The correct rate of renewal for a farm varies depending on the state of the pastures, and the goals of the operation. This section covers how to assess pasture performance across a farm and plan accordingly.

 

Rate of renewal

Pasture renewal programmes vary widely across NZ, ranging from 0% to over 30% of the farm area each year. Dairy farm renewal averages about 8% compared to 2-5% on sheep farms. The percentage of a farm renewed also determines how long a pasture must last, for example a 5% rate of renewal means a pasture must last 20 years.

 

Benefit of renewal

The benefit of new pasture is the gains it will deliver over existing pasture. So it's important to estimate the current pasture performance versus potential.

 

Current pasture growth

Pasture growth varies widely between individual paddocks across every farm. On flat farms there is typically a 100% difference in DM yield between best and worst paddocks. This difference is much higher on hill country properties.

 

Growth differences between dairy paddocks of 6 t DM/ha are common. This means under-performing paddocks may produce 300 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 much slower animal growth rates.

 

Measuring paddock performance

Comparing the performance of individual paddocks allows you to quantify the potential gains of pasture renewal on the farm. The best paddocks show what can be achieved, with the difference between those and the worst illustrating the potential for improvement, provided paddocks share similar topography, soil type etc.

One way to find out how much individual paddocks grow is to record stock grazing days. For more advice on doing this, visit www.barenbrug.co.nz.
Alternatively you can use a plate meter or visual yield estimates from farm walks to estimate pasture cover to calculate paddock growth. Some software does this automatically from weekly pasture cover data.

 

 

Create a paddock profile

Paddock performance data can be used to rank paddocks within their productive group (e.g. different soil type, topography etc). This example is for the Lincoln University Dairy Farm (LUDF), which has three different soils marked by different colours.

The soil types have different productivity, so you need to compare paddocks within each soil type. This identifies the potential of poorer producing paddocks within a soil type, for example N11 producing an estimated 5.5 t DM/ha less.

Just as farmers identify and cull the 'tail end' of their herd or flock to improve animal performance, here the same thing is done with pasture, culling tail end paddocks to lift farm pasture performance.

 

Example of paddock performance on LUDF divided by the 3 soil types

 

Low hanging fruit

While the graph above shows the potential gain from renewal, it's also important to look at the cost or difficulty in realising those gains. The best return from investment in pasture renewal is from significant yield gain achieved at a low cost. Look for your worst performing paddock(s) on the most productive part of the farm.

For example on the LUDF, DM yield gains are typically much easier to achieve on the green soils than the poorly drained blue soils, on which gains also rely on drainage work, which increases costs.

 

Evaluate success

Continuing to assess paddock performance after renewal allows you to evaluate the success of pasture renewal. Typically pasture renewal delivers good gains. If this is not the case, underlying reasons for poor paddock performance probably have not been rectified. Continual evaluation allows farmers to fine-tune renewal techniques to identify what works best for their particular system.

 

Capture benefits of new pasture

New pasture grows more so:

• More fertiliser will be required.
• A higher stocking rate may be needed.
• Change in management systems may be needed.