The Irrigation, Grazing Game - Digging Deeper

Following on from last week our guest contributor Nicole Mesman digs a little deeper into the findings from her research that looked at the effect of grazing and irrigation on soil porosity.

Soil natural capital and soil health may seem like unnecessary concepts, names that you already know the meaning of without having to learn them. However I will outline them briefly and how they relate to my findings so that you are, in turn, able to relate to them if you come across them in environmental plans, legislation or elsewhere in the future.

Soils are referred to as a stock of properties or natural capital which yield a flow of valuable ecosystem goods or services into the future. Both soil health/ quality and natural capital are similar in that they use soil indicators and parameters to determine the state or function of a soil system. However soil natural capital provides a more holistic analysis of the resource as it takes into account not only the state of the soil itself (through soil indicators) but also the effect of this state on the products and services that soils provide and the human needs that are catered for by soils.

In the soil natural capital framework macroporosity is identified as the key physical attribute. This is because macroporosity determines: water flow, solute transport and drainage through soil. As a result macroporosity influences ecosystem services such as flood mitigation and filtering of nutrients. Macroporosity and associated soil physical properties provide important services and it is important for land managers to be aware of the potential to change these properties and the ecosystem services they provide.

Research has been carried out to determine the effect of land use practices on other soil physical properties such as bulk density, aggregate stability, soil carbon and water holding capacity however macroporosity remains the main indicator of soil physical natural capital and health because of its sensitivity to intensification.

My research found that on average for the 0-30 cm increment macroporosity was significantly lower on the Dairy site (9 ± 1%) than both the Sheep farm (19 ± 1%) and the Control site (15 ± 1%). This suggests that intensification is having a significant effect on the Dairy site. Furthermore on the Dairy site the 0-10 cm and 10-20 cm depth increments both have values for macroporosity < 10%. Other researchers have proposed that macroporosity values of > 10% are needed to maintain pasture production near optimum.

Target ranges for macroporosity are given in Table 1 as part of the National Soil Quality Indicator Programme. Here, for soils under pasture, macroporosity values < 8% are considered low and could restrict pasture growth. Macroporosity for the 10-20 cm depth increment on the Dairy site was 7 ± 1%, a level where less than optimum production could be expected. Results from an AgResearch trial found similar values for and changes of macroporosity with stocking intensity.

Table 1 – target values for macroporosity for pasture, cropping & horticulture and forestry

I did not find any changes in water holding capacity within the plant available range with increasing land use intensification. This result in itself was interesting as it shows that intensifying land use practices did not have a measureable impact on the readily available water (RAW, that available to plants) of the soil. In comparison other studies have found that there is a significant decrease in RAW with irrigation and increased compaction.

Finally my study did find that there was an increase in small micropores holding water at suctions too great for the plant to overcome. These findings all highlight the importance of on farm soil testing to determine the RAW of the specific soil textures and under different land uses to increase management efficiency.

Bulk density values were found to be significantly higher on the Dairy site (1.40 ± 0.02 g cm^-3) than both the Sheep farm (1.26 gcm-3± 0.02) and the Control site (1.31 ± 0.02 g cm^-3), indicating increased compaction on the DF in agreement with macroporosity values. Bulk density is not as sensitive an indicator of compaction as macroporosity and this can be seen by the large target range 0.7–1.4 gcm^-3 that has been identified for Pallic soils (Table 2). Therefore it is not recommended as an indicator for determining the effect of land use intensification on soils.

Table 2 – target ranges for bulk density are large indicating that this is not as sensitive an indicator as macroporosity for determining the effect of land use intensification on soils.

Landcare Research has developed a tool which can be used by everyone to determine the quality of their soil based on a number of indicators.

sindi.landcareresearch.co.nz

The tool allows you to measure your soil against current understanding of optimal values for: Macroporosity, bulk density, Total N, Total C, Mineraliseable N, pH and Olsen P

It will tell you about the effect each indicator has on soil quality alongside some general management practices that can be used to improve your soil.

In addition to thinking about the effect of these indicators on your soil quality I encourage you to take a step back and also think about the long term effect of the state of these indicators/ properties on your farm’s functions and the importance of each of these functions to your profitability. 

Thanks to Nicole Mesman (BSc (Hons) Soil Science) for the content of this post!

Precision Ag update - a UK & Europe perspective - Part #1

Having just spent most of June in the UK and Europe on a tour organised by CB Norwood, looking into Precision Ag, I thought I’d give an overview of what I saw of interest.

The tour group consisted of a great mix of farmers, contractors, CB Norwood’s managers, from both the South and North Island, Tim Myers (CB Norwood CEO), myself and was run by Paul Collins (CB Norwood Partnership Development Manager) - hats off to him for an excellent job managing the whole event and his team back in NZ.

The first week was spent in the UK, going around farms and visiting the Cereals event near Duxford. There was a real mix of farms from the traditional Estates, to new corporate farms less than 10 years old with huge areas 15,000+ hectares. From the precision ag point of view, it was interesting to see that we are all using the same technologies but for different reasons. EM surveys are used to identify different soil management zones as they are here, but not for irrigation and with little use of the topography data collected at the same time. EM was used for variable intensity of cultivating, and a lot for variable rate seeding. The EM zones are identified and then the soils classified into percentage establishment zones, so then according to your thousand grain seed weight and total population your seed required was automatically adjusted. This combined with using the EM to highlight areas of potentially higher blackgrass burdens - they find much higher levels on heavy soils identified from the EM maps, so they drill at higher seed rates   areas to compete with the blackgrass more. Using variable rate seeding and cultivations the farmers where going far more even looking crops, suppressing the blackgrass marginally more and getting up to 8% increase in yield.

Image 1: Winter wheat VR seed rate from an EM map. 

The EM maps where being used in combination with combine harvester yield maps to create zones for zonal soil sampling rather than grid soil sampling. The advantage there was that you had less samples than grid sampling, so it was cheaper, and you took samples in transects from within each soil zone from the EM map. Most of these farms have no livestock and the fields have been the same size under the same management for a good length of time, which lends itself more to zonal soil sampling.

There was a greater spread use of variable nitrogen from either satellite imagery, drones, N sensor/GreenSeeker type sensors than in New Zealand. The farmers had to use their nitrogen smarter as they had strict limits and timing limitations. This was apparent at the Cereals event on the Yara and Horsch stands to name but two both showing their own real-time sensors.

Image 2: N sensor for real-time VR nitrogen application

Image 3: The Horsch biomass sensor, also for VR N

At Cereals every machinery company seemed to be developing or had its own self propelled sprayer option, from the very basic offering to the other end of the spectrum the Horsch sprayer with its incredible boom technology on the pro plus and nozzle setup, allowing it to follow the crop at a height of just 30cm even on contoured land and almost making it wind proof spraying – with a climate like the UK one, you need to be able to spray at every opportunity you can!

Image 4: The soil pit - a great way to compare root structure in different scenarios

Image 5: There are many different software options in the UK for field inputs and collecting layers of data for smarter farming

It was great to catch up with Jim Wilson and the team from Soil Essentials, one of the few Precision Ag companies who still had a stand at the Cereals Event. The consensus on the Precision Ag front was that there are a lot of interesting and innovative ideas in the pipeline, for growers to use, which is very exciting. 

Image 6: The Soil Essentials team

 All the companies seem to have started from various positions within precision ag but come to the same conclusions on what works best, all of which we are doing here too in New Zealand. Of all the cropping farms there is probably about a 50% uptake in Precision Ag in various forms. Most farms seem to use muck in some form or another to increase organic matter and help with moisture constraints.

The last farm we went to in the UK, was the Beeswax Dyson Farming, owned by the Dyson Company. They had bought over 15,000ha since 2011 and used EM surveys and drones to help them get up to speed on their various soil types to manage them better. They were also heavily involved in environmental schemes like some of the old traditional estates we saw.

Figure 7: Beeswax Dyson Farming, general storage shed

In the next article I will discuss some of the interesting ideas that we came across in Europe. 

Cheers, 

Chris 

EM Surveying - The Uses

In the previous EM survey blog, I ran through the process of conducting the survey, this time I will go through some of the uses.

The data from an EM survey is very useful for irrigation in many ways. The topography data can be used for planning the pivot design itself with your irrigation provider for example working out tower spacing and pivot positioning. The angle of slope can be used to see if the pivot stays within design parameters for insurance purposes as well as design planning.

Figure 1: Contour map on top of elevation map

After the initial pivot or irrigation design plans, we can then look at the EM data itself to determine the amount of variability within the surveyed area. Within the PCT Gateway software we can look at the value and amount of the crop being grown on the area and the cost of installing variable rate irrigation (VRI). The software needs to know the average yield and value of the crop. That way using algorithms it calculates that by not over watering the heavier soli types or under watering the lighter areas you bring the crop yield on those areas up to the average. It looks at the reduction in variability by using VRI as opposed to a blanket application. In the example below the variability from using VRI drops from 30.4% to 4.68%. So, by using the average yield and the price we can see the payback vs the cost of putting VRI on your pivot.

Figure 2: Illustrating the payback from VRI, using an EM map. 

This model just looks at the costs vs savings of VRI from a production prospective. It doesn’t take into consideration savings from reduced water use, power savings, reduced track repairs etc, which will be in addition to this.

The next stage is to make VRI maps up for the pivot, using the different soil zones, predominately we use the shallow EM results. If the area has a lot of variation in topography we can also combine the elevation layers with the EM map to make an application map for the pivot. We can also use other elevation layers to achieve the best solution used for each specific survey, as required.

The map below, shows a three zone EM map, where  red is the lightest soil, green the medium textured soil and blue the heaviest soil. This has been combined with the slope map, where the darker tone indicates a slope of 0-5% and the brighter tone of colour areas where the slope is above 5%.

Figure 3: An EM map and slope map combined to make a VRI application map. Brighter red, green and blue indicate slope for the different soil zones. 

The EM zone maps can also be used for irrigation pod placement, as well as moisture probe placement. If you only have one probe under an irrigation management zone, you want to make sure its under the right area. I will discuss this in more detail in the next blog. In the meantime, if you have any questions about EM surveying please get in touch.

Chris Smith

Operations Manager Agri Optics NZ Ltd.

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

EM surveying - Knowledge is Power... (and Potential profit!)

An Electromagnetic Survey is one of the key layers required on the precision farming journey. Precise location and understanding of soil types is a key piece of information in driving decisions around water use and nutrient placement. Not only can an EM survey be used to reduce water inputs it can form the basis of other decisions related to plant health, production and nutrient uptake. Turning the pretty maps into useful data requires some powerful software. That is where VA Gateway comes in. Gateway allows for in depth analysis of multiple layers, including Yield and EM. All Agri Optics customers have access to VA Gateway and AgCloud the online version.

With the software we create reports on the various layers of data collected. Clients get information on two EM soil profiles, one measuring the conductivity in the top 0-50 cm of soil and the other looking at changes in the top 0-125cm of your soil profile. Our report explains our findings on each layer with an explanation of what you are seeing. Depending on the variability arising from the survey, we then create different management zones based on the range in EM units. These zoned maps can then be imported into your variable rate irrigation (VRI) software if they are used for irrigation or into your VR seed drilling control box if you are using it for variable rate seeding based on your soils.

Figure 1. Top left is a shallow EM map and to the right of it a zoned map of that layer. Below is the same but for the deeper EM (0-125cm).

We also report on topography features. As we log the EM data at 2cm accuracy we are also mapping these features. This data set in its own right is very useful and gives you the surface characteristics of the area surveyed in the form of six additional maps, slope, elevation, landscape change, aspect, any depressions and witness index (which way water will move in a rain or irrigation event). This data can be a powerful management tool. The water movement models can help highlight potential areas of issue, so they can be addressed, be it nutrient movement or run off.

Figure 2. Gateway software generates water movement models based on the topography data.

The elevation data can also be used to create contour maps that can be used in the design stage of your centre pivot system, e.g. when calculating tower spacing's or to help with budgeting for any required earth works.

Figure 3. Gateway software can be used to create 3D contour maps.

We can also create moisture probe placement maps based on your EM and elevation data to find your optimum site within each management zone. These sites can also be used as ground-truthing sites with HydroServices neutron probe to put actual specific values to the different zones water holding capacities and then convert the EM map into a water holding capacity map.

A further report can be created to gauge the likely payback time from the installation of VRI based on your soil variability, the crop you are growing, its value per unit and the cost of your VRI system. This is proving very helpful for those who are unsure as to whether they have enough variability in the surveyed area to warrant VRI.

All our data is collected using strict protocols, with the highest standards in continuity and quality every time. This ensures our clients have powerful, solution-focused information. For more details check out our website www.agrioptics.co.nz.

Post credit to Chris Smith.

Improving Irrigation Efficiency for Only $50

Dr Anthony Davoren is renowned as one of New Zealand’s leading irrigation consultants, establishing Hydroservices in 1983. If you have a question about irrigation management, soil and soil water assessment or surface and groundwater water resources then Tony will have the answer. What sets Tony apart is his practical, hands-on approach and the way he communicates information in a way that farmers can easily understand and relate to… I mean how many other speakers will you find presenting from a hole in the ground!

The Waihao Wainono Group and Morven Glenavy Irrigation recently hosted a field day focusing on improving irrigation efficiency. H2Grow is lucky enough to be able to share with you some short videos from this day. In the first in this series Tony explains how the root depth of the pasture or crop you are growing should be considered when deciding on the most appropriate soil moisture measuring equipment for your property.

Considering Root Depth when Measuring your Soil Moisture Levels

Keep a look out for the next video in this series where Tony explains how to measure drainage so that you can better manage your irrigation and prevent irrigation water, and nutrients, draining through the soil... and his top tips of how to greatly improve your systems irrigation efficiency for as little as $50!

Thank you to Dr Anthony Davoren, Waihao Wainono Group and Morven Glenavy Irrigation.

Reduce the Cost of Nutrient Loss with Precision Ag (Part 1 of 3)

Precision Ag can help you in many ways with your Farm Environment Plan (FEP). Precision nutrient management, EM maps, topography data,variable rate irrigation (VRI) and moisture probes are all tools available to help you manage your FEP and mitigate any potential issues you may face - Reducing costs to your farming operation and the environment.

I will be looking at how each of these can help you over the next few blog posts (to make sure you don't miss out pop your email address in the "Follow By Email" box, to the right). In this first blog of three I am looking into precision nutrient management.

Improving Nutrient Management with Precision Ag

The objective here is to maximise nutrient use efficiency while minimising nutrient losses into water. This can be accomplished by looking at the nutrient levels in the soils themselves as well as monitoring the moisture in the soil profile to ensure you don’t leach nutrients out with over watering. Precision Ag can help you in several ways to achieve this, this week I will look at the nutrient levels themselves.

This is done through either grid or zonal soil sampling. Instead of taking one soil sample per field or block, you sample in a grid at a resolution of one site per hectare or take samples within each known soil zone from your EM survey. Whichever way the samples are collected the sites are geo-referenced that means you can go back to the same point every time you sample so you can see how you are managing your nutrient levels over a number of years. At each site 12-15 cores are taken and placed in a bag, labelled and sent off to the laboratory for that sampling point.

Picture 1: Geo referenced sampling points in a field.

When you receive the laboratory results, they look similar to those you normally get however the critical difference is they are all geo-referenced and are at a higher resolution i.e. one per hectare. The data received can then be processed to create a nutrient zone map; with nutrient levels grouped in ranges for the given area and given nutrient.  From that layer of data application maps are made to match the soil and crop requirements.  The main nutrients commonly applied using this variable rate method are potash, phosphate and magnesium as well as lime for pH.

Picture 2: A map showing the varying Olsen P values across a field.

By only applying what is needed where it is needed means you minimise any over-application of product with financial and environmental implications, and you also maximise the crops potential on a nutrient level. By using this method you can mine nutrient-rich zones reducing nutrient levels in those areas and apply only what is required elsewhere.

Chris Smith

Agri Optics NZ Ltd

FieldNET and EM Surveying. The Ultimate Moisture Management Solution.

Electromagnetic soil surveys (EM) and variable rate irrigation are two tools that when used together can have maximum impact on your bottom line and allows for optimisation of the VRI system. On top of this, systems such as the Lindsay Precision VRI and FieldNET can produce a proof of placement map which can be used for analysis with other layers. This feature adds to the power of the EM-VRI combo.

The EM Survey:

• From the EM survey individual zones of soil type can be created, each with different water holding capacities.
• Zone maps are geo-referenced which allows for further use in mapping programs.
• Ground truthing of EM zones with a neutron probe will build a profile of actual soil water holding capacities.

EM Survey Zones

The VRI plan has multiple features:

• Each soil zone has been added to have a different irrigation rate.
• Tracks have been set as avoid zones. Troughs and low points can also have variable rates.
• Pivot wheel tracks have a reduced irrigation rate.

FieldNET VRI Plan

 Once the plan has been run the FieldNET software will calculate the total mm of water applied over a given time period. This produces a map layer that can be used to further investigate relationships with other data layers such as yield data. The proof of placement map serves as excellent reporting tool as the total amount of water applied to each zone on the farm can be accounted for. It is important to remember that the combination of EM and VRI allows for greater precision and ultimately greater efficiency.

FieldNET VRI as applied map:

• Irrigates to a set plan which can be dictated by factors such as soil moisture conditions, crop growth stage and available irrigation water.
• Produces the record of water applied. This can be broken down further into water applied per zone. The reporting features enable accurate proof of water applied.
• If a cost is applied over the water applied map a cost per zone can be quantified.
• Further analysis can then be done on gross margin per zone with the cost of water applied factored in. Stay tuned to the blog to see the latest on this front.

FieldNET VRI as Applied Map

Data from irrigation proof of placement maps can be fed into OVERSEER®. The total amount of water applied can be used at a block level. This has in recent cases reduced leaching values at block level. It shows that there is merit in capturing this information and that there is potential for multiple uses for the data in the future. 

For more info see http://www.precisionirrigation.co.nz/en/pages/products/?content=7

Another post from Nick, Precision Ag Technician. 

Irrigation NZ Conference Summary

The Irrigation NZ Conference was held in Oamaru from the 5^th to 7^th of April. There was a huge range of speakers and presentations all relating to different aspects of the industry. Some of the important and recurring topics are summarised below.

Irrigation has benefits to communities and the environment.

The pre-conference tour took a bus load of delegates on a tiki-tour through the Waitaki valley to see first hand the irrigation schemes that draw water from the mighty river. It is readily apparent that irrigation water has benefits to farmers and community.  An example being a storage pond which is held in a trust to allow the public to use it for recreational use. A great example of the community and irrigators coming together to prosper together.

MGI Intake off the Waitaki River.

Also highlighted on the trip was how irrigation can have benefits to the environment.  The frequent droughts experienced by the Waitaki Valley prior to irrigation meant that rabbits and dust storms were free to wreak havoc on the area. Now, with irrigation, soil is no longer lost in howling Nor’Westers and improved soil structure has resulted in reduced sediment loadings in water ways. This draws some similar parallels to Keith Cameron’s talk at the PAANZ Conference (see: http://www.h2grow.nz/2016/03/inaugural-paanz-conference-summary.html)

The future is a scary place…

Synthetic meat and massive urban greenhouse skyscrapers are set to be realities in the future. The value and limited supply of the world’s natural resources was something that really hit home in Julian Cribb’s talk and it gave serious weight to the fact that efficient irrigation and water use is extremely important.

Another guest speaker, Peter Biggs detailed the concept of the volatile, uncertain, complicated and ambiguous world that we live in today. Complexity and uncertainty are two concepts that are a big part of the irrigation scene in New Zealand. How do we keep an eye on the future when such complex issues confront us at home on a daily basis?

Engaging with the public is important for success.

Nicky Hyslop, Chair of INZ made us aware of something we are all possibly guilty of. Not listening when we should. The idea that more often than not we just need to “shut up and listen” when dealing with the public on issues related to irrigation and agriculture and go forward in a dynamic, proactive way. The key message being that we must “engage” with the public rather than lecture them if any change is to be bought about.

 

Waitaki Irrigators Collective to bring together all irrigators in the Waitaki Valley

Management and measurement to improve efficiency.

The growth of technology in the sector is seeing efficiency gains left, right and centre. From improved efficiency of infrastructure that delivers water to the farm gate to the use of VRI and soil moisture management, irrigators have plenty of scope to lift performance. The level of data that can be easily captured from an irrigation system such as; flow, pressure and energy used is high. Not only can irrigators make use of this data to reduce energy costs but also water use efficiency. Dan Bloomer presented on how simply it is done with 2 dozen buckets to actually measure what water your irrigator is putting on the ground. Ultimately what gets measured gets managed.

This weeks post was bought to you by Nick Evans of Agri Optics. To find out more about Nick or to get in touch with Agri Optics check out our website: http://www.agrioptics.co.nz/meettheteam/ 

The 2015 EM Season has come to a close

As we fast approach the end of 2015 it is good to look back at the EM surveying season we have just had. Due to the very dry summer we didn’t get going until nearly the end of April which is about 3-4 weeks later than the season before. Stewart Darling join the team this year and many of you would of met him if we conducted any survey work for you. As Stu’s from Scotland he found the colder winter weather easier to handle than this already hot summer! We also changed our side by side Polaris for a larger capacity machine for greater capability in the field and improved downhill descent which comes in very handy at times in Otago!   We did a lot of testing with the new set up to make sure it was performing well before the season kicked off.

Field testing the EM rig on the new Polaris back in February 2015.

Like every season we have faced new challenges and found solutions and developed our protocols to take them into consideration. So next season we will be another step ahead of the previous year! We have met some varied and interesting new clients as well as continuing to work with our existing clients, helping all to achieve their goals with precision ag. through our services.

With the introduction of our AquaCheck soil  moisture probes this season we have been able to add another dimension to the service we offer, not only surveying  your soil’s variability and moisture holding characteristics but now also providing the means to monitor them very effectively.

Travelling past Mount Cook on one of many trips through the central South Island.

Moving forward to 2016 we will start surveying as soon as conditions allow; that is usually when irrigation has finished and we have had a couple of large rain events to negate the man-made influences of that seasons irrigation on the soil. This is usually anytime from late March to April depending on the year.  Our main concern is that our clients get the best data possible. This only happens when the conditions are right so please bare this in mind. If you want to book a survey in for a particular month to fit in with your on-farm management that is fine or if you just want to complete the  survey as soon as possible just let us know so we can keep in touch and start as soon as we’re able. For all enquiries be it for just more information on our services or a full quote please contact us at Agri Optics.

Wishing you all a fruitful and productive summer for what looks to be a very challenging time ahead. And hopefully you have the tools in place to help manage your water resource as efficiently as possible! Have a Merry Christmas and all the best for 2016 from the team at Agri Optics.

Chris Smith

Agri Optics 2015/16 Xmas Hours:

Closed Wednesday 23^rd December  & re-opening on Tuesday the 5^th of January. For any urgent matters over this time please call Jemma Mulvihill on 021796124. 

EM values - What the data is telling 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 0-40cm 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 85cm deeper. This is why the deep EM readings are always higher than the shallow as it is reading that extra 85cm.

Figure 1: Shallow EM of the same area with values from 1.6-27 EM units (mS/m)

Figure 2: Deep EM survey values varying from 16-43 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 factors 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!

Also of note as an aside; is that with all our readings legend red is the lowest value and dark blue the highest. This does not mean that red is bad and blue is good, there are a number of factors that determine that, and there is also a climatic influence on what is good or bad, in a dry year the heavier EM areas would be better where you don’t have VRI, and in wet years the lighter areas with more free draining soils would be more favourable. Likewise in peaty acidic soils with high organic matter they would show through as the high blue EM areas and clay soils would show up as the lighter red soils on the map. So it is always worth taking samples as you conduct the survey to see what is affecting the readings.

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

Chris Smith.

WHO SAID IRRIGATING WAS EASY?

Being an Irrigating Farmer has many benefits with increased land value and production to less reliance on rainfall events being at the top of the list.

But with these benefits comes responsibilities and duties to ensure success at being an irrigating farmer.  So, what is involved?

1. Regular System Maintenance

1.       Irrigation System checks should be undertaken pre-season and at least twice over the irrigation season.  This involves doing pressure tests, checking sprinklers and nozzles, cleaning out filters, checking and fixing leaks.  Click on the link below for checklists and guides.

http://irrigationnz.co.nz/news-resources/irrigation-resources/irrigation-system-checklist/

2. Irrigation Evalulations

Irrigation Systems need to be evaluated much like getting a vehicle Warrant of Fitness.  Evaluating your system allows you to check that it is working to the design specifications and performing as you would expect.  High distribution uniformity (how evenly the system applies water) is the key to achieving an efficient and effective irrigation system.  

Ideally, irrigation systems should be ‘farmer’ evaluated annually using the ‘Irrig8lite’ guide - http://www.pagebloomer.co.nz/resources/irrigation-calibration/irrig8lite/.  

Should your system show low performance, a full system evaluation should be undertaken by a qualified evaluator: http://www.hydroservices.co.nz/index.php?option=com_content&view=featured&Itemid=271.

3. Measuring Soil Moisture

Measuring your soil moisture is the BEST way to manage and schedule your irrigation efficiently.  If you don’t know what your soil moisture content is, it is likely you are either under irrigating or over irrigating which can be detrimental to your crop and/or the environment.  There are a number of options when it comes to measuring soil moisture whether it be an on farm service or telemetered continuous soil moisture sensors.  

Find out more at: http://www.hydroservices.co.nz/index.php?option=com_content&view=featured&Itemid=268.

The Irrigation Season has already arrived for some and is fast approaching for others.  If you haven’t completed your pre-season system maintenance checks already, now is the time to do it!

EM Surveying and Water Holding Capacity

In recent weeks we’ve been through the calendar of EMSurveying, A day in the life of an EM Surveyor and The value in ground-truthing your EM Survey in amongst other informative posts from Lindsay NZ and HydroServices. This week we’re going to shed some light on how an EM Survey by Agri Optics can be used to evaluate water-holding capacity of the surveyed area.

Predominately our clients ask us to conduct an EM survey for them to determine the differences in their soils with a view to varying their irrigation depths on the different soil types; however we can adapt the EM Surveys for many different uses, one of these being to evaluate water-holding capacity variation.

The DualEM sensor works by emitting an electro-magnetic field into the soil and measuring the returning conductivity of the soil. The conductivity of the soil in New Zealand is affected mostly by soil texture and the amount of water the different soil textures can hold (the more water the soil can hold the more conductive it is). The readings can also be influenced by salinity, however other than a few isolated areas in NZ we don’t have an issue with salinity affecting the readings. 

Figure 1: DualEM sensor being trailed behind our light weight Polaris

To fully relate the EM readings to water holding capacity (WHC), ground-truthing is needed to quantify the actual WHC at different locations as the EM Survey only measures relative difference of one area compared to another. As we have mentioned in previous blogs we create a map of EM zones and within that locate sample sites for each zone to be ground-truthed. The ground-truthing is then carried out by typically HydroServices using their neutron probe and our agreed protocols. They then provide us with the water-holding capacities for each different depth. From this we then create a map of WHC variation across the surveyed and provide a report back to the client of these additional maps with description on correlations of WHC and EM and recommendations on how these maps would be used to implement more efficient irrigation.  

In addition to getting accurate WHC maps and the associated report back the client can also use the ground-truthing sites to help site soil moisture probes and if the probes are installed before the ground-truthing is completed, the ground-truthing reading can also be used as one of the field calibration readings for the soil moisture probes.  

Figure 2: Water-holding capacity map created from an EM map

All of this information helps the client get the most of their EM data and make efficient use of their water by matching the water to the different zones and then monitoring moisture levels with their moisture probes. If the 2015/16 season is going to be as dry as forecast then making every drop count will be crucial. We not only conduct the EM surveying we can now also provide our clients with AquaCheck soil moisture probes to help manage your irrigation as efficiently as possible. Visit our website or give Jemma or Chris a call to discuss any of the above.  

Variable Rate Irrigation Pioneers

Ashburton cropping farmers Eric and Maxine Watson (Rangitata Holdings) were the South Island’s original Precision VRI pioneers. Ordering four VRI systems in 2008, after only two systems had been built and tested less than twelve months earlier, Eric and Maxine took a lot of trust and belief that the system would achieve what Precision Irrigation claimed.

This 3 News clip has been bought out of the archives from 2008. Eric and Maxine Watson along with Stu Bradbury, one of the engineers who developed the technology, showcasing the first system up and running in the South Island. And the results exceeded their expectations. The Watsons now have seven out of their nine lateral-move irrigators fitted with Precision VRI. 

http://www.precisionirrigation.co.nz/video/3news.mp4

The Watsons farm 490 hectares on the Canterbury Plains, with annual rainfall of 600mm, growing a wide range of crops on different soil types. In 2005 Rangitata Holdings water right restricted their annual and daily water take, so they started looking for ways to stretch their available irrigation water. With an annual water volume of 1,183,500m³, 3.7mm per hectare per day and 5ha of irrigator overlaps, VRI was considered as the solution to save water where it was being wasted. An unlooked-for advantage was the negated need for turning taps off and on when watering in pivot mode.

At least partly as a result of maximising water efficiency, and being able to prove minimal wastage, ECan raised the Watsons’ annual water volume to 1,420,000m³, 4.1mm per hectare per day. This consent only permits pumping 270 litres per second across all pumps. When one irrigator is watering in an over-lap situation or using different rates over different crops, they are able to use the saved water to turn on another smaller irrigator elsewhere on the property, thus ensuring soil moisture levels are maintained at critical times.

“It’s a great system with a big future... Now that I have VRI, I wouldn’t want to run the machines without it.”

Caption: Eric and Maxine say that the Growsmart Precision VRI system exceeded their expectations allowing them to maximise the use of their limited annual water volume allocation.

The couple’s dedication to efficient water use has seen them recognised with numerous awards including the 2011 Canterbury Ballance Farm Environment Award and the Environment Canterbury Water Efficiency Award. The Watsons say they were just doing what was needed to get the best out of their limited water take. Once they identified the greater efficiency with Growsmart Precision VRI, the opportunities snowballed. 

Eric and Maxine had the property electro-magnetically (EM) mapped and the soil water holding capacities quantified. Soil moisture sensors were installed to measure the actual moisture content of the soil. This allows the Watsons to schedule the correct amount of irrigation to individual zones which is then applied by the intelligent Growsmart Precision VRI system. This results in the crops getting the exact quantity of moisture required and no water is wasted. Resulting in a considerable saving of 15% of water that can then be used elsewhere.

"Being able to match application rates to the exact amount of water needed to ensure the soil has enough moisture is important to water efficiency and means that over-watering of crops is eliminated."

For More information contact your local Zimmatic by Lindsay irrigation dealer or visit growsmartprecisionvri.com.

The EM Surveying Calendar

We have had another successful EM year so far and our clients have used their surveys for many different uses. I will go into that in more detail in a future blog. Today I will cover the EM and the four seasons. I often get asked when the best time to conduct a survey is, the answer is any time from late autumn through winter into the spring right up to late November.

For an autumn survey, natural moisture is our deciding factor on start dates.  Once the irrigation on farm has finished and we have had at least a good 50mm of rain to balance out any irrigation affects, we can start EM surveying. This year we held off until the end of April and in some areas south of Oamaru and north of Canterbury later still, as we didn’t get the 50mm+ for quite a while. So we concentrated on the areas that once they got too wet we knew we would not be able to get on again! Getting this sort of information from our client’s knowledge of the land is very useful to help with the logistics and completing the survey with as little fuss as possible. Once on site we are self-sufficient and conduct the survey without the client having to get involved, but we rely on good information on the conditions to manage the logistics before we arrive!

Getting ready to start a survey in Ellesmere, early May.

Winter is ideal for surveying and the concerns here are not getting stuck and being able to get along without making a mess especially in cropping situations. We can juggle between all grassland projects and cropping regimes as the weather fluctuates between torrential rain and drying enough so we can travel on it! It involves shifting jobs around depending on the conditions to ensure we get all the projects conducted in a timely manner, not making a mess or damaging crops and without too much to-ing and fro-ing, to ensure all data is collected as efficiently as possible. On some farms we have to leave a few paddocks if they have winter feed crops in or crops in the ground still to be harvested, in that situation we can come back in the spring and drive some transects over the rest of the project and tie all the data in together. Ponded surface water is not an issue and does not interfere with the EM readings and results. If there is a big rain event between starting and finishing a project we can tie the data together be driving transects and using our robust protocols to ensure data quality is not compromised. The only weather that stops us is snow! Mainly because we can’t see the ground and any potential hazards are covered up, as well as getting to and from the site can be tricky, we had a few close calls getting in and out of regions this winter but we managed to keep ahead of the snow!

Surveying near Staveley in July once the snow had thawed.

In the spring we also get good results, the temperature is a little warmer and we can get along very well in most cases, the only issue comes in the cropping situation when the crops start to get too tall. Generally we are fine in a cereal crop until stem elongation. Again it is a matter of logistics and knowing the clients requirements, timing limitations and concerns, as long as there is good communication this is not an issue. We can and have EM surveyed right through to early December before in dryland situations where there has not been any irrigation and good natural moisture. Once clients start irrigating the influence of the irrigation pattern will start to show through in the data. In the summer itself the ground is too dry, the variation in your soil textures is still there but the low moisture levels means the range in EM units is reduced and the EM profile compressed so outside influences start to creep in and have more of an effect on the readings so reducing the quality of data – which is the main reason we make a conscious decision to stop as quality data is of paramount importance. In situations where we are just looking to gauge salinity issues then we can go later as the very high EM values (150-600 mS/m) are not affected by moisture, but for general EM work we stop and concentrate on the other areas of precision agriculture until the following autumn. 

Surveying in late August on a freshly drilled spring barley paddock near Blenheim.

Now we are getting to the end of August if you are still interested in getting a survey conducted this year please let us know as soon as possible otherwise you may have to wait until next autumn.

Chris Smith

Field Manager Agri Optics NZ Ltd