A Field Trial has it’s Challenges

As part of my PhD project I am running a long term field trial. My project examines nitrate dynamics within the landscape continuum, along flow paths to surface and groundwater, using nitrate N and O isotopes to quantify nitrate attenuation, and apparent isotope fraction factors to differentiate N processes such as denitrification.

Aiming to evaluate the influence of spatial and temporal factors on nitrogen attenuation (N removal as through denitrification) with respect to New Zealand systems. Research data from a long-term field installation will allow the identification of temporal thresholds and trigger events for denitrification.

Sounds simple enough right? throw a few sensors in the ground at different depths and a bunch of ceramic suction cups and “hey presto”.

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Wrong. Add a couple of solar panels, batteries, cell modems, radios, aerials, two different soil types, SDI12 sensors, climate monitoring equipment; rain gauge and barometer. Okay now that you’ve got all that, put it 500 km away from where you’re based, throw in some nature, human and manufacturing error, along with poor cell coverage and now we’re being a bit more realistic.

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Set up started 6 months before the actual installation of the equipment, with funding, programming and calibration of equipment taking twice as long as expected.

Challenge #1: Funding

No explanation needed.

Challenge #2: Programming and Calibration

Programming and coding isn’t something that I’d had any experience with before. The extent of my knowledge was using AND, OR’s and IF’s in Excel, the usefulness of which cannot be dismissed, but when I was sitting in-front of a computer screen staring at more lines of letters and numbers than a bankrupt mans accountant, I knew it would be a steep learning curve.

The soil department’s Technician, Neil, took me under his wing and worked with me each step of the way (very patiently). As it turned out, I found this experience invaluable.

With technology advancing at the rate it is, taking this step into the world of programming, reinforced what a lot of us know already, that we need to keep up with it but we know very little. Lincoln University Soil Science Society’s motto is “Expand your horizons”, and seems very appropriate in this case, up-skill, expand those horizons. Technology provides so many opportunities for great scientific research, but to take advantage of this, we need to keep up and grow with it to use it effectively.

 

March saw the installation of the equipment. A week of digging and installing 24 sensors (oxygen, moisture and temperature) as well as 32 ceramic suction cups. This went fairly smoothly apart from one of the soils having more stones in it than you could shake a stick at, which promptly halted progress.

Challenge #3: Rocks, Stones and Pebbles

The oxidising a.k.a ‘stony as hell’ soil decided that it wouldn’t let go of the metal rod we were using to put the ceramic cups in place. This was the one rod that had to put them in, and it was the first try, so we needed it back. Digging by hand to unearth it, using a large jack and also trying to pull it out with the digger gave us no joy. One hour later, we got it out, but only by digging it all the surrounding soil out with the digger, bending it in the process. Now we were in search of an engineer that could straighten it.  Two hours drive later and $10 down, thanks to a very kind dude at the mechanics, we were back on site with a straight rod and all 32 ceramic suction cups yet to be installed.

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However to get around the rock, stones and pebbles issues we didn’t use it (the rod that is) to install the ceramic cups at this site. I hand dug, or more like, bashed, holes into the side of the soil pit with a crow bar to put the cups into and then we back filled it. At the other site they all went in easy as pie, thank goodness.

Okay. Set-up done, back to Lincoln.

Challenge #4: Communication

Data-loggers are great. You can hook them up to the national cell network and send your data back to where ever you wish, at what ever time and update them while 500 km away! Unless of course you have no cell reception…. then you have to make that 1000 km round trip again to install radio modems so that the site that doesn’t get cell reception can communicate with the one that does, via the radio routers, and send it’s info back that way. Fixed.

Note: Make sure your Yagi aerials are pointing in the right direction and are high enough to get the signal to the other one, so your radios can indeed communicate. If it’s not high enough, improvise and use a stick that you found near by as a temporary fix. Be sure to change the stick out to something more permanent before the forecasted 90 km winds hit!

Hot Tips: Bring an umbrella, great for those days you have no choice but to be in the field to fix something and the weather isn’t playing ball. Also, make friends with the locals. They make great company and provide entertainment in those moments where you have to stand around waiting for something (there’s a few of those), and don’t forget snacks! being in the field is hungry work.

Challenge #5: When it doesn’t rain in Southland….

So the aim of the game is to collect samples from the ceramic suction cups installed at the two sites. Sampling over a two month period to capture the seasonal winter wet up of the soil, and see the nitrate leaching break through curve.

But when you’ve been in Southland for 3 weeks, the weather has been stunning and your samples are only a couple of milliliters when you get any sample at all…it starts to be an issue (if I’m honest, I really enjoyed it, was great for tramping on the weekends).

The solution to this challenge was just patience. Week 4 proved to be more successful…. that’s also when the snow came, and the ground and ceramic cup sampling tubes started freezing…but that’s another story.

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Challenge #6: RATS!

“Rats like to chew things” the pest control lady at Environment Southland said as she looked at the leaky, cut up ceramic suction cup tubes that I’d brought back from the field trial site. Over a couple of weeks I’d noticed that some of the tubes weren’t working as I tried to apply suction to the ceramic cups, meaning I wasn’t drawing in any soil solution for collection. On closer inspection the tubes had small cuts along them. I replaced a couple but it continued to happen. Feed up, I decided to find a solution.

A self resetting rat trap seemed like the ideal solution. Thanks to the pest control department at Environment Southland I got my hot little hands on one of these, installed it on the fence post near my site. With it’s intoxicating chocolate bait, the rats must’ve found it more enticing that plastic tubing and voilà, no more problem.

Challenge #7: No Comms…again

Okay people, no worries. This one was easy. Blown fuse. Changed the fuse. Fixed.

Getting good at this now (a.k.a good at listening to the technician over the phone to help me solve issues while in the field).

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Challenge #8: Oxygen Sensors aren’t playing ball

The oxygen sensors we had installed were giving very random readings, dropping into the negative 1000’s or not reading at all. Three at one site and one at the other. Two at the deepest depth we just un-plugged. The other two we decided to replace with analog sensors rather than the digital ones we were currently using.

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The technician sent these down to me, very kindly having pre-calibrated them. All I had to do was dig a couple of holes, one at each site, to the correct depths, install and wire in the new sensors. Done. The frozen ground causing no issues with the spade work…

Challenge #9: Human Error

It was the day before my flight back to Christchurch. I get a phone call from the technician. “Now all of the moisture sensors seem to be playing up, they’re giving odd readings.” Here we go…

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An early frosty Saturday morning in the field it is.

Four hours of my head in a data logger, staring at wiring, un-wiring, re-wiring, re-installing programs, testing voltage, re-testing. Thanking the technician for giving up his Saturday for this, worried that it may end up with him having to fly down with a new data-logger after none of the things we were trying was solving the issue.

The 5th hour came around and I stuck my head into the data-logger once again, lying on the ground wondering if I’d ever feel my fingers and toes again… then I saw it. That wire, that one wire that was in the wrong place! in one port higher than it should be!

I took it out, wired it into the port it was meant to be in. An exclamation from Neil, the technician on the other end of the phone and I knew the problem was solved. Feeling extremely guilty for all the extra time I’d kept Neil, especially on a weekend, he reassured me that it happens to the best of us. We’re only human right?

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Challenge #10: Lightening Strike!

You know when you get to challenge #10 that the world must be plotting against you…?? What are the chances of the field trial getting hit by lightening? Seriously?

Well, it happened. You just have to keep reminding yourself that all things happen for a reason, right?

So the comms were down again, the day after I got back from being based in Southland for 2 months and the technician was busy with other work at Uni. So a couple of very helpful people from the Environment Southland Team came to the rescue.

The radio aerial was fried. A new one needed to be ordered and sent down, along with a new radio router, then installed. Then the deep cycle battery had gone flat. A new one ordered and installed. Radios still didn’t want to talk to each other. Last straw, the awesome technician here at Lincoln ended up having to fly down for a week to fix it all.

It took about a month an a half to get it back up and running. But it is running!

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Challenge #………..well I could keep going but I think you get the picture. Field trials are full of challenges, some you can fix, some you need patience for, some you need to ask for help, sometimes you just want to scream or cry or laugh. Nature, people, animals, weather, technology. But it’s worth it.

I’d be lying if I said I’d enjoyed every bit of it, but looking back I wouldn’t have it any other way.

Bring it on PhD, love the challenge, love the science, love soil!

Seph at field trial site

A special thanks to all those that have helped me along the way so far. Neil Smith, Lincoln’s awesome technician and the very helpful Environment Southland Staff, all your time and patience is very much appreciated!

Published by

Sephrah

I am a Soil Science PhD student at Lincoln University, New Zealand.

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