My soil moisture sensor hasn’t responded as I expected? Why?

From time to time we get the query: “my soil moisture sensor hasn’t responded to recent irrigation events, there must be something wrong with the sensor”.

While it is easy and natural to blame the sensor, the reason is often found in the field. There are physical reasons why a sensor may not register an event and the problem could be caused by a combination of these.

Figure 1. An irrigation event causing a neutral change in soil moisture content.

Canopy interception

The crop’s canopy will intercept some of the rainfall and/or irrigation water. Obviously, this will vary greatly from crop to crop and throughout the growth stages. It stands to reason that a mature crop of maize will intercept more water than freshly grazed pasture.

Much of the intercepted water will evaporate, but while it is sitting on the leaf it will cool the leaf and reduce the plant’s evapotranspiration rates.

Some of the intercepted water will trickle down the stem and enter the soil at the plant base, but not in sufficient quantities to register at the first sensor depth.

This scenario will look like a neutral response on the soil moisture graph (Figure 1). The irrigation event has not caused a soil moisture increase, but it did satisfy the plant’s evapotranspiration demand, so there is no water use for the day.

Application depth –less than daily water use and/or less than 0-100mm deficit

This tends to be a problem under pivots and fixed sprinklers. Daily irrigation of 4-5mm may not be enough to result in a significant change in soil moisture content at the first sensor depth (100mm). Firstly, some of the water will be intercepted. Secondly, the application may be less than the deficit present above the first sensor site, the water will infiltrate into the soil but may be absorbed in the top 50mm of soil.  In this case the response to the irrigation event at the first sensor (100mm) will, at best be a “flattening” of the trace; soil moisture will remain at its current level.

Bypass-flow -dry soils and soil type

Bypass-flow occurs when water passes through the macro pores (or gaps between soil particles) and is not absorbed by the soil particles. Bypass-flow and soil type are linked; coarse texture soils have more macro pores, increasing the potential for bypass-flow.

Bypass-flow and soil moisture content are also linked. As a soil dries it can undergo slight structural changes which may result in increased macro-porosity. The effect of drying varies with soil type. A fine textured soil with higher clay content will tend to shrink; typically, at the surface of the soil resulting in opening of cracks in the soil. In coarser textured soils cracks will not develop, but individual aggregates will contract, increasing the soil’s macro-porosity.

Water passing through the macro pores, or cracks, may not be registered by the soil moisture sensor; firstly, because the slurry used when the sensor is installed will have fewer macro pores than the rest of the field; and secondly, because the water fails to ‘linger’ long enough to infiltrate and re-wet the dry slurry the sensor is installed in.

Lack of sensor response due to a dry soil profile is most common in crops where the readily available water is greatest, e.g. wheat or carrot seed.

It is less common in frequently irrigated crops where the readily available water is small, e.g. ryegrass pasture, vegetable seeds and peas.

Key management strategies

It is useful to think of the soil moisture sensor as any other tool on the farm; it needs to be maintained to work properly. The sensor responses will be more reliable if slurry is not allowed to dry out. Soil moisture sensor management strategies include:

Adjust application depth to overcome crop interception.

Adjust application depth to be greater than daily water use.

Adjust application depth to ensure irrigation water will replace the target deficit.

If the slurry has dried and sensor response is lost, this is resolved through long duration rainfall, rather than re-installation of sensors. Usually all sensors regain perfect contact with the soil over the winter months.

At Vantage NZ we are proud to supply you with high quality AquaCheck soil moisture sensors and neutron services and to back it up with a high standard of service and expertise. Give us a call to discuss your soil moisture monitoring requirements and get set up in good time for the 2021-22 season. 

Article written by: Jane Robb, Customer Support Specialist

Yield maps unlock further potential

Yield maps are one of the most powerful – and under-utlised – tools for decision making on an arable farm.

 

Yield maps are a record of how your crops performed under that season’s constraints, taking into account nutrient variability, soil moisture variability, application variability and much more. The final result is that often yield varies more than we care to admit and we quicky remember the good parts of a paddock and forget the poor parts.

 

Farmers making the most of their yield data insights annually are fine tuning base fertiliser applications through the use of variable rate, identifying zones of productivity potential or risk to monitor throughout the season and really enhancing not only their final yield across a paddock but also their profitability. Profit mapping is uniquely available to arable farmers and it proves a fast way to identify areas of a farm or crop rotation that need improvement. It also allows critical, justified decision making to take place based on the dollars and cents.

 

As the harvest season commences, it’s important to ensure that you’re capturing all your yield information, even if you have no intention of acting on the information this season. ultiple years’ worth of data is far more useful than one year of data.

 

To find out more on how to ensure your yield data is being captured correctly, to save data for your future use for you or to book in your yield mapping requirements for this season, give the expert team at Vantage NZ a call on 0800 482 682 or visit https://www.vantage-nz.com/yielddata

 

Article published in: Guardian Farming, February 2021

Harvest 2020/21 is nearly upon us!

Do you have yield mapping capabilities? Are you storing your data in a secure location? If your combine harvester is capable of yield mapping, do you use it? Yield map data is a powerful tool for making decisions on your farm. It is a record of how your crops reacted and performed under that season’s constraints. Constraints and variation may be apparent in your crops nutrient levels or application methods, or available water in the profile at critical times in the plant’s life cycle, and in most cases a combination of all the above, and more! The final result is that often yield varies more than we care to admit and we quickly remember the good parts of a paddock and forget the poor parts.

Your yield data is a map of how well the crop has performed under that season’s conditions and how much variability there is in the soil profile and nutrient levels within a paddock. It provides us with a ‘warts and all’ view of paddock performance so that we can then further dissect what’s worked well and what hasn’t and make a plan for the coming years, all based around dollars and cents. Many arable farmers have paid for the technology but don’t harness the power of the information that it provides. Vantage NZ is here to help with this.

One thing that isn’t stressed enough to growers with yield monitors is that they should capture the data regardless of whether they can use it at present or not. Asultiple years’ worth of data is far more useful than one year of data. The more years’ worth of data you have lessens the influence of a single seasons weather pattern or any out of the ordinary extremes. For example, in a wet year, the lighter freer draining soils may be preferable for a higher yield and vice versa in a dry season. This process of compiling several years of data is called normalisation. Data is put into a relative scale and is compared across the years or types of seasons as required. Once data is normalised, then we can identify common zones or production areas. These zones can be marked for future management decisions.

Processing or “cleaning” the data is the key to successfully utilising the captured data. Raw yield points have a large number of errors and “noise” that can significantly impact the results. With these noisy bits removed and tidied up the data becomes more representative of the paddock. Some of the factors that impact on the data accuracy are cut width, flow delay and travel distance errors.

Yield data can also be useful for identifying problems during the actual harvest of the crop. In one example, a grower saw the results of him harvesting grass seed in the hottest part of the day. He was able to spot the mistake as recorded yield dropped in the swaths that he completed in the hottest temperatures. Ultimately the yield information informed him that the decision to continue harvesting in the heat had cost him.
 

Making useful yield maps – the essential information

 

  • ‘Rubbish in equals rubbish out’ – you only get one opportunity to collect this data so ‘do it once and do it right.’
  • Start the season with an empty data card – save a copy of all previous data to your computer and external hard drive then ‘clean’ the card. If you need help, please call your local precision ag expert to help
  • Naming – use the same naming for the same paddock each year as this makes finding your data easier at the end of the season
  • Check the flow and moisture sensors – if these are not working properly then everything that follows may be a waste of time
  • Calibration – at the start of harvesting each grain type calibrate the flow sensor
  • Operation setup – make sure the cutter bar width is correct, and the flow delay is as accurate as possible
  • Card check and backup – confirm data is being logged by importing it into your mapping software or sending it to your local precision ag expert once you start for the season, not at the end of this season! Backup the data as a raw format throughout the harvest season also.
  • If you collect the data as accurately as possible in the first place, then post-processing of the data to make it a useful resource is much simpler takes less time and costs less!


Yield data is the final measure of a season’s work. Yield data allows for insights into different management practices and the old adage “what gets measured gets managed” comes to mind. 

Have a good harvest!

JM

 

Article published in: Canterbury Farming, December 2020

Variable-rate approach to fodder crops

During crop establishment and the growing season soil variability is a key driver to crop performance. This is true for both arable and fodder crops.

Lighter soils have lower water-holding capacities, and they warm up faster in the spring, which promotes earlier plant growth. Heavier soils with higher water-holding capacity take a bit longer to ‘get out of bed’ in the spring because of their lower soil temperatures.

If you can map soil variability, it gives the ability to do variable-rate seeding. On some soil types and with some crops, this can be a great way to set the crop up in a timely fashion to maximise performance throughout the season.

Typically, lower seeding rates are used in areas with lighter soils and higher rates in areas with heavier soils.

Sometimes the rates might only vary by +/- 10 percent of the originally intended seeding rate. However, it still gives the crop a greater ability to grow well with less competition for water and nutrients, particularly in lighter soil areas.

To achieve variable rate seedling and the variable rate application of subsequent inputs, you need a solid base of information in order to make the right decisions. And, of course, you need the right technology to achieve it.

Depending on the nature of the farm and the crops it supports, the information that underpins variable rate farming can range from electro-magnetic (EM) soil surveying, to grid or zonal soil sampling, to drone or satellite imagery.

EM surveying is used to map soil variability and thus, productivity potential. EM mapping has to be done when soils are at field capacity, so it is typically done over autumn, winter and spring.

The cost of EM surveying starts at $70/ha. While it is an expense, an EM survey provides information that you can use for many years. It underpins lots of future variable rate decisions, so it is a sound investment.

Soil sampling can provide another layer of information that can be used for precision nutrient management and other variable rate applications.

Precision nutrient management gives growers the ability to apply nutrients only where they are needed to optimise crop production, so it is a great way to save money and ensure that you are farming in an environmentally sustainable way. This nutrient information is used for variable rate base fertiliser and additional fertiliser applications during the growing season.

Depending on the soil sampling strategy (grid vs zonal sampling), costs can vary from $60/ha to just $200 for an entire paddock.

Drone or satellite imagery is best used for variable rate applications during the season. It allows you to vary applications depending on how the crop is performing in real-time so that you can deal with any issues before it is too late.

Satellite imagery is fairly cheap and is done without a field visit. This speeds up the turn-around time and reduces the cost for the grower.

Both options have their merits, and it depends on the issue you are addressing as to which will best give the desired outcome. Costs for drone imagery start from $4/ha and satellite from $400 per farm per year. GST exclusive.

At crop establishment, along with getting the right seeding rate for different areas, it is also important to consider the need for different nutrient levels across the paddock rather than take a blanket approach with a single rate.

Soil variability or crop history can mean that previous harvests have removed different amounts of nutrients from different areas of the paddock. This should be addressed to achieve maximise crop growth.

Variable-rate base fertiliser is a good way to start. This is linked to productivity potential, and once again, this can be determined by soil zones or grid soil sampling.

Once you have taken the initial steps needed to maximise the crop’s performance, the next step is to be proactive with crop management throughout the season. You can do this by using variable rate inputs of nitrogen, herbicides and insecticides.

Up-to-date crop imagery from a drone, satellite or crop sensors allows growers to make accurate management decisions, which could include variable rate applications to look after the crop.

We all know that seasonal weather changes can affect our crops during the season and to maximise the crop and minimise the cost of inputs we need to be able to apply only what is needed, where it is needed and when it is needed.

Variable-rate fungicide is great, particularly later in the growing season. Based on previous crop growth and weather events as well as weather forecasts fungicide can be applied at higher rates to areas with denser crop growth.

They are typically more at risk to disease pressure than areas of the crop that are less dense. Savings here can be quite considerable, based on the chemical being applied.

Critical to the success of using variable rate applications is the technology that can achieve it and technical support to pull it all together.

In addition to soil mapping and crop monitoring, this includes guidance and control systems that can recognise where different zones in a paddock are and seed drills, spreaders and sprayers that can work at variable rates.

Vantage NZ offers a robust range of Trimble guidance and control products that support variable-rate farming. They include the GFX-750 display system and Field-IQ crop input control system, and much more.

The Vantage NZ team also has the knowledge and experience to pull this technology together for you. They have a long history not only supplying and supporting these products in the New Zealand market but also using them on the farm.

For more information on variable rate crop management call Vantage NZ on 0800 482 682 or email info@vantage-nz.com.

What is Precision Ag? Put simply it’s about using the right tools.

Precision agriculture can sound complicated and technical, but it is just an extension of everyday farming, says Jemma Mulvihill from Vantage New Zealand.

“Simply put, it’s about using the right tools and products for the right application to solve a problem. The results are better environmental management and farming efficiencies,” she says.

Since it started in 2010 Vantage New Zealand (formerly Agri Optics New Zealand Ltd) has grown to be New Zealand’s leading precision agriculture solutions provider. In February 2020 the company was re-branded and re-launched as Vantage NZ, combining the highly skilled and knowledgeable staff from both Agri Optics NZ and GPS Control Systems when the company purchased the Trimble dealership for New Zealand. Jemma says the result has been a more comprehensive suite of services, products and solutions covering the gamut of what farmers may require from one source.

“We are now New Zealand’s only full-time dedicated precision agriculture provider offering a full spectrum of products so we can assist farmers the whole way through the journey, making it more efficient and cost-effective for them to get the support they are after.”

With its head office in Methven and team based around the country Vantage NZ can provide precision agriculture service and support across New Zealand. Jemma says Vantage NZ has a great team offering many years experience, which is important to maximise the potential for clients and to support them all the way through.

She points to examples, such as electromagnetic soil surveying and soil moisture monitoring, as to how precision agriculture solutions can make a real difference to a farmer’s operation.

“By understanding the soil variability across a farm, this can inform irrigation and nutrient application decisions. For example, you might lower the amount of water placed on lighter soils or apply a little frequently, whereas, on heavier soils, you may be able to apply more. Savings in water usage and electricity can be a significant return on investment and also result in the farmer growing better crops. Similarly applying nutrients in the right amounts depending on the soil maximises potential without waste or negative environmental outcomes.”

Precision agriculture solutions can also help farmers to avoid some of the dreaded paperwork, she says. For example, the Trimble GFX-750 display can connect the entire operation with innovative, fully integrated software solutions that transform the way people farm by, for example, sending jobs to tractors from a cell phone or computer and generating farm proof of placement reports etc.

Jemma says because Vantage NZ was established off the back of on-farm use through its founders and directors, this gives a grassroots understanding of what farmers really need.  “Our key focus is on helping as many farmers as we can to implement precision agriculture in a sustainable and goal-driven way in their businesses. For us, that starts with understanding the customer’s issues and bringing solutions to the market that make a real difference.”

 

Article published in: Business Rural South, September 2020