Faster, more accurate soil tests

TESTING

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Automation and improved soil tests are set to give farmers faster and more reliable analyses, as Anne Lee reports.

Wet, heavy soil samples have to be manually pushed through a 12mm sieve before they’re dried.

Ravensdown’s Analytical Research Laboratories’ (ARL) soil testing lab is bringing in home-grown Kiwi ingenuity to fully automate the surprisingly physical and mentally taxing processes of preparing soil samples for analysis.

The move to full automation will be a first for a soil testing laboratory, will help improve the accuracy of results for farmers, and build capacity so that more samples can be processed on a given day.

ARL manager Will Bodeker says the investment will be significantly more than $500,000 but Covid-19 showed just how valuable the automation process could be.

Alert Levels three and four came right at the time the lab typically sees the number of samples arriving ramp up towards its peak testing period of June, July and August.

“In March we normally take on four fixed-term people and train them ready to support us through the busy period.

“June, July, and August are our peak months when we receive 12,000 to 14,000 soils a month.

“For comparison, in December and January we receive about 1500 tests a month.” A decision was made by Ravensdown not to test soil samples through Alert Levels four and three.

Once the country returned to more normal business so did the lab but that meant a huge influx of samples coupled with the need to train people quickly. Sample numbers were 20-30% higher than

When the lab opened the samples came thick and fast. expected for this period with farmers in catchup mode.

Pressure on the lab and courier delays led to a backlog and through late May and early June turnaround times for soil test results were up to 10 days instead of the targeted three to four days.

It took until mid-June for things to return to a semblance of normal.

“One consequence of Covid though has been a different skill set of people becoming available in the labour market so that’s allowed us to get them trained quickly and operating at a fairly good speed.”

There’s a lot of physical work in handling the samples from when they arrive in bags to where they’re ready in solutions in testtubes for analysis.

Clay soils are heavy and difficult to handle, for instance.

“Some of them are in a state where we can sculpt them – we actually have our own sculpting competition amongst ourselves each year.

“Along with the manual aspect it also requires a lot of attention to detail. Obviously we have systems but it still requires people to be thinking and engaged – it’s not the kind of job you can switch off for a minute or two.”

When a sample arrives, the barcoded bag is scanned. Soil samples are then manually pushed through a 12mm sieve, which for heavier clay soils takes a bit of effort.

They are then dried overnight and subsampled, which means weighing out

FASTER N TEST

ARL is replacing its anaerobically mineralisable nitrogen (AMN) test for the faster, more accurate, potentially mineralisable nitrogen test (PMN).

Both tests predict the amount of mineralised nitrogen that will be made available for plant growth over the growing season.

But the PMN test can give results in three to four days rather than the seven days required by the AMN test.

The AMN test is a shortened version of the original gold standard test that takes 49 days.

“Nobody’s got time to wait 49 days for information and that’s why the AMN test was developed as a predictor, but the amount of nitrogen that’s actually mineralised will be affected by soil temperature and moisture,” Will Bodeker said.

Research has found the PMN test is a better predictor, and the shortened turnaround time is another benefit.

varying amounts of soil depending on the analysis being done for each sub-sample, mixing each one with a specific reagent, and shaking it for a set period of time.

The solution is then passed through a filter paper into a test tube.

Only then is it ready for analysis.

The new automation process will be installed over the coming year and has been designed from scratch to bring together some of the existing technology and equipment in the laboratory. This also served to keep costs down.

“We’ll be the first to fully automate this style of sample preparation process for soils.”

Will says they looked globally for a company to develop the process and found the best candidate was in their own backyard – CR Automation, based in

Will Bodeker – Covid-19 put the pressure on.

Hastings – a company that specialises in industrial technology, automation, and robotics.

“Once the sample preparation is automated it will eliminate the need for casual or fixed-term staff each year. It will cut down on the mundane, repetitive work, and reduce the risk of strains and sprains so we’ll have a faster, more accurate, and safer process.”

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