Silage Preparation Calculator
Calculate the dimensions of your silo pit, required volume, plastic covering area, and compaction time for corn or grass silage.
Results
How to Use This Calculator
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.
About This Tool
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.
Applicability: This calculator is designed for global livestock operations, with particular relevance for North American and European cattle, pig, and poultry farms.
How the Calculation Works
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.
Real-World Example
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 & Tips
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.
Reviewed by Agricalc Editorial Team — Agricultural engineers and agronomists with 10+ years of field experience. Our team verifies every calculator formula against peer-reviewed extension publications. For site-specific advice, consult your local agronomist.
References
Frequently Asked Questions
What density should silage be packed to?
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.
How much plastic do I need for a silage pit?
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.
How long does it take to fill and compact a silo?
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.
What moisture is ideal for silage?
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.
How do I prevent silage spoilage?
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.
