Herbaceous Measurement Device Comparison
Introduction and Scope
Inventory and monitoring are key components
to land management practices. This includes the measurements of forage
production to determine stocking rates and the effectiveness of certain
land treatments such as burning, herbicide applications, and fertilization.
Forage production values are used
in conjunction with measurements of residual forage on areas that were
previously grazed so forage utilization levels can be monitored on grazing
allotments. Wildlife habitat managers, range management specialists, and
other land monitoring employees use these plant production measurements
to monitor whether livestock use levels are in compliance with maximum
allowable use standards prescribed in the allotment management plans.
There are various methods used to
obtain plant productivity measurements. The current standard for herbaceous
plant productivity is a time consuming process of clipping, weighing, and
drying vegetation in an oven.
This study involved a comparative
analysis between various commercially available herbaceous measurement
devices. Precision, accuracy, correlation, and performance characteristics
of capacitance probe, oven meter, and sliding plate technologies were compared
to the standard clip and weigh oven method.
The Sigma Delta Technologies Pty Ltd, Fuel and Soil Moisture Meter Neosystems
II (Neosystems II) had the highest degree of correlation, accuracy, and
consistency when compared to the standard oven. It had a 94 percent positive
correlation, followed by the Tru-Test Limited GrassMaster (GrassMaster)
capacitance probe with 74 percent and Jenquip Filips Folding Plate Pasture
Meter (Filips Folding Plate Pasture Meter) with 58 percent. All other devices
had a lower correlation. The Neosystems II unit has a better than 99 percent
accuracy, unlike all the other devices tested. Development of forage constants
for specific pasture plots and the issue of minimum stubble height needs
to be addressed before field use for any application requiring less accuracy
than currently provided by the standard oven or Neosystems II.
The Neosystems II is an improvement over the standard oven. Key differences
include a decreased amount of time necessary to determine forage production
values, automation to reduce human error, and the capability to download
data to a personal computer. It takes 21 hours for the standard oven to
determine forage production values, 1 hour if using 3 Neosystems II meters
or 3 hours if using 1 Neosystems II meter.
In addition to the forage production measurements, there is a need to develop
a field users guide for sampling, collection, and processing forage production
samples, including sampling collection, handling, and processing techniques
for use with the standard oven or Neosystems II meter.
Introduction and Scope
The measurement of forage production is a key component to land management
practices. Measurements are made frequently when certain land treatments
are applied such as burning, herbicide applications, and fertilization.
By analyzing forage production on treated and untreated sites, differences
can be tracked to determine what process has been the most successful in
revegetation efforts. Forage production measurements are also used to estimate
livestock and wildlife grazing capacity when grazing allotments are analyzed.
These production values are used in conjunction with measurements of residual
forage on areas that were previously grazed so forage utilization levels
can be monitored on grazing allotments. Wildlife habitat managers, range
management specialists, and other land monitoring employees use these plant
production measurements to monitor whether livestock use levels are in
compliance with maximum allowable use standards prescribed in the Allotment
are various methods used to obtain this measure of plant productivity.
The current standard for an accurate measurement of herbaceous plant productivity
is with a time consuming process of clipping, weighing, oven drying, and
reweighing vegetation. There are more practical methods that include clipping
and weighing plant material with ocular estimates.
project involved conducting a comparative analysis between various commercially
available herbaceous measurement devices. Precision, accuracy, correlation,
and performance characteristics of capacitance probe, oven meter, and sliding
plate technologies were compared to the standard clip and weigh oven method.
optimum forage production measurement device promotes accuracy, consistency,
and efficiency for various types of forage involved in inventory and monitoring
Herbaceous Measurement Device Technologies
herbaceous measurement devices utilizing capacitance probe, rising plate,
and portable oven meter technologies were field tested and compared to
the standard cut and weigh oven method. The capacitance probe devices were
the Tru-Test® Limited GrassMaster (GrassMaster), Draminski Inc. Pasture
Meter (Pasture Meter), and Alstair George Manufacturing PastureGauge©
(Pasture Gauge). The rising plate devices were the Kencove FarmTracker™
Rising Plate Meter (Farm Tracker) and the Jenquip Filips Folding Plate
Pasture Meter (Folding Plate Pasture Meter). The field portable oven device
was the Sigma Delta Technologies Fuel and Soil Moisture Meter Neosystems
II (Neosystems II).
measurement devices typically indicate the amount of forage present within
a given area. Forage is the weight factor of any plant-like living organic
material. Forage per land area is the weight of the combined grass, seedlings,
and other small plants within a given area. Forage is usually measured
in kilograms of dry matter per hectare (kg DM/ha) or pounds of dry matter
per acre (lb DM/acre).
Rising Plate Technology
plate meters have a plate of a known area, sliding up and down a shaft
in relation to the density of the forage (figure 1). The shaft is positioned
vertically and the plate rests horizontally at the bottom of the shaft.
The device is lifted vertically and gently positioned on the ground. The
shaft rests on the ground, where the plate rises and is held up by the
movement of the sliding plate turns a manual counter or is attached to
a computer where a reading is displayed electronically, depending on the
device. The manufacturer recommends that 20 to 40 readings be obtained
per pasture. The Folding Plate Pasture Meter has a manual counter for the
number of samples taken and displays the combined estimate of forage. The
amount of forage in terms of kilograms of dry matter per hectare is calculated
by using these values in equations provided in the operator's manual. Corrections
to the measured value are recommended for each specific cover type. The
Farm Tracker has a similar design with an electronic readout for the amount
of forage. Information regarding changing the reading for specific cover
types is provided.
Capacitance Probe Technology
A capacitance probe device uses an electric field to determine the amount
of forage in terms of kg DM/ha (figure 2). The capacitance probe sets up
an electric field and measures changes to the field. The capacitance change
is directly proportional to the moisture content of the plant material.
The meter is mounted on a plastic shaft approximately the size of a walking
stick with a length of up to 4 feet (1.2 m). The shaft has a 1/8 to 1/3
in (3.2 to 8.5-mm) metal prong at the end to prevent the shaft from direct
contact with the ground. Measurements are obtained by walking across a
pasture and placing the shaft on the ground vertically, every 2 to 6 paces.
An electric field is set up at the bottom portion of the shaft. When the unit
is first activated to measure for kg DM/ha, the unit takes an air reading.
The prong is held above the forage. When the prong is placed on the ground,
the bottom portion of the shaft is surrounded by forage. The change in
density in the air moisture content of plant material changes the electric
field characteristics. This change is recorded and used in calculations
with an output reading of average kg DM/ha.
Neosystems II Meter Technology
Figure 3—Neosystems II meter.
The Neosystems II meter is a portable oven meter with the capacity to dry plant material in 4 to 20 min, depending
on the type of forage, and provide a value for forage production in terms
of kg DM/ha or lb DM/acre or (figure 3). This meter contains a small oven,
electronic balance, motorized conveyor, digital readout, and vacuum pump.
The Neosystems II meter carrier is weighed empty. Plant material is placed
on the carrier dish and into a compartment with an electronic balance scale.
A conveyor moves the carrier dish between the scale and oven. The forage
within the dish is compressed between two hot oven plates at a constant
pressure, causing moisture to be released.
The oven plates are designed with ridges and holes for the rapid removal of
moisture under compression. A high flow vacuum pump pulls moisture away
from the dish environment and water vapor is ejected through a plastic
tube on the side of the meter. The oven temperature is uniformly 284°F
(140 °C) across the plates, higher than the standard 220 °F (104
°C) oven. The manufacturer states that this increase in temperature
is offset by the substantially decreased bake time (1 h versus 21 h), oven
plate design, and use of a high flow vacuum pump.
a preset time period in the oven, the conveyor again places the dish back
onto the electronic balance to be weighed. The Neosystems II meter computer
subtracts the final weight from the initial weight and indicates the percentage
of moisture content on a liquid crystal display (LCD) screen. Using a separate
scale, the larger sample (total sample from a given area of the pasture)
is weighed and the weight is entered into the meter to determine the forage
in kg DM/ha or lb DM/acre. Other indicated values include the weight of
the carrier before and after baking, and the amount of kg DM/ha or lb DM/acre.
Various forage types can be evaluated with this device by varying the bake time.
The standard Neosystems model allows for dual bake times. Bake times are
specified at the time of purchase, or an additional add-on option allows
the user to program specific bake times. The forage production value readout
is in lb DM/acre unless otherwise indicated at time of purchase. The Neosystems
II meter also determines moisture percent of various materials, including
leaves, plant material, soil, and any material with moisture percent up
to 1,000 percent.
Cut and Weigh Oven Technology—Standard Production Measurement
The current standard method for production measurements is the cut and weigh
oven method. All plant material, within a designated sample area, is clipped
as close to the ground as possible. The material is weighed, placed in
an oven at 220 °F (104 °C) for a designated time period, removed,
and weighed again. The amount of dry matter per area, in terms of kg DM/ha
or lb DM/acre, is determined by comparing the initial and final weight,
divided by the total sample over the plot area (figure 4).
Figure 4—Mechanical convection
oven used for
cut and weigh method.
Herbaceous Productivity Measurement Devices
|Forage in kg DM/ha =
||final weight x weight of total sample of plot
||initial weight area of plot
Six herbaceous measurement devices utilizing capacitance probe, rising plate,
and field portable oven meter technologies were field tested and compared
to the standard cut and weigh method (table 1).
Table 1—Herbaceous productivity measurement devices.
||9 V dc
||9 V dc
||Ni Cd inte-
||Ni Cd inte-
||ac or 12 V dc
Jenquip Filips Folding Plate Pasture Meter—Rising Plate Technology (figure 5).
Figure 5—Jenquip Filips folding
plate pasture meter.
Standard model includes:
- A falling plate meter with no electronic parts
- Manual gear driven counter display related to amount of forage
- Top manual counter for number of operator readings taken, used in calculating amount forage
- Handle folds down, plate can be removed for storage, mounting bracket to hold plate
- All-weather notebook
- Readings from counter need to be plugged into equation to calculate average kg DM/ha
- Sphere at top for use as a handle
- Height: 37.5 in (0.97 m); diameter of shaft: 0.61 in (15.5 mm); diameter of plate: 14 in (355.6 mm).
Additional options include:
- Extra all-weather notebook
- Storage tube
- Pasture management software for Windows 3.1 or Windows 95.
Kencove FarmTracker™ Pasture Meter—Rising Plate Technology (figure 6).
Figure 6—The Kencove
FarmTracker™ rising plate.
Standard model includes:
- Electronic counter for number of readings taken
- Carrying case
- Screw-on adjustable handle and plate
- Equation calibration feature, can be calibrated for different covers
- Auto save feature when unit is shut off
- Can display average height of forage or average kg DM/ha
- Height (maximum setting): 37 in (0.94 m); shaft diameter: 0.75 in (19.1 mm); plate diameter: 14.25 in (362 mm)
- One line digital LCD display located on side
- 2 button driven interface
- Required a 9 V battery [a Nickel Cadmium (Ni Cd) rechargable may also be used]
- 20 memory files.
Additional option includes:
- Farm Tracker™ software developed mainly for livestock production.
Draminski Pasture Meter—Capacitance Probe Technology (figure 7).
Figure 7—Draminski Pasture Meter.
Standard model includes:
- Personal computer (PC) compatible (computer interface cable is not provided)
- 141 paddock memory files
- Displays output data (e.g., total DM, average DM, maximum DM, minimum DM)
- Low battery indicator
- Automatic switch off after 3 min of nonuse
- Paddock areas can be stored, area figures used for statistics
- Internal date and time
- Displays directions while measuring (raise stick, stand stick)
- Height: 47.75 in (1.2 m); shaft diameter: 0.97 in (24.6 mm)
- Alphanumeric digital LCD display
- Menu-driven interface
- Requires a 9 V battery.
Alistair George Pasture Guage—Capacitance Probe Technology (figure 8).
Figure 8—Alistair George Pasture Gauge©
Standard model includes:
- Measures in kg DM/ha, lb DM/acre, or corrected meter reading (CMR)
- PC compatible RS 232 output (computer interface cable is not provided)
- Records average kg DM/ha or lb DM/acre for each measured surface
- 1,000 paddock memory files
- Gauge index can be changed for higher or lower sensitivity
- Detachable computer box
- Carrying shoulder strap
- Height: 43.6 in (1.1 m); shaft diameter: 1.06 in (26.9 mm)
- Digital LCD device
- Menu driven interface
- Pasture Gauge polish and cloth used to clean the pole and stud prongs where computer box connects
- Power pack to charge up Ni Cd internal battery
- European male plug adapter
- Auto shut off, after 3 min (when not in measure mode)
- Quick find feature to access a file instantly
- Set index feature to suit certain pasture conditions.
Additional options include:
- Farm totals and cover functions
Tru-Test Limited GrassMaster Capacitance Probe Technology (figure 9).
Figure 9—Tru-Test® Limited
GrassMaster Pasture Meter.
Standard model includes:
- Ni Cd internal battery
- Offset calibration feature
- Changing equation for calibration feature
- PC download feature
- PC compatible with COM port via RS 232 format (computer interface cable is not provided)
- Polish and rag
- Power box for charging and downloading
- Height: 49 in (1.2 m); shaft diameter: 1.06 in (26.9 mm)
- 16 character alphanumeric digital LCD display
- Two measurement modes, fast and slow
- Battery charger and low battery warning
- UNDO feature for removing accidental measurements
- 120 memory files.
Neosystems II Fuel Moisture Meter—Portable Oven Technology (figure 10).
Figure 10—Neosystems II Fuel Moisture Meter.
Standard model includes:
- Height: 8 in (203 mm); width: 17 in (431.8 mm)
- Nylon carrier diameter: 4.6 in (117 mm)
- Moisture level indicator device
- Indicates initial and final weight of plant material
- Can measure moisture levels of plant material from 1 to 1,000 percent
- Menu driven interface
- Heater LED indicators
- Balance locking feature when unit is not in use
- Electronic balance with additional LCD display
- 12 V dc operation, uses approximately 10 amps truck battery recommended
- Two bake times, selectable by external switch (bake times to be specified by the user at the time of ordering, if not specified, it will be preset to 4 and 10 min)
- High flow vacuum pump combined with dual heating plates to remove moisture
- PC download feature via RS 232 15 pin (computer interface cable is not provided)
- 253 memory files
- Repeat function
- Carrier calibration function
- Carrier with two spare sets of mesh
- Pan clean feature to clean area around
- Low battery warning
- Reset feature to reset the unit from any function.
Additional options include:
- 12 V dc operation replaced by ac power supply
- Dual power supply option, for both 12 V dc battery and 110 V ac operation
- Additional bake times, up to eight set externally by switch
- Programmable bake times, to be set at start up
- Indicates kg DM/ha or lb DM/acre
- Replacement carrier kit (includes carrier and five sets of mesh); one mesh set includes both top and bottom mesh for carrier.
Blue M Electric Oven—Typical Standard Mechanical Oven (figure 11).
Figure 11—Typical standard mechanical
oven used for cut and weigh method.
Standard model includes:
Sampling Methods and Test Procedures
- Exterior: length 21.1 in (537 mm); width 26.7 in (678 mm); height 36.7 in (932 mm)
- Interior: length 15 in (381 mm); width 19 in (482.6 mm); height 18.3 in (465 mm)
- Temperature range 100 to 500 F (38 to 260 °C)
- 1/6 hp (1.95 kW) motor with 230 V
Pilot testing was conducted to determine the optimum forage sample collection,
the handling and processing method, and the test procedure. No publications
were found that describe detailed sampling collection, handling, and processing.
In addition, sampling methodology varies according to the specific plant
Testing with capacitance probes and rising plate devices were conducted at one
test site on a grid within the pasture boundary. There were 20 and 40 points
sampled for each device at the same sample point. For use in the standard
oven and Neosystems II meter testing, four sample points within the test
site were chosen as representative points describing the average forage
over the pasture plot. Twenty grid test points, including the four original
sample points, were indicated by flagging. Consequently, all devices were
tested on the same grid within the same sample points for the capacitance
probes, rising plate, standard oven, and Neosystems II meter decreasing
the variability of measurements.
The forage contained within these four sample points was collected by the use
of a frame of a known area of 1 cubic foot (2.4 liters.) All plant material
was collected within the plot frame to bare soil (refer to: USDA Forest
Service publication Rangeland, Analysis and Management Guide, August
1996 and the National Wildfire Coordinating Group–Forest Service publication
"Measuring Moisture Content in Living Chaparral). Testing was conducted
in Los Angeles County in California, elevation 1,100 ft in uniform grassland,
June in the year 2000.
Sample collection was conducted in the afternoon, with a temperature range of
80 to 90 °F. Samples were not collected in shaded areas or within 24
h of rainfall. Plastic gloves were worn to prevent moisture and oil from
the hands contaminating the samples. All samples were cooled below the
condensation temperature. Cooling was achieved by using a plastic lunch
pail and an ice pack. Samples were stored in a refrigerator during processing.
All samples were placed in zip-lock plastic bags, and double bagged with
as much air removed as practical. Samples were handled with care to prevent
moisture contamination during processing. Bag contents were examined and
extra debris (e.g., dirt, rocks, and pellets) were removed. Plant material
was cut into 1-in (25.4 mm) pieces, the minimum sample size, to ensure
uniformity and the desired accuracy of 10 g for the standard oven and 7
g for the Neosystems II meter tests. The greater the variability of plant
material, the smaller the pieces need to be cut. The larger the sample
size, the greater the accuracy, but a larger sample size necessitated a
longer the bake time. By cutting the samples into smaller pieces, accuracy
was not affected. The sample was spread uniformly across the surface of
the carrier dish.
Before processing the test samples, the Neosystems II nylon oven carrier was preheated
in the oven meter for 20 min to remove moisture typically absorbed by nylon
at room temperature. The carrier must be preheated to ensure accuracy.
Large errors will result if preheating is not done. All the test samples
were placed inside the pan or carrier with no plant material hanging over
the edges. All equipment was calibrated daily. Bake times for this test
were 16 and 20 min. This consisted of a 4 min bake with 3 repeat cycles
for a total time of 16 min and a 10 min bake with 1 repeat for a total
of 20 min. The method used to determine an accurate productivity measurement
to represent a pasture plot was with 4 representative samples. Each sample
was tested 3 times for a total of 12 tests at 20 min each. The total test
time used in this project was 4 h. Further analysis indicates that at this
test site, this accuracy can be achieved with 3 representative samples,
each sample was tested 3 times, for a total test time of 3 h using only
1 Neosystems II meter. However, the total test time is reduced to 1 h using
3 Neosystems II meters, as compared to 21 h for the standard oven.
A mechanical convection oven was used in the standard oven method at 220
°F (104°C) with a bake time of 21 h. The aluminum pans were weighed
cold and hot. These weights were used appropriately in the calculation
of initial and final weights.
Changing the Forage Constant
rising plate and capacitance probe devices are indirect type measurement
devices; therefore these devices require a change of the forage constant
in the productivity equation to allow for different pasture types and seasonal
variations. The standard oven and Neosystems II meter do not require this
change in forage constant because these devices take a direct measurement
of the plant material.
The development of a forage constant for indirect measurement devices requires
a productivity measurement by a direct device, (i.e., by the standard oven
or Neosystems Oven Meter in order to determine a new forage constant).
The GrassMaster Pasture Meter Company has developed a software program using
statistical analysis to develop this forage constant. The input values
necessary to develop a new constant are obtained by supplying a direct
measurement of productivity measurement obtained by use of the standard
oven or Neosystems unit. The GrassMaster provides the optimum method to
determine the appropriate forage constant.
The Effect of Minimal Stubble Height
Grazing practices, based on established agronomic principles, indicate that stocking
rates on grazed forages be managed to allow for a minimum stubble height
of 2 to 3 in (50.8 to 76.2 mm) in order to maintain a productive pasture.
This minimum stubble ensures that the plant has enough energy reserves
after grazing to support regrowth, allowing roots to become stronger and
deeper, providing for a pasture with adequate forage, resistance to insect
and disease damage, and drought and weed resistance. Erosion control and
water quality are also improved. Stubble also includes residue and litter
Sampling protocol for obtaining productivity measurements with the standard oven
and Neosystems II meter is to collect the total residual biomass to bare
mineral soil. This total residual biomass is weighed and used in the forage
In contrast, rising plate and capacitance probes are not able to measure total
residual biomass by design. The shaft of the rising plate has a 1.25?in-
(31.75-mm-) diameter metal washer on the end, preventing the tip from penetrating
the residual biomass. Capacitance probe shafts are 1 in- (25.4 mm-) diameter
with a 0.25-in (6.4?mm) metal prong tip at the end. The tip is designed
to prevent the shaft from direct contact with the ground. However, the
residual biomass mat is thicker, typically 2 to 3 in (50.8 to 76.2 mm)
in some pasture plots. The 1?in- (25.4-mm-) diameter shaft prevents the
probe from penetrating the biomass mat beyond the 0.25-in (6.4-mm) tip
for a complete measurement of the residual biomass.
Consequently, the rising plate and capacitance probe device measured values were expected
to vary from the measured values for the standard oven method and the Neosystems
Seven herbaceous measurement devices were used to collect data from the same
pasture plot. The standard error and correlation between all devices and
the standard oven were determined. The findings are indicated in tables
2 and 3. There is significant variability between the direct and indirect
type measurement devices. This is anticipated due to a need to change the
forage constant for all indirect devices and the effect of collecting on
bare soil rather than minimum stubble height, as is the current practice
in the direct measurement devices.
Table 2—Productivity measurement device data analysis.
oven (lb DM/a)
ples Ope-rator Ave-rage
|Dram-inski (lb DM/a)
||Ali-stair (lb DM/a)
Standard error—Standard error is a measure of variability or dispersion of data
compared to the standard oven method. The least variability is indicted
in the Neosystems II meter at less than 1 percent, with all other devices
indicating a high standard error.
Correlation coefficient—The correlation coefficient (r) is a measure of
the degree that the measured data from two devices move together or in
opposition. When r = 0, there is no correlation. When r =
1.0, there is perfect correlation. The higher the r, the greater
the correlation. General practice indicates that r values be generally
evaluated as follows:
r = 0.00 to 0.25 = doubtful correlation
r = 0.26 to 0.50 = fair correlation
r = 0.51 to 0.75 = good correlation
r = 0.76 to 1.00 = superior correlation
The Neosystems II unit had a 0.94 correlation with the standard oven. This
degree of positive correlation is considered superior. The GrassMaster
had a 0.74 correlation and the Filip Folding Plate Pasture Meter had a
0.58 correlation, all considered good. However, forage constants for the
GrassMaster and Filip Folding Plate Pasture Meter devices need to be developed
for specific pasture plots and the issue of minimum stubble height needs
to be addressed before these devices are used in the field for any application
requiring less accuracy than currently provided by the standard oven or
Neosystems II meter.
Precision denotes degree of repeatability in taking of the measurement. The range
of percent differences is an indicator of precision. The data reduction
results are presented in table 3.
Table 3—Data reduction.
||Folding Plate Pasture Meter
|Inaccuracy to standard oven
all oper-ators (%)
|Bias all oper-ators
|Range of percent differences compared to standard oven
Percent inaccuracy—Percent inaccuracy is the specification that could be met
at the 95 percent confidence level. Assumptions are made that the data
here was not a 1-in-20 or rarer anomaly and that the test measurements
follow a normal distribution with the mean equal to the standard measurement.
Accuracy denotes the absolute nearness to the true value. The smallest
inaccuracy determined was with the Neosystems II meter at 2.6 percent;
with the Pasture Gauge at 61 percent less than the oven measured value.
All other devices had less accuracy.
Accuracy can be improved, up to a point, with some devices by the collection of
more samples. Testing was conducted using sample sizes of 10, 20, 30, and
40, with each of two operators. These values were compared to the standard
oven method. The greatest increase in accuracy with increased sampling
was realized with rising plate technology by increasing the sample size
bias—Percent bias indicates if the device is consistently over or under
measures values. Bias can be used as a correction factor for measured values
to obtain the true value. This correction factor is specific for each device
and may vary across the range of measured values. The smallest bias standard
is met by the Neosystems II meter at 0.4 percent, followed by the Pasture
Guage, the Farm Tracker, the Filip Folding Plate Pasture Meter, and the
difference—Percent differences were calculated between measured values
for the standard oven and the test device. The smaller the range of percent
differences the better. The smallest range of percent differences is met
by Neosystems II meter, followed by GrassMaster, Farm Tracker, and Filip
Folding Plate Pasture Meter.
is significant variability between all sliding plate and capacitance probe
devices as compared to the standard oven method. However there was minor
variability between measured values for the Neosystems II unit and the
of variation contributing to these variable results include differences
among operators, ambient atmospheric conditions, test procedures, test
instruments, and differences over time. Pilot testing, conducted prior
to testing, determines the best test method with decreased variability
and increased repeatability. A detailed test plan was developed from pilot
testing with concise specific instructions for each device, including standard
test conditions, test procedures, and test conditions. Testing of all devices
was conducted over a minimum time period to reduce the variability over
was expected between the direct and indirect measurement devices. The Neosystems
II and standard oven methods take a direct measurement. A direct measurement
can be expected to have improved accuracy over an indirect method, such
as capacitance probe and rising plate technology (see previous section).
Findings of this study support this with the best accuracy and lowest standard
error from Neosystems II, followed by capacitance probe and rising plate
Comparison Between Neosystems II Meter and Standard Oven
The Neosystems II portable oven has the highest degree of correlation, accuracy,
and consistency of all devices when compared to the standard oven. The
time to obtain a productivity measurement representing a pasture plot with
best accuracy is with 3 representative samples for the lot, each sample
was tested 3 times at 20 min each. It takes 1 h to determine productivity
measurements if 3 Neosystems II meters are used or 3 h if 1 Neosystems
II meter is used. This is an improvement over 20 to 24 h for the standard
oven. The Neosystems II does not require the determination of the forage
constant. In addition, this device is designed for use in various types
of forage involved in inventory and monitoring activities. Consequently,
it is recommended that consideration be given to designating the Neosystems
II meter as the standard for obtaining production and utilization measurements.
Comments were solicited from the operators participating in pilot and field testing.
Their comments are recorded in table 4.
Table 4—Summary of the comments concerning the different devices tested.
|The Jenquip can measure small, dry grasses, unlike the capacitance probes. Folds up and is easy to carry. No electronics. This eliminates problems and dying batteries while in the field. Easy to use.
||Cannot see results right away. Requires manual calculations. No reset button on bottom counter. No memory feature. The handle is uncomfortable to hold. A carrying case is not provided. The height of the holding rod is too short.
|Kencove is the only device that has a carrying case with a strap. Dry cured grasses can be measured easily. Stores away easily. This plate meter gives readings right away. Easy to change out the 9 volt batteries in the field.
||Electronic display is located in an odd position where you have to pick it up to read it and press the buttons. Requires manual calculations. No memory to store readings. Single readings are shown as a number with little information until calculations are completed. The handle is too small. The plate can be difficult to remove from shaft for transport.
|The Draminski has an easy to read display. Nice foam grip on the handle. Menu driven. Gives stats like minimum and maximum field measurement and average field measurement. Easy to change out the 9 volt battery. Does not require manual calculations.
||Doesn't work on dry cured grasses. For a single representative plot measurement the rod has to be cleaned several times in grasses with a lower moisture content. Hesitant on some readings. Cannot see single readings. Not much to the operator's manual.
|The Alistair PastureGauge© has an easy to read display, showing single readings and running average. Display options are shown on the screen. Decent operator's manual. Does not require manual calculations.
||Meter falls off the shaft too easily. Doesn't work in dry cured grasses. Measuring shaft too small. No carrying case provided. Too many buttons makes it confusing what to press at times. Sometimes it pauses, (causing) confusion. The rod requires frequent cleaning. Inconvenient if battery runs low.
|The GrassMaster is easy to use. Easy to read display. Electronic case is attached strongly on measuring shaft. Comfortable to hold. You can see each single reading. Has the best operator's manual of all the capacitance probe devices. Does not require manual calculations.
||Doesn't work on dry cured grasses. The GrassMaster needs a carrying case or carrying strap. Requires frequent cleaning of the probe. Battery life is too short. Inconvenient to charge after batteries die. Requires special handling to use battery charger. Cannot pause measuring to maneuver over or around bushes.
|Neosystems II is easy to learn. Takes 4 to 20 min for measurement depending on forage type. Nice display with easy controls. Field portable if needed. Good operator's manual. Simple instructions. Stores readings in memory. Can download to a PC into Excel or typical data acquisition software. You can let it run and leave for a few minutes. Can repeat bakes easily. Baking times can be switched. Uses ac or 12 V car battery to run. Does not requiret manual calculations.
||Like the standard oven method, requires a lot of preliminary work to go out, cut the grasses inside a frame, and collect in bags. The balance display needs to be at eye level. Carrier requires preheating so it takes longer to perform readings. Carrying case is extra. Scales have to be locked into place for transport.
Cut and Weigh
|As the current standard, is a proven technology. Capital investment of equipment already made. Personnel already trained to this method. Accurate measurements.
||Takes up to 21 h for results. Like the Neosystems II meter, it requires a lot of preliminary work to go out, cut the grasses inside a frame, and collect in bags. Overall labor intensive, increasing chance of human error. Room gets hot with oven going. Takes a long time to prepare and process samples. Additional cost for scales and calibration of equipment. Cannot download data to PC. Requires manual calculations.
The Neosystems II meter temperature is set at 284 °F (140°C) across
the plates. The temperature for the standard oven was set at 220 °F
(104°C), 64 °F (18 °C) lower than the Neosystems II meter.
This increase in oven temperature alone would typically increase the release
of volatile oils from the plant material and adversely affect the accuracy
of the measurement. The manufacturer of the Neosystems II meter states
that this was taken into consideration in the design. A fine balance was
developed between an increase in oven temperature, offset by a substantial
decrease in time to bake (1 h versus 21 h), oven plate designed with ridges
and holes for the rapid removal of moisture, vacuum pump, and oven plates
compression. All focused on significantly decreasing bake time, without
increasing the release of volatile oils from the plant material.
Differences in readings between operators are due to technique, such as using a greater
force in positioning the rising plate meter or capacitance probe onto the
ground. Also, all readings must start in open air and the device must be
brought straight down (vertically). The capacitance probe shaft picks up
debris and must be cleaned frequently. This must be recognized and performed
by the operator.
probe meters were having difficulty picking up readings in the plant material
with low fuel moisture content, such as dry, cured grasses. Occasionally,
the capacitance probe would indicate a reading and display a value of "500
kg DM/ha," in dry, not cured grass. This was determined to be a minimum
reading for the given unit and did not reflect an accurate measurement.
Capacitance probe measured values are directly proportional to plant moisture
is important that the operation of the device be understood and followed
to obtain accurate measurements.
The findings are as follows:
- The Neosystems II portable oven has the highest degree of correlation,
accuracy, and consistency compared to the standard oven. Use of the Neosystems
II requires more labor than the sliding plate or capacitance probe meters.
- The Neosystems II meter has 94 percent superior correlation with the standard
oven. The GrassMaster capacitance probe has a 74 percent correlation followed
by the Jenquip Sliding Plate with 58 percent. The Kencove sliding plate
and Alistair capacitance probe have fair correlation, and the Draminski
has doubtful correlation with the standard oven method.
- The type of device appropriate for use in a particular application will
depend on the required accuracy for that application.
- Rising Plate devices have a low correlation and accuracy when compared
to the standard oven method. Capacitance probe correlation and accuracy
- The most accurate capacitance probe was the GrassMaster Capacitance Probe.
The GrassMaster had a 74 percent correlation with the standard oven method
and accuracy much lower than the Neosytems II or standard oven method.
Forage constants must be developed for specific pasture plots and the issue
of minimum stubble height needs to be addressed before field use of the
GrassMaster capacitance probe for any application requiring less accuracy
than currently provided by the standard oven or Neosystems II Meter.
- The most accurate sliding plate was the Jenquip Sliding Plate. The Jenquip
had a 58 percent correlation with the standard oven method and accuracy
lower than the Neosytems II or standard oven method.
Consideration should be given to the Neosystems II meter as the standard
for obtaining production and utilization measurements when replacing the
There is a need for a field users guide for sampling, collection, and processing
forage production samples for use with the standard oven and/or Neosystems
II oven meter. This evaluation should consider minimum stubble height.
Based on the findings of this study, the following is recommended:
- Use the Neosystems II meter to obtain accurate forage production measurements
in the determination of stocking rates and the effectiveness of certain
land treatments such as burning, herbicide applications, and fertilization.
- A field users guide for sampling, collection, and processing be developed
regarding forage production samples for use with the standard oven or Neosystems
II meter. This guide should address sampling considerations regarding minimum
- Forage constants need to be developed for specific pasture plots and the
issue of minimum stubble height needs to be addressed, for the GrassMaster
capacitance probe or Filip Folding Plate Pasture Meter, before field use
for an application requiring less accuracy than currently provided by the
standard oven or Neosystems II meter.
Herbaceous Measurement Devices Manufacturer Information
Owocowa 17, Poland
Fax: 011–48–89–527–84 44
web site: http://www.draminski.com.pl
11915 Starcrest Drive
San Antonio, TX 78247
Tel: 1–800–874–8494, 210–495–9130
Filips Folding Plate Pasture Meter
Reid Line East, R.D. 5
Feilding, New Zealand
Tel: 0800 35 35 37 / (06) 323–6146
Fax: (06) 323–6116
web site: http://www.Jenquip.co.nz
KencoveFarm Fence Inc.
Farm Tracker Rising Plate Meter
344 Kendall Lane
Blairsville, PA 15717–8707
Tel: 1–800–536–2683 / 724–459–8991
web site: www.kencove.com
Alistair George Manufacturing
23 Citrus Avenue
Waihi Beach 3060; New Zealand
Sigma Delta Technologies Pty Ltd.
Fuel and Soil Moisture Model Neosystems II
Attn: Peter Grey, Technical Information and Sales
444 (Rear) Cambridge Street
Floreat, Western Australia 6014, Australia;
or P.O. Box 117, Floreat
Western Australia 6014, Australia
Tel: 001–61-8–9285–8611; Fax: 001–61–8–9285–8622
Neosystems II Meter—Model Fmm-1
Please see the operator's manual for specific detailed instructions.
- DO NOT remove power from the meter until a run is completed or it is in the main menu.
- Ensure the RED lead is connected to the POSITIVE of the battery and the BLACK lead to the NEGATIVE.
- DO NOT move the meter unless the balance is locked. This is indicated by no display on the balance LCD. If there
is a display showing, then reset the meter (press STOP) again until the display shows nothing. If this fails to occur after a number of tries,
then remove the nylon base plate under the meter and screw the lock pulley clockwise until the lock is in place (i.e., it is fully up). DO NOT over
tighten or else it will not be able to be unlocked by the lock motor. DO NOT ship the meter with the balance pan in position, remove it and put
- DO put the meter on a level surface free of any vibration. Keep the meter clean and free of dirt.
- Turn off the meter by use of the switch at rear of the unit.
- Connect the red lead to the positive of the battery and the black lead to the negative.
- Turn on and wait for approximately 10 seconds for the meter to initialize. When complete, the message "NORMAL OP'NS" will be displayed.
- This is the start of the main menu. If you wish to have normal operations, press the "SELECT" button. The message "WAITING FOR TEMP" will be displayed until
the set temperature of the bottom and top heating plates is reached.
- Then the message "READY" will be displayed. Place the sample in the carrier holder and put in on the balance pan within the balance ring. Close the
lid and press "START" to initiate a measurement.
- The sample will be moved to the left and the balance will be tared. The sample will be placed over the balance and the wet sample weight taken.
- The sample then moves to the left, over the bottom hot plate. This plate is then raised until the sample is firmly compressed between the two plates
and the lift motor will be turned off. When the lift motor starts to operate, the vacuum pump will be turned on. This is to start heating up the vacuum
- After approximately 3 1/2 min, the bottom plate will be lowered to put the sample level with the balance. The vacuum pump will be turned off and the balance
will be tared. The sample will be conveyed to the balance, weighed, the moisture percentage calculated, and the result displayed.
- The operator is then given the choice of repeating the run, by pressing the "REPEAT" button. A repeat is necessary in the event of very wet samples.
- If a new sample is to be run, press the "START" button. This process can be continued indefinitely.
- After a reading is displayed, there is the option to store the result by pressing the "STORE" button. The memory can store 253 results. To return to the
main menu, press the "STOP" button.
See the full manual for specific detailed features and other functions.
Sampling and Obtaining Consistent Results
At each point of the sampling (collection, measuring, and putting into the carrier) there is a potential source of errors. These errors may even be
cumulative so care should be taken at each step.
- Make sure that when collecting samples you collect enough to be representative of what you are trying to measure. Do not let anything contaminate the
samples. To avoid this, wear gloves when collecting samples and do not let any moisture come into contact with the samples at any time. If not
measuring the samples right away then bag each sample and ensure an airtight container is used. Keep the samples cool if they are not to be measured
- When preparing the sample, ensure that the full sample is homogeneous and uniform throughout. For instance, Chemise is very uniform and pieces as large as
1 to 2 in (25.4 to 50.8 mm) can be used. In the case of grasses, there can be great variability so care must be taken to cut the sample into small
portions so that the sample to be measured is representative of what was collected. If you do not follow these steps, then you will find wide variations
in the readings measured. This is particularly evident in high moisture samples.
- Once having prepared the samples in step 2, mix the sample thoroughly using gloved hands. Next select a "bunch" from the sample and place it in the
outer carrier holder. You should try and get a minimum of 7 g in the carrier. DO NOT select one leaf, blade, etc at a time. "Grab a handful" so that
the sample is more representative. Spread the sample out evenly in the carrier and place the inner the carrier on top of it. Press down to ensure
that the inner carrier does not protrude above the outer carrier. If this happens it may interfere with the weighing mechanism and lead to false
results. Also, ensure that no sample protrudes above the outer carrier.
- Place the carrier and sample on the balance pan by first making sure that the pan is clean and centrally placed. Close the lid and press "START." Allow
the meter to measure the moisture percentage.
- The outer carrier is made from nylon, which is hygroscopic and thus will vary in weight. The carrier needs to be dried out completely or alternatively
the weight should be continuously entered into the meter (see CALIBRATE function). Calibrate the Neosystems meter only after preheating the oven
carrier. Using old values of calibration can lead to significant errors. The time to drive off all the moisture in the nylon carrier will vary.
However, 24 h in an oven at 221 °F (105 °C) should accomplish this. On existing meters a 10-min bake with the nylon carrier empty, carried
out for a number of cycles would suffice. Further checks need to be done to determine the optimum preheat times of the nylon carrier.
- The larger the sample size and the larger the sample pieces, the longer it takes to remove all the water; and the smaller the size, then less representative
it is. If the sample is cut into small pieces, the drying time will be quicker and you will also be able to use more samples and be more representative.
Sigma Delta suggests that you experiment to see what is optimal at each area of moisture percent. Each species will be different. Trial and error
will show the size versus time considerations.
Data may be downloaded from the oven meter to the PC. This is achieved with Hyperterminal. In Windows 95, Hyperterminal is located in the accessories
folder and in Millennium Edition it is located in accessories/communications.
The Hyperterminal program can be used to capture the data coming from the Neosystems II meter in ASCII, comma delimited data. From there the file can be imported
into a spreadsheet program or data acquisition program, such as Labview.
Incorrect results—Results of 0.0 percent can arise if no sample is put in the
sample holder and "START" is pressed.
Readings too low—This will occur if you have not prepared the sample. It could
also occur if the sample moisture is very high. This may mean that a repeat reading is necessary. It could also result from some species where bound
water is such that a longer time is necessary in the oven. Repeat samples will get over most of these problems. Another solution where the sample
is uniform is to reduce sample size. Reducing sample size when the sample is not uniform will lead to variable results.
Readings too high—This could be due to incorrect balance readings or oils being
driven off. High readings can be due to the inner carrier or sample protruding above the level of the outer carrier. The high readings may also show on
the display as D12.5% for instance where the alphabetical character may be A, B, C, D, E, or F. This says that the readings are above 1,000
percent, which should never occur. This indicates that the initial wet weight is higher than it should be and is caused by an incorrect balance
reading. If you encounter this continuously, leave the lid open so you can observe any interference to the weighing operation.
Error on results—This will be due to the dry weight being more than the wet weight, something that should never occur. The cause of this could be incorrect
balance readings due to the sample holder not being free of the balance ring.