Reduce the Cost of Nutrient Loss with Precision Ag (Part 2 of 3)

In the last blog post we looked at nutrients and how Precision Ag can help with your Farm Environment Plans (FEP). This blog post looks at how an EM survey can help with identifying your soil types for your Farm Environment Plan.

An EM survey illustrates the relative variability in soil characteristics including soil texture that can be potentially related to water holding properties within that soil profile, this can help you manage water application through the use of variable rate irrigation technology. When combined with the use of soil moisture probes you have the data and technology you need to be able to retain nutrients within the soil profile itself. 

EM surveys can be ground-truthed to find the correlation between the EM value and water holding capacity (WHC).  From that you can create a WHC map and site-specifically place moisture probes to monitor the soil moisture levels within each identified zone.

Ground-truthing sites are identified within each zone (shown on the left). The graph illustrates the correlation between the EM values and WHC in the top 55cm of the soil profile for this paddock.

In the image above we can see the correlation between EM value and WHC at this site has an R2 of 0.97 (R2 quantifies goodness of fit. It is a fraction between 0.0 and 1.0, higher values indicate that the model fits the data better). We can then use the equation in VA Gateway, one of the PA software platforms supported by Agri Optics, to create a water holding capacity (WHC) map out of the EM values map.

The EM map converted into a Water Holding Capacity map

This water holding capacity map can then be used in conjunction with soil moisture probes and VRI to maintain the moisture levels between field capacity and critical moisture. This not only reduces any potential yield loss from moisture stress but it also ensures that you aren't saturating the soil profile, and therefore avoid leaching nutrients out of the root zone.

It’s all about balancing crop requirements, real-time moisture levels, rainfall (when it comes!) and application rates with irrigation return times as precisely as possible to keep everything at an optimum level.

An AquaCheck soil moisture probe graph showing soil moisture levels and how they are affected my irrigation or rain events on this soil profile.

As can be seen above by keeping the moisture between upper and lower readily available water levels you ensure yield isn’t compromised and eliminate leaching. The rooting depth used for the probe profile can be tailored to the crops specific needs on the moisture monitoring website.

Next time we will discuss how the EM maps and topography data can help you with your FEP.

Chris Smith

Agri Optics NZ Ltd

Workshop: Technology to Reduce N Leaching

If you're under pressure to mitigate N leaching and improve efficiency and profitability on farm - then the PAANZ Technology to Reduce N Leaching is for you!

Note registrations now close on March 18th. 

Register: paanz-workshop.lilregie.com

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. 

Variation in Electro-magnetic (EM) Readings

When talking to clients about Electromagnetic (EM) surveying of soil’s conductivity, I often get asked what a low or high EM variability is. This is quite a hard question to answer, as there are so many factors that you need to take into account. These include:

1.       The region of the country where the land to be surveyed is located.

For example, as a general rule there is a big difference between the readings we get in Otago compared to the Canterbury Plains. However within each of those regions we can also get big variations from the stony soils to the areas of heavy clay. So it is definitely site dependant within a certain range of values. In areas like Seddon and Ranfurly we have also come across salinity issues that take the EM readings to a different level all together. 

Figure 1: A vineyard in Otago on sloping ground.

Figure 2: The relatively flat, stony river bed soils on the Canterbury plains.

Figure 3: Salinity issues near Ranfurly can be visibly seen to effect crop growth and can dramatically increase EM readings.

2.       Geography and topography features.

These features can also influence factors affecting the soil depositions and therefore the EM readings. We often find that weathering and water movement over many years can create areas of higher EM readings. Topography data from an EM survey also backs up this finding. We use the VA Gateway software platform to analyse these different layers side by side, bringing all the different data together.

3.       The time of year the survey is conducted.

We take this in to consideration in our EM reports. At Agri Optics we don’t start our surveying season until the Autumn and then not until the ground has had enough rain to bring it nearer to field capacity, eliminating the effects from that summer’s irrigation. In previous blogs we have shown why surveying in Summer does not provide good data and I would be extremely cautious of the quality of data provided by anyone offering to conduct a survey for you in the summertime. The EM readings in Autumn are slightly less than you would get in the Winter and early Spring. Winter generally is the season that gives the higher readings followed by Spring. Our main concern in Winter is that the ground can be travelled on safely without damaging the crop and without getting our light weight EM buggy stuck. We continue to get very good data Spring, but as we get into further into Spring the EM season is draws to an end as farmers start  up their irrigators. At this stage we stop EM surveying, as we start to pick up the influence of the irrigation applications on the soil maps. So if anyone is still thinking about having a EM survey conducted this year, you should get on to it straight away, as time is slipping away.

When we carry out an EM survey the sensor is measuring the soils conductivity at two depths simultaneously, the shallow EM and deep EM. In a pastoral situation we recommend using the shallow EM layer to base decisions off as the crops roots are predominantly within this shallower profile. In an arable scenario where you have crops roots going deeper into the soil profile we would recommend using the deep EM layer to make your management decisions from. These readings are generally higher than the shallow EM readings as they measure deeper into the soil profile.

In the next few blogs I will go into more detail on how historic management practices and historic boundaries can sometimes come through on an EM survey and how the EM survey can be used to identify salinity issues. For more information on EM surveying or if you have any questions please contact us at Agri Optics.

~ Chris Smith

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

A guide to S-Map

What is S-Map?

S-Map is a map containing information of the soils across the country. It is being developed by Landcare Research and information is continually being added to it. The project was started to collaborate and update information on New Zealand’s soils into one easily accessible map of the whole country with different layers of information for different applications and to support land management at different scales.

Anyone can access the information freely. Mapping is carried out by Landcare scientists who either use old soil maps or go to the area and undertake traditional soil surveying. This is where soil core samples are taken to determine the soil type and this information, alongside the history of the area, is used to present what they think the pattern of soils will look like. The most detailed information available is currently on the lowlands while the uplands of the country are being mapped using digital modelling based on the soils having similar characteristics to other known soil types.

How to use it

In the previous blog (identifying soil textures) you see how the content of sand, silt and clay determines soil physical properties such as WHC, porosity and bulk density and how there are different horizons in a soil profile with different quantities of these three particle sizes. S-Map also uses soil horizons to determine soil characteristics.

You can search for your location on S-Map and select to see polygon layers to view the soil types present on your farm as shown below for Methven, Canterbury.

S-Map Online is freely accessible for anyone; smap.landcareresearch.co.nz

You can then select the ‘Soil information’ tab at the top of the screen and click on a point on the map. S-Map will show you the percentage of each soil type present around this point and you can select to view the factsheet of the dominant soil type (and the other soil types present). In the figure below the Greenvale farm near Methven is shown by S-Map to have three dominant soil types: 50% is a shallow, well drained Eyre, 25% is a shallow Darnley and the final 25% is a moderately deep Mayfield.

The soil will have been given a series of names using the New Zealand Soil Classification System however don’t worry about this too much, the information contained further down in the factsheet has more practical applications. The fact sheet tells you:

• ·         How stony the soil is which relates to its drainage class
• ·         The amount of water expected to be held at different depth increments
• ·         The clay content
• ·         Potential rooting depth
• ·         Soil phosphorus retention
• ·         Water management such as the potential for waterlogging and drought
• ·         Nutrient management such as nitrogen and phosphorus leaching vulnerability. 

Page 1 of an S-Map report for an Eyre soil, downloaded from smap.landcareresearch.co.nz

You can also select different layers to view on the map, on the left hand side of the screen: soil drainage, depth to hard soil/ gravel/ rock and soil moisture. The map will then update using the colour scheme from the legend for this layer which is shown on the right hand side of the screen. The figure below shows that for the Greenvale farm the soil drainage depth layer has been selected and on the right hand side the legend explains what each drainage class means.

Positives

S-Map brings all information on NZ soils into one database that can be easily accessed and used by all land users and interested parties. It is the largest national resources on soils that NZ has and it contains a range of information that is relevant and useful for all scales of management. However there are also aspects to S-Map that limit its usefulness, especially to farmers.

Drawbacks

According to S-Map the Greenvale farm, shown in the S-Map figures above is a mix of mainly three soil types. However an Electromagnetic map carried out alongside soil sampling showed that there was, in fact, a much more complex pattern of soils present on the farm. The picture below and top is the Electromagnetic map of the property and the different colours represent different textures while the picture below and bottom uses the patterns from the EM map alongside soil sampling to identify the pattern of soil types (families) on the property. 

Top, EM map by Agri Optics Ltd. Bottom map of soil types developed from soil sampling.

These maps provide a substantial amount more information than the map of the farm from S-Map (discussed above). The soil information used by Overseer to determine nitrate leaching is supplied by S-Map and this can result in inaccuracies in N leaching figures when S-Map believes the soil pattern on a farm is more simple or different than it actually is. Furthermore using soil information from S-Map for irrigation scheduling could mean over or under irrigating areas which can decrease yields as well as creating inefficiencies in water and power use.