Tuesday, May 21, 2024

Huge soil loss requires change to farming methods

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Land restoration will take a toolkit of methods such as tree planting, wetlands, fencing-off of gullies and streams and more.
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The multiple heavy rain events this year have underlined the threat to the landscapes beloved by New Zealanders and tourists alike and the soils that underpin agricultural production, essential to our economy. 

Landcare Research reports an annual loss of 192,000 tonnes of soil as a result of earthquakes, intense rain events, agricultural intensification, loss of vegetation, urban spread, and industrial pollution and waste disposal. 

The outcome of these factors is loss of production, nutrients and soil biodiversity.

I recently attended a workshop on land restoration in the Mahurangi region as part of a programme organised by Auckland Council in collaboration with local iwi, Ngāti Manuhiri. 

The programme began in 2020 with $5 million of funding from the council for project applications from local landowners on a 60/40 shared basis with the goal of increasing the health of the Mahurangi Harbour and its waterways through reduced sedimentation run-off from both private and public land activities.

Since its inception, 92,000 native trees have been planted on private land and 55,000 on public land, 6.8km of fencing erected, and 29ha of wetland created. Auckland Council provides programme management, technical advice and support, planting assistance and help with completing applications.

Duncan Kervell, a land management consultant based in Whangārei with substantial experience of the soil types in Northland and North Auckland, gave a presentation on how best to control sedimentation run-off by adopting a resilient toolkit of targeted treatments. 

The components of the toolkit include tree planting, wetlands, fencing-off of gullies and streams, livestock exclusion, native regeneration and good farm practice. He said all the ingredients for success – good science, funding, GIS mapping, engaged support and partnerships – are present in the Mahurangi district, although time is of the essence, especially with the loss of topsoil from heavy rain events like the Anniversary Weekend and Cyclone Gabrielle floods.

He told the audience the soft rock in this part of the country was originally seabed, and that is responsible for the soil structure instability, causing erosion of hill country, stream and riverbanks, and soil under pasture. This geological weakness means sediment run-off occurs with only 4mm of rain compared with 50mm in Canterbury.

It is therefore essential to slow the erosion process with tree planting in the right places, whether permanent native afforestation, production pine forestry, or space planting of kānuka, mānuka and totara to maintain adequate pasture.

The introduction of kikuyu over 100 years ago has slowed the rate of sedimentation, while the amount of planting more recently has also helped. But heavy cattle on vulnerable land cause worse erosion and, while it is important to balance ecology with economic imperatives, there is a limited time left to fix the problem.

Encouraged by the evident commitment to tackle the erosion problem, I was curious to find out how much these solutions have in common with the fashionable trend towards regenerative farming. I spoke to a friend’s son who used to run a successful organic dairy farm in Waikato to find out if it was possible to maintain production without eventual collapse of the soils by following regenerative methods, especially on the vulnerable soils of much of the North Island. 

Obviously a sample of one is not a completely reliable research base, but he made some very interesting and apparently logical assertions.

In retrospect he would not go down the organic path again because it is so prescriptive, whereas regen is more focused on outcomes without specific prescription. Regenerative farming is by definition lower input than conventional farming, but it does not preclude using animal health remedies and fertiliser as necessary to maintain soil health, which is a major concern for agricultural production. 

Because of the lower level of inputs, regen is more in balance and resilient than high-input conventional farming, which can be very stressful for both land and farmer, especially when weather extremes or sudden market price falls occur. 

A key aspect of regenerative farming methods is the health of the landscape, which is a function of water, nutrient and carbon cycles and biodiversity. If these things are in balance and the soils are friable instead of compacted, more water is stored in the soil with a positive effect on its biodiversity.

Unlike biodiverse farming systems, conventional, high-input farming and more particularly exotic forestry planting impose a large externalised cost on the environment through damage to the landscape, on the consumer because of the reduced nutritional value of food production and the presence of pesticides, and ultimately on the taxpayer. 

Land clearance and pine planting of unsuitable hill country by successive generations, while facilitating economic productivity, have also resulted in substantial damage to the landscape at huge environmental and community cost.

My contact admits regenerative farming has some disadvantages and he isn’t keen on the evangelical attitude of some of its proponents, emphasising the importance of taking it slowly, rather than going in “cold turkey”. 

The regenerative industry is still immature, without an academic base, and there is a shortage of consultants available to help farmers wishing to transition to a lower-input method of farming. 

Consequently there is no prescribed way of doing it, unlike conventional farming, which has a solid scientific and academic basis.

Regenerative farming will not be the way every farmer wants to go, but it may be worth considering, if there are concerns in particular regions about soil loss and land erosion or where the high input farming model is generating diminishing returns.

Production may not necessarily reduce too much and the stress levels may come down.

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