Farm Weekly News.

For Investors.,

"This season's and next season's field trials on Waddi Park are a straight comparison of the response of crops to identical applications of 40 units of potassium delivered via sulphate of potassium (SoP) fertiliser and via muriate of potash (MoP) fertiliser.

As reported in Farm Weekly over the past fortnight, WANTFA is overseeing two-year field trials of SoP versus MoP on Waddi Park and another four properties in the northern, eastern and southern Wheatbelt.

At the same time, researchers at The University of Western Australia (UWA) Institute of Agriculture will conduct two-year greenhouse studies comparing and measuring reaction of wheat, canola, barley and lupins to identical applications of SoP and MoP across a range of criteria.

When Farm Weekly visited Waddi Park last week it was with WANTFA's executive director Dr David Minkey and marketing manager Graeme Currie.

Accompanying them were UWA researchers Dr Zakaria Solaiman and Muhammad Izhar Shafi to fill 17 bags each with 20 kilograms of soil samples dug by hand from the 154ha paddock where the SoP versus MoP field trials will be conducted on Waddi Farm.

Soil sample collection was to continue last week and into this week on the other four farms to provide the base material for UWA's research.

A normal commercial source of bulk MoP costing $560 a tonne, will provide one lot of fertiliser, while Australian Potash Ltd - identified as APC on Australian Securities Exchange listings - will provide the SoP.

Early this year APC produced its first SoP samples in Perth from harvest salts collected by solar evaporation of potassium-rich brine pumped from beneath Lake Wells, a remote Northern Goldfields salt lake 200 kilometres north east of Laverton.

APC plans to begin commercial SoP production in time for next year's growing season with a project that on its own could supply the 40,000t of SoP imported into Australia each year, plus create a major export industry for WA SoP into China.

Previous research, much of it from North America and tied to the chemical companies historically producing brine-originated SoP there, shows potassium is an essential plant nutrient.

It has a propensity to strengthen cell walls making plants more robust and resistant to disease and pest attack and, importantly for WA, can influence the amount of water a plant retains by controlling opening and closing of stomata on the leaves.

There are also indications potassium in some way aids plant usage of mineral nitrogen, another essential nutrient promoting grain crop vigour and yields.

But potassium is easily leached from sandy soils, particularly in higher rainfall areas, and is also lost from the soil via migration into crops later harvested, so regular replenishing is recommended.

A sign of potassium deficiency is lighter green or yellow striping on old leaves, but it is often mistaken for something else.

For the field trials on his farm Mr Syme has chosen a high-yielding paddock - hence the 40 units of potassium for the Waddi Farm trial when other farms are getting between 25 and 10 units for poorer ground - that as far as soil types go is representative of his whole farm.

"It's got every soil type we've got on the farm in this paddock so it's going from red clay to white sand all within the same paddock," he said.

Previous soil tests have shown varying rates of ground available potassium across the paddock, ranging from 11 parts per million right through to 500-600ppm.

In a normal season, Mr Syme said, he would apply potassium as MoP - because of the $350t price difference with SoP - in a blend at seeding time with a compound fertiliser.

"Normally we put MoP below the seed and just a little bit with the seed," he said.

"But we're finding we need more and more potash of some description each year."

With the SoP versus MoP trial, Mr Syme said he will split most of the applications into pre-sowing and at sowing.

"We will be spreading some pre-sowing and then we'll put some - about 30pc - in with the seed and 70pc below the seed at seeding time," he said.

"We'll also do a couple of runs with all of the MoP in with the seed and all of the SoP in with seed.

"We won't band down any fertiliser, we'll put it all with the seed to see if there's any difference on those runs."

Mr Syme said the paddock would be sown with either Trojan or Scope wheat into lupin stubble with alternate plots of SoP and MoP applications across the entire paddock and for its full length of about a kilometre.

"We're controlled traffic, so it's 36-metre wide alternate slots all the way across the paddock," he said.

"We'll rip skip all the way across the paddock with the MoP and then we'll clean out and fill up with SoP and come back and do the in-between runs.

"It's all about keeping it simple because all we're comparing is MoP with SoP.

"At harvest, we'll just harvest the paddock as normal and then they've (WANTFA and UWA) got a program that can pick out the alternate runs."

Mr Syme said from his perspective the field trial on his farm was all about identifying and then trying to eliminate the "next limiting factor" for crop yield.

"I know what these paddocks have yielded and I know what they are yielding now," he said.

Yields on Waddi Farm are above average and with his considered and science-based approach Mr Syme has not necessarily followed what other farmers in the district have done.

"Others are putting a heap of nitrogen on but nitrogen is not a (yield) limiting factor," he said.

"You can't put a heap of nitrogen on without potassium, they work hand in hand in every soil type," he said.

"The potassium is helping the nitrogen we're finding, so we are lifting both.

"Also, if your pH is good, everything else seems to work better.

"Being controlled traffic has got rid of the (soil) compaction, so our crop roots can access more available moisture, so we're trying to find what's the next limiting factor.

"Moisture falls out of the sky, there's nothing you can do about it but use it to your absolute benefit.

"So we've got that, we've got our pHs right, we've got our pHs right at depth so there's no reason why the roots can't go down.

"We're keeping weeds out of the paddock, so it's all about identifying what's the next thing that limits growth of the crop?"

GLTA.