How do I calculate how much silage is in store?
1. Calculate the average DM of silage in the clamp as follows:
- Take several cores representing the whole clamp
- Mix the cores together very thoroughly on a clean, dry poly sheet then sub-sample.
- Weigh a suitable dish and measure exactly 100g of forage into it. Note the total weight. Repeat for 3 separate silage samples.
- Dry the sample down using a microwave oven or put it in a 60oC oven for 24 -48 hours (eg the warming oven of an Aga).
- Weigh the dish + dry sample
- Calculate the DM for each sample then average them.
%DM = (dish + dry sample) – empty dish
2. Use the silage DM and silage DM density from the tables below to tell you how much fresh silage or silage DM you would have in 1 square metre of clamp space.
3. Calculate how many metres cubes (m3) of silage you have in your clamp based on the width, length and height, eg 20m x 50m x 3m = 3,000 m3, eg
From the table, a 30% DM grass clamp with a 3m high face would contain 205 kg (0.205 tonnes) of silage DM per m3 of clamp space.
4. Calculate how much you have in the whole clamp (3,000 m3) = 900 x 0.205 = 615 tonnes of silage DM.
Depth of clamp (m)
|Depth of clamp (m)|
|% DM||Depth of clamp (m)|
For bales, weigh a few or estimate their weight then calculate your total fresh silage stocks. Do an oven DM on samples from several bales then calculate DM stocks as follow:
Tonnes DM = Tonnes FW x % DM ÷ 100
*DM – dry matter; FW – fresh weight
Fermented wholecrop cereal silage of 50% DM will have a freshweight density of about 600kg/m3 (200kgDM/m3).