Sunday, August 14, 2022

Diversity for sustainability

Adam Cullen, of Ararua in the Kaipara District, has rediscovered his enthusiasm for agriculture and applies his curiosity to finding new ways of dairying better, says his wife Laura.

Adam and Laura Cullen have a newfound enthusiasm for dairying in Northland when multi-species cover cropping has become the first stage of maize growing.

Concern for the soil structure after summer maize cropping with conventional tillage has led Northland dairy farmers Adam and Laura Cullen to introduce multi-species cover crops over the prior winter and use direct drilling where possible. They are only beginning to see the benefits of this regenerative approach, they told Hugh Stringleman.

Adam Cullen, of Ararua in the Kaipara District, has rediscovered his enthusiasm for agriculture and applies his curiosity to finding new ways of dairying better, says his wife Laura.

The change of mindset prioritises improving the environment and the farm resources rather than constantly driving for production.

But the Cullens are not following a formula or prescription, rather being adaptive to their circumstances and farming conditions.

The young couple with two small boys, Hugh and Gilbert, have a 450-cow split-calving herd on the 200ha effective predominantly Waiotira clay loam soil, previously the family farm of parents Bill and the late Gael Cullen.

One of five children, Adam was born and brought up on a drystock farm near Paparoa before going to University of Waikato to study for a Diploma of Forestry Management, followed by a Science Degree in Resource and Environment Planning.

He met marketing and communications specialist Laura in Hamilton and after some overseas experience Adam spent two and a half years as a Ravensdown fertiliser representative learning the fundamentals of nutrient management.

In late 2008 they moved back to Ararua for Adam to farm manage then sharemilk for Bill and Gael, while Laura continued to work in Auckland.

The farm was reconverted to dairying, with a 50-bale rotary, cup removal, teat spraying, effluent system, roading and paddock subdivision and Adam began what he now calls his conventional drive for more milk.

After growing the herd size to 550 cows in 2014, half-and-half autumn and spring calving, with a winter milk contract for Fonterra, and annual production of 175,000kg milksolids, Adam was working continually through the year.

“It was my ambition to get to 1000kg/ha, with what was probably System 3 with conserved fodder, but that was never achieved,” Adam said.

“The peak of 950kg has now come back to 750kg, with fewer cows and a more sustainable pace.

“That 150,000kg production feels more consistent in good and bad years rather than chasing the occasional great season.

“My success is no longer defined by milk production, but gaining knowledge for genuinely improving what we have here,” he said.

Adam Cullen

Adam Cullen fields a question from a cow, “when are we going to get another break of the summer crop?”

The fine clay soil structure and its compaction by the maize cropping and pasture re-establishment was always a concern for Adam and he looked for ways of mitigation.

Ararua can get very wet in winter, when pugging is a big risk, and very dry and solid in the summer.

Despite using different ryegrass varieties and some alternative species, dry matter eaten by the cows was slowly declining, which Adam put down to poorer soil health.

“Tighter soil structure not allowing root growth and aeration. Hard and discoloured soil that took months and many inputs to recover,” he said.

“We lost pasture growth rates in the shoulders of the season and we were slow to get started again after rain.”

Purchase of the farm five years back came after a period of even longer hours for Adam and a degree of disillusionment and being burnt out.

Laura suggested he attend a three-day soil management workshop led by Nicole Masters, director of Integrity Soils.

“I went along with an open mind and I found the messages clear and easy to understand,” he said.

“I was re-energised by the possibilities and motivated to shift from cultivation to using cover crops to feed and aerate the soil before maize sowing.”

Cropping and regrassing has been a way of maintaining ryegrass and clover pastures and keeping kikuyu inundation at bay.

Up to 20ha of summer maize is grown each year and now 10ha is still established with conventional cultivation and the other 10ha direct drilled after a cover crop during the winter.

Multi-species cover crops for grazing and/or baleage establish diverse and deeper root systems and feed the soil biota, including worms, before allowing the conditions for direct drilling of maize.

The visual soil assessments, before and after, have been eye-opening in terms of soil colour, structure and worm population.

Adam Cullen

Adam Cullen in a paddock of summer maize he sowed with a tyne drill after a cover crop when the local direct drill wasn’t available.

David Wordsworth, a rural contractor and farmer from Dargaville, uses no-till sowing of maize with fertiliser and slug bait placement in one pass, saving on fuel, labour and nutrient loss.

This past year, when the sowing window was closing and David was not able to respond quickly, Adam used his own Taege tyne drill behind the 125hp Valtra 114N tractor.

He also sowed another cover crop with different species for summer break feeding, featuring sunflowers, cereals, chicory and many others, all expressing its own unique set of exudates to feed soil biology.

A multi-species mix contains at least 20 species, many of them procured from Wesco Seeds in Canterbury, and then added to and blended by Adam in his new concrete mixer.

They contain an annual ryegrass; cereals like barley, buckwheat, hairy vetch and peas; brassicas such as kale, pasja, mustard and radish; legumes like clovers and lupins; and other species, such as phacelia, sunflower and flaxseed.

The mixes are drilled at 50kg/ha and a seed cost around $400 to $500/ha, plus spraying out, tyne drilling and follow-up spraying of fish hydrolysate and effective microbes.

Those costs offset what would be ploughing and rotary hoeing and more tractor hours.

Adam said conventional maize crop establishment is now in the thousands of dollars a hectare and his method is considerably cheaper with only a small drop in silage yield.

In Northland’s milder winters, in three to four months the cover crop has grown 8-10t/ha.

When lightly grazed by the cows, the aim is to leave one-third to one-half of the cover behind to be flattened and sprayed with glyphosate before drilling maize.

Adam has also cut and stacked the crop instead of break feeding.

The residual cover crop keeps weeds invading the maize and feeds organic breakdown material.

The benefits for soil health and structure stay well into the regrassing, as verified by visual soil assessments on a regular basis.

“I am happy with a slightly lower maize yield to get another tonne of pasture per hectare per year thereafter for a decade,” he said.

No stranger to soil testing, he found both soil pH and Olsen P have improved without specific fertiliser inputs.

The farm still gets annual fertilisers where necessary, although not under paddocks scheduled for cover crops, but the use of superphosphate has reduced.

Budget savings in fertiliser have been redirected to multi-species seed mixes.

Now in their fourth year of cover crops before maize, Adam and Laura expect to do all their maize paddocks in 2022 and beyond.

Autumn has added importance, not only for autumn calving and the set up for the very worthwhile winter milk contracts, but also the cover crop choices and establishment, which excites Adam.


Some of the Cullen cows after feeding on a break of multi-species like sunflowers, cereals, chicory, brassicas and legumes.

Maize has always been the preferred crop for silage and supplementary feeding, but because of the dry summers in the north that may have to change in the future.

Bill Cullen and Rabobank have been financially supportive of Adam and Laura’s farm changes and their farm consultant, Paul Sharp of Nutrition Services, has advised both right through the process.

He has modelled possibilities and results, while listening and encouraging as a rural professional should, building the Cullens’ confidence in the moves.

Adam looks at multi-species pastures quite differently now, for the benefits in carbon capture, diverse micro-organisms and rhizobia and the improved soil structure and porosity.

“We have the science to understand that process of adding diversity and sustainability,” he said.

Intercropping and companion planting offer further avenues for development, along with herbal pastures of chicory and plantain.

Silages with more nutrients, energy and variety are worth looking for, he said.

The Cullens have not promoted their cropping changes and do not want to be labelled or pigeon-holed, but they are happy to explain their journey to farmers keen to listen.

“I now have enough of a story to tell that I am happy to share,” he said.

They may be early movers on dairy farm emission mitigation, reducing cow numbers and alternative pasture species, providing test beds for pastoral science of the future.

“I remain very proud to be a dairy farmer, and it is now the new ways of doing it which gives me a real purpose.”

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