Tips for Capturing Yield Data this Harvest

Do you have a yield monitor in your header? Do you use it? Do you want help to extract value from the data? These are some of the first questions we are asking growers this time of year. With the mad rush on to get the crop off the paddock the yield monitor is one thing that is easily forgotten and seldom used to its full potential. Many growers have paid for the technology but aren’t able to harness the power of the information that it provides.

Yield monitor showing real time recordings

One of the key points that isn’t stressed enough to growers that have yield monitors is that they should capture the data regardless if they want to use it or not. Having multiple years of data is immensely more useful than one year of data. Multiple years of data means results that have seasonality factors removed. This process is call normalisation. Data is put into a relative scale and is compared across the years. Once data is normalised then we are able to identify common zones or production areas. These zones can be marked for future management decisions.

The difference between raw and processed data. 

Processing or “cleaning” the data is the key to successfully utilising the captured data. Raw yield points have a large amount of errors and “noise” that can significantly impact on 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.

A processed yield map

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 had cost him.

Some tips to consider

• Make sure that the paddock names and IDs are correct on the monitor before you start the paddock.
• Utilise labels or tags to help identify different operations.
• Avoid overwriting data from previous years. Make sure that the data is separated by year.
• Back up the data regularly! Utilise the free cloud services such as Dropbox or Google Drive to save a copy. 

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

Post by Nick.

Raw vs processed image from http://extensionpublications.unl.edu/assets/pdf/ec2005.pdf

Why my soil moisture sensor might be lying to me?

After choosing the type of moisture sensor you are going to invest in, the most crucial thing is to get the installation correct. It goes back to the old adage; rubbish in rubbish out, if you don’t get the installation correct everything that follows will at best be very marginal data.

Most probes are measuring a very small volume of soil within 10-20mm of the sensor itself, so good soil contact is imperative as well as a crop cover around the probe that is representative of the rest of the field being monitored.

If you are looking at installing a probe for next season or looking at maintenance on an existing probe then read on! These few basic does and don’ts will be of good use!

Don’t!

• Don't leave the excess cables on the ground – it is an accident waiting to happen!
• Don’t leave exposed cables for wildlife that want to see how tasty it is!
• Don’t site the probe on a ridge or in a hollow!
• Don’t site the probe in bare soil. Is there a crop growing over the probe site to give you a true representation of what is happening in the rest of the field? 
• Don’t site under the fence line

Don't leave cables on the ground

Do!

• Ensure you use good consistency of slurry around the probe to ensure good soil contact.
• Ensure you know the soil type your moisture sensor is located in and how that compares to the rest of the area you are monitoring.
• Make sure any tramlines or irrigation tracks miss the probe site by metres rather than millimetres!
• If your probe is near an electric fence, do ensure any metalwork is earthed.
• Do install the probe as early in the season as you can, so it has time to bed in and the crop over the top of it time to establish like the rest of the field.
• Do ensure a competent and trained person installs the probe with the right equipment to do so!
• If checking an old installation make sure there are no cracks around the probe site, the soil around the probe hasn’t sunk and the wires are in good order.

AquaLINK telemetry unit, away from AquaCheck probe out in the paddock

If you have any doubts about the site or installation of your probe, by installing it as early in the season as you can means that it can be moved and still have the winter to bed in again.

AquaCheck WEB, induvial sensor graph responding to irrigation and rain events.

Monitor your probe data and its response to rain or irrigation events, the beauty of the capacitance probes is that moving them is not an issue.

This article contains information from a post previously written by HydroServices but has been updated to include the experience from the Agri Optics team installing AquaCheck probes.

A Guide to Making Sense of Soil Moisture Data

With an increasing amount of soil moisture monitoring sensors on offer in the market today there is growing importance on not only having sensors installed but actually understanding the information they provide. This blog is written to give some insight into the data they you might receive from one of these devices. The following traces are the output of an AquaCheck soil moisture sensor with 3G telemetry. The sensors measure soil moisture and temperature every 30 minutes. The data is available to Agri Optics clients from the AquaCheckWeb platform. For more info see our website http://www.agrioptics.co.nz/portfolio/aquacheck/

The key to getting the most out of your soil moisture sensor is to have an accurate field capacity (FC) and refill point for the probe site calculated. The most convenient way of identifying Field Capacity is to have the probe installed prior to the winter period. Typically there will be enough precipitation to allow the profile to recharge to FC. FC can also be identified by saturating the profile manually with a large quantity of water. The key points we are looking for when identifying FC is a repeated filling to saturation then drainage of the profile. The point where drainage ceases can be identified as FC. Night time events are more accurate as ET is not a factor.

Fig 1. Identifying field capacity

The next key feature to identify is drainage. Drainage is classified as the loss of soil water past the effective rooting zone. The effective rooting zone varies dependent on the crop. Once the depth of plant roots has been identified we can identify any drainage. For the graph below if the crop has a rooting depth of 600mm. The bottom pink line represents the sensor at 600mm. We can see the lift and subsequent drainage of soil water past the effective rooting zone of 600mm.

Fig 2. Drainage events

The third key piece of information that the AquaCheck package provides is the ability to set variable management allowable deficit (MAD) lines. These lines create the target “Green Zone” typically between 85% and 15% of readily available water (RAW). Using MAD lines leaves room for any rain so that any free rain water is not wasted as drainage. It also gives an indication when soil moisture is approaching stress point. The MAD is able to be adjusted to give a desired target soil moisture zone for crop and pasture growth stages e.g. establishment or harvest.

Fig 3. MAD Lines

The final bit of information that becomes available once the crop starts growing is the daily soil water usage. The staircase like moisture trace is showing us evapotranspiration and it allows us to see the impact that increasing crop biomass and increasing temperatures are having on crop or pasture water usage. Crop rooting depth can be identified by seeing how far down the water usage is occurring. In fig 2. above below the roots are drawing moisture down to 600mm vs a later spring sown wheat in fig 4. which is only drawing water to 400. Note the size of the usages. This relates to the root mass at the given depths.

Fig 4. Crop water usage

I hope these tips are useful when interpreting your soil moisture data and that it results in more efficient scheduling of your irrigation this summer. Irrigation New Zealand also has some more tips and info on their website http://irrigationnz.co.nz/news-resources/irrigation-resources/

Post By Nick

We Hope You Have A Green Christmas!

From all the H2Grow team we'd like to wish you a Merry Christmas and Happy New Year. We will be leaving the airways clear for a couple of weeks to allow all the Christmas messages and holiday photos to get through. And will be back in touch from mid-January.

Know your Soil Better than your Bank Manager - Continued

Identifying Soil Texture

Soils are made up of particles of different sizes, the largest sand, followed by silt, to the smallest clays. Together these make up the soil’s texture. Soil texture has a direct impact on soil physical properties: porosity, water holding capacity and bulk density. Furthermore soil clay content determines soil chemical properties and the soil’s ability to hold onto nutrients.

This blog will discuss hands on ways to determine your soil texture, how texture relates to key soil physical properties and the role of clays in the soil. You can determine your soil texture at the same time as you carry out the VSA described in the previous blog post and together these practices will improve the quality of your information.

The change in a soil with depth, the cross section down through the soil, is referred to as the soil profile. It normally consists of a number of soil horizons (layers) each with different characteristics (texture and/or stone content). The picture below shows a soil profile with six distinct soil horizons. When scheduling irrigation you need to know information about the hydraulic (water) properties of each soil horizon that plant roots occupy within the soil profile to determine the amount of water available to the plant. This determines how frequently you need to irrigate (return period) and the maximum irrigation you can apply in one application (irrigation depth).

Example soil profile

Soil texture is an important characteristic because it gives a good indication of other soil properties such as water storage, drainage and nutrient supply. It is a stable soil property and is not likely to change with normal soil management. Soil texture can be estimated in the field by some practical tests involving the feel of the soil and these are outlined below. To determine the textures and get an idea for the ability of your soil to hold water it is beneficial to dig a pit and expose an open face on the soil profile so you can determine the different horizons visible down the profile. You should identify the soil texture of each of the horizons that plant roots are found to grow in, or down to about 60 cm.

Hands on method to determine your soil texture.
Found in the joint Irrigation NZ and Plant and Food resource - Click here to visit the webpage.

The graph below shows typical soil water holding capacities (WHC) for different soil textures in % or mm of water per 100 mm of soil depth. It also shows their typical permanent wilting points (WP) and field capacities (FC). The relationship between WHC, porosity and bulk density is straightforward. Sand has the largest particles, the lowest WHC and therefore the lowest porosity. This translates into the highest bulk density because less space is occupied by air. As shown by the WHC of silt and clay below, silt has a higher porosity and lower bulk density which is very similar to clay soils although clays tend to have the highest porosity. This is because clay is made up of lots of small particles which create lots of air spaces between them. Therefore clay also has the lowest values for bulk density.

Relationship between soil texture and soil water content.
Found in the joint Irrigation NZ and Plant and Food resource.

Another role of clay in the soil is in terms of nutrient management. The structure of clay's means that they tend to become negatively charged around the surface. This means that positively charged nutrients are attracted to the surface of the clay and, depending on the conditions, can move between this surface and the soil solution from where they can be taken up by plants. It is helpful to have an idea of how much clay your soil has because this will determine its ability to store positively charged nutrients such as potassium, calcium, magnesium, sodium and resist changes in pH. Clay also holds phosphorus by allowing it to be adsorbed into the clay structure; some clay's allow this more than others. This is important to note because when phosphate is adsorbed it is less likely to become available to the plant and more phosphate will need to be applied to the soil to avoid deficiency in plants.

For more information on soil texture and water holding capacity you will find a great resource by following this link.

Once you have an idea of your soil texture and water holding capacity mapping tools can be used to get an idea of the representation of this soil type across your whole farm. Simple mapping such as Google Earth images (see the Ground Truthing your Soil Variability blog) and S-Map (which will be discussed in a future blog post) are helpful resources. It is important to be aware that these are tools to increase your understanding but to provide the detail required for efficient farm management tools such as EM mapping and determining exact water holding capacity are greatly beneficial.

Blog post written by Nicole Mesman - BSc (Hons) Soil Science.