- Aim for optimal rates of renewal; identify poor producing paddocks.
- Manage new pasture appropriately to capture benefits.
Rate of renewal
Pasture renewal programmes vary widely across NZ, typically ranging from 0%-15% of farm area each year. The average on dairy farms is 5-10% compared to 2-5% on sheep farms. The amount of new pasture that should be sown depends on the performance of existing pastures, and the potential gains that can be delivered by new pasture in the system.
How much pasture is being grown?
The percentage of a property renewed each year also determines how long a pasture must last before it is renewed again. For example a 5% rate of renewal will mean a pasture renewal rotation of 20 years.
Pasture growth varies between individual paddocks on every farm with differences of 6-8 t DM/ha. On a dairy farm this means under-performing paddocks may produce 400 kg MS/ha less than better ones (based on 75% utilisation and 15 kg DM/kg MS conversion). On a sheep and beef farm the poorest paddocks could be carrying 30- 50% fewer stock with slower animal growth rates as well.
Comparing the performance of different paddocks allows farmers to quantify the potential gains of pasture renewal on their farm. The best paddocks show what can be achieved, with the difference between those and the worst paddocks illustrating the potential for improvement, provided paddocks have similar soil type etc.
Measuring paddock performance
One way to find out how much individual paddocks grow is to record stock grazings. See Table 1 as an example. Alternatively you can use a plate meter, pasture cage measurements or visual yield estimates from farm walks to estimate pasture cover to calculate paddock growth. Some software (e.g. Pasture Coach) does this automatically
At the end of the season, grazings for each paddock can be added up to identify total grazings. Include other growth such as silage made.
Where the paddocks are different sizes, divide the total grazings by the paddock size, so you can compare total grazings/ha.
In this simple example paddock A is carrying 25% more stock than paddock B, and twice the stock of C.
Create a paddock profile
This data can be used to build an efficient renewal programme by ranking paddocks in order of most to least total grazings/ha, and graphing them to produce a profile of individual paddock performance across the property. Here are two examples:
Just like farmers identify and cull the 'tail end' of their herd or flock to improve animal performance, here you do the same thing with pasture, looking to cull the tail end of poor performing paddocks to lift pasture performance.
The paddock profile for Property A is well above average, and would be typical of a flat farm undertaking a high level of pasture renewal. Most paddocks have excellent performance. But there is still potential for renewal, starting with the two poorest paddocks.
Property B has a greater number of paddocks that could be severely limiting production. Depending on the underlying factors behind the poor paddock performance, this farm is likely to gain from a more aggressive renewal programme over the next few years, renewing a higher number of paddocks to correct the situation and give large productivity gains.
Continuing to assess paddock performance during the following years allows you to evaluate the success of pasture renewal. Typically, but not always, pasture renewal delivers good gains. If this is not the case, are all underlying reasons for poor paddock performance being addressed? This feedback allows fine-tuning of renewal techniques.
Capture benefits of new pasture
New pasture grows more so:
- A higher stocking rate may be needed.
- More fertiliser will be required.
- New management systems may be needed.