Thursday, 3 May 2018

EM Values - What the data is telling you

Today we've got the second part of a 4 part series on EM Surveying and all it's uses. This week we've been into the EM Surveying over on the West Coast (check out our Facebook page if you want to see more) and it's certainly an important part of the job being out there doing the survey and seeing the physical aspects of the job to help make sense of the data and what it's telling you. Today we look at what the EM data does tell you...

An electro-magnetic (EM) sensor generates a constant electro-magnetic field that penetrates into the soil profile. It measures the bulk electrical conductivity of the soil profile. As we conduct an EM survey the sensor is taking readings at two different depths simultaneously. These two depths are known as the ‘Shallow EM’ and the ‘Deep EM’. The depths the DualEM reads depends on the height the machine is off the ground. With our EM setup we are reading the soil profile depth of 0-50cm for the shallow EM and the deep EM at a soil profile of 0-125cm. So the deep EM values are the same as the shallow plus another 75cm deeper. This is why the deep EM readings are always higher than the shallow as it is reading that extra 5cm.
Figure 1: Shallow EM survey values varying from 2-20 EM units (mS/m)

Figure 2: Deep EM of the same area with values ranging from 14-30 EM units (mS/m)
In this survey the same features are showing in the shallow EM and deep EM results, however sometimes this is not always the case the deeper profile can have a different underlying soil type that the shallow EM doesn’t pick up but the extra 85cm of deeper soil does and it changes the overall structure.

Generally speaking and depending on what part of the country you are in and the time of year the survey is carried out amongst other things, we would class a range in EM in the shallow profile of 1-3 units as low variability, 4-8 units as moderate variability and over 8 units range as high variability in the shallow layer/soil profile. In the deep EM/soil profile layer a range of 1-6 would be low variability, 6-15 moderate variability and over that high. It is often dangerous to generalise like that, but it gives you an idea of the type of ranges we look at, and as previously stated there are a lot of other factories that determine if the readings are low, medium or high variability. You also have to look at the distribution of the values as well, if the majority of the values are within a certain range and a few rogue values outside that but on a minimal area of the total, then the range in variation may not be as much as it first looks. How much the variability is costing you in terms of blanket irrigation applications compared to variable rate irrigation applications be it water, seed or fertilizer is a subject for another day!

For more information on EM Surveying please contact us at Agri Optics NZ Ltd.

Chris Smith.facebook

Thursday, 26 April 2018

EM Surveying - it's that time of year again!

With all the early season rainfall we've had the EM Surveying season has started a lot earlier than most years. It's great in a couple of respects: 1) we can get across the ground before it all gets really wet (if that happens) and the potential to make a mess increases and 2) it gives you more time to analyse and incorporate the data into your decision making over the winter months. 

As we're already into it this year, we thought it was time to give you a reminder about EM Surveying and how it all works. Today you'll get the first of a two part blog looking at the process, what you get from an EM Survey and what it can all be used for. 

EM Survey – Part 1 - the process.

When we conduct an EM survey we are measuring the electrically conductivity within the soil profile, the values have close links to the soil texture properties, where clay gives a higher reading than silt that in turn gives a higher reading than sand. So, by driving over a block of land you pick up the differences in the soil texture at two different depths 0-50cm and 0-125cm. Other factors have varying degrees of influence on the readings such as soil bulk density and moisture within the profile at the time of the survey. High salinity readings can have a huge influence on readings, but this is only in specific areas of New Zealand. The EM data is logged using 2cm accurate RTK GPS, so not only do we map the relative changes in soil texture, we are also collecting valuable topography data at the same time.

Agri Optics' EM Survey setup with soil profile shown. The measurements penetrate 1.25m into the ground. 

We drive most commonly at 12m swaths across the area, but closer resolution can be used for more intensive situations such as viticulture. Once the survey has been conducted we write a report about the findings from the two different EM layers, we then zone the EM data up into different management areas and run topography generated maps. Once you have had time to read through the report we arrange a meeting to then run through the report with you in person if you so desire. We also supply the client with software to view the data on their own computers and look at the different layers plus make your own management zones if required. From this point we can then focus on the areas of interest for your requirements.

The survey data has many uses, depending on the farming type and location and includes but is not limited to the following;  being the basis of variable rate irrigation application maps, moisture probe placement, used in zonal soil sampling, in dryland farming areas knowing where to put your effluent, to varying your nitrogen use depending on the underling soil types and used for flood modelling. It can also be used in conjunction with other layers of data such as yield maps, biomass maps and as happens frequency used with the topography data. Over the next few blogs I can drill into more detail on these different uses.

The EM season runs form the end of irrigation in the autumn through to Spring, but from now onwards is the ideal timing. For more information on EM surveying or to book one in for this season, please contact one of the Agri Optics team. Cheers, Chris. 

Monday, 12 March 2018

Regulatory Update

Below is a quick update on where things have gotten too from a regulatory perspective. 


2017 saw Environment Canterbury (ECan) introduce Good Management Practices (GMP) into its Land and Water Plan framework.  This is known as Plan Change 5.  Plan Change 5 also introduced the Waitaki specific nutrient management rules.  The decisions on the plan were appealed by a number of parties, particularly in relation to how the irrigation and fertiliser GMP’s were being treated in the Farm Portal (the online tool developed to determine exactly what GMP is at a farm level).  Appeals are still yet to be resolved, and therefore, it is likely to be mid-2018 before this plan is made operative.

Plan Change 2, which is specific to the Hinds Plains region, is also still under appeal, however, Plan Change 3, which is specific to the South Canterbury Coastal Streams area, had all its appeals resolved in November 2017, and is now fully operative.

ECan has also been doing a big push in the areas where a consent to farm is required, to encourage those who need one to go through the process.  There has been a good response to this (contrary to the opinion of Dr. Mike Joy) as the process is new to many, and requires professional help and a change in mindset for many. 


Otago’s nutrient management rules are now two years away from kicking in (the date is 1 April 2020).  Otago Regional Council has been encouraging farmers to get their Overseer done.  They have also taken the initiative in the more sensitive catchments such as the Kakanui, and have been providing resources and funding to assist with this.

Southland’s Land and Water Plan is nearing the completion of hearings.  Council gave its reply report and recommendations (a summary of all the information and submissions presented to the hearings panel, and answers to all questions from the panel during the hearing) in November 2017.  Watch this space.


Horizons One Plan struck a major hurdle in early 2017, with the Environment Court deciding that the way in which the Council was implementing its plan was not what the plan actually said.  This has left the council with a plan that effectively doesn’t practically work as it was written, and wondering what to do now.  Implementing the plan as written creates a massive cost to farmers and other consent holders, and doesn’t necessarily achieve the desired water quality outcomes.  Given this, in August 2017, the council voted to investigate the possibility of a partial plan change.  However, this will not be a quick or easy process as it is both a legal and public process.

Hawkes Bay

Irrigators in the Tukituki catchment are left high and dry (literally) after the Ruataniwha Dam project is put on the shelf indefinitely.  The Tukutuki River minimum flow is still going up, and without the dam to augment and flush the river, the increase in minimum flow will mean the possibility of severe restrictions for irrigators in this catchment.  Effectively, the raise in minimum flow was coupled with the dam, but the impacts of de-coupling are now about to be realised.


Gisborne’s Freshwater Plan decision was released in August 2017, and was subsequently appealed.  The appeals are still to be worked through and there is no timeframe at this stage on when appeals are likely to be resolved.  Gisborne’s Freshwater Plan was actually pretty kind from a nutrient management perspective when compared to Canterbury for example.  There is no requirement for on farm limits using Overseer, and they have adopted a Farm Environment Plan approach to managing water quality.  However, it does have some issues with water quantity.  As horticulture, and kiwifruit in particular, look set to increase, those looking in the Gisborne area for plots to develop are soon realising that there is basically no water available for allocation unless you are prepared to take high flow water and store it.  Therefore, this is limiting the potential for the Gisborne region.


As well as all that is going on the regions, we have a new government who looks set to wind up funding irrigation scheme development, has already taken a stand on climate change, and will undoubtedly want to stamp its feet on the water issues.  2018 will be an interesting year…

By Keri Johnston, Irricon Resource Solutions
Phone 0272 202 425 or email

Wednesday, 20 December 2017

The Importance of Timeframes – Resource Consent Timeframes That Is…

Christmas seems to be a magic deadline for people – apparently the 25th of December is the date at which the professional world as we know it will cease to exist and heaven help us if we miss it.

While Christmas is more of a perceived deadline for things, there are some real resource consent timeframes or deadlines that you should be aware of.   As over-allocation of our resources has become an issue, so has the methods by which councils can use to reduce over-allocation.  This is where timeframes around consenting are beginning to bite and councils are actually using their powers. 

Lapse Date and the Cancellation of a Consent

The first is the lapse date on a resource consent.  This is not the expiry date, but rather the “use it or lose it” date.  From the date of grant of a consent, you have up to five years to use the consent, or you lose it.  This is particularly important in over allocated water catchments for example as lapsing a consent is one of the mechanisms that a council will use to claw back over allocation.  You may apply to the council to extend your lapse date, but you have to be able to demonstrate to the council that you have taken considerable action towards actually using the consent.  The maximum extension that would normally be given is a further two years.

Even if a consent has been used before the lapse date, it can still re-lapse if it is not used for a five-year period after that, so this is something that you also need to be aware of.   This is referred to as cancellation of a consent. 

Renewal of Existing Consents

There are also important deadlines around renewing resource consents.  An application to renew a consent that is received by the council at least six months prior to the expiry of the consent is guaranteed to be given ‘continuation’.  What this means is that you can continue to operate under your existing consent until such time that a decision is made on the replacement.  Getting continuation is critical if processing the renewal is likely to take considerable time like we have seen here in Canterbury where renewal applications have spent years in process waiting on plans to be developed. 

A renewal application received after six months but before three months of the expiry date may get given continuation, but it is at the council’s discretion. 

Securing continuation also means that you have priority to a resource over someone else competing for the same resource.  So again, if we think water permits where a resource is nearing its full allocation, you want to be able to re-secure your access to that water ahead of a new user.   

If you find yourself within the three-month window, then continuation cannot be given, and you must cease your activity at the expiry date.  If you are in an over-allocation situation again, this may cause issues with your renewal, and there is a risk of the council not granting the renewal consent (another way to claw back over-allocation). 

Expiry Date

Once a consent expires, and if no application has been received by the council to renew the consent within the required timeframes, then you no longer hold a consent to undertake that activity or have any right at all to renew it.  If you find yourself in this situation, and you do want to carry on undertaking your consented activity, then you have to apply as if you are a brand-new consent.  In over-allocated areas, you may not even be able to apply for consent as many councils have now made it a prohibited activity to apply for consent in over-allocated areas.  Prohibited means that you cannot even apply to the council – the door is shut tight. 

These dates are all things that any consent holder needs to know.  A resource consent is not an unlimited right for unfettered access to a resource, or to undertake an activity.  It can be revoked by not using it, or by failing to meet the timeframes around the renewal process.  

Also, a small request from this consultant.  An application for resource consent can take a fair amount of time to prepare – even if it is for a renewal, the amount of information required to be supplied is just the same as it is for a new application.  Therefore, please give your consultant plenty of time to get the application in – it is no good fronting up a week before the application must be submitted and expecting that it can and will be done in that timeframe, and the same goes for that magic Christmas deadline…

By Keri Johnston, Irricon Resource Solutions
Phone 0272 202 425 or email

Wednesday, 29 November 2017

Useful Farming Technology Apps and Websites

Technology – there are those who embrace it with open arms, and then there are those who don’t… but love it or hate it, there are some very good pieces of technology that could be extremely useful for farmers wanting help with environmental compliance, or even just some advice and support.  And, with the increased need to be accountable and “doing things right”, these are some of the technology tools and resources that I have come across in my day job that I thought were worth a mention. 

Riparian Planner

This is an online tool developed by DairyNZ.  It is a step by step process to design, budget and prioritise water management on farm.  It is extremely user friendly, and a good starting point if you are considering riparian planting on your farm.  This is a useful tool for all types of farms.  The web page address is as follows:

Check-It Bucket Test app

This is available for both Apple and Android devices via the App Store or Google Play Store.  The app walks you through an annual performance assessment of your irrigation system, provides the results instantly to your device and e-mails a final report to you.  This is a great way to check whether your irrigation system is performing as you expect.  Is water being applied evenly?  Are you putting on what your control box says you are putting on?  You do need to own a few buckets to carry out the test, but the insight into your irrigation systems performance is well worth the trip to town to invest in the buckets.  Some irrigation schemes do have buckets that you can borrow for this purpose, so ask around too. 

Soil Moisture Monitoring

Soil moisture monitoring equipment is by no means new technology, but the amount of it now on the market has increased substantially and understanding what is the right tool for you can be difficult to work out. You must choose the right equipment for your soil, land use activities and irrigation system type, and then locate, install and calibrate (if necessary) it correctly. Accessing, managing and understanding the data is also important. If soil moisture monitoring is to be successful, each of these aspects has to be carefully worked through.  Irrigation New Zealand has developed a resource book for this very topic and it can be found here:

Online GIS systems

For those of us here in Canterbury, Canterbury Maps is an amazing resource.  Not only can you create farm maps, but it can be used to search for information about any property, consent information, bore information, and any other relevant information that you may need such as nutrient allocation zones, the location of wetlands or Runanga sensitive areas.  This can be found here:

Other councils do have online GIS systems, but none are quite to the level of Canterbury Maps.  But check out what your local council does have.  Understanding what is of interest and/or significance on and around your farm is key these days. 
FDE Calculator app

Dairy NZ has developed an app to allow you to work out how to manage your Farm Dairy Effluent (FDE).  You can easily calculate nutrient loadings and application rates, therefore enabling application of effluent with greater precision.  It can be used for diluted dairy effluent as well as for slurry tankers and muck spreaders.  This is also available for both Apple and Android devices via the App Store or Google Play Store.

I hope you find this information useful, and please let me know of any others that you think might be worth checking out.

 By Keri Johnston, Irricon Resource Solutions
Phone 0272 202 425 or email