply the nutrient-rich portion of your forage — everything that’s left after the water is removed. This includes sugars, protein, fibre, and minerals.

DM is important because:

• It affects fermentation quality
• It determines nutrient density
• It influences animal intake and digestion

Target Range:

🟢 Ideal Dry Matter: ~30%
🔴 Too Wet: <25%
🔴 Too Dry: >35%

Why is 30% the Magic Number?

Hitting around 30% DM gives you the best balance between preserving nutrients, achieving rapid fermentation, and producing silage that cows will voluntarily consume.

Let’s look at what happens if you miss the mark:

❌ If DM is Too High:

• Harder to compact → More air in the clamp
• Aerobic spoilage risk rises → Yeasts and moulds thrive
• Headed grass results in silage becoming fibrous and less digestible
• Lower intake → Animals eat less, performance drops

❌ If DM is Too Low:

• Poor fermentation → Bad bugs thrive in moisture and can dominate
• Increased effluent loss → Nutrients literally leaking out
• Lower energy content and less palatable
• Risk of toxic compounds from undesirable fermentation

✅ If DM is ~30%:

• Easier to compact, consolidate and seal (minimal oxygen penetration and circulation)
• Supports rapid lactic acid fermentation
• Retains lactic acid, energy and protein
• Results in palatable, sweet-smelling silage
• Boosts intake and animal productivity

Precision Microbes Silage Additive is a liquid, ready-to-use (RTU) formulation containing live bacterial agents, specifically lactic acid forming bacteria (LAB) and homofermentative bacterial populations. Designed for efficient crop preservation, it promotes a rapid pH drop in both clamps and bales, ensuring high-quality silage. The product is organic certified and can be applied using either ultra-low dosing or standard dosing methods, offering flexibility and ease of use for farmers aiming to enhance silage fermentation and nutrient retention.

What Affects Dry Matter Levels?

There are several key factors that influence your DM levels at harvest:

1. Grass Maturity at Cutting

• Younger grass = higher digestibility and lower fibre
• Aim to cut before heading out for the best feed value (DMD)

2. Time of Day

• Afternoon cutting = higher sugar content (thanks to photosynthesis)
• More sugar = better fuel for lactic acid bacterial fermentation

3. Wilting Time

• 24 hours of wilting is ideal to deactivate bad bugs (if the weather permits)
• Use tedders to speed up drying by spreading and rotating the crop
• Rotate mown grass 2–3 hours after cutting to aid even drying

4. Weather Conditions

• Dry, sunny days = faster wilting
• Rain delays or poor drying = higher moisture → lower DM

Let’s face it — the Irish climate isn’t always cooperative. But smart decision-making during harvest can still bring you close to that target.

Hitting the Sweet Spot: Step-by-Step

Here’s a simple action plan to help you consistently hit the 30% DM sweet spot:

Step 1: Cut Young, Leafy Grass

• Avoid letting crops go too mature — aim for leafy, fast-growing grass. This is a conundrum faced every year: silage quality versus silage quantity.

Step 2: Harvest in Dry Weather

• Easier said than done but gives you the best shot at wilting and sugar retention.

Step 3: Wilt for 24 Hours

• Target 24 hours of wilting
• Rotate the crop after 2–3 hours of cutting to speed drying

Step 4: Compact & Seal Quickly

• Poor compaction = oxygen in the clamp = spoilage
• Wrap bales tightly and stack neatly (avoiding penetration)

Step 5: Use a Proven Silage Additive

• Homofermentative lactic acid bacteria additives, like those from Precision Microbes, help retain up to 99% of sugar energy
• Promote rapid fermentation, discourage bad bugs, and protect DM and crude protein

Watch Out for Red Flags in Silage Analysis

After making silage, your forage analysis is your best friend. Here are some common signs your DM was off:

Review last year’s results before cutting this year — and adjust accordingly.

Final Thoughts: Small Changes, Big Results

Dry matter might sound like just another number, but it’s one of the most powerful tools you have for improving silage quality. Aiming for 30% DM ensures your crop:

• Ferments correctly
• Preserves nutrients
• Keeps animals eating and thriving

In Ryan Duffy’s words:

“We need to hit that dry matter sweet spot to ensure we get great fermentation and have a final product that will drive future intakes and productivity.”