How do I calculate how much silage is in store?

Clamps

Use our Clamp Stock Levels Tool

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)

Grass (kg/m³)
% DM
	Depth of clamp (m)
	2		3		4
	DM	FW	DM	FW	DM	FW
20	156	778	176	881	191	954
25	172	690	193	773	208	831
30	186	620	207	689	221	738
35	198	565	218	624	233	666

Maize (kg/m³)
% DM	Depth of clamp (m)
	1.5		2		2.5
	DM	FW	DM	FW	DM	FW
25	185	730	195	770	200	800
30	205	680	215	720	225	750
35	215	620	230	660	245	700

Bales

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).