Top 10 lessons learned

in 6 years of on-farm sensor demosPeter Scharf

University of Missouri

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123 fields123 fields

#11: Works with any kind of equipment

Crop sensors can be used for Crop sensors can be used for sidedressing anhydrous…sidedressing anhydrous…

sensorssensors

…or sidedressing solution

…or with a high-clearance spinner

…with a big sprayer

…or a big injector

#10.5: Farmers like toys#10.5: Farmers like toys

…With Raven, Raven Viper, Rawson, Falcon, or MidTech controllers (thanks, Scott!)

…but not AgLeader InSight, Deere, New Leader: no serial input!

#10: Lots of preparation goes into a successful demo

(or adoption)

Preparation

• Recruit cooperators• Build brackets to hold sensors

on the applicator• Controller: port?!,

communication parameters, programming

• Coordinate plan for preplant N• Apply high-N reference area• Plan for yield documentation

#9: It’s important to filter out readings from bare soil

Filtering soil

• Not as easy as it sounds• Different ‘reflectance’ for:

– Different soils– Same soil with different moisture levels– Same soil with different residue levels

• If you don’t, you’ll put high N rates on thin (or nonexistent) stands

• Angled sensors may also solve this problem

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V7, 2009

High-NHigh-Nreference valuereference value

N rate = 220N rate = 220

Average N rate with all data = 248

Bare soil cutoff?Bare soil cutoff?Average N rate with cutoff = 161

Bare soil cutoff value

• When we do a demo, measuring bare soil is the first thing we do when we pull into a field

• Then we set a cutoff value to discard any data at or near this value

#8: We can combine sensors with other information sources to make

N rate decisions

We’ve combined sensors real-time with:

• Yield zone maps– Add to sensor-based N rate in high-yield zones– Don’t modify in medium-yield zones– Subtract from sensor-based N rate in low-yield

zones

• Future N via lagoon effluent through pivot– Calculate sensor N rate, subtract lagoon N

from rate

Productivity Zones and Treatment LayoutYield zone example

Low: subtract 25Medium: don’t changeHigh: add 12

#7: Varying rates of liquid N (anhydrous or UAN solution) is hard

Varying flow rates is difficult

• Double flow requires 4x pressure

• Highest rate = highest pressure (100 psi?)

• What happens as you drop pressure?– Distribution along bar or boom becomes

uneven– Starts at about ¼ max (25 psi?)– N rate = ½ max

• If top rate = 150, bottom rate = 75

Is this good enough?

• Yes, but it would be better to have a wider range

• New nozzle bodies with spring-loaded orifice– Orifice gets bigger as pressure increases– Available from Greenleaf, SprayTarget– Gives wide rates, even spread, and doesn’t

pop hoses

#6: A good reference value is crucial

What about Virtual Reference Areas?

Virtual reference exampleHigh-N reference area

Average N rate = 96

Best 5% from strip with 75 lb Pre-plant

Average N rate = 73

Best 3 sec from strip with 75 lb Pre-plant

Average N rate = 43Producer N rate = 60

This N rate out-yielded producer rate by 18 bushels

#5: Sensor values drift

(Nitrogen need doesn’t)

Sensor values drift during the day

Sensor values drift during the day:Vis/NIR

6AM 8PM

8 days of measurements

Same plant all day long

Error in N rate due to drift:Crop Circle Vis/NIR

6AM 8PM

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Error in N rate due to drift:Greenseeker Vis/NIR

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Greenseeker error in N rate reduced using NDVI equation

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Greenseeker error in N rate reduced even more using

correction equation

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Why do sensor values drift during the day?

Water effects on sensorsWater effects on sensors

Strips with producer N rate

PM

Next AM--dew

Water changes sensor values

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Greenseeker Crop Circlewatering

My recommendation:To avoid bad N rate

decisions, re-measure high-N reference area at

least every 2 hours (especially with Greenseeker)

Crosswise high-N reference strips: Crosswise high-N reference strips: a slick way to update high-N valuea slick way to update high-N value

High-N High-N reference reference stripsstrips

Program system to Program system to update reference update reference value every time value every time you drive across you drive across them (Scott!)them (Scott!)

With a plane, With a plane, you could do a you could do a lot of these in a lot of these in a hurryhurry

#4: Watching the sensors work sells them

#3: Sensors can’t do everything

What can’t they do?

• Sensors can’t distinguish between low N need and zero N need

• ‘Top up’ is the wrong idea

• Sensors can distinguish between low, medium, and high N need

• Give them room to work by applying low or zero N preplant

#2: Timing is the biggest issue to producers, retailers, advisors

N sensor meeting, March 2009

• Producers, retailers, consultants, agencies, researchers, extension folks

Topics we could discussTopics we could discuss

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7%

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38%

21% 1. Obstacles to success2. Timing risks and benefits3. Need for preplant N4. Sensor availability, pricing, issues5. How many sensors are needed?6. Producer vs. retailer applicators7. Features you’d like to see8. Corn vs. wheat (vs. cotton)

Obstacles to successObstacles to success

9%8%2%8%7%22%20%13%11% 1) Need for high-N reference area

2) Cost of application equipment3) Risk of not getting done at planned time4) Good equations to predict N rate5) Sensor cost6) Limited range of liquid rates7) Sensor values drift during the day (return to ref area?)

8) Conflicts with other field activities9) Emergence skips = soil interference

Timing risks and benefits

• Want to go early!

• Sensors: 7-10 days later than normal sidedress– True for corn, cotton, wheat– Even people who always sidedress balk– Why?– Farmers like to get things done!

Timing risks and benefits

• Risk:– Don’t get done with planned equipment

(tractor, for example)

• Solution:– Limit acres using sensors

• Most variable land• Or land with biggest chance of reducing N rate

– OR Have plan B for those years when you don’t get finished using planned equipment

Corn N timing: Full yield can be Corn N timing: Full yield can be achieved even with late applicationsachieved even with late applications

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Yield response to N depends a lot Yield response to N depends a lot on need, not much on timingon need, not much on timing

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Eight production corn fields, 19978 small-plot trials in producer fields, 1997

Field with low need for N

Field with high need for N

Timing risks and benefits

• Benefit:– Low risk of N loss before crop uptake

• How much of a benefit is this?– It depends on the weather—big benefit when wet– I estimate an average yield hit of 20 bu/acre this year

between here and Missouri (windshield survey)

• Big benefit last two years in Missouri• Widely used in southeastern U.S.

– More rainfall than midwest

180 N at 180 N at planting: LOST!!planting: LOST!!

110 N at knee high:110 N at knee high:DELIVERED!DELIVERED!

Sidedress N kicks butt in 2008Sidedress N kicks butt in 2008(and 2009)(and 2009)

+38 bushels+38 bushels

Wheat: topdress N timingWheat: topdress N timing

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April: probably too late

#1: We can make money managing N with sensors

Making money with sensors

• Compared to what?

• Compared to current producer practice

• Head-to-head comparisons– At least 3 sensor, 3 producer rate strips/field– Total 55 fields 2004-2008

ProducerProducerRate = 100Rate = 100

Sensor RateSensor RateAve. = 73Ave. = 73

August 1 Aerial Photo after the June 13 UAN Application

215.4 212.1 204.2 212.4 215.5 204.9 206.6

214.1 208.0 208.5 206.6 206.6 211.6 205.4

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Making money with sensors

• 55 side-by-side comparisons

• Sensor outcomes:– 2 bu/acre yield increase– 14 lb N/acre saved– $13/acre at this year’s prices– $19/acre at last year’s prices

• Making money with sensors is easier when prices are high

Making money with sensors

• Different in different years

• 2004-2007– No effect on yield– Saved 24 lb N/acre

• 2008 (very wet year)– Used 15 lb extra N/acre– Made 8 extra bushels

– Adjusted for wet weather and N loss!

Making money with sensors

• Even easier with program support• Missouri NRCS: EQIP-approved practice since

2006– 2006: $60/acre ($20/acre x 3 years)– 2007: $38/acre ($19/acre x 2 years)– 2008: $73/acre ($36.50/acre x 2 years)

• But not easy for grain farmers to get EQIP conracts

• Rumor: substantial 2010 EQIP money for nitrogen management

Making money with sensors

• We’re making money:– At any growth stage from V6 to V16

– Whether we lower or raise N rate relative to the producer’s rate

– At any yield level

– At any preplant N rate

• We’re losing money when the reference area is bad

An advertisement to end:Nitrogen Watch feature on my

website

Areas shown in cross-hatch are ‘danger areas’

Nitrogen watch for well- and moderately well-drained soils