This question might sound obvious, but are rising plate meters worth it?
Let's find out by looking at the costs of reading pasture growth with a rising plate meter. And compare it to a satellite measurement service.
As a bit of a spoiler, one of the highest costs with measuring pasture covers with a rising plate meter is not just inaccurate measurements but that of wasted time. So let’s not waste any more and get into the case study.
Case Study:
- A 150-hectare milking platform on a dairy farm in the South of New Zealand.
- Predominantly irrigated and in a high rainfall area with fertile soils and favourable climate.
- Target pasture utilisation of 16 to 18 tDM/ha/year with 200-300 Kg N/ha/year.
- Beukes et al. 2018 suggest $385/ha in additional farm profit from using your eye to making informed grazing decisions from measurement data.
- Potential in additional profit $57,750 on this farm by using the eye to make grazing decisions to making informed grazing decisions with pasture measurements.
- The minimum wage is a conservative approximate of $30/hr (including oncosts) for calculating the labour component of this case study.
The Rising Plate Meter (RPM):
Labour:
- To walk this property each week consumes at least 3.5-hours to cover the required ground, collecting the RPM and returning it to storage, performing any maintenance, cleaning and so on.
- The weekly farm walk is generally performed once a week, 48 weeks per year due to weather, the health of the person walking, and holidays.
- Given that some paddocks are skipped or included from the measurements week to week, setting the RPM’s automatic paddock order is not feasible. At the end of each paddock, the operator stops and writes the measurements on a paper map.
- After the farm walk, the operator boils the jug for a cuppa, sits down at the computer and starts to realign their spreadsheet to handle this week’s farm walk data entry. (They don’t use the software that came with the RPM, as it is too restrictive).
- After an hour of entering data, fixing the spreadsheet, and deciding where the cows should graze next, an entire 1-hour has elapsed. The farmer re-visits this spreadsheet from their home’s comfort, mainly because the spreadsheet doesn’t play nice on their phone.
Equipment:
- The rising plate meter or RPM is the central hardware component. The RPM is usually replaced every 3-5 years, if not earlier, with poor maintenance.
- Your computer, because spreadsheets don't work that well on phones, do they?
- Clunky and outdated software that comes with the plate meter or a spreadsheet is utilised to analyse the measurements. This is why we started building Pasture.io, about 5 years ago!
Readings:
The frequency of measurements is typically one per week or 48 per year, which calculates to one pasture measurement every 7.6 days.
However, this frequency oftens slips, due to poor weather conditions such as rain that makes the grass and soil to stick on the rising plate meter. This in turn, makes it difficult to record the measurements accurately. And, who likes to trudge along with full wet weathers in wet paddocks with horizontal rain?
The rising plate meter by our analysis has a mean absolute error (MAE) of approx. 150 KgDM/ha, which surprisingly is better than most farmers’ eyes are when it comes to measuring pasture covers. However, this MAE leaves a lot to be desired.
The walk must be performed by the same person week in week out to avoid any discrepancies with operator bias. The issue here is that if the operator goes on holiday or is sick, then the walk is invariably missed, or someone else steps in to measure the pasture.
With the relief operator, they may walk a different transect of the paddock, roll the RPM with each plonk or bias the readings in many other ways. This bias then changes the growth rate considerably to what it may have been with the regular operator. And, when the operator starts again, their first reading will again skew that of the relief operator’s.
Also, let’s not forget that most RPM operators take 30 or 40 measurements across the path of least resistance, to get to the next paddock. This may not accurately represent DM growth on a particular paddock.
Costs:
We can calculate the cost of labour across the year with the three and a half hours to walk the farm, maintain the RPM, and all other associated costs, plus the one hour spent sitting down at the computer, entering in the pasture measurements, and then deciding where to graze the herd. The total billable hours comes to 3.5 + 1 = 4.5 hours.
Across 48 weeks, that amounts to 48 weeks x 4.5 hours x $30 per hour = $6,480 per year in labour costs alone.
The rising plate meter itself is hardware and, like anything used on a farm, needs constant maintenance. Bent poles, buckled plates, flat batteries, dried and clogged poles, oh the pain goes on - believe me, I’ve done my fair share of walking, and I wouldn’t wish it on anyone.
Rising plate meters cost somewhere around $300 to $1,200, depending on the model you buy. Let’s not even consider the hardware cost, as the labour component alone is expensive enough!
Satellite Modelled Automatic Pasture Measurements (Pasture.io)
Labour:
Pasture.io’s satellite pasture measurement service provides an automatic feed of pasture covers, pasture growth rates, and ryegrass leaf emergence rates. This automation means that there is no labour component in delivering these measurements to worry about collecting.
As compared to the 1 hour for entering data, fixing a spreadsheet, finding where to graze your cows next and so on, the satellite pasture measurement takes around 20 minutes each week to analyse and enter your grazings from your phone per week to get the modelled readings to hum.
Equipment:
You can choose to get your readings on your phone, computer and tablet. We set up your account and make sure that you’re comfortable with the process and can essentially work from any device of your choice.
Readings:
We tap into more than 160 satellites that fly around the planet daily. These satellites allow you to get up to daily pasture measurements - well, if it is cloud-free, otherwise the cloudy days model kicks into gear.
Across our entire customer base, our farms average a reading approximately every 3.3 days. This frequency is 2.3 times the number of measurements taken with an RPM each year!
As discussed earlier, RPMs have a mean absolute error (MAE) of approximately 150 KgDM/ha. In contrast, our satellite measurements have less variability, with an MAE of only 56 KgDM/ha.
Remember that we talked about the rising plate meter being better than most eyes? Well, our customers are amazed to see with their eyes what is in the paddock lining up with our satellite pasture measurements.
And, unlike the rising plate meter, which is typically measured across a crude transect, the satellite measurements analyse each three-metre squared (3m2) pixel across the paddock, bringing in a spatial resolution and spatial size into the equation. For example, it is beneficial to bring in that bare bank and not just measure the dense plateau!
Costs:
Our annual subscription has an annual fee of $1099 plus $8 per hectare per year. For a 150 hectare farm, that amounts to $1099 + ($8 * 150 hectares) = $2,299
Let's summarise the findings:
Weekly labour requirements:
- With a rising plate meter = 4.5 hours
- With Pasture.io satellite measurements = 20 mins
Method of measuring pasture growth:
- With a rising plate meter = 30 to 40 plonks across a paddock
- With Pasture.io satellite measurements = spatially analysing each pixel across the entire paddock and using other details such as grazing and fertiliser activities
Additional hardware required to carry out pasture measurements:
- With a rising plate meter = Yes. Includes RPM, computer and software.
- With Pasture.io satellite measurements = Nothing. You get automatic readings on the device of your choice.
Number of pasture measurements, across an entire year:
- With a rising plate meter = 48 measurements
- With Pasture.io satellite measurements = Over 160 measurements
Cost of measuring your pasture, across an entire year:
- With a rising plate meter = $6,480 for 48 measurements. And $14,904 if you need 160 measurements.
- With Pasture.io satellite measurements = $2,299 for 160 measurements.
That brings us to the end of this article. We trust that this was useful to you.
If you're looking to learn more about pasture measurement tools, you may be interested in The hierarchy of pasture measurement tools.
Until we meet again, Happy Measuring!
- The Dedicated Team of Pasture.io, 2021-04-01