Graziers cannot afford to waste a drop

On-going drought highlights the importance of ground cover in livestock production systems


News
Containment paddocks can help manage drought ravaged pasture by limiting the impact of cattle on-farm.

Containment paddocks can help manage drought ravaged pasture by limiting the impact of cattle on-farm.

Aa

Maintaining ground cover above 70 per cent is critical for any livestock production system and there are simple ways to achieve this so patchy rain is not wasted through runoff.

Aa

Good graziers are managing climate variability right now, but their approach is not written down like a recipe, it is more "artisanal" says Manilla consulting agronomist Lester McCormick.

The present drought is making things difficult and pasture management is now more important than ever, with ground cover - including litter at two handfuls for every square foot - key to maintaining microbe survival, soil softness and the chance of capturing rain when it falls.

Mr McCormick, who used to co-ordinate extension advice on tropical pastures and rangelands when he worked for the NSW DPI, described original summer native pasture on the north-west slopes of New England as soft and rich in biodiversity prior to rabbits and winter burning.

Now the dominant species are wiregrass with some redgrasses that can handle paddocks with a poor level of soil moisture.

"We are fortunate that native grasses are resilient," he says. "There is a great seed bank there for regeneration but who manages that?"

A good native pasture has 100 species, a third of which are grasses which dominate the bulk. But over grazing and a hard soil surface will encourage the survival of weeds like Coolatai grass, affecting fertility, encouraging erosion and reducing a paddock's ability to soak up a sudden 50mm rainfall event.

Growing grass cover to reduce water runoff is a central objective of the modern farmer, made all the more difficult by the increasing nutritional demands of modern livestock genetics.

For those who measure things, a healthy paddock requires 1500 to 3000 kilograms of green dry matter for every hectare, but as grasses mature digestibility can quickly drop to 50pc at which point they are regarded as non-productive and livestock will lose weight without supplements.

Dry sheep need at a 75pc digestible pasture only require 400kg dry matter per ha, according to figures generated by MLA's Prograze program. However, if a paddock falls to 60pc digestible pasture, then the dry matter requirement increases to 1200kg/ha.

Lactating ewes with twins require 1500kg/ha dry matter at 75pc digestibility. Anything lower won't do the job. To meet 90pc of lambs' growth potential requires a pasture with1600kg/ha of dry matter at 75pc digestibility. Anything less won't work.,

"Producers have to ask, "is my paddock meeting livestock requirements or by leaving animals in behind the gate, are they further degrading that pasture?" suggests Mr McCormick who advises that livestock on supplements should be kept in a containment paddock to allow surrounding groundcover to be maintained or regenerate.

This over-grazed paddock will take a long time to recover.

This over-grazed paddock will take a long time to recover.

Grass conservation prepares for rain

The importance of ground cover in retaining moisture might seems obvious, but it took three decades from the late 1970's before research by Soil Conservation Services' Des Lang was adopted by catchment management authorities and now local land services, reminds consulting agronomist Lester McCormick, Manilla.

Ground cover allows better management of the water cycle by reducing evaporation, increasing green dry matter for better transpiration and, in turn, more grass production.

"Bare paddocks are hard to recover from drought and there is a lot of dust in the west right now," Mr McCormick says. "Pastures that have 70pc ground cover or greater are still soft on the surface, even though it's been dry for so long."

One study collected rainwater runoff over four years from a paddock with 40pc cover and another at 70pc cover and measured 116mm running off from the former and just 4mm from the latter.

Mr McCormick advocates rotational grazing as the best way to increase paddock ground cover.

"If we lose rain through run-off," he says, "we miss an opportunity."

Related reading:

Aa

From the front page

Sponsored by