Learning Lessons Again

This article first appeared in The GROWER magazine in 2012. We were getting more reports of cropping paddocks disappearing in the wind, something I regard as a disaster. With a comprehensive flood protection system in place stopping alluvial deposition, no ice age looming to create more loess and hopefully no more major volcanic eruptions donating ash, our local Heretaunga Plains soils are no longer replenished. Once gone, they are gone.

Learning Lessons Again

Do we really forget strong winds are a regular feature in Spring?

Clouds of soil need not be part of this picture. Why do we not plan, or plan not, to account for these winds? I admit to frustration – wind is normal!

Many New Zealand cropping soils are loess covered gravels. Loess is wind-blown silt, ground out of the ranges during the ice age, and exposed by retreated glaciers. Unless we have another ice age, we are not going to get much re‑nourishment.

Many others are volcanic ash – such as from Taupo. Unless we have another (really, really) major eruption, we’ll not get more of that either. So we need to look after what we have.

The very simple message on light soils is that is if you open them up, they can blow away. And blow away they have.

When first developed, horses were used to till land for pasture and cereals. The late soil scientist, Elwyn Griffiths, said that in some parts of the Ruataniwha Plains “about three feet” of soil was lost within a few decades.

Mechanisation replaced horses, powered implements created fine seed beds and wind erosion continued. In the mid-1990s severe erosion events were reported.

A local field rep said, “We lost over 50mm of soil this Spring. I know we did; we planted peas an inch deep, the wind blew and the pea seed bounced across the highway. We replanted and that lot blew away too. Then it was too late to grow peas so we planted sweetcorn instead. Even that got damage.”

In 1999 LandWISE set out to stop wind erosion.  Valuable knowledge about how to keep soil from drifting across the plains and out to sea was gained and disseminated.

Direct drilling or no-till stops wind erosion completely. So long as there is effective ground cover, the particles are retained.  No-till was good for grass and cereals, but less promising for process crops and squash.

LandWISE developed and proved strip-till techniques that allow for seed bed creation yet keep soil intact. With half to two-thirds of the ground still covered with thatch or residues, the soil avalanche can’t get started: strip-till stops wind erosion too.

The additional benefits are numerous: Better water holding capacity, better drainage, reduced fuel consumption, no sand-blasted young crops, less grit in your eye, a soil resource to pass on through the generations, time and energy savings, reducing costs and carbon footprint into the bargain.

Minimising tillage consistently proved viable and cost effective on light soils. It rapidly showed benefits on heavy soils too. The soils were stronger, better draining and generally in better condition. Machinery cost and fuel use were halved.

“It’s a no-brainer,” we said, and devoted several years to demonstrating the techniques, pitfalls and benefits.

Labour weekend 2012, thirteen years later, and across Hawke’s Bay we see clouds of topsoil leaving fully cultivated paddocks. The wind is taking away the richest part of the soil, removing nutrients and water holding capacity and damaging developing crops.

My frustration is amplified. One of these disappearing paddocks is the very one where all our work started. Others are paddocks where strip-till or no-till has been used very successfully in the past.

Why do we have to learn these lessons again and again?

Dan Bloomer, LandWISE

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