A spade (r) up his sleeve

24 Jan, 2014 01:00 AM
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Three Springs machinery dealer Bruce Cunningham.
Last year saw wheat yield results 2t/ha better than unspaded areas
Three Springs machinery dealer Bruce Cunningham.

IT is generally agreed rain is between 90 and 95 per cent of the equation for growing crops. Last season was a classic example.

For all the complexity associated with controlling weeds, nutrient targeting and soil renovating, WA grain growers put a record 15.8 million tonnes of grain in the bins; on the back of mainly below average but timely rain.

What it also highlights is an increasing focus on getting the one per centers right; ie, between five and 10pc of the equation; to maximise water-use efficiency, in a dryland farming environment.

For Three Springs machinery dealer and farmer, Bruce Cunningham, the one per centers mainly concern the soil, or more accurately, improving soil health.

The old adage, look after Mother Nature and she will look after you, still holds true today, in an era flooded with the latest technological advances.

One of the tools Bruce uses in his quest to improve water-use efficiency on his farm, is an Immants spader. And yes, it's one of his franchises.

Reviewing the results of four years of spading and liming trials last week, Bruce is quietly confident he is on the right track to lift crop productivity levels; one of a handful of options farmers have to combat more than two decades of declining terms of trade.

He had trialled spading with various lime treatments ranging from 1.8 tonnes a hectare to 5.4t/ha and last year saw wheat yield results 2t/ha better than unspaded areas of the paddock, which had received a lime treatment (spread but not incorporated).

Not bad for a season which delivered only 200mm of growing season rainfall with only a little subsoil moisture.

"It's a long-term strategy to lift the surface and sub surface pH to get the soil back into a better balance," Bruce said.

"Our problem with pH is in the top 30cm (12in) of the soil profile; the deeper subsoil pH okay.

"We're recording from the high fives to low sixes (pH) on the surface but our real problems are occurring in the sub surface with figures up to 4.7 to five.

"A lot of guys using spaders are having success in eliminating water-repellency and also improvising amelioration of clay and gypsum.

"We don't have water-repellent soils but we've found problems with aluminium toxicity in the subsoil, which inhibits root growth and prevents plants from accessing deeper subsoil moisture.

"You can spot the problem areas where crops don't fill out the head due to moisture later in season."

The other aspect of soil acidity is the long term use of fertilisers which contribute to acidifying soil.

According to Bruce, the spading trials have conclusively proven to him that spading is the best way to thoroughly mix the soil, with a lime application, to a depth between 20 and 30cm (8-12in).

Such action means that lime is evenly spread, preventing familiar strips which occur with conventional tillage machines.

"It also means we're getting benefits from the lime at depth within a year," he said.

"Depending on the soil type, you could be waiting up to 10 years for a response to lime, using conventional methods."

To achieve the best soil mix, Bruce says optimum working speed is 4km/h.

"The slower you go the better the mix," he said.

Using a spader almost requires a new paradigm of thinking because it is a slow process with 4.5 metre (15ft) working width and a default focus on cost, much like deep tillage or mouldboarding.

But a spader should be regarded as a tool to achieve management objectives.

Obviously that involves farm maps which identify areas of concern.

"We've tested a lot of paddocks for soil pH and aluminium toxicity and identified that spading is best carried out on our sandplain and white sandy areas," Bruce said.

"Because of soil types we can only spade a third of our property.

"We've identified the poorer-performing patches and while you do get a response (from spading and liming) it has become a matter of prioritising what you want to do.

"We can lift yields on the poorer country from say one tonne (a hectare) to two tonnes but on the more reasonable soil, we can achieve a two tonne gain.

"So the focus at the moment is turning the good patches into better patches."

The cost benefit analysis of spading is compelling.

"Even if you use a contractor at $150 a hectare, a reasonable yield will recoup a lot of the costs in one year," Bruce said.

"And with the residual benefits, which could last up to 10 years in some soils, gross margin figures on spading should improve and over such a period, you're talking hundreds of thousands of dollars in extra income."

Because of the obvious limitations of spading (eg, rocky country, gravelly ridges) Bruce is keen to look at other strategies, including deep tillage and a new method using a Vaderstad Top Down machine, which is likely to be the machine he uses on country he can't spade as well as being used as a deep tiller.

"It employs hydraulic shears that shatter the subsoil to a depth about 30cm (12in) without bringing up any sour soil," Bruce said.

"I did a trial last year and got a good response so we're looking at more trials.

"Basically I'm on a learning curve to improve our soils.

"In this low rainfall environment, we've got to get more out of any available moisture, and that means getting the soil into a healthier state."

Bruce's thoughts about the soil were stirred two years ago observing half-buried straw from the previous harvest.

"It was obvious nothing much was happening in the soil because the straw wasn't breaking down as quick as I thought it should," he said.

That opened up thoughts about improving soil microbial activity and improving soil health.

"Liming with the spader has convinced me we're on the right track," Bruce said.

"If we can get the pH up, we won't have plant roots taking right or left hand turns because they've hit an ally tox (aluminium toxicity) zone.

"If we get roots down at depth, it creates a whole new game, creating new pathways for oxygen and surface moisture.

"And roots decaying at depth means creating subsoil humus which improves our ability to deepen topsoil depth.

"If you look at where fence posts rot, that generally is where the limit of oxygen is in the soil.

"We want to get past that zone and start building the soil, almost from the bottom up."

Another machine Bruce is evaluating is the Vaderstad Carrier for stubble mulching and incorporation.

Working on the principle of mixing stubble, rather than burying trash like a traditional offset disc, the Carrier's closely-spaced (12.5cm, 5in) front double bank discs, aim to mix and cut the crop residue into the aerobic top 50mm to 75mm (2-3in) of topsoil.

The depth of the double bank of front discs can be altered hydraulically from the cab.

The discs are rubber-mounted on a parallelogram framework linked to a rear steel packer roller, which levels the soil and ensures the bruised and cut stubble is in contact with soil to aid breakdown.

It also creates a fibreglass effect stitching the stubble into the top soil aiding water penetration, eliminating surface run-off and preventing wind erosion.

With an operating speed between 12km/h and 15km/h and widths up to 12 metres (40ft), the Carrier can cover a lot of ground quickly.

"It's another tool that can play a role in breaking down stubble quickly with the added benefit of providing an even weed germination for more effective weed control," Bruce said.

FarmWeekly
Ken Wilson

Ken Wilson

is Farm Weekly's machinery writer

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