Friday, March 29, 2024

Beeting the weeds

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​Anne Calcinai follows up five past​ Country-Wide farmer case studies​ and their pasture renewal. Since buying her farm three years ago Suzie Corboy has been working to increase the area of finishing country. The goal is to renew 10% of pasture each year. This renewal rate is in-line with the target advocated by the Pasture Renewal Charitable Trust. While Corboy has not quite reached 10% the pasture renewal programme is progressing well. Corboy sowed fodder beet (SF Brigadier) for the first time last year and cattle were due to start grazing the new crop in mid-June. Wet spring weather delayed sowing by almost one month until early December, when the six ha crop was precision drilled at 90,000 seeds/ha.
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“It’s very sensitive to weeds and I had to do two very expensive sprays – just after sowing, then again two weeks later,” she said.

At 20 tonnes/ha the yield was not as high as Corboy had hoped. It could have been 30t/ha.

She hopes fodder beet will allow cattle to gain weight, rather than just maintaining weights, by utilising a higher yield in a smaller area. To avoid acidosis problems Corboy plans to introduce the cattle slowly on to the fodder beet, allowing them half a kilogram each per day and building it up to 6kg. She has barley straw to feed out to cattle grazing the fodder beet and a paddock of grass saved up next to the crop.

Cattle were weighed before going on to the different winter crops so Corboy could compare weight gain after grazing.

“If fodder beet works I might be tempted to grow more. I’ll have to plough the grass earlier for sowing early to mid-November, which will take feed away from the ewes and lambs one month earlier than normal.”

The fodder beet cost $1940/ha to grow including sprays, fertiliser, seed and application, plus cultivation which Corboy did herself so that component is an estimate.

A swede-kale mix was sown on 21ha in early December. The ground was ploughed first by a contractor then, using her own 18-row drill, Corboy sowed four rows of kale at 3kg/ha and 14 rows of swedes at 1kg/ha. She tried HT Swede for the first time this year in an effort to combat weed problems.

“I spray the paddocks with glyphosate before ploughing but there’s been quite a lot of weeds in the swedes the past few years.

“I’m trying to get a better weed-free winter crop and hopefully it will carry through to the pasture.”

Ewes would graze the swede-kale from mid-June to mid-August and yearling steers from late June to early September. Corboy said this year’s swede crop was far better than the previous year, which she put down to better weed control.

She was also happy with her first attempt at over-sowing swedes, on 10ha of steeper hill country, which yielded 10t/ha. The area was sprayed once with glyphosate before the swedes went on at 2kg/ha.

Wet weather delayed sowing of 30ha of new pastures until December 30 and the seed bed was less than ideal. 

Lambs were able to start grazing new pastures in early March, which had more weeds than Corboy would have liked.

“Because it was late in I didn’t get as much lamb grazing off it as I had hoped.”

Corboy opted for Prospect ryegrass because it should provide good, early growth when it’s needed but still maintain quality later in the season.

She avoids using too much Hunter brassica because it shades the grasses but finds it very good for lamb finishing. Pasja is also included for its lamb finishing value.

Corboy broadcasts the grass seed herself with a drill.

“I find the grass sowing quite stressful – I don’t want big bare patches when it starts growing.”

Farm facts

  • Suzie Corboy, Owaka Valley
  • 495ha (420ha effective)
  • 2500 breeding ewes plus progeny for finishing
  • 250 finishing steers
  • Calving 82 once-bred heifers
  • Mostly hill country with 160ha cultivatable

New pasture mix

  • 18kg/ha Grasslands Prospect AR37 ryegrass
  • 0.4kg/ha Pasja
  • 2kg/ha cocksfoot
  • 4kg/ha white clover
  • 0.8kg/ha chicory
  • 0.9kg/ha plantain
  • 0.4kg/ha Hunter Brassica

Weed control goal

Why does Suzie Corboy hope HT Swedes will help her get on top of weeds in her crop and pasture?

PGG Wrightson Seeds extension agronomist and nutritionist Wayne Nichol explained that HT Swedes are used as part of the Cleancrop system, which uses a broad spectrum herbicide called Telar, allowing the majority of weeds to be controlled in the HT brassica crop.  

Cleancrop is the combination of Telar chemical being applied (normally pre-emerge) to an HT brassica that is tolerant to the chemical. This includes the control of weeds that are traditionally hard to control in brassica, including shepherd’s purse and wild turnip which are themselves brassicas. 

With these weeds controlled there is reduced weed seed in the soil and no seed set from weeds while the brassica is growing. The result is far less weed seed to germinate in the next crop or pasture sown.

​Anne Calcinai followed up five past​ Country-Wide farmer case studies​ and their pasture renewal. See the others:

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