Precision Farming Midterm
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PLSC 244 Cal Poly Winter 2025 Dr. Wong
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What is Precision Ag?
The combination of Agronomy and Technology
Smaller regions such as Europe and Australia depend more on precision farming because of less farmland and labor supply so they have other learn to be way more efficient
how has site specific crop management changed over time?
smaller fields allowed for more specific management if crop
farmers “knew” the land and the plants
precision farming is the use of technology for site specific management
back when we knew the land better it allowed for more specific management techniques, could develop it based off of what the land needed
getting into the 80s sizes of farms and rates of consolidation increased
instead of relying on the farmer to know the land, rely on computers….
the accumulation of so much data makes it hard to know how to manage the land in a site specific way
USDA Farm statistics
definition of a farm is based on total sales: need to reach $1,000 or more a year
average size in the US is 444 acres (relatively small….)
40% of all farms in the use have $500,000 or more in sales
this group are the ones who are using precision agriculture
What is Precision Farming?
the proper and effecient management of a specific unit of area or space
all inclusive system that’s going to allow for us to monitor and detect
where when and how much we apply to every square inch at every point in time
technology we’re talking about wasn’t designed for us in CA
goal is to produce more efficiently with less inputs
it is truly about proper and specific management of a specific unit of area
which we’ll define the specific unit of area later
if we can define those units we can treat them differently in a way that is needs to be successful
How long has precision farming been practiced?
can argue for as long as farming has been existing
depends on the management unit you are discussing/how you define it
technically since agriculture began
Concept of precision farming?
use of technology to delineate space and time
Overlaying of data to create a “Complete Picture”
Tailoring of management practices within a field
how is the use of technology to delineate space and time a primary concept of precision farming?
trying to create an image of difference across an area/time
each area of space have specific requirements and the goal of precision farming is to be able to tell you the difference between the spaces
getting into your tractor and telling it to identify a certain place and it will take you there
how is the Overlaying of data to create a “Complete Picture” a primary concept of precision farming?
harvest all the plants and account how much it produced and overlay it and ask yourself the question of can you improve that spot and if you can how?
sometimes you will never improve that spot, dont farm there
concept is to produce more with less
how is the Tailoring of management practices within a field a primary concept of precision farming?
”farming by the foot”
can come up with a prescription for how much you need to each area
so you only use the fertilizer that you need
what are the main tools of the trade used in precision ag?
Global Positioning System (GPS)
Geographical information systems (GIS)
yield monitoring
remote sensing
variable rate technology
Global Positioning System (GPS)
system developed in US
live in the 90s
found in almost everything now
Geographical information systems (GIS):
kind of like a catchall, talk about it all the time but not specifically
extremely powerful if you know how to ask the right question
allows for us to collect the information so we can compare it and observe the differences to know how to manage areas differently
most of us dont have the ability to take in all the data and come up with solutions = decision support
collect info on specific attributes based on wherever you are in the world
accumulates all the info/data collected from yield monitoring and remote sensing
yield monitoring
system to collect attributes
how one specific area performs
remote sensing
system to collect attributes
The ability to scan and read differences in growth from a distance
no different than standing next to your field and looking at it
allows us to identify differences we can’t see
can do it from far distances (satellites so a great job)
variable rate technology
what we load out management strategy into
allows us to apply needed corrective measures per unit area
none of the rest of the tools matter if you can’t do this
what is variability? (in the context of ag)
variation in crop, soil, and environmental characteristics over space and time
how does precision allow for growers to manage variability?
spatial variability
distance and depth
how things change over distance and depth like how soils can change
Temporal variability
time
measure of how in this specific area how year to year changes causes differences
like weather, pest pressures,
Both of them together can create big differences
like having clayey soils and when it rains a lot it becomes water logged and plants die
some areas of sandy soils and do great when its rainy but not when its dry
one can exacerbate the other
what was the primary vision of precision farming?
Fully integrated system where all decisions are data driven
ie coming up with your fertility scheme
most popular/heavily used is auto steering because it requires no decision support (dont need to compile data to come up with a solution, you’re just driving straight)
simplest way to add more plants per unit area
can work longer
what are the barriers to the vision of precision farming?
technology is expensive
larger farms have more use for technology and can afford it
smaller farms began purchasing them because the realized they could make more money by using it
what were the results from the survey the university of Nebraska did on how the precision technology/ data was being utilized?
mostly are creating yield maps
almost all farmers had them and drew pretty pictures but they dont/didnt use the data to make data driven changes to yield production
How important is precision farming now that you have the technology?
How Goldman Sachs sees it:
Market Potential of Precision Agriculture
Goldman Sachs said precision ag is where you should put your money
Talked to companies, growers, academics
How will Agriculture keep pace with population?
Precision ag is where you should put your money
what are the promises of precision agriculture?
Economics
Should save us money
we’re not going to apply more than what we need
only going to invest in the things that need to happen so we’re not wasting resources
fuel and time
Brings back a huge amount of economic return
Efficiency
optimization
allows for us to match our application, seeding, irrigation rates etc to the soil. Utilizes the inputs we need in a more efficient manner
Production
able to ID where you can and can’t improve production and where you can apply your inputs to get the most benefit
Environment
not applying things in excess and not being wasteful of limited resources
what are the pitfalls of precision agriculture?
Too big and complicated
too expensive
what does that mean? - added cost
cost of data collection
inability to evaluate the benefit
dont often see huge improvements
what are the most important things to remember when navigating and thinking about using precision farming technology?
Precision farming will not make you a better farmer
Precision versus accuracy
Precision is measuring the differences where accuracy is the delivery of the application of those differences
don’t tend to spend enough money in the accuracy of our application
Resolution
smallest management zone you want to deal with whether it be 1 ft one yard 1 acre etc
higher the res the higher the cost
pick the one that’s profitable for you
Yield maps
only be developed for some crops
the creation of one is possible in every crop though
Traceability
issue, not as big in CA,
it all goes to John Deere and then who really owns your data
Why is GPS such a significant technological advancement in precision agriculture?
all other tools in the trade in precision ag rely on GPS
it can get precise to the millimeter
requires no decision support
What does GNSS stand for?
Global navigation satellite system
which country created GNSS?
designed by the US for US citizens to provide us with global navigation
which other countries now have GPS and what are the corresponding names?
GLONASS = Russia
EGNOS (Galileo) = European
BeiDue = China
What is a National navigation satellite system and how is it different than GPS?
NNSS requires less satellites because its at a national scale, not a global scale
allowed countries to know where you were in that specific country
only required to be in communication with 3-4 satellites because of the narrowed area
a lot cheaper
which countries have their own national navigation satellite systems?
IRNSS = India
QZAA = Japan
How many satellites do we have in orbit and how many are required for the accuracy of GPS?
we have 31 plus satellites in orbit but we only really need 24 however we use about 27 to tell us where in the world we are
communicating with other countries data like the europeans and the russians
tractor usually in communication with 27-31 satellites
Who first started the development of GPS?
Ivan Getting
during WWII he was the first one to develop microwave tracking for incoming missiles into Germany from England
first system other than radar
he died in 2003 but got to see the creation of his idea
he worked with Bradford Parkinson (a navy or airforce officer), a private company, and the US military for progress the development of GPS
What are the significant dates in the history of GPS?
1960s: feasibility run
1969: defense navigation satellite system (DNSS) formed
1973: pentagon appropriates funding initiating the exponential development, NAVSTAR GPS developed
1978: first 4 are launched
1995: in April the system is declared fully operational
took a while to become fully operational because the need at least 24 satellites in orbit to be a global system so there were a few holes to work out
what is selective availability and what did the government do to protect it?
allowed you to determine latitude and longitude to define a specific location
a code that was embedded into the satellite tech so enemies couldn’t access the technology
an error code and you need a decrypt key to unlock it
is selective ability still used today?
no, in 1999 the realized how essential this technology was becoming to the economy so they removed the embedded code on May 1st which allowed anybody in the world to find anything the chose
every satellite thats been built since 2018 no longer as the option to turn the crypt key back on so we’ll never lose the ability to figure out where in the world we are.
what are the three segments that go into making direct signaling/tracking to work?
Space: the 31 satellites
Control: the master station, monitor stations, and ground antennas
User
what is the significance of having the control segment?
it acts as a kind of checks and balances for the entire system. without it there would be degradation in our ability to identify location
it maintains the system so we can continuously provide correct locations over time.
which entity controls the GPS system and satellite launches?
Space force
Vandenberg has done the most recent launches in 2023
NASA and airforce used to do it
What are the primary components attributed to the space segment?
31 satellite vehicles distributed across 6 orbital planes with a 55 degree incline respect to the equator and each separated by 60 degrees
no matter where you are can pick up 3-4 satellites, without this the system wouldnt work as well
20,200 km in elevation
orbital period of 11 hours and 55 minutes
based off of elevation
5 to 8 satellites visible from any point on earth
what is contained in the GPS satellite vehicle?
three atomic clocks
three nickel cadmium batteries
two solar panel
S band antenna - satellite control
12 element L band antenna - user communication
what are the characteristics of the atomic clocks located in each GPS satellite?
its the key to the entire system because its how we are able to make it keep track of time and position is based on time
based entirely on time of signal i.e. it counts how long it took the signal to be sent and receiver can determine where it is in space
1 signal can tell where you are in a sphere along 1 orbit line
does not rely on atomic decay, it counts oscillation frequncy of electrons interacting/circling the nucleus
measured in the microwave region of the spectrum
1 second = 9,192,631,770 cycles of the Cs-133 Transition
not quite perfect, means we lose 1 second every 1.4 million years
what is the significance of the 12 element L-band antennas?
what communicates with out devices
collect the signal
determines where you are
how does satellite ranging work?
Basic trigonometry of triangulation to determine angle and distance to get height
gps we don’t have angles we have time so we use trilateration instead which uses time to determine location
given how long it takes for 3-4 satellite positions to travel to your designated location you can use those intersections of time to determine where your location is
your location is space is only as good as the geometry of the satellites you’re trying to communicate with
without a proper spread your data will be skewed i.e. why having a lot of them is good because their signal is based on line of sight
What are the different kinds of error you have to account for satellite signal interference?
orbital error
clock error
atmospheric error
multipath error
receiver error
these 5 affect your ability to determine location accurately leading to total error accounting for 10.4 meters (30ft)
what is orbital error and how do we try to overcome it?
controlled by control segment
can have a degraded orbit causing the satellite to not be in the same orbit
monitoring stations constantly communicating with satellites to know what time do they say it is and where they are in space
if the satellite is off, the monitoring station informs the base station that something needs to change and then it goes to a ground antenna
ground antenna can communicate to the satellite to fix their time and or location at any given moment
what is clock error and how do we try to overcome it?
controlled by control segment
the clocks have to be in synch to determine the correct location (the 4 of them) to they synch to each other and tell the receiver what the time is
can still lose time from gravitational pulls, etc
if the clock was off by one thousands of a second it would produce a position estimation error of 186 miles
if its off by a nanosecond its off by 3 meters
what is atmospheric error and how do we try to overcome it?
atmospheric refraction
delays satellite signal
troposphere
ionosphere: can delay a signal as is passes through, it can slow it down pass the speed of light which can be problematic because we’re relying on the signal traveling to us directly and at a constant speed
delay is variable: signal has to travel through a greater distance the closer it gets to the horizon so the system has to account for this
what is multipath error and how do we try to overcome it?
a lot of things can reflect the signal
surface that reflects and or blocks the signal like metal buildings, water, trees, etc
it has to go a greater distance if it bounces therefore your location will be slightly off
why autosteer in orchards are so hard
when theres a clear sky the quality of the signal is better
Example of a lawsuit by FAA towards 3 Georgia farmers whose center pivot irrigation system was interfering with their signal for air traffic
what is receiver error and how do we try to overcome it?
location ID is really based on how good your receiver is
quality of signal depends on if your single or dual frequency
the L-band antennas of the satellite is what the receiver connects to so if you can only connect to one the accuracy is less so that’s why you want dual frequency so you can connect to more than 1 L-band
how well so YOUR receiver keep time? it has to be able to keep and maintain time
receiver needs to have correction
there are three kinds: Differential, WAAS, RTK
What is DGPS?
differential correction
simplest form of correction (we dont use this one)
developed for shipping
satellites are in motion
location of base stations: closer you are the more accurate it is because you are communicating with the same satellites the base stations are correcting
these stations asks the satellite where the station is and can correct for any differences/error the satellites say because the stations position is fixed
What is WAAS?
Wide Area Augmentation System
better than DGPS
developed for airplanes
has base stations (similar to DGPS) called reference stations: in constant communication with air traffic and satellites account for how much correction is needed
corrections are uplinked to geostationary satellites which then distributes correction (augmentation signal) to a wide area
AG equipment uses WAAS
GPS will be 1-3 meters off
cheaper and GPS is free
accurate for flat plains, not super useful in CA so we use a different system
Privately held satellite based augmentation systems
Omnistar
Swift
NAVCOM (John Deere)
What is RTK?
Real Time Kinematic = “the Tractor that Einstein Built”
the airplane landing itself story
1984: NASA gravity B programs begins
1994: GPS integrity beacons
1999: RTK autosteer
it can recognize where it is at any given second without being off for more than a …..
how does RTK work?
Clock analogy
embedded within the L-band (the GPS within all satellites) is a pseudo random code which repeats itself every millisecond
when you want to know where you are it waits for the pseudo random code to come along and to be the starting point and then counts how long it takes for the code to repeat itself allowing it to determine time
if we know what the millisecond it, we can determine the hour (too long, and not specific enough)
theres a carrier signal within the RTK GPS which repeats much faster (0.365 microseconds) which allows for the calculations of seconds, minutes and hours so we have a more precise location at any given moment
What are some of the qualities of precision guidance that were significant to its development?
the differences between passes tractors would make in and out of the field were less than a millimeter
the straighter you could drive, the more plants you can fit per area and it was hard to do that as a human steering. took a lot of skill
guidance trackers were one of the first adopted technologies for large acreage growers
What are some significant dates to the development of autosteer/guidance trackers
Early 1980s = disc marker or nothing at all on a wing up pull machine (a pain)
cut a groove - hard to see
lost accuracy over time
Late 1980s = foam marker introduced
on the end of the tratter, leave little foam marks - kinds like shaving cream
easier to see
1990s = chemical and fertilizer and seed cost steadily increase
overlaps started costing you more money
especially with over planting - loosing plants
what was the light bar system/display?
a past example of auto guidance tracker/ Autosteer
has red lights that start all the way out and three green lights in the middle
if you are three feet off to the right, you see 3 red lights, correct then you see 3 green light
most people would overcorrect
How accurate is the RTK system?
very accurate = was tested in 2 ways
basic: circle track with people driving around it with RTK system at different speeds
pass to pass error: went around the track and would flip around to see how much variation there was. there was up to 4 mm variation which was really good
what are the differences of accuracy between GPS correction systems?
accuracy is the selling point for most companies
WAAS guarantees 1-3 meter accuracy when in actuality its 3 ft or less 90% of the time
RTK guarantees 1-2 inches
Submeter and decimeter are not as common
what are user supplied base stations and why are the helpful?
location on a designated location
provides differential correction to local area
transmits signal via AM, FM, or cellular
size of area dependent on signal strength
most FM transmitters are line of sight
can’t have any obstructions - higher you can get it the longer the line of sight
RTK clusters/networks
John deere came up with this and maintained them
30 RTK towers that cover 8 million acres
different clusters owned by different companies
John Deere has a sub service that allows you to cross clusters
how has the adoption of RTK GPS systems increased overtime?
its on the rise
larger farms ~ 5,000 to 10,000 farms: in CA veg growers would hire wilbur ellis who would list their fertilizer and they would use RTK
growers didnt need it but companies did
ever increasing inputs cost make RTK attractive to better optimize resources
using RTK you don’t need high visibility
allows for almost anybody to operate it helping with issues related to labor shortages
machine efficiencies: machine never sits and just rotate out emloyees
what are the downsides to GPS?
most of the basic systems are designed to drive straight until they cant anymore which means it will do that until you tell it not to, it didn’t matter is there was a power line, highway, or pond
more of an operator error
evolution of Autosteer
an attachment was made for the steering wheel column but wasn’t very accurate because of slippage
direct attachment to hydraulic system of the steering column i.e. behind the seat which is what we have now
what are the three qualities essential to keeping the tractor straight?
need to be able to detect 2 of the 3 dimensions at any point at minimum
Roll: change in elevation from light to right
has to work against gravity
Pitch: change in elevation from back to front wheels
Yaw: Tail swing/sliding or turning motions to the left or right
how do the tractors accommodate effects of roll-pitch-and yaw?
using terrain compensation sensors
inertial sensors calibrated for roll, pitch and yaw
some companies couldnt do all: Autofarm could do all of them but it was a massive device
most look like the Starfire one from John Deere (looks like a little globe)
integrated GPS/GNSS receiver
what can cause degraded position in RTK GPS systems?
loss of satellite or radio signal (solar storm from a massive sunspot disrupted the signals last spring)
what are the main benefits of Autosteer?
reduced overlaps and skips
increased speed of field operations
extended workday
greater flexibility in labor
appropriate placement of inputs
What are two examples of driverless tractor systems
Supervised Autonomy: Case IH and John Deere
human sit in tractor while tractor does work
Fully Automated: Kinze and Fendt
functions completely by itself
could be remotely handled
Example of a supervised autonomy driverless tractor
John Deere: Machine Sync
Operator of the grain cart stays with the tractor–set up within the
combine a certain area–as soon as the tractor enters that area,
the grain cart relinquishes control to the harvester finding a speed
and location directly underneath the harvester, once full-it releases
the control back to the operator to be unloaded
The harvester and wagon are about 4 ft from each other, taking
the pressure off
This is not free, costly
Each harvester is preset with wifi signal, tractor picks up signal, can see harvester analytics
Can steer tractor within combine
Example of a supervised autonomy driverless tractor
Kinze: created to save time during harvesting so the tractor wasn’t sitting idle. 2 operators running the truck and 1 for the harvester. allowed for a constant harvest and to do more with less people however it required too much back and forth from truck to tractor and ended up being idle lol
John Deere: very sensitive to shadows, different moisture content, colors, etc which cause it to stop and be idle to burn 10-15 gallons/acre of fuel that’s not being used for anything. seems annoying
What is GUSS?
Global Unmanned Spray System
automated blast sprayer (liquid)
safety accuracy and manpower….?
is radar over gps but is programmed with GPS coordinates
has a series of cameras and if anything moves in front of it, it stops
only thing that goes wrong = replacing nozzles causing a change in pressure so they i set pressure thresholds (max and min) to regulate this. if it passes the threshold it turns off
very little goes wrong with this than seeders or rippers
10 of the machines can be operated by 1 person
What is the Farmwise Titan?
cultivator that has a series of knives that cut out soil- recognizing where a plant is and where it isnt
a truly automated tractor
but does it really kill the weed?
John Deere and Case fully autonomous
fully electronic
both do not have a tractor seat in them (has a cabby that attaches the front so you can drive it down the road)
drive it with a remote
hook up to implement and run
case
no cab, remote control system
does fully autonomous make sense or is having it be semi better?
what would be the value of implement guidance?
guidance systems as of right now can detect slope and the implement should follow however its only designed for the tractor to go straight which doesn’t include the implement
it would:
minimizing sliding on hills
prevents walking across old rows, sub-surface rip lines, or variable soils
reduced climbing plant beds or jumping rows in minimum tillage practices
what are the two kind of implement guidance?
passive
active
what is passive guidance and what are some examples?
the implement doesn’t do anything but the tractor does everything I.e. the implement is passive to the system: ex - tractor moving opposite to how gravity is pulling seeder to keep seeder where it needs to be
Trimble - true tracker
John Deere - iGuide
have to have a gps receiver on the implement too so that it can be in communication with the tractor
what is active guidance?
on the implement itself they put a rutter (smooth discs) to steer the implement
moveable hitch: hydraulically attached hitched that has the ability to swing certain distances
coulters (the discs) allow you to see the implement where you want it so if you need it to shift/steer it’ll stay there
people put cameras on them so the implement can track and stay clear of the the plants
need to put a gps receiver on the implement so tractor and implement can be in communication
allows implements to turn easier
really good time saver
total people using them is pretty slim
used in CA mostly for cultivating
examples
auto farm - AFTracker
sunk - acura trak
rothmans - GPS ready tractor
what are the main takeaways from GPS and RTK systems in the context of Precision Farming?
great systems for simplifying farming so the operator can move in a straight line
allows us to utilize controlled traffic farming
what is CTF?
controlled traffic farming
been around for a long time, had projects for this before GPS
could you improve agriculture by reducing compaction was the main goal
what is RTF?
random traffic farming
creates random amounts of soil compaction at different parts
changes from day to day and place to place because of variability weather, soil types/textures, etc
fields had varying levels of productivity with differences in height, color, etc because of compaction
driving angle you’re breaking up some of the compaction but also leaving some
what are the benefits of CTF?
lower energy for driving and cultivation: easier to drive on a compacted soil bc you’ve basically put a highways in your field and the tractor rolls easier
more reliable field access: bc infiltration of water in lower compacted areas and more run off on compacted areas resulting in quicker processing of water that fell on the field
lower machinery investment: less horsepower required to break compacted
better seed beds
better utilization of minimum and no-till
improved crop yields
improved soil structure
improved field efficiency
improved environmental conditions
what are the drawbacks of CTF?
doesn’t work well in all systems
does well in grain and cotton
Seasonal CTF
organic farm in Netherlands couldn’t use CTF year round
vegetables
wheats
herbs
found that even not doing it all of the time means he lost some improvement but there were still benefits for doing it some of the time
Other uses of CTF
standing stubble: kind of like rotating intercropping by changing your planting lines from season to season to reduce soil disturbance and will eventually will get to the same starting point
shielding sprayers for specific sprays (RTK)
why do we want to sample our soil?
to maximize yields and to make informed-data driven management decisions for the health and productivity of our crop
determine fertility req to minimize crops inputs. the more specific the better but thats really costly
it also really determines our ability to be precise
what is the average soil sampling recommendation?
most people tend to do the bare minimum cuz its $
recommended 1 for every hectare (2.4 acres)
gallup pole example
interviews 100 people to represent 170 million people
pulling 50 soil cored in a 160 acre field is like gallup interviewing 2
how can you get a quality recommendation based off this
what are the implications of having a small sampling size?
small # of samples may not show variability
if variability exists don’t we want other measure it?
what are the most common sampling methods?
composites: bas because it averages all the needs across the entire field
grid sampling: has some value, simple concept, depends on how many the the size of your grids
direct sampling: requires more info than the others, what are the different soil series? what were the previous uses? yield mapping
different methodologies determine how we can use the data
what is the relatively common procedure to conduct grid sampling?
create a field boundary
assign the grid
create a grid map using gps/gis for your area to 1. know where the sample was taken 2. measure the distance between samples 3. create an interpolation map
match sample ID to grid
whats a soil interpolation map?
a way visualize what’s happing with the soil as you go from here to there
What is soil test pro?
mobile App
draw field boundary
develops grid: effect of grid size on map resolution: how much detail do you want? larger, the less detail
identifies GPS sampling coordinates
sample
send
wait for results
wha tare the advantages to gris sampling?
assess nutrient variability present in the field
no field history needed
identified hot spots/trouble area (assuming its large enough in size)
targets inputs where needed (within reason assuming that sample point represents that 2.5-5 acre grid)
minimum skill level
what are the disadvantages to grid sampling?
no justification for grid sizes
grid arbitrarily places in field
grids aren’t perfectly square
ignores soil properties and field characteristics
labor and time intensive
expensive
what is directed sampling?
looks at your field and makes certain determinations about it for example if you have a known area that’s higher in saline or you have slope
another name for zone sampling is directed sampling because our awareness of different zones in a field “direct” us to sample them
in order to make a good zone you need to know the field
zones take years to create
farmer knowledge becomes very important for this method
what are the advantages of zone sampling?
zones delineated based on past field performance and intrinsic properties ( ie a creek running through it, etc)
classified spatial variability: defines why we see differences
reduced time and labor: specifically with sampling
more economical based on the qualities listed above
provides some information that the other ones doesn’t
disadvantages to directed sampling
greater initial time and financial investment to implement zone management
higher skill level required
requires field knowledge
what is essential to the interpretation of grid and direct samples?
NEEEEEEED GIS/GPS data
if you dont know where it was taken what good is that
maps are drawn according to the estimation between two points
interpolations: different kinds can be used depending on the dataset
automated soil samplers
to capitalize on higher density soil sampling several companies have developed machines to simplify the job
falcon soil sampling
agrobotics autoprode
winter 1000 soil sampler
how often should you sample?
every year do a general 5 acre grid
monitors how much change is going on
every 5 years do a high intensive grid
soils change with time
what are the limitations of traditional soil testing?
they’re relatively inadequate about determining overall soil quality
inadequate recommendations algorithms
high cost of soil sampling and analysis
what are the seven on the go soil sensor types?
electrical capacitance and resistance: (correlated with soil parameters)
optical and radiometric: most of what we do in class
electrochemical: like taking pH
mechanical: measure force (can help determine compaction)
acoustic: sound waves
pneumatic
top three are the most commonly used and when you combine them you get a pretty good sense of overall soil quality bc each one targets a different soil characteristic (except doesn’t do compaction)