# How to Make Silage: Step-by-Step Guide for Small Farms Silage is moist forage preserved by fermentation in the absence of oxygen. Good silage depends on four linked conditions: the crop contains enough fermentable carbohydrate, moisture is suitable for the storage structure, the material is chopped and compacted well enough to remove air, and the silo is sealed quickly and kept airtight. If any of these fail, plant respiration, molds, yeasts, clostridia, or other undesirable organisms can consume nutrients and produce spoiled or unsafe feed. This tutorial explains the planning and physical process for small farms using chopped forage in a bag, drum, pit, bunker, or other properly designed storage system. Crop-specific moisture, chop length, additives, fermentation time, and feed-out rate vary. Test forage and work with a livestock nutritionist, veterinarian, or extension specialist, especially with drought-stressed, frost-damaged, manure-contaminated, or unfamiliar crops. Never enter a silo or enclosed fermentation space without a formal confined-space and silo-gas safety program. ## At a Glance | Stage | Objective | Key failure to prevent | | --- | --- | --- | | Plan | Match feed need, harvest capacity, and storage size | A silo too large to fill or feed out efficiently | | Select crop | Use clean forage at suitable maturity | Soil, manure, toxins, or poor fermentability | | Check moisture | Harvest within a structure-appropriate range | Effluent from forage too wet or air pockets from forage too dry | | Chop | Produce material that packs uniformly | Long, uneven particles that trap air | | Fill | Move forage rapidly into storage | Extended exposure to oxygen | | Compact | Remove air throughout the mass | Loose layers and heating | | Seal | Create and maintain an airtight barrier | Holes, uncovered edges, water entry | | Ferment | Leave the silo closed and undisturbed | Repeated opening before stabilization | | Inspect | Evaluate odor, temperature, color, mold, and analysis | Feeding obviously spoiled material | | Feed out | Keep a smooth face and move through it steadily | Air penetration and secondary heating | ## How Silage Preservation Works Freshly cut plant cells continue to respire while oxygen is present, consuming sugars and producing heat. Packing and sealing limit oxygen. Lactic acid bacteria then ferment water-soluble carbohydrates into acids, reducing pH and suppressing many spoilage organisms. The goal is a rapid transition from a brief aerobic phase to a stable anaerobic fermentation dominated by desirable acid production. [FAO ensiling guidance](https://www.fao.org/4/y1936e/y1936e08.htm) identifies moisture, water-soluble carbohydrate, compaction, and sealing as major determinants of fermentation quality. Crops that are very wet can release nutrient-rich effluent and favor undesirable clostridial fermentation. Crops that are too dry resist compaction, leaving air pockets that support molds and heating. Silage is not sterilized feed. Fermentation preserves material by creating an unfavorable environment for many spoilage organisms. Air, water, soil contamination, damaged plastic, slow feed-out, or poor crop selection can destabilize that environment later. ## Step 1: Calculate How Much Silage You Need Estimate the number and type of animals, feeding days, expected silage inclusion in the ration, dry-matter intake, storage loss, and feed-out loss. Work in dry matter first, then convert to as-fed weight using expected forage dry matter. For example, if a group needs 200 kg of silage dry matter per day for 150 days, the delivered requirement is 30,000 kg dry matter. If planned storage and feed-out losses total 15%, divide by 0.85: ```text Required ensiled dry matter = 30,000 / 0.85 Required ensiled dry matter = 35,294 kg ``` At 35% dry matter: ```text As-fed forage = 35,294 / 0.35 As-fed forage = 100,840 kg ``` These are planning estimates, not guarantees. Yield, moisture, packing density, spoilage, and ration needs change. FAO planning guidance similarly starts with animal numbers, feeding period, ration share, and available resources before selecting silo capacity [2]. Choose a storage size you can fill quickly and feed out at a rate that prevents the exposed face from heating. A very large bunker may be economical to fill but unsuitable for a small herd that removes only a thin layer each day. ## Step 2: Choose an Appropriate Storage System Common options include: - **Plastic bags or small sealed sacks:** low capital cost and useful for small batches, but punctures and poor hand compaction are common risks. - **Sealed drums or barrels:** useful for demonstrations and small farms if they are food safe, clean, structurally sound, and fitted with an airtight lid. - **Pit silos:** can use local labor and materials, but require good drainage, stable walls, safe access, and a durable liner or cover. - **Bunker silos:** allow rapid filling and tractor packing, but create rollover, face-collapse, traffic, and packing hazards. - **Upright silos:** conserve land and may limit exposed surface, but introduce serious silo-gas, confined-space, fall, and unloading hazards. - **Wrapped bales or tubes:** useful for wilted forage, but film damage, bale density, and handling affect preservation. Locate storage on a firm, well-drained site away from wells, streams, drinking-water sources, and areas vulnerable to flooding. Plan how silage effluent will be contained. Effluent has high biological oxygen demand and can pollute surface and groundwater. Design vehicle routes before harvest. People should never stand between moving tractors and walls, beneath raised loader buckets, on unstable forage, or near an unsupported silage face. ## Step 3: Select the Crop and Harvest Stage Corn or maize, sorghum, small grains, grasses, legumes, and some crop by-products can be ensiled, but they do not behave identically. Corn often has abundant fermentable carbohydrate and good packing characteristics. Legumes have higher buffering capacity and may require more careful moisture management. Mature straw and some residues contain little fermentable sugar and can be difficult to ensile without pretreatment or additives. Harvest stage balances yield, nutrient value, moisture, and fermentability. Crop calendars alone are insufficient because variety, weather, soil, and planting date change maturity. Sample the field across several representative locations. Do not judge the crop from a single edge row. Exclude or separately evaluate forage contaminated with soil, manure, dead animals, chemicals, weeds, or flood water. Soil contamination can introduce undesirable organisms and increases ash. Some weeds and stressed crops contain toxic compounds that fermentation does not reliably eliminate. Drought-stressed corn can accumulate nitrate. [University of Minnesota Extension](https://extension.umn.edu/agriculture/crop-production/corn/harvesting-drought-stressed-corn-silage) advises testing moisture during chopping and assessing nitrate risk because crop appearance is unreliable. Frost, hail, herbicide injury, or unusual fertilization can also change risk. Consult local extension guidance before harvest. ## Step 4: Measure Moisture, Do Not Guess Collect a representative composite sample from multiple field locations or loads. Chop and mix it as it will enter storage. Measure moisture with a calibrated forage moisture tester, Koster tester, drying oven, or a validated microwave method. Repeat during harvest because moisture can change within a field and across the day. The best target depends on crop and structure. Many chopped silages are ensiled near 30% to 40% dry matter, but a bag, bunker, pile, upright silo, and wrapped bale can have different optimal ranges. Follow current crop-specific extension guidance and the storage-system recommendation. Warning signs of material that is too wet include free liquid, heavy seepage, and a sample that compresses into a dripping mass. Excess moisture can cause effluent, nutrient loss, sour butyric fermentation, and poor intake. Material that is too dry springs apart, resists compaction, and traps air. [FAO smallholder guidance](https://www.fao.org/4/X8486E/x8486e0l.htm) describes moisture above 75% as potentially harmful and emphasizes enough moisture for good compaction without excessive wetness. Treat those values as broad principles, not a substitute for local crop targets. ## Step 5: Prepare the Silo Before Harvest Do not wait for the first wagon to arrive. Clean old feed and spoiled material from the structure. Repair floors, walls, doors, drains, and covers. Remove sharp objects that can puncture plastic. Arrange enough plastic, sealing tape, edge weighting, tires or other cover weights, and repair materials for the entire structure. For a bag or drum system, wash and dry containers and inspect seals. Do not use containers that held pesticides, petroleum products, industrial chemicals, or unknown substances. Food-contact safety and structural integrity matter. For bunkers and piles, establish a packing plan that keeps tractors away from unprotected edges and steep slopes. Tractor rollover during silage packing is a major hazard. Use a competent operator, appropriate rollover protection, seat belts, safe slope limits, and exclusion zones. Confirm staffing and communication. Filling must not outrun compaction. [FAO harvesting guidance](https://www.fao.org/4/X8486E/x8486e0w.htm) recommends matching filling rate to compaction capacity and completing the process as quickly as possible, ideally in one day and no more than three. ## Step 6: Chop the Forage Uniformly Chopping reduces particle size so material distributes evenly and packs with fewer air pockets. The correct theoretical length of cut depends on crop, moisture, processing, ration design, and equipment. For corn silage, University of Minnesota Extension gives example targets of about 3/4 inch for processed silage and 1/4 to 1/2 inch when unprocessed, with adjustments for dry forage [3]. Do not adopt one chop length for every crop. Overly long particles pack poorly. Extremely fine particles may reduce effective fiber, increase processing energy, and affect rumen function. A nutritionist should consider the whole ration along with storage needs. Inspect several handfuls from each load. Look for long uncut stalks, uneven distribution, whole kernels when processing is expected, soil, stones, and excessive shredding. Adjust knives, shear bar, and processor as needed. Dull knives increase power use and produce ragged material. ## Step 7: Fill in Thin, Even Layers Move chopped forage to storage without unnecessary delay. Spread it across the full working surface in thin, uniform layers. Thick heaps are difficult to compact evenly and leave hidden air pockets. In a small drum or bag: 1. Add a shallow layer of chopped forage. 2. Compact it firmly with a clean, dedicated tool or safe mechanical system. 3. Pay attention to edges and corners. 4. Add another shallow layer. 5. Repeat until the container is full with minimal headspace. Do not climb into a narrow container or enclosed pit. Use tools and designs that keep the operator outside. In a bunker, distribute forage continuously while tractors pack. Keep people on foot out of the vehicle path. Never permit passengers on packing tractors. Avoid building a slope steeper than the equipment and safety plan allow. ## Step 8: Compact to Remove Air Compaction is not a final task performed after filling. It must occur throughout filling. The goal is high, uniform density without soil contamination or unsafe loading. Wet forage usually packs more easily but may produce effluent. Dry forage requires more time, thinner layers, shorter chop, and greater packing effort. If material cannot be compacted safely and adequately, stop and reassess. Covering a loose mass will trap air. Hand packing can work for small bags and drums when material is chopped appropriately and each layer is compressed. Protect the liner from punctures. A hole below the surface can admit enough air to spoil a large zone. Do not use bare feet for compaction. Sharp plant material, contaminated forage, unstable footing, and biological hazards make this unsafe. ## Step 9: Use Additives Only for a Defined Reason Microbial inoculants, acids, enzymes, molasses, absorbent dry feeds, and other additives can be useful in specific crops and conditions. They cannot compensate for wrong moisture, slow filling, poor packing, or a leaking seal. Choose additives based on forage analysis, crop type, expected challenge, independent evidence, and local expert guidance. Apply the correct product rate uniformly using calibrated equipment. Too little may be ineffective. Too much can waste money or create handling concerns. Molasses is sometimes used to provide fermentable carbohydrate in low-sugar materials, but it also adds moisture and must be distributed evenly. Acids require chemical handling controls. Inoculants contain living organisms and need correct storage and water quality. Follow the label exactly. ## Step 10: Seal Immediately and Completely Once filling and final compaction are complete, cover the forage without delay. Smooth the surface so plastic lies close to the material. Use an oxygen-barrier film or approved silage plastic suitable for the system. Overlap seams as specified, seal edges, and weight the full surface so wind cannot pump air beneath the cover. Inspect the perimeter, corners, pipes, doors, and penetrations. Direct water away from the cover and prevent ponding. Protect plastic from birds, rodents, livestock, machinery, and sunlight according to its design. For drums and bags, expel headspace without damaging the package, close the seal, and label the batch. Record crop, field, harvest date, moisture, additive, operator, and expected opening date. Check the seal soon after filling and after storms. Repair holes immediately with clean, compatible silage repair tape. Ordinary household tape may fail in weather and on dirty plastic. ## Step 11: Allow Fermentation to Stabilize Leave the storage closed. Opening repeatedly introduces oxygen and disrupts fermentation. Many farms wait several weeks before routine feeding, but required time varies by crop, moisture, inoculant, temperature, and storage system. Use crop-specific recommendations and feed analysis. During early fermentation, silos can produce carbon dioxide and nitrogen dioxide. Nitrogen dioxide may appear yellow-brown and can cause severe respiratory injury or death. It can collect near silo openings, feed rooms, and low areas. Never enter an upright silo, enclosed pit, or gas-affected area to investigate. Use emergency services and trained confined-space personnel. External warming during initial fermentation can occur, but persistent high temperature may indicate excessive oxygen. Do not puncture a sealed system merely to check heat unless the monitoring method is part of the storage plan. ## Step 12: Open and Inspect Silage Safely Open only the surface needed for feed-out. Stand clear of unsupported faces and overhangs. Silage faces can collapse without warning and bury a person. Never park or work beneath an overhang. Evaluate: - **Odor:** Good silage often has a clean acidic or mildly fermented smell. Rancid, putrid, sewage-like, burnt, or strongly musty odors require investigation. - **Color:** Color varies by crop, but extensive blackening, white or blue-green mold, and slimy zones are concerning. - **Temperature:** Heating after exposure indicates aerobic activity. - **Texture:** Excessive slime, visible spoilage, or dry moldy pockets indicate poor preservation. - **Analysis:** Dry matter, pH, fermentation acids, nutrient profile, nitrate, mycotoxin, and other tests may be needed. Do not decide safety by smell alone. Mycotoxins may occur without dramatic visible mold, and not every mold has the same risk. Consult a veterinarian or nutritionist before feeding suspect silage. Do not simply mix spoiled material into good feed to dilute it. ## Step 13: Manage the Feed-Out Face Remove silage in a way that leaves a smooth, tight face. Avoid digging holes into the mass because they increase exposed surface and allow oxygen to penetrate. Advance across the entire face at a rate appropriate for temperature and storage type. Remove loose material promptly and feed it before it heats, within the ration-management window. Keep the remaining cover weighted and sealed. Prevent rain and runoff from entering. In hot weather, yeasts and molds can grow rapidly at the face. [FAO guidance for warm climates](https://www.fao.org/4/x8486e/x8486e0q.htm) emphasizes maintaining a smooth face and limiting air penetration during feed-out. If heating is persistent, review density, face size, removal rate, seal quality, crop dry matter, and inoculant strategy. ## Common Silage Problems | Problem | Likely causes | Prevention or response | | --- | --- | --- | | Heavy effluent | Forage too wet, high silo pressure | Harvest at appropriate dry matter, contain effluent | | Butyric or rancid odor | Very wet forage, low sugar, clostridial fermentation | Improve crop and moisture selection, then seek feed advice | | Mold under cover | Air leak, loose plastic, poor weighting | Repair holes and improve sealing | | Heating at feed-out | Slow removal, rough face, yeast activity | Increase face advance and reduce oxygen exposure | | Large dry pockets | Poor distribution or compaction | Use thinner layers and uniform packing | | Soil contamination | Low cutting height, dirty equipment, muddy traffic | Raise harvest hygiene and exclude soil | | Poor animal intake | Spoilage, poor fermentation, ration imbalance | Analyze silage and reformulate with a nutritionist | | Frozen or unstable face | Seasonal weather and unsafe removal | Use a safe removal plan and avoid undercutting | ## Small-Batch Drum Example For a teaching or small-farm batch, a clean food-grade drum can demonstrate the principles: 1. Select clean forage suitable for ensiling. 2. Measure moisture and adjust harvest timing or wilting as advised. 3. Chop uniformly. 4. Fill the drum in shallow layers. 5. Compact every layer with a dedicated tool while keeping the operator outside. 6. Apply a selected additive uniformly if the plan calls for it. 7. Fill with minimal headspace. 8. Fit an airtight food-safe liner or lid. 9. Label and store upright in a cool protected area. 10. Leave sealed for the recommended fermentation period. 11. On opening, inspect and sample before feeding. 12. Once opened, remove silage quickly enough to prevent heating. Do not use a sealed vessel that cannot tolerate fermentation pressure or was not designed for this purpose. Do not enter, reach deeply into, or place your head inside a container where gases may accumulate. ## Quality Records Worth Keeping - Field and crop identification. - Variety and maturity stage. - Harvest dates and weather. - Representative moisture results. - Chop length and processor settings. - Load count or harvested weight. - Additive product, lot, rate, and application method. - Filling start and finish times. - Packing equipment and operators. - Plastic or container type. - Repairs and seal inspections. - Opening date and fermentation analysis. - Feed-out temperature and spoilage notes. - Animal intake, refusal, and health observations. These records connect feed quality with management decisions and make the next harvest easier to improve. ## When to Involve a Veterinarian or Nutritionist Get professional help when silage smells putrid, is unusually hot, contains extensive mold, has suffered manure or soil contamination, or comes from drought-stressed, frost-damaged, or unfamiliar crops. Stop feeding and contact a veterinarian promptly if animals develop reduced intake, digestive upset, neurologic signs, abortions, weakness, or sudden illness. A forage analysis, fermentation profile, and targeted toxin or nitrate testing may be needed before a feeding decision. ## Frequently Asked Questions ### Can any green plant be made into silage? No. A material needs suitable moisture, fermentable carbohydrate, manageable buffering capacity, safe composition, and the ability to compact. Some residues require wilting, carbohydrate sources, additives, or a different preservation method. ### How wet should silage be? There is no universal target. Crop and storage system determine the safe range. Measure dry matter and use current extension recommendations for that combination. ### Can spoiled silage be fed after removing visible mold? The visible area may not show the full extent of heating, toxins, or microbial change. Segregate suspect feed and obtain veterinary or nutrition advice. Do not rely on dilution with good feed. ### Does silage need molasses? Not always. Corn often contains adequate fermentable carbohydrate. Low-sugar crops or residues may benefit in some systems, but additives should be chosen from analysis and expert guidance. ### Why is my silage hot after opening? Oxygen permits yeasts and molds to grow. Slow feed-out, a rough face, low packing density, air leaks, and dry forage commonly contribute. ### How long should silage ferment? Several weeks is common, but the correct interval varies. Follow crop-specific advice and use fermentation analysis when quality is uncertain. ## Related Animal Farming Guides - [Livestock Feed Storage and Preservation](/knowledge/animal-farming/farm-management/livestock-feed-storage-preservation-hay-silage-grain) - [Dairy Cow Feed Storage and Silage Management](/knowledge/animal-farming/dairy-cattle/dairy-cow-feed-storage-and-silage-management) - [Goat Feed Quality Assessment](/knowledge/animal-farming/goats/goat-feed-quality-assessment-evaluating-hay-silage-grains) - [Sheep Silage and Fermented Feeds](/knowledge/animal-farming/sheep/sheep-silage-fermented-feeds-safe-use-rations) - [Browse the Animal Farming Knowledge Hub](/knowledge/animal-farming) ## References 1. Food and Agriculture Organization of the United Nations. [Ensiling Crop Residues](https://www.fao.org/4/y1936e/y1936e08.htm). 2. Food and Agriculture Organization of the United Nations. [Harvesting and Ensiling Techniques](https://www.fao.org/4/X8486E/x8486e0w.htm). 3. University of Minnesota Extension. [Harvesting Drought-Stressed Corn for Silage](https://extension.umn.edu/agriculture/crop-production/corn/harvesting-drought-stressed-corn-silage). 4. Food and Agriculture Organization of the United Nations. [Silage from By-Products for Smallholders](https://www.fao.org/4/X8486E/x8486e0l.htm). 5. Food and Agriculture Organization of the United Nations. [Silage from Tropical Cereals and Forage Crops](https://www.fao.org/4/x8486e/x8486e0q.htm). 6. Food and Agriculture Organization of the United Nations. [Small-Scale Dairy Farming Manual: Silage Making](https://www.fao.org/4/t1265e/t1275e05.htm). > This article is educational and is not a substitute for veterinary diagnosis, treatment, public-health guidance, or regulatory reporting.