How to calculate how much grass silage is in a clamp?
Use our Clamp Stock Levels tool. Alternatively, use the method below:
1. Calculate the average % dry matter (%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 silage 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 (e.g. the warming oven of an Aga). You know when all the moisture has been removed because the weight stops decreasing
- 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 as a guide* to tell you how much fresh silage or silage DM you would have in 1 cubic metre of clamp space. E.g. from the table, a 30% DM grass clamp with a 3m high face would contain 207 kg (0.207 tonnes) of silage DM per m3 of clamp space.
3. Calculate how many metres cubed (m3) of silage you have in your clamp based on the width, length and height e.g. 20m x 50m x 3m = 3,000 m3
4. Calculate how much you have in the whole clamp (3,000 m3). E.g. 3,000 x 0.207 = 621 tonnes of silage DM
* Please note: the bulk densities shown in these tables are a guide only, and may also be influenced by silage compaction, chop length and fibre content. E.g. if a compactor has been used, silage could be much denser.
*DM – dry matter; FW – fresh weight
Fermented wholecrop cereal silage of 50% DM will have a fresh weight density of about 600kg/m3 (200kgDM/m3).