Thursday, March 28, 2024

Farmers urge river weed kill

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Helensville farmers Barry and Annette Bradly knew the problem with glyceria weed growing over the Kaipara River, which borders their property, was getting steadily worse.
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A series of floods caused by less rainfall than had previously been the case made them realise it was time to take action.

“We had to do something about the river,” Barry said.

He’s a third-generation farmer in the area. His grandfather bought up 15 and 20ha blocks of land during the Depression and amalgamated them.

“We go back a little ways,” Barry said.

Until 1998 they milked 180 cows on their 59ha property, which included 54ha of raupo swamp on river flats bordering the Kaipara. They were milking three cows a hectare on the land which they’d laser drained using Novaflo piping at 40m spacings and mole-ploughed at three-year intervals.

“It turned virtually unusable land into very productive land,” he said.

“Production was coming. We just had to get the tucker into them.”

Their Friesian cows were in the top 5% for production and they supplied bulls for herd improvement. More than 400kg milksolids(MS)/cow or 1200kg MS/ha was being produced with silage grown and young stock grazed on a 33ha block of land closer to the home farm, and all bull calves reared and grazed on a development block of 60ha at Parakai.

But issues with stock crossing busy State Highway 16 between Auckland and Helensville three or four times a day to be milked led to their switch to buying in yearling steers and finishing them at 630kg. They’re run in mobs of 60 with the top 10-15 taken out on a regular basis to “wait in the Koru lounge” before being sent for processing.

Around 320 head will be wintered, with the stock putting on 2kg/day.

Barry Bradly on his Helensville farm looking over the Kaipara River.

While Alligator weed grew on the river’s banks the arrival of glyceria, which quickly became dominant, restricted this plant pest to the water’s edge. A photo on the Bradlys’ lounge wall shows the river in the 1970s, meandering in twists and turns towards the Kaipara Harbour. Now water flow is down to a narrow channel.

Glyceria grows up to 2m tall, then after it flowers will die back leaving a bank of litter.

“In autumn it grows right out over the water in rafts and keeps growing,” Barry said.

“Its root structure means it’s like kikuyu in water.”

It’s not known how or when it arrived in the Kaipara.

In the past drag lines were used to clear some of the river banks every seven to eight years to keep a channel for water flowing from the Waitakere Ranges during heavy rainfall. Now 35-40mm of rain will trigger a flood when it used to take 50-60mm, flooding farms, State Highway 16, and once washing out the railway line.

“It comes in a wave now – there’s no warning. And new subdivisions going in at Kumeu will make the problem worse with more stormwater.”

When a log washed down the river and lodged 2km upstream of the railway bridge, weed built up behind it then dislodged after heavy rain, eventually lodging on the railway bridge, blocking the river again.

“Hunks the size of a house were breaking off and coming down the river.”

Spraying has been tried, with local farmers footing some of the cost.

In April a meeting was organised between two local Auckland councillors and five dairy and drystock farmers, and council staff visited their farms in May. The farmers urged spraying the weed along 8km of riverbanks, saying this option would be quick, easy, and cheap with cost estimates of about $12,000-$15,000.

The council agreed to pay for excavations under a railway bridge connecting the Bradly and Narbey farms to stop further weed build-up. Heavy machinery came in across the Bradly land in June, with work able to be done only during a four hour window at low tide. A strip 100m either side of the bridge was cleared over five days.

‘It comes in a wave now – there’s no warning. And new subdivisions going in at Kumeu will make the problem worse with more stormwater.’

Seeing the result has intensified the farmers’ calls for action to be taken on clearing or controlling the remaining weed so flooding danger is reduced.

“As it grows quickly in the spring that would be the time to get the best kill,” Barry said.

More importantly he believes a long-term strategy is needed for the river on which both landowners and the council can agree.

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