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