Subterranean clover management on a dryland hill country station
Over the past 15 years David and Jo Grigg have taken advice from Lincoln University researchers Derrick Moot and Dick Lucas, and others, to enhance the role of subterranean clover (an annual clover) on their dry hill country Tempello Station for spring grazing for ewes and lambs, with follow-up cattle grazing.
Sub clover had been on the farm since the 1950s but it was only in the 2000s that the Griggs really started to manage it for better total pasture legume content.
Meat and wool returns for Tempello Station have risen considerably from increases in lambing percentage, lamb weaning weights, winter stocking rates, high body condition scores, and more lambs and cattle finished prime rather than sold store.
The property has been in the Grigg family for 104 years. It is 4800ha (around 2500ha effective) of hill country running from the Wairau Plains south-west of Blenheim (Renwick) at 100m ASL up to 909m ASL (The Ned) in the ranges between the Wairau and Awatere valleys. It contains 560ha of “front country” nearest Renwick that is medium and steep hill country facing north.
Annual rainfall varies from only 500mm at the northern (Wairau) end to 900mm at the south-west (Awatere) end.
Tempello runs 10,500 stock units, 50/50 sheep and cattle. The ewe flock is both Corriedale and Merino and in June 2017 there were 2090 ewes and 550 capital hoggets (ewes and wethers). It also carried 1450 merino wethers and 1000 trading lambs/hoggets. Lambs are weaned at 10 to 12 weeks and sold prime. The cattle population was 335 breeding cows and all steers and cull heifers are finished to 290kg CW by 20 to 22 months.
Peter Anderson, their local vet, first identified the huge potential of sub clover after talking to Dick Lucas at a field day. It is a prolific seed bearer and the clover content of mixed pastures can have a help-along by treating the blocks in a certain way every 10 to 15 years, to really promote the seed establishment success.
Ten or more Australian sub clover cultivars are available in NZ, six of which are stocked by seed merchants (Antas, Bindoon, Coolamon, Monti, Narrikup and Rosabrook).
It is now commonly sown at the rate of 10kg/ha and the recommendation is to sow 5kg each of two cultivars. Yields of up to 16 t DM/ha/yr are achievable from sub clover monocultures under ideal conditions. In grazed swards mixed with grasses or herbs sub clover DM contribution ranges 1 to 5 t DM/ha/yr. Woogenellup is currently the dominant sub-clover cultivar on Tempello’s front country.
The Lincoln University Dryland Pastures Research Team says subterranean clover is better adapted to dryland pastures in New Zealand than white clover, and provides more high-quality biomass in late winter and spring than perennial white clover.
Legumes have great benefits for farmers on dry hills (of which there is 2-4 million ha in New Zealand) because of its ability to fix nitrogen and higher energy content than grasses. Sub-clover grows earlier in late winter than other legumes. Sub-clover flowers and buries its burrs (seed pods) before the onset of summer drought. This adaptation allows it to provide valuable late winter/early spring feed for stock before it dies off during the dry late spring/early summer months. The buried seed germinates in the autumn as soil moisture increases. Sub-clover seed is large in comparison to other clover seeds (10 times heavier than white clover seed).
However, sub-clover is a poor competitor and sensitive to shading.
The system is managed as follows: a block is fallowed during spring, allowing natural re-seeding late December, clearing off the grass competition in summer then allowing a germination in the autumn rain. No grazing is done until the tiny clover plants have 4-5 leaves, so they don’t pull out. The enhanced clover content then fixes nitrogen in the soil, benefitting the other grasses.
The Woogenellup cultivar of sub-clover was initially over-sown by plane at a low rate of 3kg/ha in the 1970s and now forms part of the pasture species mix along with browntop, danthonia, cocksfoot, barley grass, silver tussock and perennial ryegrass.
Lincoln researcher Dick Lucas says the fact that it persisted and was sufficiently widespread to be able to respond to management designed to exploit the potential productivity showed the excellent adaptation of Woogenellup to the Tempello environment.
Sub-clover was present on Tempello since the 1950s and was over-sown by air in the 1970s. However it was over-powered in spring by grass growth and sheep preferentially grazed different areas of large paddocks, resulting in uneven feed quality. Following sub-clover germination in autumn, plants could not always be protected from close grazing during vulnerable stages of the clover’s life-cycle.
Without a big contribution from legumes, the Tempello stocking rate on the front country was 8.2su/ha wintered, lambing percentage around 120% and supplementary feeding was needed to get ewes back to tupping weight.
A trough water scheme was installed, and subdivision brought the block size down from 30-120ha to 9-18ha, using 30km of five-wire fences with an electric top wire.
Block numbers went up from six to 30. Key was recognizing the potential of sub-clover as a feed source and altering grazing management to suit it. Competing grass must be hard grazed in selected blocks by cows during summer and ewes during winter. Total development cost has been $670/ha or $375,000.
The enhancement of sub-clover and the nitrogen fixation means that no bagged nitrogen is now used on the hills on Tempello.
David and Jo Grigg joined the Sheep for Profit programme in 2001 and used ewe body condition scoring and weight records to devise a system to regularly meet ewe weight targets using sub-clover as a cornerstone. Ewes are rotationally grazed and break-fed on saved pasture in winter. More cattle mouths were added for pasture control, for prime cattle finishing, and the stocking rate over winter has gone up by 2.9 to 10.5 to 11.5su/ha.
Sub-clover blocks are spelled for seven to 10 weeks to growing feed for lambing on August 20. In spring, ewes are set-stocked for lambing and cattle mixed in depending on feed covers. Lambs are weaned at 10-12 weeks, sold as prime lambs and replacements returned to the sub-clover area.
In summer cows clean up the lambing blocks when the sub-clover is dormant, so that when autumn rain comes the sub-clover has space to germinate, grow, and compete with grass.
In autumn the ewes are typically tupped on the short green pick of grass and young sub-clover.
Lamb weaning weight has increased from 27kg to 35kg average and lambing percentage from 128% to 138%. The increased stocking rate in winter enables home-bred beef cattle to be grown on and sold prime as rising-two-year, rather than sold store as yearlings
Ongoing pasture maintenance costs are minimal and supplementary feeding has been cut down to bulls and rams only.
Building the sub-clover seed bank in the soil means selecting a block in spring to put through the “enhancement process”. The block is grazed down hard by cattle in January/February, shut up during autumn for sub-clover seed germination and growth.
Grass competition is removed by grazing ewes from mid-June to mid-August. The clover base survives this grazing down to 600kg DM/ha. Sub-clover is then left to recover in spring, up to 3500kg DM/ha when long runners can invade bare ground or areas with no clover. The block can be grazed from December onwards when most seed burrs are safely buried by the plant.