Transcript Farms, sensors and satellites

Farms, sensors and
satellites
Using fertilisers
Farming practice are changing
Sensors and satellites
Growing quality crops in good yields depends on
many factors, including adequate amounts of
water, air and light. Plants also need nutrients.
Sensors and satellites are changing the way growers
go about their business. They are enabling growers
to:
Nutrients are obtained from the growing
medium, usually soil. If there are insufficient
amounts of one or more of the required
nutrients, fertilisers may be used to supply them.
•
use less fertiliser, which reduces their costs and
reduces potential adverse environmental effects.
•
increase the yield of crops by maximising the
potential of each field.
But how do growers know
• what type of fertiliser to use?
• where to apply it?
• how much to apply?
Even though growers have known for a long
time that yields from a field can vary from place
to place, the field was still treated on a ‘field
average’ basis. But the liberal use of fertilisers
can cause environmental harm and be costly to
the grower.
Sensors and satellites are helping the decision
making.
More information about EGNOS
Nitrogen sensing
Not all systems require satellites
Some systems are designed to be carried on board
the fertiliser vehicle.
The sensor detects and measures reflected
electromagnetic radiation from the plants.
The information is processed by an on-board
computer. This automatically adjusts the rate of
fertiliser application in response to the information
received.
The Yara N-Sensor is an example of such a system.
Sensors
Absorbance
Filter
Sample
Sensing electromagnetic radiation
Some sensors can detect and measure
electromagnetic radiation.
They are used detect absorbed, transmitted
and reflected radiation.
•
•
In a colorimeter or spectrophotometer,
they detect and measure
electromagnetic radiation in the visible
region that passes through an object
(transmission). This can be used, for
example, to determine the concentration
of a solution of a coloured solute.
In some other instruments sensors
detect and measure electromagnetic
radiation that has been reflected from a
surface. The nature of radiation reflected
from leaves gives important information
about the health of the plant.
Sensor
White
light
source
Emits full
spectrum of
visible light (much
simplified here)
Some of the
Light with the
same colour as ‘filtered’ light
is absorbed
the filter is
by
the sample
absorbed
Reflectance
Sensor
The light source
might be natural
sunlight or an
artificial source.
The amount of
light that
passes through
is measured
Green light is reflected, but
more importantly for analysis
so is some near infrared
radiation. The remaining
radiation is absorbed or
passes through.
White
light
source
Green leaf
Photosynthesis
Relationships
Photosynthesis, chlorophyll, reflectance from a green
leaf, nitrogen content and healthy plants are closely
linked.
Chlorophyll is essential for photosynthesis
The rate of photosynthesis is highest when
electromagnetic radiation between 400 and 500 nm
and between 600 and 700 nm.
Reflectance of electromagnetic radiation by green
plants is dominated by chlorophyll and the
concentration of chlorophyll often correlates closely
with the nitrogen content of leaves.
chlorophyll and
carotenoids
absorb radiation
in these regions
Chlorophyll exists in two forms - a and b. Both absorb
red and blue radiation, so little of this radiation is
reflected from green plants.
Almost zero
photosynthesis
Rate of photosynthesis (%)
Reflectance spectrum of a typical green leaf:
Low rate of
photosynthesis
High rate of
photosynthesis
High rate of
photosynthesis
What do the results tell us?
Electromagnetic radiation that is not absorbed may
• pass through the leaf (transmitted);
• be reflected from the surface of the leaf.
Measuring reflected radiation provides information
about the chlorophyll content of leaves. In turn this
provides information about the nitrogen content of the
plants.
Rate of photosynthesis (%)
Absorption, transmission and reflectance
Green leaves
absorb blue and
red light
– and these are the
wavelengths (400500 nm and 600-680
nm) that bring about
the highest rates of
photosynthesis.
The higher the density of green plants
• the more electromagnetic radiation of wavelengths
below the red edge that is absorbed and less that
is reflected.
• the less electromagnetic radiation of wavelengths
above the red edge that is absorbed and more
that is reflected.
So measuring the reflectance of electromagnetic
radiation can be used to map the density of crops in a
field. This allows growers to match the quantity of
fertiliser applied to specific parts of the field.
% Reflectance
Interpretation of reflectance spectra
Red edge
EGNOS
Using GPS and sensors in tandem
EGNOS and precision agriculture
The European Geostationary Navigation Overlay
Service (EGNOS) is a European Space Agency
(ESA) project.
EGNOS can help farmers in aerial crop spraying or
precision farming. It increases the reliability and
accuracy of existing GPS systems. Typically GPS is
accurate to 5 to 10 metres. Coupled with EGNOS, an
accuracy of 1 to 2 metres is achieved. Enhanced
navigational data means enhanced efficiency.
“EGNOS is the first pan-European satellite navigation
system. It augments the US GPS satellite navigation
system and makes it suitable for safety critical
applications such as flying aircraft or navigating ships
through narrow channels.
Back to Using fertilisers
Consisting of three geostationary satellites and a
network of ground stations, EGNOS achieves its aim
by transmitting a signal containing information on the
reliability and accuracy of the positioning signals sent
out by GPS. It allows users in Europe and beyond to
determine their position to within 1.5 metres.”
Source:
http://www.esa.int/esaNA/GGG63950NDC_egnos_0.
html
The potential market for EGNOS includes:
aeronautics, maritime, land transport and
and numerous other diverse potential uses.