Post on 27-Oct-2014
ASEMINAR REPORT
ON
Semi-Automatic VRT-Based FertilizationSystem Utilizing GPS
Presented ByMr. Hemchandra R. PawarT. E. - (AGRIL. ENGG. )
Under the Guidance ofMr.: A. J. Deokar
Department of Agricultural Engg.
S.V.E.R.I’S
COLLEGE OF ENGINEERINGPANDHARPUR.
(2006-2007)
E-mailPawar.hemchandra@rediffmail.com
This is to certify that, the seminar report entitled,
Semi-Automatic VRT-Based FertilizationSystem Utilizing GPS
has been duly completed by Mr. HEMCHANDRA R. PAWAR of third
year Agricultural Engg. During the academic session 2006-2007 in satisfactory
manner in partial fulfillment of the requirement for the degree of
“AGRICULTURAL ENGINEERING”
SOLAPUR UNIVERSITY, SOLAPUR.
COLLEGE OF ENGINEERING,
PANDHARPUR.
(Mr.: A. J. DEOKAR) (Prof. A. V. Zambare)
Guide H.O.D.
(Prof. B. P. Ronge)
PRINCIPAL
I feel happy in forwarding this seminar report as an image of sincere
efforts. The successful seminar reflects my work, effort of my guide in giving
me good information.
My sincere thanks to my guide respected Mr. A.J. DEOKAR who has been a
constant source of inspiration and guiding star in achieving my goal. I give my
special thanks to respected H.O.D. Prof. Mr. A.V. Zambare for their constant
interest and encouragement throughout the completion of my seminar.
I express my deep gratitude to all staff members who lend me their valuable
support and co-operation to enable me to complete my seminar successfully.
I am also equally indebted to our principal PROF. B.P. RONGE for his
valuable help whenever needed.
Mr.HEMCHANDRA R.PAWAR
T.E. (AGRICULTURAL ENGG.)
INDEX
1. Abstract ……………………………………………………………………… 42. Introduction ………………………………………………………………….. 53. VRT (Variable Rate Treatment)……………………………………………… 54. Materials and methods ……………………………………………………… 7
i. GPS Technology………………………………………………………... 7ii. VRT controller …………………………………………………………... 8iii. Sprayers and Spreaders …………………………………………………. 9iv. Hydraulic system…………………………………………………………. 9v. Grid soil sampling ………………………………………………………. 10vi. Developing GPS guided VRT system…………………………………… 10vii. Using DGPS and RTK technology …………………………………….. 11viii. VRT based system………………………………………………………. 12
5. Case study…………………………………………………………………… 156. Conclusion …………………………………………………………………… 187. References……………………………………………………………………. 19
ABRACT
.Variable Rate Treatment (VRT) is one of the most growing arenas in the agricultural
engineering field. Employing real-time GPS positioning methods, made it easy to build
accurately guided machines. On the other hand, environmental concerns made it necessary to
apply Variable Rate Treatment (VRT) concept in fertilization.
Precise fertilizer application is used widely where fully automatic systems are extensively
presented commercially. In this research, a new semi-automatic system is designed and
developed locally. The proposed system employs a real time GPS positioni.ng system to guide a
tractor mounted rotary spreader to apply phosphate to the field. In order to estimate soil re-
quirements, the field was divided into a 50-meter mesh grid and soil samples were collected from
eight GPS defined locations. Soil analysis results were mapped and studied to determine the
needed amount of Calcium Super Phosphate to be added per hectare and a prescription map was
developed. In order to evaluate system performance and its feasibility, soil chemical analyses of
the same GPS defined locations were made after applying the fertilizers using the designed
system. It was noticed that assessment of VRT-based systems is clearly stated anywhere in the
literature. Different methods of performance assessment are presented in this research. The
developed system was tested and evaluated in AI-Oha experimental farm, UAE University.
INTRODUCTION
VRT (Variable Rate Treatment):
● VRT is the implementation of gathered information and decisions for site specific agriculture.
● VRT consists of the machines and systems for applying a desired rate of crop production materials at a specific time (and, by implication, a specific location).
● Materials:○ Seed○ Fertilizer○ Pesticides
By definition, VRT implies that the rate varies, although sometimes simply maintaining a
constant rate is challenge.
By rate, we generally mean:
And is usually expressed as (lb/acre, gal/acre, kg/ha, l/ha) and typically we consider this as:
Application rate =flow rate of material/ rate of land coverage = material discharge rate/ land rate.
area/tLand rate is the product of implements width and ground speed
Land rate = width (length)*speed (length/ time)
Historically, VRT methods were introduced by industry during the mid-1980s. Dry nitrogen,
phosphorus, and potassium fertilizer application rates were simultaneously varied on commercial
spreader applicators based on a predetermined map strategy (developed from earlier data
collection such as photographically derived soil maps or grid sampling). Farmer-owned
machinery has been equipped with VRT for fertilizer applications requiring a standard liquid
blend.
Variable rate treatment is one of the most promising technologies in the agricultural systems
arena for the surrounding environment, in addition to its economical feasibility. The concept
itself is based on the belief that the field cannot be treated as one unit because of the variation
among its finite areas. Fully automatic granular fertilizer broadcasting systems are widely
available in most of the developed countries. In this research, a semi-automatic GPS-guided
system is designed, built and tested. Many mechanized crop producers and agribusinesses are
fascinated with precision agriculture technology, but adoption has lagged behind the
expectations. Among the reasons for slow adoption of precision agriculture technology is that
initial users focused excessively on infield benefits from variable-rate fertilizer application using
Global Positioning Systems (GPS), geographic information systems (GHS), yield monitoring
sensors, and computer controlled within field variable rate application (VRA) equipment. ASAE
standard (1999) was used to evaluate uniformity distribution of granular broadcast spreaders in
one direction. The evaluation process had two considerable bases. It evaluated the uniformity
distribution compared to machine path and compared readings to its average. It is crucial to
evaluate the whole GPS-guided Variable rate fertilizer applicator to judge the feasibility of using
it. In this research, two evaluation indexes were presented to assess performance of the VRA
system as a function of distribution uniformity. The resulted indices would not be possible
without refereeing to geostatistics studies.
MATERIALS AND METHODS:
GPS technology:
Global Positioning System (GPS) receivers provide a method for determining location anywhere
on the earth. Accurate, automated position tracking with GPS receivers allows farmers and
agricultural service providers to automatically record data and apply variable rates of inputs to
smaller areas within larger fields.
A GPS receiver can be compared with a simple AM or FM radio. A GPS receiver “listens” for
the signals that are broadcast from the satellites of the United States Department of Defense
(DOD) Global Positioning System. Orbiting around the earth at an altitude of 12,550 miles, these
satellites are in predictable locations; hence, we refer to the system of satellites as the GPS
constellation. Each satellite broadcasts almanac information containing the position of all
satellites in the constellation.
GPS receivers use the almanac to determine the position of the satellites. Minor variations in the
orbits of the satellites occur due to gravitational forces from the sun and the moon. The DOD
continuously monitors. The satellites and adjusts the almanac information to represent the actual
orbits of the satellites. The broadcast signals also contain a precisely timed predictable code that
a GPS receiver can use to determine how long the signal required to reach the receiver. A
microprocessor within a GPS receiver uses these delays and the position of the satellite to
calculate the distance to each satellite, and then uses this information to determine location
through triangulation. Triangulation is a mathematical method for locating points on a plane in
three-dimensional space. If the distances to each of three satellites and your approximate
Installation
GPS antennas should be mounted on the centerline of a combine, tractor or truck and above any
part of the machinery that might obstruct a line of sight to a satellite. If the cab is centered and
the top of the cab is above important for most agricultural applications and especially, for
guidance with applicators and aircraft. New technology in GPS receivers has shortened
reacquisition time. Receivers that can track 8-12 satellites are less susceptible to acquisition loss.
Width is usually fixed by the m/c or vehicle but ground speed is highly variabl
VRT controller:
The core of the VRT system is the flow rate controller. The heart of variable rate application lies
in the controller, which is a microprocessor or PC-type computer that ties in with the machinery
and controls and monitors application rates. A controller may be built specifically for a system,
or may be an entirely separate unit that can operate on many different types of machinery. A
controller may specifically control only one type of application (ie. sprayers), or may control six
channels through which different seeds, herbicides and fertilizers may be applied simultaneously.
Most controllers contain a ten year non-volatile memory.
Many controllers are used simultaneously with a laptop PC in the cab of the tractor, with this
system and DGPS an operator may see his/her position on the display as they move through the
field as well as the application rates, speeds, etc. Controllers that do not work directly with a PC
have some type of LCD display that shows application rates, travel speed, amount applied, area
covered etc. for most units described below this will be referred to as travel and application
information.
Essentially, the flow control system receives the set point flow rate from the application system
(likely a GPS / GIS system on-board the vehicle and then manipulates a number of actuators in
an attempt to adjust the actual flow rate to match the set point. At this point the error would be
zero.
There are two general types of control systems, open-loop and closed-loop. The open-loop
system does not use any sensors to determine feedback information. The actual rate is inferred
from actuator settings. This is roughly equivalent to driving a car with no speedometer and
attempting to control speed by your foot position on the throttle. You have no speed feedback
(the speedometer) and you don't know how to compensate for wind, vehicle loading or slope.
This approach is cheap but not adequate for the control.
With closed-loop control, the feedback is used to correct actual rate. In the case of liquid
application, flowmeter is generally used for feedback.
Sprayer and Spreader Technology:
In order for VRT electronic controllers to properly function, the mechanical technology must
exist that can change rates accurately in response to the control units. Traditionally sprayer and
spreader systems have been PTO driven, with rate control from the engine rotor; however, this
was for constant rates, and some uncontrolled rate variability remained. This problem has been
solved primarily through the use of hydraulic drive motors for chemical injection control and
granular metering. Systems that have remained PTO driven have been controlled via maintaining
a very high chemical/carrier pressure, with a pressure relief valve to maintain the desired nozzle
pressure. Solenoid valves are increasing in use due to the direct and accurate electronic control
allowed; a solenoid valve may be connected to a nozzle and be opened for a fraction of a second
in order to release a precise amount of chemical at a desired pressure and droplet size. Droplet
atomizers or micronizers are available to decrease the size of fluid droplets, thus increasing the
surface area of the applied chemical.
Hydraulic System
A simple hydraulic system was designed and installed on the tractor using the available hydraulic
resources in the tractor. As shown in Fig. 2, the system consisted of flow and pressure meters,
flow control valve and low speed hydraulic motor. Due to temperature concerns in this part of
the world where ambient temperature exceeds 50°C, oil temperature before and after flow con-
trol valve was monitored using two thermometers. A Praker Haniffen M030 gerotor drives the
calibrated rotary broadcasting spreader.
The angle between motor shaft and the spreader drive shaft exceeded 20° when spreader was
lifted to the upper level of the hydraulic hitching mechanism. A 2-universal joint shaft was used
to connect the two shafts together.
GRID SOIL SAMPLING
Grid soil sampling is a commonly used method for assessing variability in soil fertility and provides the
basis for variable rate fertilizer recommendations. In order to estimate soil requirements, the field was
gridded in 50-meter mesh and soil samples were collected from eight
Fig.1. GPS identified locations for soil sampling.
GPS defined locations. Soil analysis results were mapped and studied to find out the needed amount of
Calcium Super Phosphate to be added per hectare. In order to evaluate system performance and its
feasibility, soil chemical analysis of the same GPS defined locations, were carried out no later than two
ours after applying the fertilizers using the designed system under.
Developing the GPS-Guided VRT System:
A semi-automatic real time GPS guided, VRT-based system was developed locally. A 75 HP
Fiat tractor was used to vehicle and energize system components where traditional hydraulic
resources of the tractor were used as a power source to power a rotary spreader. System opera-
tion depended on using GPS sensors to precisely locate the vehicle's coordinate in the field and
using a specially developed prescription table to add the prescribed amount of fertilizer in the
associated location. To map P205 level in an experimental field with 50-meter mesh grid, eight
soil samples were collected from GPS-identified sites in the field. The prescription table was
developed as a result of knowing nutrient level in the field's different plots and next crop
requirements. Rhodes was the regular forage crop on the farm. A laptop received coordinates
information from a GPS unit where it was displayed and recorded. The driver followed the
instructions on the laptop to change hydraulic valve settings to change hydraulic motor RPM
accordingly. The spreader was calibrated according to ASAE Standard 341.3 (1999) and the
overall system was calibrated.
The calibration of the overall system was performed to develop the relationship between control
valve setting and the broadcasting rate. A color code of the valve settings was developed as a
result of both system calibration and prescription table for the three presumably homogenous
zones. The developed color code is a simple control guide to fit to the driver's educational
profile. According to soil sample analysis, the field was divided into three, presumably,
homogenous areas. Corresponding fertilizer application rates were calculated according to
technical recommendations and soil analysis results. The Green, Red, Blue (G, R, and B) code
was shown in the control valve area in front of the driver.
As shown in Fig., coordinate information flowed from the GPS receiver to the laptop, which dis-
played it in front of the driver. According to the prescription table and the color code of valve
settings, the software advised the driver of what valve setting was needed in this specific location
as a color message. When the driver changed a valve setting to the recommended one, hydraulic
motor speed changed along with spreader RPM and broadcasting rate.
Using DGPS and RTK Techniques:
The DGPS approach used corrections of the code measurements computed at the base (reference
station) to eliminate similar correlated measurement errors at the rover. This included satellite
clock biases and orbital errors as well as atmospheric (ionosphere and troposphere) errors. The
corrections are combined and formulated as range corrections, which are estimated as the
difference between the measured and the true satellite-to-receiver ranges, where the latter are
computed from the known coordinates of the base station and the observed satellites. The base
corrections are transmitted to the rover through data links.
On the other hand, the RTK positioning technique uses either phase measurements or their
corrections sent from the base to determine rover positions accurate to the cm level. Due to data
latency, which is the time taken to gather and send the data from the reference to the rover; the
corrections are sent instead of the raw measurements of the base. This is because of the fact that
the corrections change slowly with time while the raw measurements change rapidly. In addition,
due to latency, a method of predicting the phase corrections at the exact instant of measurement
of collection at the rover should be employed, which should take into consideration the expected
type of rover dynamics. From the known position of the base station, its phase measurements can
be constructed, and after solving for the carrier phase ambiguities On-The-Fly (OTF), a model
similar to that of code measurements, can be used to determine the coordinates of the rover
receiver.
VRT-Based Systems:
Present commercial VRT systems are either:
1. Map-based, requiring a GPS/DGPS georeferenced location system and a command unit that
stores an application plan of the desired application rate for each location within the field 2.
Sensor-based, which does not require a georeferenced location system, but includes a dynamic
command unit that specifies application through real-time analysis of soil and/or crop sensor
measurements, for each location within the field as it is encountered.
Lida et al (200 I) constructed a prototype of variable rate granular applicator for paddy field to
apply Nitrogen fertilizer. They mentioned that over fertilization is a potential source of pollution
in the form of Ammonia, Nitrate and Nitrite, which may pose a hazard to human health.
Therefore, a contemporary issue is how to give an effective dose at the accurate position and
right time for optimum growth of crops while preserving the environment without causing
economic losses. They added that, during the top-dressing operation.
Fig2. System Diagram
The field with Variable rate application consumed 12.8 % less of NK fertilizer than that of the
uniform rate application.
United States Environmental Protection Agency identified the agricultural sector as one of the
major contributors to soil and water pollution. They concluded that a better understanding of
yield variability across the field improve management practices by including spatial information
about the availability of soil water and nutrient status of the various field unit.
The standard deviation refers to the mean as a reference value; therefore, it may be used to
quantify the variability of soil fertility as stated by Jin and Jiang (2002). On the other hand, using
it to assess VRT based system performance would not be realistic. System assessment requires
the referred value to be the targeted nutrient level.
One of the means to measure and characterize application accuracy is computing the coefficient
of variance (CY). The coefficient of variance provides a quantification of spread variation and
accuracy. Low CYs indicate a more uniform spread distribution with 5 % to 10 % being a
desired range for spinner disc spreader. They added that, many factors affect fertilizer
distribution and application accuracy, such as systematic errors associated with machine
calibration and metering efficiency. However, Sogaard reported that CY's could be more in the
range of 15 % to 20 % under field-testing. These higher CY's are probably due to rougher
surfaces experienced under field conditions.
Parish (1991) reported CYs in the upper 20's to the lower 30's in some test cases with these high
variations resulting from terrain irregularities. They added that, ASAE standard Procedure for
Measuring Distribution Uniformity and Calibrating Granular Broadcast Spreaders (ASAE
S431.2, 1997) provides a uniform procedure for testing, assessing the performance, and reporting
the results of broadcast spreaders. It specifies test setup, c devices, test procedures, effective
swath width, and determination of the proper testing application rates. When using the outlined
procedure, the results provide a quantification of application accuracy and possible spread
pattern deviations. However, this standard does not cover the testing of broadcast spreaders with
VRT.
Guiding the tractor along a predefined path for tasks such as parallel swathing and to prevent it
from either leaving areas uncovered or over-fertilizing some areas was also possible since
positions were determined in real time. The software compared the current and target locations,
and the difference in distance (off-course distance) could be displayed to the driver, as well as
the direction to follow to reach the correct location. This feature was performed based on
computation of the azimuth between the two positions from their coordinates. Thus, on-line
guidance by GPS guarantees proper fertilization of all needed spots according to their actual
needs. In addition, if the fertilization process had to be continued for a second day, the stored
GPS positions when drawn on the field map would show the driver the exact area still to be
fertilized. Similar arguments are also valid for the herbicide and pesticide process.
CASE STUDY
The experimental field is a part of AI-Oha farm, a research facility of the UAE University.
Testing of the system was carried out in an open area of approximately 8.25 acres (33,000 m2).
The test area was rehabilitated sandy land prepared for cultivation and surrounded by a belt of
high trees for its four sides. The positions of the eight samples, as well as the test area
boundaries, were determined using a handheld GPS receiver. Vehicle path way was recorded.
CV was calculated for both cases before and after treatment as mentioned in (ASAE 1999).
Mean = X = ∑ (Xi/N), (2)
Standard Deviation = SD = {∑(X-Xi)2/ (N-1)}.5
CV = SD X 100, (4)
X
Where
X is arithmetic mean,
Xi is nutrient (P205) level in a GPS-identified location, ppm, and
N is number of GPS-identified Locations.
Table1. P2O5 level before and after treatment at GPS identified points
They compared yield under uniform and variable rate treatment. When they studied the effect of
variable rate application on yield variability, they concluded that the VRT had the lowest co-
efficient of variation in 5 of 6 blocks. They collected the spread fertilizer using 13x13 matrix of
collection pans to gather material spread by a spinner spreader truck. The result shoved that
spread variability existed with spinner spreader.
Fig.3 P2O5 levels in the field before and after treatment
Due to its vital importance in arid lands, super phosphate was the focus of this research where
Calcium Super Phosphate is the phosphate source. To evaluate P205 level in the field before
fertilization, eight soil samples were collected from eight identified locations in an 8.25 acre field
as shown in Fig. 2. The field was treated according to Rhodes grass fertilizers recommendations.
Points0f approximately equal P205 levels were given the same mark (G, S, or R), where each
group was recognized as a homogenous zone to simplify the control process. The resulted P205
levels were used to produce an interpolation of the whole field mapping of P205 as shown in Fig.
Table2. Targeted and actual P2O5 levels after treatment
P2O5 analysis before and after treatment was plotted in fig.3. It is clear that, P205 changed in the
field to some extend. In some parts there was an over dosage and in the other not enough
fertilizer was applied. Nutrient variability in the field is a major concern when system per-
formance to get evaluated. Other performance parameters should be considered such as accuracy
that indicates how successful it was to add the right amount of fertilizer in the corresponding
location.
For this specific research, CV values for P205 levels in the field before and after treatment were
86.66 and 51.29 respectively. That means, regardless the targeted level satisfaction, the system
improved uniformity of P20S levels in the field by 60 %.
A variable rate applicator, with GPS guidance, was designed and built locally. The semi-
automatic system depended on the driver to use the software recommendations to take a specific
action and change control valve setting to change application rate to suit a specific site. Driver
training allowed him to improve his time of response to deal with the prescription table. This
human factor could cause a great deterioration of system performance if the driver is not well
trained or is tired. This design saves money for the farmers who are not able to invest more
money in such a VRT based system. On the other hand, third world technological infrastructure
does not help farm machinery designers or manufacturers to use ultimate technology. The perfor-
mance of the developed system improved the uniformity of P20S presence in the field. Testing
procedures of the overall performance should be established in order to quantify system quality
and make it easier to compare between different systems working under different conditions.
CONCLUSION
According to result, variable rate fertilization was effective on reducing fertilizer without yield decrease and decreasing variations of growth and yield. And quality of grain in VRT plot was improved as compared to uniform rate application.Regional over-application of nutrients or pesticides can be avoided through variable rate technologies which is the need of sustainable agriculture. The rate-limiting steps of developing the appropriate maps and prescriptive treatments are rapidly being eliminated through the innovative use of emerging technologies such as remote sensing. Determined operators now have all the tools at their disposal to make environmental protection through input management a reality. In future VRT will be the only tool to reduce the soil, water, and air pollution caused by agriculture. There is no doubt that legislated regulations would force all farm operators to rapidly adopt such technology. However, the strong ethic common to farmers will result in voluntary adoption and implementation of those technologies that will ensure environmentally responsible agricultural input management.
REFERANCES
Books: 1. AMA (Agril. Mechanization in Asia Africa and Latin America)
2. Applied Engg. in agriculture.
Websites: 1. www . PrecisionAg . Org 2. www . google . com 3. www . snu . ac . kr