grass height meter
operating instructions
On these operating instructions

!
If the text follows a mark (as shown on the left), this means that an important instruction follows.
If the text follows a mark (as shown on the left), this means that an important warning follows relating to
danger to the user or damage to the apparatus.The user is always responsible for its own personal protection.
Introduction
The grass height meter is a very effective and suitable auxiliary tool allowing for an accurate estimate of the quantity of grass
on a parcel of grassland. The grass height meter is therefore suitable for cattle farmers who need to optimise the management of their grassland. In addition it is a much used tool for research and education.
For proper grassland management it is essential to mow the grass or to rally cattle at the right stadium. If the quantity of
grass on the parcel is too great then unnecessary loss of grass may occur during grazing. If grass is mowed when it is too
high and dense then the quality of the grass often is reduced and re-growth often is hampered.
In addition fertilising suggestions are based on the content of the next cut. Grazing or mowing too early or too late thus often
means unnecessary reduction of yield or that the utilisation of the fertiliser added is unnecessarily low. From the point of
view of costs and environmental awareness, knowledge concerning the expected yield of dry material is of vital importance.
Research using the grass height meter proves that the relation between
grass height and yield of dry material is fairly reliable.
With its grass height meter type NMI Eijkelkamp Agrisearch Equipment
offers a simple, non-destructive method for measuring the grass height
on a parcel of grassland. It is possible to quickly make measurements at a
relatively great number of locations without the need to mow any grass.
By measuring at different locations it is not only possible to establish the
average grass height but also to research differences in yield within a
parcel. Using a table it is possible to determine the yield of dry material
(kg/ha) of a parcel.
3
Description
The grass height meter consists of a round measuring disk of synthetic
material (1) with an outer tube (2) and a measuring rod (3). The measuring
disk is placed flat and stable on the grass and is not sensitive to water or
dirt. The outer tube is connected to the measuring disk. The measuring
rod, which is fitted with a graduation at its upper end from which the grass
height can be read, runs through this outer tube.
2
The outer tube and the measuring rod can be taken apart which allows
for storage in a cardboard box.
1
All it takes for environmental research
P.O. Box 4, 6987 ZG Giesbeek,
the Netherlands
© May 2015
T
F
[email protected]
I www.eijkelkamp.com
+31 313 88 02 00
+31 313 88 02 99
1
M1.19.30.E
Technical specifications
PartDimensionPressureMaterial
Measuring disk
Ø 50 cm, thickness 5 cm
0,178 g/cm2
polystyrene
Outer tubeca. 1,40 mpvc
Measuring rod
ca. 1,75 m, Ø 18 mm
10 g/cm2 pvc
Use of the grass height meter
1. Create a test diagram in which 30 measuring points are included, well spread over the entire parcel (thus also including the rims!). Copy this diagram on a copy of the field list. The measuring points are pre-determined as once in the
field this often is executed selectively, which means that for instance only the “best” spots are measured.
2. Before use you should mount the outer tube and the measuring rod by sliding the parts tightly together. Subsequently
these parts must be connected to the measuring disk (checking: the grass height meter should indicate “0” on a hard
flat surface).
!
Handle the grass height meter with care. The measuring disk is relatively vulnerable and thus there is
a risk of minor damaging.
3. Next you should place the measuring rod at a measuring point on
the ground.

Do not measure at a location where, when setting out
the measuring points, footprints were made. The grass
is flattened there and thus unsuitable for accurate
measurement.

As the ground surface never is entirely flat the measuring tube will sometimes stand a little higher or lower.
After 30 measurements these effects automatically
average out.
4. You should place the outer tube with the measuring disk on the
grass in such a way that the grass ends are bent only by the weight
of the outer tube and the measuring disk.
5. At the upper end of the measuring rod you can now read the grass
height. This value must be noted on a copy of the field list.
6. After all 30 measurements are concluded the average of the parcel
can be calculated.
7. In the table (see following page or the field list) the yield of dry material (kg/ha) which agrees with the average height
of the grass can be read.
It should be considered that:
 the table provides an estimate for a standard field with a standard grass density. There are situations in which the
estimated yield deviates from the value indicated in the table for instance in case of open turf, wet or flattened grass,
or in case of a deviant botanical composition.
 there are differences in yield between grazing and mowing in case of the same grass height. This is caused by the
fact that the average grazing height is approximately 1 cm higher then the mowing height.
2
Notes:
 In the event of less then 30 measurements as well as in case the measurements are not spread correctly, the average
found is not an accurate reflection of the actual grass height (and thus of the dry material yield) in the parcel.
 It is possible that growing differences occur within the parcel. When researching the variation in grass height within
the parcel, the parcel can be subdivided into sections. The average is then calculated from 30 measurements for each
section.
 In case of a dry material yield exceeding 3 to 3.5 ton/ha the relation between grass height and yield is no longer reliable and is therefor not included in the table.
Applications
The grass height meter type NMI is used to determine the dry material yield (kg/ha) of a parcel on the basis of the grass
height. This is particularly done in the context of:
 Estimation of yield for determination of optimum time for mowing or grazing.
 Estimation of yield for fertilisation recommendations.
 Grazing tests in relation to grassland research.
 Precision agriculture to which purpose the variation in grass yield of a parcel is determined (for this purpose a geographical information system is often applied).
Education.
Maintenance
 If not carefully used small parts may break of the measuring disk. This makes the measurements slightly less accurate.
Small damages however have little influence on the measuring results. As soon as larger sections break off then the
grass height meter becomes useless.
 After use one should de-mount outer tube and measuring rod. This prevents bending as the result of storage in the
wrong position. In particular in the event of high temperatures, for instance inside a car, the tubes are sensitive to
bending.
 After use the grass height meter is best stored in its cardboard box. This prevents damaging of the measuring disk.
In addition it is easier to transport the complete set.
References
Keuning, J.A. (1988), Grashoogtemeter hulpmiddel voor schatting grashoeveelheid [Grass height meter for the estimation of the quantity of grass]. In: Meststoffen 1-1988.
NMI Nutrient Management Institute, Agro Business Park 20, 6708 PW Wageningen.
3
FIELD LIST GRASS HEIGHT METER
Name:
Date:
Parcel:
Notes:
P.O. Box 4, NL-6987 ZG Giesbeek
Nijverheidsstraat 30, NL-6987 EM Giesbeek
T 31 (0313) - 880200
F 31 (0313) - 880299
[email protected]
Iwww.eijkelkamp.com
4