Pasture.io

Topping Pasture: When Is It Worth It?

Practical pasture decisions for farms that need clear, reliable information.

Ever finished a tedious farm job and thought, “Was it worth the bother?” Topping can be one of those jobs. It can also leave you wondering whether you’ve done much more than burn diesel and tidy the paddock. So, is it worth it? It can be, for a small surplus or stemmy residuals, after checking whether a grazing change or conservation would make better use of the feed.

One thing topping has taught me is to look at what the cows leave behind. Stemmy clumps around dung can still look like perfectly good feed, yet the herd has walked past them. That gets my attention, but it doesn’t settle the mowing decision. Is it a few patches, or is the whole round getting ahead of demand? Sometimes a cut makes sense; sometimes changing the grazing plan or conserving the surplus is the better job.

What is topping pasture or paddocks?

Topping means mowing a grazing paddock to remove standing stem or rank material. You may hear it called “topping grass”, “topping a field” or “topping paddocks”. “Pasture topping” describes the same job.

I’ve sometimes thought it should be called “bottoming”. You’re looking down into what’s left after grazing, not just admiring the seed heads. That’s a paddock observation, not an instruction to set the mower lower. The job is to manage the material left behind while keeping useful leaf for recovery.

Post-graze topping cuts material left after the cows have grazed. Pre-graze mowing cuts standing pasture before they enter. Topping is a mowing job: the purpose is to remove rank material rather than harvest a crop. Slashing describes a mowing method or machine rather than a separate answer to the feed-balance question. Cutting a paddock for silage or hay is different: the aim is to conserve useful surplus feed rather than leave cut material in the paddock. This is also different from spray-topping, which uses herbicide to reduce seed set.

*Pre-topping completed, showing cut pasture lying in rows after mowing.*

When should you top grass or paddocks?

Mid-spring to mid-summer is a common topping period in temperate systems, as temperate ryegrass moves into its reproductive phase. Treat that as a seasonal observation: your pasture species, reproductive stage, growth, weather and feed demand decide the timing.

This guide starts with temperate, pasture-based dairy systems in Australia and New Zealand. The same choice can arise on UK, Irish and other temperate grazing farms. Pasture species, growing seasons, residual targets and local guidance vary, so use the comparison below as a decision framework rather than a universal cut height or calendar rule.

Check the surplus before starting the mower

Those clumps around dung are easy to spot. The lesson I take from them is to look beyond the one paddock that caught my eye. Are growth rates above feed demand? Are several paddocks sitting above your target covers? Have residuals risen after the last few grazings? One untidy paddock is one thing; surplus building across the round is another. Walk the paddock too. A cover figure will not show how much is leaf or stem, or whether the ground is fit for machinery.

Pasture mower splattered with dung and grass clippings after topping. — *Topping can be a dirty job, especially around dung patches.*

A feed wedge puts paddocks in cover order so you can see the wider pattern. Read the feed wedge alongside current growth and demand before taking paddocks out of the round. Pasture.io’s map and wedge can help identify candidates; the grazing and mowing decision still needs a look in the paddock.

Top, change the round or conserve?

DairyNZ’s surplus guidance compares the options. There is no prize for mowing feed that could be grazed or conserved. Use this comparison as a starting point to choose the job that fixes the feed problem without creating a bigger one for the next round.

Adjust grazing or allocation. Surplus is still developing and the round can be changed without compromising cow intake or later cover. Watch residuals and the next round; simply speeding up can leave more feed behind.
Conserve as silage or hay. Enough suitable feed and paddock area can be taken out, with weather, access and harvest timing on your side. Avoid shutting up too much area or harvesting feed that is already too mature.
Post-graze topping. A limited number of grazed paddocks have stemmy material or high residuals and a small surplus persists. Allow for cut-feed loss, cost and safe machinery access.
Pre-graze mowing. A tactical response when the situation and pasture conditions justify it, after considering the other options. Do not assume extra intake or milk production; manage contamination and uneaten material.

Sometimes enough useful feed remains after a light grazing to justify a small hay or silage cut. Check quality, recoverable yield, contamination and harvest costs, as well as the next grazing round. If rain intervenes, reassess whether recovery is worthwhile rather than assuming little loss. Where you can identify a suitable surplus beforehand, conserving it before grazing remains the first option to assess.

If conservation is the better fit, use our guide to choosing silage paddocks to decide what can leave the grazing round. Then plan surplus paddocks for silage or hay and revisit the selection if the feed position changes.

What are the benefits and trade-offs of topping?

The claim: Topping is sometimes credited with faster regrowth, earlier grazing and more milk. Pre-graze mowing is also used in the hope of improving intake.

What the evidence shows: A UK study of continuously stocked dairy pasture found topping improved tiller density, leaf content and digestibility in neglected patches, but did not increase milk per cow. Better-quality regrowth does not automatically mean more feed across the season.

The NZ trials: A 1999 trial found faster January growth and higher summer milksolids per cow after mowing or topping, but less pasture production overall, spring milk penalties and small or negative overall benefits for milksolids per hectare. In the later four-month Lincoln trial summarised by DairyNZ, pre-graze mowing did not improve intake, milksolids or body condition; less silage was conserved and more was fed back.

Where it may fit: Pre-graze mowing remains a tactical option when surplus prevents target residuals being met. Check grazing and conservation alternatives first. Judge the next round by actual recovery, rather than assuming an earlier return or higher stocking rate.

How to top a paddock without losing sight of the next round

Keep watching what the cows leave behind: topping is no substitute for managing grazing residuals and avoiding overgrazing. If a cut is justified, walk the paddock for rocks, old posts, wet patches and uneven ground. A slasher that clears a hollow can scalp the next hump.

Choose the cut for the pasture species, target residual, machine and ground, leaving useful leaf for recovery. There is no one blade setting or boot-toe rule for every paddock. If the ground is wet, use our wet-soils and pugging guide to assess access and recovery before taking machinery in.

To ensure clean cutting, keep blades sharp and maintain the mower according to the manufacturer’s instructions. Match the operating speed and cutting height to the machine, pasture and ground conditions. Where dead material shades green feed, slashing or mulching may improve access to that feed, as a NSW pasture demonstration found. Avoid heaps of residue; don’t assume mulching acts as fertiliser or guarantees faster growth.

A quick word on thistles: identify the species and check local advice. Timely mowing may suppress flowering and seed set, but Californian thistle (Cirsium arvense) can still spread through roots.

Did it actually help?

In farming, timing is gold. But a paddock looking tidier isn’t enough: check it again next grazing. Is the feed ready, are residuals closer to target, and is the round on track? Count the fuel, labour and cut feed left behind too. The next round is where you find out whether the time invested paid off.

If you’re reaching for the mower every round, it’s worth stepping back and looking at your grazing decisions. Are the cows getting to paddocks at the right stage? Does the allocation match their demand? Could surplus pasture have been picked up earlier for conservation?

Check the surplus before you cut

A feed wedge helps you see whether one paddock is ahead or the whole round is pulling away from demand. See how to read a feed wedge before choosing which paddocks, if any, need a cut.

How does topping fit into your system? I’d love to hear what you’ve found with ryegrass or other pasture species: when it earns its keep, and when you’d leave the mower in the shed. Share your experience in the comments below.

Happy farming!