Calculate the dimensions of your silo pit, required volume, plastic covering area, and compaction time for corn or grass silage.
This calculator sizes a bunker silo based on total tonnes of silage and desired pit dimensions. It computes volume needed, required pit length, plastic cover area (with 20% overlap), and estimated compaction time. Critical for silage quality and storage planning.
Planning 100 tonnes of corn silage (700 kg/m³ density) in a 6 m wide × 3 m high pit: volume = 100,000 ÷ 700 = 143 m³. Pit length = 143 ÷ (6×3) = 7.9 m. Plastic cover = ~150 m² × 1.2 overlap = 180 m². At 25 tonnes/hour compaction, ~4 hours of tractor traffic needed for proper density.
✓ Expert Reviewed: This calculator and its content have been reviewed by agricultural experts. Formulas are based on NRC, FAO, and university extension recommendations. For site-specific advice, consult your local agronomist or veterinarian.
Select silage type (corn or grass — affects density). Enter total tonnes of silage, pit width in meters, and pit height in meters. Click Calculate to see volume, required length, plastic area, and compaction estimates.
The Silage Preparation Calculator helps plan bunker silo construction. Proper compaction density (600-700 kg/m³) ensures anaerobic fermentation and prevents spoilage. FAO recommends filling pits quickly (1-3 days) and sealing immediately.
Volume = tonnes × 1000 ÷ density (kg/m³). Pit length = volume ÷ (width × height). Plastic area = (top + 2 sides + end) × 1.2 (20% overlap). Density: corn 700 kg/m³, grass 600 kg/m³. Compaction: aim 1/4 tonne silage per 100 kg tractor weight per minute.
Corn silage 100 t. Density 700 kg/m³. Volume = 100,000 ÷ 700 = 142.9 m³. Pit 6×3 m: length = 142.9 ÷ 18 = 7.94 m. Surface = (7.94×6) + 2(7.94×3) + (6×3) = 47.6 + 47.6 + 18 = 113.2 m². Plastic = 113.2 × 1.2 = 135.8 m².
Common mistakes: poor compaction (causes mold and spoilage), leaving too little packing time, not sealing airtight immediately. Tip: layer silage in 15-20 cm lifts, compact each thoroughly. Fill in 1-3 days. Use 2 layers of plastic with weight on edges. NRC recommends silage DM at 30-35% for best fermentation.
Target density: corn silage 650-750 kg/m³ (30-35% DM), grass silage 550-650 kg/m³ (35-40% DM). Achieve by: filling in 15-20 cm layers, tractor weight ≥ 1/4 tonne silage per 100 kg tractor weight per minute, slow and steady packing. Poor compaction = more oxygen = mold and nutrient loss. FAO recommends testing density with a probe.
Plastic area = (top surface + two side walls + end wall) × 1.2 (overlap factor). For a 8 m × 6 m × 3 m pit: top 48 m² + sides 48 m² + end 18 m² = 114 m² × 1.2 = 137 m². Use 2 layers of 6-mil black-and-white plastic. Weight edges with tires or gravel bags. Budget for 10-15% extra for repairs.
Fill in 1-3 days for best fermentation. Compaction rate: about 25 tonnes per hour with a 50-75 hp tractor on a 30-50 tonne load. For 100 tonnes: ~4 hours of tractor work spread across the filling period. Fill layers thin (15-20 cm) and compact each before adding more. Longer fill times increase aerobic exposure and spoilage risk.
Ideal silage moisture: corn 60-70% (30-40% DM), grass/legume 60-70%. Too wet (>75%): effluent loss, clostridial fermentation. Too dry (<50%): poor compaction, mold, heating. Test with a microwave or lab. Wilting grass for 24-48 hours after cutting to reach target moisture. NRC recommends 30-35% DM for corn silage.
Key practices: (1) Chop to 1-2 cm length, (2) Fill quickly (1-3 days), (3) Compact thoroughly in thin layers, (4) Seal within 24 hours of completion, (5) Use 2 layers of plastic weighted down, (6) Feed out 10-15 cm/day from the face to prevent aerobic spoilage, (7) Keep the face clean. NRC recommends monitoring temperature and pH during fermentation.