Once the preserve of a keen eye or a graduated stick (or simply markings on a Wellington boot), measuring and recording grass volume and growth has gone high-tech with plate meters and ultrasonic sensors.

While technophobes may want to stick with experience, intuition or hand-written records, the new devices are designed for those prepared to embrace technology to gain a more comprehensive and accurate picture of grazing resources.

The simplest systems provide readings for hand recording. The more advanced ones come with a USB connection, which makes it easy to download data to computer software that analyses and presents the results in tables and graphics.

At the top end of the technology scale, sensors fitted to ATVs make it practical to cover a lot of ground and can provide the ultimate in data collection through digital mapping and auto-uploading to the farm management computer.

See also: Revolutionary grass monitor on demo

Originating from New Zealand dairy farming, plate meters are now regularly used by British producers to give an accurate weekly indication of the amount of grass available for all livestock, as well as an overall assessment of how each field or paddock is performing.

How often should you check?

Agricultural and Horticultural Development Board (AHDB) Dairy regards regular walking of pastures as a key component of its three-step approach to successful sward management, mainly to check the amount of field cover available.

© John Eveson

It recommends this as a weekly activity from early February until early December, but more often during periods of peak growth.

Estimating sward height and density is particularly difficult when swards are grazed unevenly as a result of poaching, spoilage and/or contamination with urine and faeces. But measuring will enable an overall cover to be assigned to the field.

The wellie-boot method provides a useful rule-of-thumb assessment. A cover of 1,500kg DM/ha roughly equates to a couple of inches, while ankle-height grass represents about 2,000kg DM/ha.

However, measuring with a plate meter will clearly give more accurate information and enable the farmer to rank fields in the order in which they should be grazed, as well as decide the best time to start and finish each grazing session.

So what’s on the market?

Agricultural Supply Services

FarmWorks Platemeter F200

Agricultural Supply Services has one of the biggest selections of plate meters from the Farm Works range produced in New Zealand, including a mechanical-to-electronic upgrade for £275.

These start with the F75 at £295, which records grass height and the number of measurements taken using two mechanical counters so that cover calculations can be made by hand.

At the other end of the scale is the £650 F400, which can store records for up to 280 paddocks, calculates average height, cover and grass grown since last walk, and downloads the data to a PC using a USB cable.

The F200 digital model, which costs £450, remains the most popular, says ASS, especially for users who want to manually input the data into the P-Plus Pasture Covers computer software supplied with the device.

Total height and number of measurements are recorded and the F200 calculates average height and average cover. It also tells the user when 30 measurements – or plonks into the sward – have been taken.

The F300 (£550) is a more sophisticated unit that will suit users for whom computers hold no fear as it has the USB download facility to save the time and risk of errors inherent in manual inputting. It also has a 100-paddock memory.

The top-end F400 model is reckoned to be ideal for beef and sheep farmers. It uses Farm Works P-Plus Pasture Covers management software and produces several reports – cover on date, cover over time, feed wedge and growth rates.

This can also be supplemented with Map & Paddock and P-Plus Feed Forecaster-Budget modules to help devise a comprehensive feed management programme.

Kingshay

Independent dairy consultancy Kingshay offers the Filips mechanical plate meter from NZ Agriworks. This comes with a folding handle and costs £325, with optional conversion kits to give electronic recording and calculation.

Kingshay also offers two electronic devices from Jenquip – a subsidiary of NZ Agriworks, whose products are imported by the UK arm of the country’s Livestock Improvement Company.

The newly redesigned – to make it more robust – EC 09 at £470 counts the number of measurements and provides average height or cover readings, while the EC 10 (£530), which has a folding handle, stores data for up to 99 paddocks and downloads it via USB.

Both devices come with Pasture Manager software and discounts apply to Kingshay consultancy members.

GrassOmeter

Monford Ag Systems

In Ireland, Monford Ag Systems takes an altogether more high-tech approach with its GrassOmeter ultrasound sensor device, which the company reckons can be attached to a walking stick or a Wellington boot.

It is linked to a mobile phone app via Bluetooth to record the location and data as the user walks the paddocks.

It automatically calculates the grass wedge and uploads data automatically to the GrassOmeter website, where analysis in greater detail and historical comparisons can be performed.

What if you have big areas of pasture to monitor?

Agricultural Supply Service’s AgHub feed uses an ultrasonic sensor mounted on the front of an ATV and is connected to a display console attached to the handlebars, front rack or some other convenient location, which calculates the height of pasture in millimetres after calibration on a hard, flat surface.

AgHub feed reader

Three versions are available – the Bronze model at £2,500 measures sward height and calculates the average kg of DM/ha, while the Silver (£3,100) has memory for multiple farms and grazing paddocks, and data download by USB or wireless data network, so the console can remain in place.

The Gold, priced at £3,850, adds GPS location of readings and automatic recording against individual paddock identities, so little more is needed other than starting up and driving the ATV. Large units in New Zealand are reportedly measuring swards at a rate of 140ha/hour.

Massey University, NZ

An alternative approach is offered by the ATV-towed pasture meter developed by Massey University’s New Zealand Centre for Precision Agriculture and transformed into a commercial product by ATV implements manufacturer C-Dax.

Average pasture height is measured by using a light-emitting and sensing photodiode array and the device can operate at speeds up to 20kph. That gives 200 measurements/second – 18,500 readings in a 500m pass – compared with roughly 250 using a rising plate meter.

The device is towed to the field then lowered to the ground, either by manually repositioning the wheels on basic models or using the power system on more advanced versions.

There is also scope for a contract service providing data for farmers to calculate their grazing resources.

The entry-level C-Dax In-Ex Pasture Meter displays results for manual recording but others are used with either the firm’s XC1 Smart Control console, which can also be used to operate other C-Dax equipment, or the more advanced XC3 tablet with GPS tracking and wireless data transfer.