Chemicals and management has seen a Banks Peninsula couple raise the legume content of their pasture from 5% to 40%. Sandra Taylor reports.
The benefits of legumes for animal production are well documented but what management practices enhance the production of both resident and introduced legumes on uncultivable hill country?
This was a focus of a field day on Hamish and Annabel Craw’s Banks Peninsula hill country farm. While the field day was held to summarise the results of the couple’s four-year Beef + Lamb New Zealand innovation farm programme, four other hill country farmers from along the east coast of the North and South Island shared their experiences of establishing and managing legumes.
While all farmers were sold on the benefits of increasing legumes in their hill country pastures to lift the quality and quantity of drymatter grown, the type of legumes grown and management of them differed in different environments.
For the Craws, the combination of chemicals and management have been effective in increasing the legume content of their sward from 5% to 40% over four years in the areas targeted.
They prioritised the enhancement of resident clovers – which included subterranean clovers – but also tried introducing new varieties of clovers with mixed results.
Speaking at the field day, Hamish and Annabel went through the timeline of the innovation farm programme, describing how they started with plot trials in year one to identify the most effective spray options before upscaling and fine-tuning their management from years two to four.
Measuring the quantity and energy density of the trial versus control, estimated that increasing the quantity of legume in the sward lifted the energy value of the pasture over October and November from 13,658 megajoules of metabolizable energy (MJME) to 22,197MJME/ha. This represents an increase in total available ME of the pasture by 63% over those two months when the Craws are trying to maximise pre-weaning lamb growth rates.
The agrichemicals have proved critical to the breakdown of the thatch that is idiosyncratic of the Craws steeper hill country.
Opening the thatch allows clovers to thrive and once opened, management will allow the legumes to regenerate and proliferate. Hamish and Annabel believe they will have to go back with a spray every five to six years to break down re-formed thatch.
The sprays are applied in spring and this gives the resident subterranean (sub) clovers the opportunity to flower and set-seed without competition from grass. Hamish admits it is difficult taking an area out of rotation in spring, particularly when feed supply is tight, but it is a case of short-term pain for long-term gain.
With the right management, clovers can produce 400kg of seed/ha which at a modest strike rate of 5%, generates 20kg of clover seed/ha. At a clover seed cost of $9.45/kg, this is $189 worth of seed/ha – simply with the correct management.
After spray and spelling in late spring and early summer, the Craws have a bank of high-quality feed for weaning lambs onto and then for flushing ewes at mating.
The Craws have been set-stocking twin and triplet ewes on this high-quality feed and these ewes are producing what Hamish describes as “some of the best lambs on the property”.
These improved pastures are growing an average of 56kg DM/ha/day between August 28 and October 10 and at their peak, were growing at 90kg DM/ha /day.
Initially the Craws were using Haloxyfop and found it to be very effective at breaking down thatch and opening up the sward. However, withholding periods of Haloxyfop meant they had to change to Clethodim and the Craws are still fine-tuning the use of this chemical.
In their early plot trial work, they found glyphosate hit the clover too hard and it was considered too much of risk to use. Also, opening up the ground too much with chemicals allows thistles to proliferate.
Hamish and Annabel are looking to increase the proportion of cattle in their sheep and beef business to keep the grazing pressure on their improved pastures to remove grass competition and allow clover to flourish. They believe a 50:50 cattle to sheep ratio would be ideal.
“We need a stock policy that is financially rewarding but by increasing cattle numbers, we will get the sheep to perform even better.”
The Craws farm in a typically summer dry environment which is ideal for subterranean clover, but they also have white clover in their sward and this also does well in wet springs and summers.
Speaking at the field day, clover expert Dick Lucas from Lincoln University, says sub and white clovers can’t be managed at the same time – one needs to take priority.
Annual clovers such as sub are active in the cooler season which is important at lambing and during early lactation.
In Banks Peninsula’s relatively mild climate, sub clover can start growing from mid to late August and grow vigorously over September and October.
The quantity of sub clover in the sward is dependent on autumn rains to allow the seeds to germinate.
“Autumn strikes drive the sub clover supply in early spring,” Lucas says.
He recommends hill country farmers actively manage a block each year to favour sub clover production. This means allowing the clover to flower from mid-October and then shutting the block up from mid-November- earlier if it is dry- to let clovers send out runners and set-seed.
If there is not enough resident sub, then over-sowing should be carried out in autumn.
“Think of sub clover as a nitrogen factory on your sunny faces.
“Assess blocks each year and decide what needs a boost – they might need additional seed and fertiliser.”
The Craws have applied additional seed but have not had the results they hoped for. They believe the delayed application of seed in autumn and possibly slugs may have impacted on strike rates in the introduced seed.
PRODUCTION INCREASE
Unimproved Area:
Spring
- 5 – 6 ewes/ha mainly twins
- Lamb weaning wt – 31 kg
- Ewe Weaning wt – 67 kg
Summer
- Rotation – 12 lambs /ha @ 125 g/d
Autumn
- Rotation – 10 ewes/ha
Winter
- Rotation 5 – 6 ewes/ha
- Improved Area (ave. over 5 years)
Spring
- Lamb Weaning Wt + 1.4 kg
- Ewe Weaning Wt + 2 kg
Summer
- 300 g/d – dropping to 150 g/d (year 5)
- Average increase + 85 g/d (+7.6 kg/lamb)
Autumn/Winter
- Ewes heavier at mating – lamb 3% higher
NB: assumes any increase in stocking rate offsets destocking in first spring.
