Better autumn pasture mgmt could net $150k more

Northland pastoral specialists told 80 farmers at a Far North beef and lamb field day at Te Mataa Station, late July, that drystock animals were harvesting 30-50% less pasture than their dairy counterparts. Good use of grazing and fertilizer could compensate.

One thing drystock farmers could do was increase average cover length, says a specialist with AgFirst, consultant Gareth Baynham. He claims that lifting average pasture cover from 1300 kgDM/ha to just 1700kgDM/ha could double pasture growth.

Bayhnam says pasture regrowth was initially dependent on stored carbohydrates with only the emergence of the first leaf promoting pasture growth from sunlight.

Once a ryegrass tiller had grown its second or third leaf it was harvesting more sunlight and grew faster. Pasture grazed down to 1500kgDM/ha, then closed up, were more likely to ‘take off’, Baynham says. While pasture was grazed harder, or if stock grazed regrowth shoots, paddocks took longer to be ready for the next grazing.

To maintain this cover, Far North dairy farmer David Gray says farmers need to match their rotation length to leaf emergence; for most farmers this means having a long rotation in the winter when pasture growth is slow.

By stretching a winter rotation from 30 days to 60 days pasture is getting a longer time in the 2-3 leaf stage and stock are more likely to go onto paddocks filled with high quality grass with covers around the 2600--2900kgDM/ha mark. 

“You’re not so much farming grass as you’re farming sunlight.”

By doing this, says Baynham, farmers will be able to get good consistent liveweight gain in stock, resulting in larger animals, meeting liveweight targets earlier.

Northland sheep and beef farmers stand to gain 65-100kg more production or $75,000--$150,000 more income per year for a 300ha farm by focusing on pasture growth and pasture quality, he says.

However, Gray says it is possible to have too much of a good thing with pasture; farmers shouldn’t let growth get away from them. Once grass has grown past the three leaf stage it starts to lose its feed quality, Gray says.

As the fourth leaf emerges, the first leaf starts to die and decay, reducing net pasture growth and feed quality for stock.

This can be an issue for farmers, especially during peak growth periods in spring and early autumn and Gray recommends keeping control of pasture to make sure pastures retain overall quality.

Dairy farmers are often limited to mechanical methods of controlling excess pasture, including cropping or the harvesting of silage. Baynham says drystock farmers often have a few more tricks up their sleeves.

Some options farmers might consider include adding a new stock class, setting land aside for hay or silage, changing the grazing rotation, for example by using leader and follower mobs.

“We have a few more tools in the toolbox than dairy farmers.”

Mulching and mowing does work

Meanwhile Baynham says managing ryegrass can become more complex when dealing with pervasive grasses like kikuyu.

Common in pastures in Northland, Auckland and northern Waikato, kikuyu is a drought tolerant grass variety which can take over if left unchecked during the autumn, reducing the proportion of valuable ryegrass available during the winter.

While being fairly hardy, especially in summer, kikuyu often doesn’t match the feed quality of ryegrass, especially in late autumn when kikuyu dies off and stolon builds up in pasture.  

Baynham says this can reduce liveweight gain in autumn, and if not actively controlled can slow the establishment of winter active pasture species like ryegrass.  

There are autumn kikuyu management options, he says, which improve winter pasture growth and set up feed quality for the spring through either hard grazing or mulching or mowing.

Mowing or mulching paddocks in late autumn breaks up kikuyu stem and stolon, allowing ryegrass to emerge earlier and reducing the amount of low energy fibre in pasture. 

Mulching is the process of cutting autumn pastures with a slasher or mulching mower, usually to a length of 1cm-2cm.

As mulchers break up material finer than mowers, they take longer to travel over ground than mowers requiring more fuel and tractor hours.

Mowers don’t break up material as well, resulting in material needing a longer time to break down.

A study on Far North sheep and beef farmers Grant and Peggy Morrison’s 390ha farm north east of Kaitaia revealed that mulching and mowing did improve the edibility of pasture.

Mulched and mown pastures both produced pasture with extra 2 megaJoules of metabolisable energy/kgDM than uncontrolled pasture and 7% extra protein.  Stock grazing the mown or mulched pasture would be expected to have double the liveweight gain of animals grazing the unmown pasture.  

While initial studies on the Morrison’s farm revealed little difference between the mown and mulched plots, research completed by the Kikuyu Action Group found that mulched pastures will take off earlier than mown ones.

However, with costs of an extra $30-$40 in fuel and tractor time Baynham says costs and benefits must be weighed.