INSTRUMENTACIN MEDIO AMBIENTAL
JOAN COSTA
SPRING 2010
INTRODUCTION
Objective
The intent of using the LAI-2000 Plant Canopy Analyzer in this
experiment will be to measure and evaluate the canopy coverage of
Crocus sativus. The objective of this study is to calculate the
Leaf Area Index of the crocus, which we will later relate to both
the stamen yield, and the irrigation system. High biomass in plants
is proved to lead to a larger flowering structure. Crocus plant and
flower size is directly related to proper watering techniques; and
it is proven that bigger flowers lead to bigger stigmas. The crocus
stigma is the harvestable, edible and economically desirable flower
part. Irrigation tubes have been set up to feed water via emitters
that are set on the ground at the end of each row. This experiment
will allow us to evaluate the effectiveness of water velocity and
flow throughout the entire system in relation to biomass
accumulation.
The LAI-2000 is an ideal instrument for the project because it
can measure canopy coverage from a distance or at a very close
range in an accurate, rapid and non-destructive manner. The
instrument works by sending a beam of radiation through a distance
of vegetative canopy, and then calculating the average number of
contacts per unit length of travel that a probe would make passing
through the canopy at zenith angle .Crocus sativusCrocus sativus is
commonly known as saffron. It is a flower which is native to the
Mediterranean environment, characterized by cool to cold winters
with an autumn-winter wet season, and warm dry summers with little
rainfall. It can withstand substantial frosts (-10 C) and can
tolerate some moderate snow. Saffron has extra long stigmas, which
are harvested in autumn, shortly after planting. The traditional
flower reproductive parts are sterile, so the plant reproduces by
means of corm multiplication. It is a curious plant because
vegetative plant parts will appear sometimes before, sometimes
with, and in some cases after flowering. Corm biology consists of
an underground vegetative food source that gains the majority of
biomass in the beginning of the summer, whence they are replaced by
1 to 10 cormlets. These cormlets can be removed from the mother
part, and replanted in the beginning of autumn, early September,
for autumn flowering shortly thereafter. Ideal soils for saffron
cultivation are light and friable with a high nutrient content.
These soils facilitate easy root penetration. Study LocationThe
crocus fields are located in the Ebro Valley, in the Northern
region of Rioja, Spain. In this particular cultivation, rows are
oriented directly East-West and spaced 6 cm. apart; a common
orientation in Spanish saffron farms. Corms within furrows are 3
cm. apart and were planted at a depth of 10 cm. The soil is light
and friable with a high organic matter content, and good drainage.
300 - 400 mm water is applied per year via irrigation tubes which
run North- South on the East side of the field. Emitters are spaced
8 cm. apart so that they fill each between row space
simultaneously.Measurements and ConditionsSince overly bright light
conditions have a high probability of altering results, we will
take measurements at 8:30 am on October 20, 2010. The date is 50
days after the corms have been planted. On average, a properly
handled crocus corm takes 40 days to reach full flowering maturity,
upon which it will then flower for approximately 20 - 30 days. At
this time in the morning, the sun is closer to the horizon and is
not at its brightest; moreover, there is often morning cloud
coverage in the sky to disperse the existing light. The two error
causing effects to be considered when taking measurements are:
scattered radiation within the canopy and azimuthally non-uniform
sky brightness. The flower crops are in a completely exposed field,
thus the other option to minimize direct sun or sunlit leaf area
would be to utilize the lenses. If you use a lens, place it at a 45
angle to the row direction. Orienting a view restrictor down the
row generally underestimates the LAI, while orienting it across the
row overestimates LAI. A common technique for measuring row crops
is taking 3 or 4 evenly spaced readings along a diagonal transect
that runs between two rows, and do several transects. Taking the
measurements in this configuration reduces error attributed to
overly weighted measurements in in-row and between-row conditions.
Since these rows are very closely spaced, measurement technique
needs to be precise. Each row is spaced 6cm. apart, and so to take
4 readings per transect, the LAI 2000 must be moved 2 cm., over and
diagonally after taking an initial reading between two plants in
the furrow. A total of 3 transects will be measured. 1.) In the
center, but far north side of the field (close to the irrigation
water source, 2.) Directly in the middle of the field, and 3.) In
the center, but on the far south side of the field (the irrigation
here is furthest away from the source). Conducting measurements
according to irrigation flow will allow us to analyze if irrigation
is properly reaching and watering all crops in the field. A common
problem with this type of irrigation is that the water pressure is
very high in the beginning of the tubing; and then due to
residuals, or incorrect water pressure calculations, will be very
low at emitters further away from the water source.
As Crocus sativus is a low growing plant, you will need to lay
on your stomach to get an accurate below canopy reading.As a rule,
the plot size should be 3 times the canopy height. It is said that
if the plot is too small, then the sensor will see out the sides of
the plot, and underestimate the size of the plot, especially in the
case of a less dense canopy. Canopy height will be estimated to be
15 cm. from the bottom of a furrow to the tallest leaf tips. The
plot will be 45 cm2.
PROTOCOL
Pre-field preparation
Before leaving to gather data in the field,
Check to make sure that you carry with you all the opaque masks/
lenses. These masks can restrict the field of view to 270 , 180 ,
90 , and 45 to limit the sensor view (which is normally 360 ). You
may need to limit the sensor view for special purposes; such as
blocking undesired objects, like yourself, or the sun, from view to
reduce errors, or to study canopies with leaves asymmetrically
distributed about the azimuth. Bring 6 marker flags, if you have
them. These will serve to help you mark out the boundaries of your
3 transects. You can leave these marker flags in the field too, so
that we may take another set of identical readings on another day,
if needed.Check that the batteries within the receiver box have
enough charge to stay in the field for 2 hours. You will not be
taking measurements for 2 hours, but this is to just be well
prepared. The LAI-2000 requires 6 D Cell batteries, which last a
total of 270 hours. You can turn the instrument on and make sure
that there is not a low battery symbol on the display. A low
battery symbol implies that the battery life is 15% or lower.Since
the field may be muddy, wear a pair of sturdy boots. Do not forget
to bring water, sunglasses, and a light jacket.In the field
When you arrive at the site, set up the LAI-2000 by plugging the
sensor into the 'X' portal of the receiver and turning the machine
on. You will have to input some basic data to start. The following
is a checklist table for properly managing the sensors before
starting to take data. FCT is the input command button. The numbers
below FCT are command codes which will activate the Action.
#FCTAction
1Attach sensor to X port
201, 02Verify calibration data*
304Set resolution
405Check Clock
511Set operating mode and avg. number
612Define prompts
715Begin taking data
*Calibration notes: If you need to use a lens, calibrate the
sensor with the lens in place. A Reading - Above canopy, B Reading
- Below canopy.1 SENSOR X : Set the reading to This setting will
ensure that you take one Above canopy reading for every four Below
canopy readings, a total of three times. This data collection
method has been defined in the experiment parameters. Post-
measurement
When you have taken all of the data that you think is
sufficient, you can carefully wipe down (to remove any residual
dirt), and pack up the LAI 2000. In the lab, all of your data must
be transferred to the computer for analysis. You must first
configure the port. Data is transmitted to the computer via RS-232,
so your computer must have an RS-232 port. This port is configured
as Data Communications Equipment (DCE); so it transmits data on pin
3, and receives data on pin 2. You will need a null modem cable for
connection. If your computer's port is configured as Data Terminal
Equipment (DTE), then you will need a straight through cable.
Command FCT 31 sets the baud rate, data bits, parity, and
handshaking for the RS-232 port.
You are now ready to connect to your computer. The computer must
execute a program that takes incoming data from the RS -232 port
and stores it. Install the COMM program, included in the LAI 2000
box on a diskette. To transfer data files from the LAI 2000 to the
computer, the file transfer process is the following:1. Connect the
computer to the LAI 2000 with the appropriate cable.2. Run the
computer program3. Make sure the LAI 2000 and the computer's RS-232
port are configured compatibly.4. Specify the destination for
incoming data on the computer (file, printer, etc.)5. Define the
output format (FCT 33) to be used; spreadsheet or standard, then
transfer the desired files (FCT 32).
Once you have imported the data, you can analyze it. The table
can be divided into three main sections; the header, statistics,
and observations. The header makes basic LAI calculations and
defines all prompts and remarks that were recorded during the time
of data collection. Abbreviations are as follows:
AbbreviationSignificance
SELStandard error of the LAI determinations
DIFNFraction of the sky visible beneath the canopy
MTAMean Tip Angle
SEMStandard Error of the MTA
SMPThe number of pairs of below and above observations used to
calculate these results
ANGLESThe mid-angles of each of the five rings' field of
view
CNTCT#The mean contact frequencies of all the computed
transmittances
STDDEVThe standard errors of the contact frequencies
DISTSPath lengths
GAPSThe fraction of the sky visible for each detector ring
The observations (the third block of information) each have a
label (A or B), a sequential number, a time stamp and 5 values. The
five values are the signals from the five rings of the detector,
and A and B indicates whether it was Above or Below the canopy.
Irrigation
E
S
N
W
Row
Row
Row
2
