Validation and Practical Implementation of the Nitrachek 404

Have you tried to match soil test strip colours against the colours on the tin, and found yourself wondering if you’re seeing the right shade of purple? Those days of guesswork can be over.

The Nitrachek 404 is like having a portable lab right in your paddock. Instead of relying on visual colour matching, this electronic device reads test strips and displays precise digital readings. No more uncertainty about whether the lighting is affecting your colour judgment.

Proven Results

With funding from Te Ahikawariki, we worked with vegetable growers and agronomists to test the Nitrachek 404 across Hawke’s Bay, Manawatu, Pukekohe, and Gisborne. When comparing soil sample Quick Tests against Hill Labs analysis, we achieved 95.5% correlation with laboratory methods when proper protocols were followed.

The economics are compelling too. Laboratory tests cost ~$40 per sample, while Nitrachek strips are about $3 each. For farms requiring frequent monitoring, the device pays for itself very quickly – delivering 90% cost savings per sample.

We have conducted well over a thousand Nitrate Quick Test soil assessments over the last five years. We have identified four key sources of error: sample collection, sample preparation, reading the test strip accurately and reliably, and adjusting for soil moisture content. We have prepared resources for growers taking soil samples so check out our LandWISE Online Learning pages.

We had some major issues comparing our quick test results with those from the commercial laboratory. In some cases, the samples were badly affected by heat or wetness during transport to the lab, resulting in dubious results. But the biggest issue was properly applying the correct soil moisture. To get accurate results, we found that using the soil moisture percentage was critical. We used the online calculator that estimates soil moisture based on your soil type and whether you think the sample is wet, moist or dry. On our MicroFarm soils, this put us 30% out compared to Hill Labs – far too much for budgeting. We worked through issues with Matt Norris from BSI – Plant and Food and found that an equation using actual measured soil moisture made all the difference.

Getting the right answer

We make sure to measure actual soil moisture percentage. We either use a Hydrosense twin-prong soil moisture tester in the field, or we weigh the soil samples that we collect. After sieving the sample for the Quick Test, we dry 100 g of the left-over soil and weigh it again dry. That is easy to do and the most accurate method.

There are still a few maths steps to get from the test strip to the amount on nitrogen in your paddock! You need to calibrate the device, each batch of test strips, adjust for actual soil moisture, soil density, sample depth and, if you want maximum accuracy, add a final lab correction factor to have Quick Test results exactly match laboratory results. That is a bit of a nuisance and leaves lots of room for mistakes, so we developed an online calculator for you.

The online calculator eliminates the complexity of converting raw readings into useful field values. You enter your Nitrachek reading, correction factors, soil moisture content, and soil density, and it converts the data into the nitrate nitrogen values you need (kg/ha).

Practical Considerations

The device isn’t perfect for every situation. Some growers found the one-minute testing time slower than visual estimation for quick field checks. If you just need approximate values for immediate decisions, visual methods still work well.

However, for precise nutrient budgeting, regulatory compliance, or entering specific data into management software, the Nitrachek delivers laboratory-level accuracy at a fraction of the cost.

Getting Consistent Results

Success depends on following proper protocols. The research identified sample handling as crucial – keeping samples cool during transport and processing them promptly significantly improves accuracy. Device and strip calibrations are also essential, as each batch of test strips requires calibration due to manufacturing variations.

We found the device was accurate within the 2-75 ppm range we tested. That should cover most typical pre-planting conditions in New Zealand vegetable production. The graph below shows results from the MicroFarm and shows an average 7% difference between the quick test and lab results. You might not worry about 7%, but if you do, the online calculator lets you correct it.

For growers focused on precision agriculture and environmental compliance, this represents genuine progress – laboratory-quality soil testing that’s both affordable and immediate.

Download our full report here>

Many thanks to Te Ahikawariki for funding and supporting this work. And many thanks to the growers who took part, tested the method and the device, and gave us useful feedback. And special thanks to Matt Norris for helping us crack the puzzle and providing the “Norris Equation” that properly accounts for soil moisture levels.

A Te Ahikawariki / VICE Project

SLAKES: a cost effective measure of soil structural stability is one of two projects I have been running as a part of my Te Ahikawariki/VICE internship. A key part of the project was engaging with growers to demonstrate and support valid paddock sampling and correct use of the test methods. Our aim was for growers in each regional community to know how to use and understand results from a standardised assessment methodology consistent with SHI guidelines. As part of the Slakes project, we ran individual farm workshops with growers in Hawke’s Bay, Pukekohe, Palmerston North/Levin, and Gisborne. 

Soil aggregate stability

Soil aggregate stability is a measurement of aggregates’ ability to resist degradation and maintain structure when being affected by external forces such as rainfall, vehicle traffic, and tillage. It is correlated with soil erosion, water retention, aeration, root growth, soil microorganisms, and soil carbon. 

Soil aggregate stability is one of the three key soil health indicator tests recommended by the Soil Health Institute (SHI), alongside soil organic carbon concentration and carbon mineralization potential. The SHI recommends the Slakes method for testing aggregate stability as it is practical and cost-effective.  

The Slakes method uses a free app that was developed by the SHI and the University of Sydney, to test aggregate stability. The app is used to take images of sets of three aggregates, initially dry and again after they have been submerged in water for 10 minutes. The Slakes app takes photos, times submersion, and calculates an Aggregate Stability Index, which is the ratio of initial to final soil area. 

The Slakes Project outline was to: 

• Compare the Slakes aggregate stability index and Manaaki Whenua – Landcare Research wet sieving aggregate stability results 

• Correlate the results to a visual soil assessment (VSA) score, bulk density, and total carbon 

• Engage with growers while demonstrating valid paddock sampling and how to use the Slakes app 

Most samples collected throughout this project were taken from an uncropped and a cropped area within the same paddock. When comparing the Slakes aggregate stability index and the Manaaki Whenua Landcare Research wet sieving aggregate stability results, there was a clear trend in both methods that the uncropped areas had higher aggregate stability.  

When comparing the VSA and aggregate stability results, most of the cropped paddocks had good VSA structure scores but weak aggregate stability. This suggests that the tilth created by cultivation looks good, but it lacks the strength of true aggregates that are the basis for good soil structure.  

There was a moderately strong relationship between the Slakes aggregate stability index and the total carbon percentage in the soil (R² = 0.69), with the uncropped areas (blue dots) having higher total carbon and aggregate stability than cropped areas (brown dots). 

Throughout the Slakes project, we received positive feedback from growers about the Slakes app, as it provides a quick, simple, and affordable way to gauge the soil’s aggregate stability without needing to send samples away to a lab. However, some growers asked how they can use it to aid their management. Most are keen to know if there is an aggregate stability index threshold that indicates when poor stability will impact productivity.  They recognise the test is low cost, but some would like the option to send it to a laboratory to save time.

Many thanks to Te Ahikawariki, the Vegetable Industry Centre of Excellence, for supporting me in my internship, and for funding LandWISE to undertake the Slakes research project. And thanks also to the farmers, growers and consultants who spent time trying out the Slakes method with us and giving us their considered feedback.

Olivia

Download the Project Report

The LandWISE Conference, Getting to Carbon Positive, attracted more than 80 people who heard speakers on a wide range of topics related to ongoing sustainability.

Day 1 discussed ways to assess our emissions levels, how we can reduce our environmental impact through diverse farming techniques including regenerative practices and soil health, and new research around pest management.

Pii-Tuulia Nikula opened with an introduction to emissions accounting, which was followed by Uttam Floray outlining how Toitu certifies emissions. Ron McFetridge from WaterForce said he was asked by key clients about WaterForce’s emissions, which set them on a journey to reduce their emissions and environmental impact. Olivia’s take:

“I enjoyed listening to Ron discuss how WaterForce has been installing solar panels on their offices, putting in electric vehicle chargers, and deploying electric and hybrid vehicles for their staff. Given that they travel 4.5 million kilometres annually as a company, WaterForce saw electrification as an effective way to reduce emissions and environmental impact. By doing this, they are setting a precedent for other companies.”

Dan Bloomer presented results from the Carbon Positive trial including the 2024-2025 cropping programme and a Carbon balance for each of the treatments, which showed nitrogen fertilisers and diesel were the largest CO₂^-e contributors. The introduction of livestock added significantly to overall emissions, even if on farm for a relatively short time. Matt Norris presented results from regenerative cropping trials, including use of composts, at LeaderBrand in Gisborne, Angus McKenzie described how Wairuna Farm is applying the principles in Canterbury, the various things he had been trialing on his farm, and how they created a wetland to treat drainage water. Sam McNally addressed ways to increase soil carbon and explained fundamental changes in our understanding of soil carbon sequestration and carbon pathways. Photosynthesis feeds the whole system!    

Three speakers discussed beneficial non-crop plants. Dan talked about the lessons from growing multispecies cover crop mixes in the Carbon Positive trial. Charles Merfield provided information about cover crops for regenerative cropping and the need to ask what functions you wanted cover crops to perform. Jeff Smith presented lessons from biostrip and insectaries research through the A Lighter Touch project.

Day 1 was wrapped up with Asha Chhagan talking about new technologies to assist pest and disease management, and Bethan Shaw reporting on work done looking at earwigs recolonising orchard sites that had been devastated by Cyclone Gabrielle. Daniel Sutton and Chris Lambert reporting on trials with a camera equipped AI enabled pest trap.

Olivia’s take:

“The conference was a good opportunity for me to do my first conference presentation! I talked about the Slakes app and things we have learned from using it to assess soil aggregate strength, and I spoke about the Nitrachek device project that I have been running as a part of my Te Ahikawariki/VICE internship.”

Many thanks to all our sponsors, speakers and delegates!

The LandWISE Conference, Getting to Carbon Positive, attracted more than 80 people who heard speakers on a wide range of topics related to ongoing sustainability. Day 2 had a strong focus on electrification options to increase profitability and reduce emissions. New Zealand is reaching a point where solar power is the cheapest energy available – as Mike Casey noted, the cheapest form of energy ever.

Uttam Floray introduced Rewiring Aotearoa and the local chapter, Electrify Hawke’s Bay which are focused on helping promote and activate electrification. Mike Casey described the electrification of his cherry orchard and laid out a huge set of statistics and examples of ways New Zealanders can profitably swap fossil fuel machines for electric ones. Becks Smith now helps farmers work out how solar can add to their businesses having set up a solar system for irrigation pumping in Otago.

Lincoln University has chosen major investments in solar electricity to reduce emissions at the university, and Pieter-Wilem Hendriks is part of a team investigating ways to combine agricultural production with energy generation. At smaller scale, Aaron Duncan explained options for home and SME solar systems, using the Centre for Land and Water system as a case study. Boyd Benton discussed the way Ripple Tech transplants electric motors into fossil vehicles and, in a second talk, introduced micro-hydro as a viable option for sites with streams. Olivia said

“It was fantastic to hear Uttam Singh Floray, Mike Casey, Becks Smith, Pieter Hendriks, Boyd Benton, and Aaron Duncan discussing electrification and reducing emissions. You could sense their genuine passion for the topic, which made their talks even more engaging. I particularly enjoyed Mike Casey’s talk on his electric cherry farm. I found it fascinating that every piece of machinery used on the farm is electric, including the truck that transports the cherries to the packhouse. That means there are no fossil fuel carbon emissions until after the cherries have been transported from the farm.”

Horizons Regional Council Field Session

The field session on Thursday afternoon provided delegates with opportunity to get first-hand experience of some of the techniques and technologies that had been discussed. We thank “A Lighter Touch”, WaterForce, Freenergy, RippleTech, PowerSpout, Vegetables NZ, Autonabit, and Agovor for bringing their wares to demonstrate. Gadgets, machines and systems to excite, save time and money, and enable systemic changes. Olivia said

“I didn’t make it around to all the field event demonstrations, as I was demonstrating the Slakes app and the Nitrachek device. I did manage to see the smart trap, the off-grid hydro pump, the Govor robot, and the Avvy bird scaring robot. They offer so much, and we expect to see a lot more of these technologies in years to come!”

We gratefully acknowledge all our sponsors, presenters, demonstrators, and delegates!

Carbon Positive Field Walks

We hold regular open field walks for our community to visit the Carbon Positive research plots, hear updates and contribute to future plans. Our email LandWISE Updates give details – sign up to receive notifications.

LandWISE Events Archive

Others’ Events

Merfield Agronomy Physical and Ecological Weed Management Workshop

Tuesday 22 July 2025, Waimate, Canterbury 

Learn about the latest in mechanical weeding and how to integrate that and herbicides in this one-day workshop.  Hard registration deadline is Friday 4th July. 

NZAPI EXPO 2025 – New Zealand Apples & Pears

30 July – 1 August – Nelson

2025 NZPPS Symposium – “Resistance Management – Today’s Tools for Tomorrow”

11 August, Christchurch

NZPPS Conference 2025

12-14 August, Christchurch

Potatoes NZ Conference

12-13 August 2025, Christchurch

New Zealand Horticulture Conferences 2025

26-27 August, Wellington

NZARM 2025 Changing Landscapes

11 – 13 November – Blenheim Marlborough

Getting to Carbon Positive

Wednesday 21 – Thursday 22 May
Havelock North Function Centre

In 2025 we’re delighted to bring you a conference with focuses on regenerative crop production, carbon footprinting, and electrification. We’ll have new technologies to think about and see, we have speakers with proven track records, and we’re looking forward to catching up with old friends and new.

Do we know the footprint of our activities? How do international markets assess them and what will we need to report? We are proud to present Associate Professor Dr Pii-Tuulia Nikula to open the managing our footprints conversation. We’ve done the numbers on our Carbon Positive cropping treatments, and we’ve others talking about what they are doing to address their footprints too.

If we are going to get to Carbon Zero (or better) we need to think about both inputs and outputs from our systems. Can we soak up more than we lose? Which inputs have the greatest impact?

We will report on progress and lessons from another year of our regenerative cropping research and present some new tools for growers to assess nitrate levels and soil stability. We’ll have examples for viewing at the Horizons Regional Council Field Session. Others will update us about new technologies for pest and disease control and reintroducing insects to cyclone impacted orchards and discuss the use of bio-strips and insectaries to encourage beneficial insects.

We’ll need energy, of course, but how much can we generate on-site? Is electrification realistic now? Where to in the short to medium term? We are delighted to have Mike Casey of the Electric Cherry Orchard and CEO of Rewiring Aotearoa opening the discussion on electrification and alternative energy case studies. We’ll have electric vehicles for perusal.

Thanks to our Sponsors!

We look forward to seeing many of you again in 2025.

LandWISE 2025 Getting to Carbon Positive

Doing what we can to reduce our greenhouse gas emissions is not about meeting regulations, it is about meeting the expectations of our markets and others in our supply chains (and ourselves and the planet!). Most large companies must report on their own emissions and those of their suppliers and clients. We are part of their emissions profiles, and they want us to do our part.

What is it all about? What emissions are we talking about? Who is implementing changes to lower their impact? How do we start?

At LandWISE 2025: Getting to Carbon Positive, you’ll get these answers and more. You’ll hear and see examples, and hear that people are reaping benefits, because it isn’t all about adding costs, it can save money. And in another session, you’ll hear how it can even provide an alternative income stream.

The Greenhouse Gas (GHG) Protocol applies the measurement of emissions across three scopes. These are Scope 1, which includes the direct emissions from sources that the organisation owns or controls, such as fuel use for farm-owned vehicles, natural gas used for heating buildings and greenhouses, fertilizer use, leaks in refrigeration and cooling processes, as well as emissions from soil management. Scope 2 includes indirect emissions from purchased energy. Scope 3 includes all other indirect emissions in the organisation’s value chain, such as emissions from freight/transportation of products, business travel, waste, and emissions from purchased goods and services.

Pii-Tuulia Nikula (PhD)

Greenhouse Gas Accounting: Scopes Solutions Target Setting

Pii-Tuulia Nikula is an Associate Professor in the School of Business at the Eastern Institute of Technology (Hawke’s Bay), where she teaches courses on Sustainable Organisations and Research Methods. Her research has explored emission trajectories and climate disclosures of New Zealand businesses. Pii-Tuulia will cover key questions that apply to the application of the GHG Protocol, such as common issues and challenges with data collection and practical solutions available for emissions reduction across all three scopes. Finally, she will discuss how organisations can use their emissions baseline to start thinking about their emissions reduction targets. 

Uttam Singh Floray

Reporting for primary producers, processors and exporters

Uttam Singh Floray is a seasoned Sustainability Consultant with extensive expertise in Environmental, Social, and Governance (ESG) frameworks, carbon accounting, and compliance solutions. As Team Lead – Account management (Government) at Toitū Envirocare, he has headed the implementation of the Carbon Neutral Government Programme and guided organisations toward achieving emissions compliance and sustainable development goals. Uttam has a lead role with Electrify Hawke’s Bay, a regional Rewiring Aotearoa group promoting adoption of low carbon alternative energy sources.

Ron McFetridge

Minimising emissions at WaterForce

One of three founders, Ron McFetridge is the Managing Director at WaterForce. Established in 2002, WaterForce has operations throughout New Zealand, with a large concentration on the South Island, and about 250 staff. Ron is working to reduce the emissions footprint of the company through careful management of energy including establishing rooftop solar and electrifying the vehicle fleet. He is speaking about the process, seeking suitable equipment and changing culture in an organisation.

Dan Bloomer (PhD)

Carbon Positive progress – relative footprints

Dan Bloomer is the LandWISE Manager and an independent consultant. He brings a diverse set of interests and extensive experience in field trials and extension to his role overseeing the LandWISE research portfolio. Together with Olivia Webster, he will present a study comparing the emissions from the three farm systems that form the Carbon Positive trial. What are the main drivers of emissions in an intensive process cropping scenraio?

Of course, knowing our emissions is only a starting point. We also want to know how we can minimise them. And that is the subject of the Electrification and Alternative energy case studies sessions!

At LandWISE 2025 you’ll hear about regenerative cropping systems (however they be defined, or not), soil carbon and sequestration, and the use of cover crops in vegetable and arable systems. Add in the role of biology and ecology in pest and disease management, and some new systems and gadgets to monitor crop pests, soil nitrates and soil health, and the programme has much to offer!

Havelock North Function Centre
21 – 22 May 2025

We will update delegates on our Carbon Positive regenerative intensive process cropping project. Matthew Norris will describe the research completed and take-away knowledge from the Leaderbrand Regenerative Cropping project, with fascinating insights around the use of composts. And Angus Mckenzie will describe his own farming approach and that of others in Canterbury seeking to apply regenerative principles in day-to-day management. A common factor with all projects is the focus on lifting soil carbon levels, a topic that will be drilled into by Sam McNally.

Our Carbon Positive Operations Group has learnt some hard lessons with cover crops over the last three years, but we think we are now much better informed and positioned. We will present a list of questions! Also, with support from Te Ahikawariki/VICE, we’ve begun a small study of cover cropping with interviews of farmers who do and don’t use cover crops. We hope to have some preliminary findings by the conference. Charles (Merf) Merfield, one of the team interviewing will discuss cover cropping, an area he has researched and implemented for many years.

Drawing from “A Lighter Touch” research, Jeff Smith will discuss the use of bio-strips and insectaries to encourage beneficial insects to aid in pest management. Daniel Sutton will report on research using “Smart Traps” to automate collection of pest presence data. From Plant and Food Research, Asha Chhagan will talk about new technologies for pest and disease control and Bethan Shaw will discuss work reintroducing beneficial insects to orchards impacted by Cyclone Gabrielle.

Rounding out New Tools, Olivia Webster will present LandWISE work using a new soil slaking measurement app and a device to more precisely determine soil nitrate levels when using Quick Test strips.

LandWISE has three pilot projects being run with Te Ahikawariki, the Vegetable Industry Centre of Excellence based in Pukekohe. The projects include cover cropping, soil stability testing and use of a device to read nitrate test strips more accurately.

Te Ahikawariki/VICE is a government-funded project that is setting up a cutting-edge vegetable research farm in Pukekohe. The project is a collaboration between mana whenua and vegetable growers that aims to create a central location for research to support the entire vegetable industry and protect the land.

Cover crop options for vegetable growers – preliminary scoping study

Over the last few years, we have been posting reports of trials and tribulations with our cover cropping activities at the MicroFarm. Growing a cover crop is easy. Growing a cover crop that ticks boxes for maximum species diversity, non-herbicide termination, and allows the land to be ready for a crop on a certain date specified by processing companies is quite another thing. Our discussions with growers in Tairawhiti and Canterbury confirm we are not alone!

The Te Ahikawariki project involves us and regional contacts interviewing leading growers and industry people with experience in or desire to introduce cover cropping in vegetable production systems. By including five regions, Hastings, Pukekohe, Levin, Gisborne, and Canterbury, we are seeking to compile findings to give a national overview that identifies regional and sector specifics.

A summary from interviews, a resource inventory and literature review will identify where suitable information is available and where key gaps lie. This will provide a base on which to develop a longer-term research strategy and work programme for VICE. 

Farmer Friendly Nitrate Testing

Since 2018, we have been using and promoting the Nitrate Quick Test from the University of California Davis (Hartz, 2010). The method was tested for NZ conditions under a previous SFF project through FAR and Plant & Food Research. The Nitrate Quick Test has much potential to help growers identify required nitrogen base and side-dressing rates and to justify applications.

Our Te Ahikawariki project is comparing results from Nitrate Quick Test strips using the current visual concentration assessment and estimate of soil moisture bands with the Nitrachek concentration and moisture determined by microwave drying soil and with commercial laboratory mineral nitrogen tests. A key part of the project is engaging with growers to demonstrate and support valid paddock sampling and correct use of the test methods, thus ensuring the knowledge is held within each regional community.

In parts of Europe, farmers must have approved soil nitrate testing completed before nitrogen fertiliser applications may be made. One accepted European methodology uses the Nitrachek device to read the test strips, removing the human eye variable and providing much more accurate readings. It also includes drying test-soil so there is no need to estimate soil moisture.

SLAKES: a cost-effective measure of soil structural stability

Soils with stable aggregates are usually found to be more productive than soils with poor aggregate stability. They typically have more organic matter present in the soil, which acts as a glue holding aggregates together, retain more moisture and have higher infiltration rates, and plant roots can penetrate deeper into the soil which means crops will be more drought tolerant and have better productivity. During rain events, soils containing unstable aggregates will disperse filling pore spaces and making the soil susceptible to erosion and compaction. Eroded soil will remove nutrients with it reducing soil fertility, compaction can cause aeration reduction, water logging and root disease which will affect crop health.

Many different methods have been used to measure aggregate stability, including Cornell University’s wet aggregate stability, Yoder’s wet sieving and Landcare Research – Manaaki Whenua’s (LRMW) wet sieving. However, these methods are time consuming and costly. The Soil Health Institute recommends testing aggregate stability with a smartphone app called SLAKES which was developed by the University of Sydney (Soil Health Institute, 2024).

Our SLAKES project is comparing results from SLAKES with the LRMW wet-sieve aggregate stability test and looking for correlations with VSA scores, bulk density, and total soil carbon levels. In March and April, we are trialling SLAKES with selected growers in Pukekohe, Gisborne, Hastings, Palmerston North and Levin. This will give us a range of soil and crop types to see how the methods compare in our young New Zealand soils.

We will report on our progress at LandWISE 2025! See you there.

In June this year, I was chosen for one of two teams attending the 2024 International Food and Agribusiness Management Association (IFAMA) Case Study Competition and Conference in Almeria, Spain. The theme of the conference was Food Security Through Innovation & Sustainability. We were then invited to attend a weeklong food and agri-innovation tour to Bologna, Cologne and then through the Netherlands.

I am lucky to have been in a team with four clever individuals from across the New Zealand Agri-Food sector. Our team included Dan from Silver Fern Farms in Dunedin, Fatima from ANZ in Auckland, Braydon from Perrin Ag in Rotorua, and Katie from Auckland University. We brought a diverse range of skills to our case study analysis, as well as a diverse range of opinions and perspectives on agriculture.

We were incredibly excited to learn that we won first place in our division, with the other New Zealand team coming in second place. Not bad for a little country at the bottom of the world!

While travelling together after the conference we were able to explore food provenance and food culture in Bologna, agricultural research and development in Cologne, and agricultural and horticultural innovation in the Netherlands. We will all be spending the next few months digesting what we have seen, discussed and learnt, and how our experience links to food production back here in New Zealand.

Many thanks to LandWISE (Dan & Phillipa) for allowing me the time away to learn, grow and explore the agri-food sector at a global level.

Applications are open!

Applications are open for the 2024 STAMP intake so if you have talented young people in your business (under 27 at the time of application), encourage them to apply! Click here for more information. Applications close 31st Aug 2024.