Lucerne, lupins and much, much more

 Two crops commanded an unusually high percentage of papers at this year’s New Zealand Grassland Association conference: lucerne and lupins.

From the scene setting opening papers to the closing session research reports, lucerne’s renaissance and ability to revitalise dryland productivity and lupins’ potential as an alternative on low pH, high aluminium soils featured.

Given the venue and theme – Alexandra; “Farming in a land of extremes” – their dominance was understandable but it wasn’t all about the L-crops: the latest science on ryegrass, clovers and various other forages was relayed, as was some grazing management and fertiliser work.

For example, AgResearch’s David Stevens showed how adding 100-150kgN/ha in spring to regular dryland hill country inputs phosphate, sulphur and lime at a site near Roxburgh increased drymatter production of tussock country from about 3200kgDM/ha/year with no fertiliser or just lime, to 6000-8000kgDM/ha depending on the season. Phosphate and sulphur alone boosted production to 4000-5000kgDM/ha.

“Where we weren’t using fertiliser the feed was extremely poor quality and where we were using only nitrogen the feed was also extremely poor quality because we were suppressing legumes,” he pointed out. 

Those pasture production gains could increase stocking rate from under 5 ewes/ha to nearly 10 ewes/ha, adding a potential increase in net margin of $200/ha.

“If we can grow 7t/ha in that environment we are getting close to what we could achieve using the plough,” he added.

Lincoln University’s professor of dairy production Grant Edwards presented data from the irrigated light land of Ashley Dene showing there’s little to choose between kale and fodder beet as winter feeds, so long as you feed plenty of them.

“The drivers should be how cheap is the crop to produce, how well can you grow it on your farm and how it fits the farm system, rather than how well it will put condition on the cow,” he said, reflecting on work where mobs of 50 cows on kale, either early or late sown, and fodder beet, all achieved well over the target 0.5 gain in body condition score through June and July.

Fodder beet did yield more than kale in the second year’s work but by sowing forage oats behind late sown kale and harvesting them as green chop silage in November for subsequent winter feeding, annual dry matter per hectare was on par with beet.

Answering questions, Edwards stressed transition of cows onto winter crops, particularly fodder beet, needs care, with alternative feeds during transition to keep intake at about 150MJ of ME/day, as it should be throughout winter if that target of 0.5 BCS gain is to be achieved.

Costings from the trials came in at 9-10c/kgDM for fodder beet, 13c/kgDM for early-sown kale, 15c/kgDM for late-sown kale, and 12c/kgDM for the forage oats. But when the cost of supplement was added – fodder beet was allocated at 8kgDM/cow/day plus 6kgDM/cow/day of baleage, early kale at 14kg with 3kg of barley straw, and late kale at 11kg with 5kg of greenchop oat silage – Edwards said the net cost/cow/day of all the diets was similar at $2.30-2.50/cow/day.

Meanwhile, Lincoln colleague Professor Derrick Moot presented papers on lucerne and lupins, showing how the latter lifted production off high aluminium, low pH land at nearly 800m above sea-level to 10tDM/ha.

“It’s currently being used as lamb feed and the lambs seem pretty happy to be in amongst it,” he commented.

In the trial 40-60% of the lupin drymatter was eaten. 

“They ate it and they ate the material between [the lupins],” he said, showing slides of stalks but little else left.

Sowing rates of 2kg/ha to 32kg/ha were tested, all with 2kg/ha of cocksfoot, though the lupins produced 79% of yield overall, and 90% in spring.

Seed emergence was only 40% regardless of sowing rate.

“It is quite hard seed and if you put it fresh in the ground it won’t germinate. It needs scarifying. That’s why it turns up in the rivers…. but 8kg/ha is probably enough seed,” he reflected.

Despite its being a big seed, sowing depth is also critical, at 10-20mm, and into soil, so if there’s a thatch of dead material intended sowing areas should be taken through a cycle of ryecorn or two.

Ryecorn’s use as an entry crop also featured in David ‘Gundy’ Anderson’s paper on how lucerne has transformed their system at Bog Roy Station in upper Waitaki. The 2860ha station runs from 400m by the shores of Lake Benmore up to 1000m, with only 420mm of rain. “So it’s much the same as around here,” he told the Alexandra audience.

Spraying out pasture, taking two ryecorn crops, then sowing lucerne has established the deep-rooting legume across 200ha which they now lamb ewes on, albeit with a “light touch”, low set-stocking rate of 7/ha.

Ewes are scanned for foetal age, grouped by lambing date, then ideally go onto 15cm stands of the crop just before lambing, though a cold spring this year meant it was 10cm. “But it was 20cm when they came out.”

In previous years continued rotation of ewes and lambs round the lucerne paddocks has lifted pre-wean growth rates from 205 to 235g/head/day, dropped lamb mortality from 30% to 21%, and boosted pre-winter ewe lamb replacements to 38kg from 35kg. In turn that’s lifted two-tooth scanning from 111% to 129% and weaning percentage to 100% from 84%.

Anderson stressed the “ripple effect” the crop is having on the property, reducing overgrazing on native and oversown hill country so that too is now more productive.

As for the lucerne itself, that’s lifted annual drymatter production from a 3-8tDM/ha range, depending on the season, to 10-12tDM/ha/year. “There’s a real consistency with this plant if you look after it.”

Anderson wasn’t the only farmer speaker lauding lucerne’s dryland productivity. On a field trip to Greenfield NZ Pastures delegates heard how sowing 2300ha of the crop, sometimes mixed with fescue, has more than doubled carrying capacity of its 3900ha Hills Creek Station.

And in a scene-setting paper in the conference’s opening session, former NZGA president Pat Garden touched on how he’s planning to use lucerne and fodder beet to finish cattle in 15 months.

Meanwhile Moot, who co-authored seven papers presented at the conference, drilled down into the detail of winter weed management in lucerne, presenting findings from an on-farm herbicide trial at Hills Creek showing successful weed control with atrazine and glyphosate during July and August when the crop’s dormant and had cover below 100kgDM/ha.