Extending the Grazing Season & Grass Budgeting

 

Cows grazing in early spring

So just how do we go about extending the grazing season? It isn't just a question of opening a gate, it requires management and planning. The first requirement is to prepare a grass budget based on expected growth and demand. This will give you a set of targets to aim for. You need to keep measuring the grass situation on the farm so you can detect problems and stop them becoming crises. You must make grazing your top-priority and graze the whole farm, cutting ground for silage only out of genuine surpluses. You should also optimise your calving pattern so that feed demand matches supply as closely as possible. By using fertiliser at key times of the year we can encourage more grass to grow in the shoulders of the grazing season.

Grass Measurement

Grass is measured using a device called a rising platemeter. This measures compressed sward height in half centimetres. 30 readings are taken across the field and the result is fed through an equation which gives us a reading of how many kilos of dry matter there are per hectare. This is known as a grass cover.

 Measureing grass with a rising plate meter
Inputing grass measurements

Each field on the farm currently in the grazing cycle is measured. To ease calculation these results are fed into a computer spreadsheet. We can then determine the:

  • Yield per Field- which is useful for deciding which paddocks to graze next and which paddocks should be removed for silage.
  • Average Farm Cover- gives us an indication of how much grass there is over the entire farm.
  • Growth Rate- which tells us how fast the grass is growing.

Grass Budgeting

Grass budgeting is the most important thing we do. It is critical to the success of the system.

Put simply Grass budgeting is a method of quantifying growth and intake in the same way that financial budgets balance income & expenditure. This enables us to store grass in the field rather than in the clamp for when demand exceeds growth

There are a number of occasions in the year when having the right average farm cover is critical:

Cover at "magic day" is the most important figure, everything else works back from that

Magic day is when the amount of grass growing on the farm equals the demand for grass. It is only at this point that we can start closing up parts of the farm for silage production. At 297 Cow Equivalents magic day will occur when growth reaches 60 kgDM/ha/day. This growth rate will typically occur on my farm around the 25th April.

The grass budget runs from Oct - April (The period when growth is less than demand).This is broken up into half-month segments. From historical records we can make a fairly good guess as to what the grass growth rate will be during each half-month period. With a tight controlled calving pattern we can also predict animal intake. Taking one figure from the other we can predict how much grass cover will rise or fall.

Sowing fertiliser with a quad

However it is important to note that things don't always turn out exactly as you plan. Depending on the weather and other circumstances grass growth may be higher or lower than expected. If cover is too high we can: turnout any stock still housed (e.g. dry cows), reduce fertiliser application or make silage out of the surplus. If covers are too low then we can increase fertiliser, bring silage ground back into the grazing cycle, or supplement the cows with concentrates or silage.

Preparing for Spring

In order to have grass in the spring you must start planning in August. Grass covers are built up in a grazing wedge until the average farm cover reaches 2,800 - 3,000 kgDM/ha at the end of September. It is vital that prior to building high covers that the paddocks are grazed out well. Otherwise the sward will develop a rotten base.

Building a Grazing Wedge

We employ a range of measures to build a grazing wedge:

  • We can bring in more ground (formerly cut for silage).
  • Lengthen the grazing rotation
  • Cull cows who are not in calf
  • Purchased feed can be used to reduce demand.

It should also be pointed out that as the spring calving cow nears the end of her lactation her intake will naturally fall.

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