How to measure grass silage yields?

Tommy Armstrong measuring grass silage yield
Tommy Armstrong measuring grass silage yield

One of the most common questions around silage making time is: how many tonnes per acre are there?

Provita’s Tommy Armstrong suggests the following method.

“Silage yield can be assessed very easily by simply weighing the actual quantity of grass cut from a half metre by a half metre quadrat.

“When doing farm trials this year I wanted to be very accurate in the application of our silage inoculant Advance+.

“When I was researching a method to do this I looked at the calculation used for usable grass dry matters per hectare for grazing. I figured out that the same method can be used with a little modification.

“It is important to cut the grass to mower height with clippers. Once the grass has been weighed in kilos it is simply a case of multiplying this figure by 40,000 to get to a KG output per hectare figure.

“For example, if the cut grass weight is 0.6kg multiplied by 40,000 and then divided by 1000, this translates to a total fresh forage output per hectare of 24 tonne. By dividing this figure by 2.4, you get an output per acre figure of 10 tonne. A simplified version is to multiply the weight in kg by 16.7 e.g. 0.6kg x 16.7 = 10 tonne yield per acre.”

Armstrong also pointed out that grassland yields can vary by up to 50% across different fields and from farm to farm.

He continued: “If using a silage additive it should be applied accurately so that it works but not higher than it needs to be as this wastes money.

“Assessing grass fresh-weights is a very straightforward process. And I would encourage all farmers to look at this option at silage-making time.”

The Provita representative said that an accurate estimation of the grass tonnages to be harvested will allow farmers and contractors to accurately estimate the amount of inoculant they will need.

“An application rate of 400g for granular inoculant per tonne is the norm,” he said.

“So it’s a good idea to have the inoculant applicator calibrated accordingly.”

According to Armstrong, the output from an applicator on the harvester should be measured for 1 minute.

“Just time the output using a jug for one minute. Then a representative load of grass should be timed and ideally weighed. This will then give the harvester tonnes-per-minute rate. Alternatively this can be calculated using harvester speed and row widths. For trailed harvesters, this averages around 1 tonne per minute. But this will be different for each machine. Farmers using Advance+ silage inoculant can have their yields assessed and their applicator output checked so that our inoculant is being used at the correct rate ensuring no wastage, a good fermentation and less spoilage at feed out.”

Provita’s Tommy Armstrong commented that silage making conditions have become more difficult recently.

“Early on most of the fields we have tested were low in nitrogen and high in sugars but now after this growth spell grass has taken nitrogen back into crops and some are coming back with higher than expected nitrates and low sugars. DM is also low so this doesn’t help, ideally crops need to be dried for longer as they are also heavier now. However due to the mixed weather conditions this might not be an option. In these sorts of conditions using an approved silage inoculant designed for Northern Ireland’s challenging conditions is essential to improve fermentation.

“When combined with good crop and clamp management it will act to ensure a much faster fermentation, better forage quality, plus better stability at feed out.”

For more information call Provita on 028 8225 2352 or Tommy Armstrong on 0772010144 or Kieran Donnelly on 07739099230.