Pasture management hacks for dry weather

DAIRY 101 SOIL MOISTURE

When the sky stays stubbornly blue.

Story and photos by: Karen Trebilcock

Journalists know as soon as we start writing about dry conditions or droughts it’s sure to rain, usually before publication date.

So for any region of the country that is currently a bit on the dry side, fingers crossed, I hope this works for you.

Knowing how to deal with dry periods is becoming more and more important as climate change occurs.

However, we’ve had dry periods in the past as well. If you have been reading the ”50 Years Ago” in the Dairy Exporter each month you will know that at the start of 1970, drought affected the whole of the country causing many farmers to dry cows off early.

Milk production was halved for the first few months of the year compared with the same time the year before. Imagine production taking a hit like that today.

Now we have ways to mitigate dry periods that they didn’t have back then – pivot irrigation, balage, and the importation of cheap feeds such as palm kernel – keep our cows fully fed and milking when the sky stays stubbornly blue.

Decades ago we dried off cows and our income took a hit; now it’s the expense side of the balance sheet that shows the effect.

Rain is free but unfortunately it never falls in regular amounts throughout the year. A nice 20mm soaking every Friday night would be great and make farming a breeze.

But it’s not rainfall that necessarily keeps droughts at bay. Soil moisture is the more important measure because rain can be quickly evaporated away by sun and wind.

There are some expensive gadgets out there that measure soil moisture but there is nothing wrong with a spade. Dig a hole in a paddock, away from fences and water troughs, and see how much moisture there is.

At the same time, look at your soil structure and see how far the roots of your pasture go down.

Knowing what you have to work with under your cows’ hooves can make sure you ask the right questions to find the solutions.

When it does rain, the soil stores the moisture but some types of soil, especially those high in organic matter, store moisture better than others and some plants can access that moisture better than others too.

But it is also how you look after those soils.

Whatever you think of regenerative farming, its principle of keeping covers high and pasture in a growing state as much as possible is hard to argue with.

Plants shade soil from the sun and lessen moisture loss from the wind. They keep the moisture where it should be – trapped in their root zone, which is exactly where they need it.

High covers also help to prevent soil compaction since animals are less likely to pug or compress the ground beneath them.

All soils have pores that hold the water between the different aggregates. Compressing these pores lowers the soil’s moisture holding potential. A cushion of

While you keep your covers up on your best paddocks to keep them growing, stack the cows on your poorer areas and feed supplement there.

plant material helps to stop it. But those plants could use the water available to them a bit more economically.

Of all the water they take up, they use less than 1% in producing dry matter. The rest is lost through their leaves as water vapour, which is called transpiration.

Transpiration is important for plants to cool themselves in hot conditions and also it’s part of their photosynthesis process.

Some plants, such as cacti that live in very dry climates, have figured out transpiration is not a great idea. Unfortunately they will never make it onto New Zealand’s Forage Value Index (FVI).

But there are other solutions such as deep rooted grasses, herbs with long taproots, and sub clovers.

White clover doesn’t handle the dry well as its root system is usually near or at the surface of the soil. Subterranean (sub) clover (Trifolium subterraneum) is an annual clover but sets large amounts of seed in early summer that germinate at lower air temperatures (10C to 15C) compared with perennial legumes (20C to 25C), so in late winter and early spring it’s there when you need it.

But you mustn’t let the cows eat it as it is seeding in summer or there will be no plants next year.

Another alternative is red clover, which has a long tap root so can access soil moisture deep down.

Also replace ryegrass with tall fescue, which can handle the heat better and its roots reach down much further seeking moisture.

Sow it with cocksfoot, another deep-rooted dryland grass, prairie grass and phalaris from across the ditch. Many Australian dryland farmers grow phalaris, which has good winter growth.

Then of course there is lucerne, also known as alfalfa in Europe and North America, a favourite of Kiwi sheep farmers.

Chicory is classed as a herb and can be sown either on its own or in a pasture mix.

With its long tap root it gives high yields of palatable feed from spring through to autumn, even in the heat and the dry.

All of these alternatives to ryegrass and white clover have different management and grazing strategies to keep them persisting, and some, such as phalaris, can cause animal health issues if grazed at the wrong time so make sure you do your research before planting them.

On dry, sun- and wind-exposed parts of your farm they might make the difference between having to buy in feed or not so you can keep your cows milking.

But they need to be established before it gets dry – it is no use getting into summer and thinking about them then.

And if the weather doesn’t turn dry, many of them don’t like wet feet.

Forget about keeping a rainfall chart, instead look at your soil moisture.

Besides looking after soils and growing the right type of pasture, managing your farm under dry conditions will make a difference too.

Just like in very wet conditions, sacrifice paddocks are also necessary in the dry.

While you keep your covers up on your best paddocks to keep them growing, stack the cows on your poorer areas and feed supplement there.

Not only are you looking after your good pasture, you’ll be improving the organic matter of the sacrifice paddocks – which are the ones that probably need it.

And when it does finally rain, don’t sigh with relief and go back to life as normal. Let the grass grow to the three tiller stage before you let your cattle eat it.

Plants need to build up their carbohydrate reserves to regrow well. Grazing the first “green pick” can kill a pasture.

Moving House?

Update your address now to ensure you don’t miss your next issue of NZ Dairy Exporter

log in and update your subscription address at nzfarmlife.co.nz/my-account/