On livestock farms, the key metric of profitability per hectare is how much grass is utilised per hectare. On farms that can grow and utilise high tonnages of grass and can keep costs under control, high profit usually follows.

In recent years, grass growth rates have declined in Ireland due to a number of factors such as weather, reduced nitrogen use and management factors.

In terms of weather, it certainly feels like the climate is changing with ground conditions swinging from being too dry to too wet at various times in any given year.

Even this week, many farmers are discovering that a lack of rainfall is impacting grass growth rates. Some will have to feed extra silage and meal at a time when surplus grass would ordinarily be generated.

In years gone by, feeding silage or a lot of meal during the summer to fill a grass deficit brought about by drought-like conditions would have been a one in seven- or eight-year event. In recent years, many farmers have fed silage on more than one occasion each summer.

This makes the challenge of utilising grass more difficult because if the grass is not grown, it cannot be utilised. This is making grassland management much more difficult. In times gone by, when nitrogen fertiliser was easily available and the weather was more reliable, farming was easier.

Optional

Since the 1990s, when the principles of extended grazing, grass measurement and grass budgeting came into vogue, many farmers decided to opt out and continue to manage grass in a more haphazard way.

For some, this was a finger-to-the-wind approach while for others, not routinely measuring grass didn’t impact their farm because they were already good farmers. Would they gain from measuring weekly? Probably, but it was marginal.

However, in the current climate of weather and grass growth volatility, not routinely measuring and managing grass and expecting to get good results is just impossible.

Therefore, in order to become more resilient to these weather and climate issues and to maintain our grass based competitive edge, Irish farmers should be learning and re-learning the skills of grassland management.

How to measure grass using the ‘cut and weigh’ method.

Terms used

Average farm cover is the average amount of grass cover on the farm at any one time. This changes daily because grass is always growing and cows are always eating it.

Growth rates will vary depending on sunlight, soil moisture, soil temperature and soil fertility, including availability of nitrogen.

The other part of the equation is demand and this refers to how much grass is eaten per day. Demand is the intake requirement of the animals grazing grass on the farm and is measured in kilos of dry matter per hectare per day.

For example, a herd of 100 cows eating 18kg DM/day is a demand of 1,800kg per day. Across a 40ha farm, this is a demand of 45kg/ha/day.

If growth is bigger than demand then average farm cover will increase and if it’s lower than demand then average farm cover will decrease. Working out average farm cover involves measuring the amount of grass on each paddock.

We do this by measuring the amount of grass in a hectare and then multiplying this rate per hectare by the number of hectares in the paddock.

Adding up all of the grass on the farm and dividing this by the number of hectares on the farm gives the average farm cover. The average farm cover per cow is the average farm cover divided by the stocking rate.

A key understanding after measuring grass is to understand what is happening at any point in time.

By looking at the numbers, farmers will know if the farm is growing more than the demand – in this case the average farm cover will be getting bigger.

If on the other hand, the growth is lower than the demand then the average farm cover will be decreasing.

There are times of the year when farmers want to see both happening and times of the year when farmers want to see average farm cover remain static.

For example, in August and September average farm cover should be increasing as farmers need to build up grass for the autumn and spring.

Whereas in springtime, the average farm cover should be reducing, but at a pace which will allow sufficient grass for grazing until 'magic day'.

Magic day in springtime is the day when grass growth rates equal demand and so average farm cover goes from being in a state of decline to a place when it is increasing.

By measuring grass regularly, farmers will be in a position to take action on either increasing or decreasing demand by using supplements sparingly and wisely.