Spatial Variability in Precision Agriculture What is it? What is it? – Precision n. The quality or state of being precise. Used or intended for precise.

Spatial Variability in Spatial Variability in Precision AgriculturePrecision AgricultureSpatial Variability in Spatial Variability in

Precision AgriculturePrecision AgricultureWhat is it?What is it?

–Precision Precision n.n. The quality or state of being The quality or state of being precise.precise.

Used or intended for precise measurement.Used or intended for precise measurement.Made for the least variation from a set Made for the least variation from a set standard. (Webster, 1995)standard. (Webster, 1995)

–Precise Precise adjadj. Capable of, caused by, or . Capable of, caused by, or designating designating an actionan action, performance, or , performance, or process process carried outcarried out or successively or successively repeated repeated within close specified limitswithin close specified limits (Webster, 1995).(Webster, 1995).

What is it?What is it?–Precision Precision n.n. The quality or state of being The quality or state of being precise.precise.

Used or intended for precise measurement.Used or intended for precise measurement.Made for the least variation from a set Made for the least variation from a set standard. (Webster, 1995)standard. (Webster, 1995)

–Precise Precise adjadj. Capable of, caused by, or . Capable of, caused by, or designating designating an actionan action, performance, or , performance, or process process carried outcarried out or successively or successively repeated repeated within close specified limitswithin close specified limits (Webster, 1995).(Webster, 1995).

Precision AgriculturePrecision AgriculturePrecision AgriculturePrecision AgricultureWhat is it?What is it?

–Precision in management?Precision in management?–Knowing more precisely the Knowing more precisely the

size of fields, size of fields, level of inputs (rates), level of inputs (rates), yields, yields, $ costs, and $ costs, and $ returns?$ returns?

What is it?What is it?–Precision in management?Precision in management?–Knowing more precisely the Knowing more precisely the

size of fields, size of fields, level of inputs (rates), level of inputs (rates), yields, yields, $ costs, and $ costs, and $ returns?$ returns?

Precision AgriculturePrecision AgriculturePrecision AgriculturePrecision Agriculture

What is it?What is it?–Management of production inputs in Management of production inputs in relation to more precisely delineated needs relation to more precisely delineated needs (Johnson, 1/18/01).(Johnson, 1/18/01).

Recognizes Recognizes spatial variabilityspatial variability of production of production needs needs withinwithin a population of a population of production units, production units, where production units are where production units are smaller than they smaller than they used to be.used to be.

What is it?What is it?–Management of production inputs in Management of production inputs in relation to more precisely delineated needs relation to more precisely delineated needs (Johnson, 1/18/01).(Johnson, 1/18/01).

Recognizes Recognizes spatial variabilityspatial variability of production of production needs needs withinwithin a population of a population of production units, production units, where production units are where production units are smaller than they smaller than they used to be.used to be.

Spatial variability among Spatial variability among production units.production units.


What is the size of a production unit?Depends on the enterprise.

– Small dairy = single dairy animal.– Wagoner Ranch, TX = 7,000 – 8,000 acre

wheat field.Agronomic units = “fields”

What is the size of a production unit?Depends on the enterprise.

– Small dairy = single dairy animal.– Wagoner Ranch, TX = 7,000 – 8,000 acre

wheat field.Agronomic units = “fields”



What causes field delineation.– Natural boundaries.

Rivers Rock out-crops

– Political boundaries. Roads Survey units

– Land ownership Consolidation

What causes field delineation.– Natural boundaries.

Rivers Rock out-crops

– Political boundaries. Roads Survey units

– Land ownership Consolidation



What causes field delineation.– Soil productivity appropriate to the crop (e.g. bottom land

for alfalfa).– Size determined by land use

Government acreage restrictions (CRP) Tees, fairways, greens

– Size that is “convenient” to the operation for administering production inputs.

Cultivation Planting Harvesting (mowing) Fertilizing Irrigation Etc.

What causes field delineation.– Soil productivity appropriate to the crop (e.g. bottom land

for alfalfa).– Size determined by land use

Government acreage restrictions (CRP) Tees, fairways, greens

– Size that is “convenient” to the operation for administering production inputs.

Cultivation Planting Harvesting (mowing) Fertilizing Irrigation Etc.

Spatial variability (macro) for Spatial variability (macro) for agronomic land use.agronomic land use.


Inherent (natural).– Related to soil productivity and soil

forming factors Time Parent material Climate Vegetation Slope

Inherent (natural).– Related to soil productivity and soil

forming factors Time Parent material Climate Vegetation Slope

Soil acidity and Oklahoma Soil acidity and Oklahoma rainfallrainfall

Soil acidity and Oklahoma Soil acidity and Oklahoma rainfallrainfall

Usually acidic

Usually not acidic



Acquired (use induced). Influence of historical crop production on

soil properties.– Alfalfa vs. wheat for acidification and soil organic

matter. – Fertilizer use and change in soil fertility (Garfield

County).

Acquired (use induced). Influence of historical crop production on

soil properties.– Alfalfa vs. wheat for acidification and soil organic

matter. – Fertilizer use and change in soil fertility (Garfield

County).

Soil Test P Variability Among First 50 Free Soil Tests for Garfield County Oklahoma, 1997

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1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49Entry Number

Soil T

est P

Soil Test P Variability Among First 50 Free Soil Tests for Garfield County Oklahoma, 1997

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1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49Entry Number

Soil T

est P

C.V. = 54; ave = 73C.V. = 54; ave = 73

Acquired spatial variability (macro).Acquired spatial variability (macro).Acquired spatial variability (macro).Acquired spatial variability (macro).

Garfield Co. Farmer’s Use of Soil Testing and FertilizationGarfield Co. Farmer’s Use of Soil Testing and FertilizationGarfield Co. Farmer’s Use of Soil Testing and FertilizationGarfield Co. Farmer’s Use of Soil Testing and Fertilization

PreviousPreviousPreviousPrevious GrainGrainGrainGrain Normal FertilizationNormal FertilizationNormal FertilizationNormal Fertilization Soil Test ResultsSoil Test ResultsSoil Test ResultsSoil Test ResultsAcresAcresAcresAcres Soil TestSoil TestSoil TestSoil Test YieldYieldYieldYield NNNN PPPP2222OOOO5555 KKKK2222OOOO pHpHpHpH NNNN PPPP KKKK

SurSurSurSur SubSubSubSub86*86*86*86* 1981198119811981 35353535 100100100100 46464646 4.54.54.54.5 24242424 54545454 106106106106 445445445445

118*118*118*118* 1981198119811981 25252525 100100100100 46464646 4.94.94.94.9 53535353 108108108108 88888888 41141141141130*30*30*30* 1989198919891989 34343434 100100100100 46464646 5.15.15.15.1 44444444 43434343 75757575 37737737737765*65*65*65* 26262626 100100100100 46464646 4.44.44.44.4 115115115115 118118118118 159159159159 75275275275250505050 1981198119811981 29292929 100100100100 46464646 5.55.55.55.5 0000 70707070 44444444 551551551551

*Savings from no fertilizer to four fields = 299 acres X $24.50/acre, = $7,325*Savings from no fertilizer to four fields = 299 acres X $24.50/acre, = $7,325*Savings from no fertilizer to four fields = 299 acres X $24.50/acre, = $7,325*Savings from no fertilizer to four fields = 299 acres X $24.50/acre, = $7,325

Cost of not managing acquired Cost of not managing acquired spatial variability (macro).spatial variability (macro).

Cost of not managing acquired Cost of not managing acquired spatial variability (macro).spatial variability (macro).

Acquired spatial variability (micro).Acquired spatial variability (micro).Acquired spatial variability (micro).Acquired spatial variability (micro).

pH=4.9pH=4.9BI = 6.6BI = 6.6N = 10N = 10P = 93P = 93K = 435K = 435

BottomBottompH=5.2pH=5.2BI = 7.0BI = 7.0N = 13N = 13P = 54P = 54K = 354K = 354

Terrace 1Terrace 1

pH=5.3pH=5.3BI = 6.9BI = 6.9N = 10N = 10P = 44P = 44K = 415K = 415

Terrace 2Terrace 2pH=5.7pH=5.7BI = 6.9BI = 6.9N = 20N = 20P = 23P = 23K = 397K = 397




UplandUpland

pH=7.3pH=7.3BI = --BI = --N = 67N = 67P = 22P = 22K = 343K = 343

““BadBadSpot”Spot”pH=5.2pH=5.2

BI = 6.8BI = 6.8N = 14N = 14P = 49P = 49K = 408K = 408

FieldFieldAverageAverage

pH=4.6-5.7pH=4.6-5.7BI = 6.6-7.0BI = 6.6-7.0N = 10-20N = 10-20P = 23-93P = 23-93K = 310-522K = 310-522

FieldFieldRangeRange

““Cow Pocks” in wheat pastureCow Pocks” in wheat pasture““Cow Pocks” in wheat pastureCow Pocks” in wheat pasture


STP 1996, EFAW

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Feet North

Soil

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P

STP 1996, EFAW

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Soil

Test

P


Ave = 47; CV = 30Ave = 47; CV = 30

1x1 1x1 (60-acre cell)(60-acre cell)1x1 1x1 (60-acre cell)(60-acre cell)

6x4 6x4 (2.5 acre/cell)(2.5 acre/cell)6x4 6x4 (2.5 acre/cell)(2.5 acre/cell)



50x3250x32 (0.0375 acre/cell) (0.0375 acre/cell) 50x3250x32 (0.0375 acre/cell) (0.0375 acre/cell)

100x64 100x64 (45 yd(45 yd22/cell)/cell)100x64 100x64 (45 yd(45 yd22/cell)/cell)

200x127 200x127 (11 yd(11 yd22/cell)/cell)200x127 200x127 (11 yd(11 yd22/cell)/cell)

472x300472x300 (2 yd (2 yd22/cell)/cell)472x300472x300 (2 yd (2 yd22/cell)/cell)

Management ZonesManagement ZonesManagement ZonesManagement Zones

A

BC

Fundamentals of Nutrient Fundamentals of Nutrient ManagementManagement

Fundamentals of Nutrient Fundamentals of Nutrient ManagementManagement

Plant Growth and Soil Nutrient Supply Relationships

•Mitscherlich (1909)“…increase in yield of a crop as a result of increasing a singlegrowth factor is proportional to the decrement from the maximum yield obtainable by increasing the particular growthfactor.”

dy/dx = (A - y) c

Law of “diminishingreturns”


•Mitscherlich (1909)“…increase in yield of a crop as a result of increasing a singlegrowth factor is proportional to the decrement from the maximum yield obtainable by increasing the particular growthfactor.”

dy/dx = (A - y) c

Law of “diminishingreturns”

x1 x2x1 x2

y2y2

y1y1

A-y for x1 and y1

A-y for x1 and y1

Yield (y)Yield (y)

Increasing level of growth factor (nutrient, x)Increasing level of growth factor (nutrient, x)


•Mitscherlich– Soil deficiency levels could be expressed as a “percent sufficiency”


•Mitscherlich– Soil deficiency levels could be expressed as a “percent sufficiency”

% of MaximumYield or “Yield Possibility”


Soil Phosphate (P) or Potassium (K) Supply(soil test index)Soil Phosphate (P) or Potassium (K) Supply(soil test index)

100100

5050

7575

10 40 70 10010 40 70 100


•Mitscherlich

Soil Test Correlation and Calibration

Soil Test Percent FertilizerP Index Sufficiency P2O5

0 25 8010 45 6020 80 4040 90 2065+ 100 0


•Mitscherlich

Soil Test Correlation and Calibration

Soil Test Percent FertilizerP Index Sufficiency P2O5

0 25 8010 45 6020 80 4040 90 2065+ 100 0


•Bray “…as the mobility of a nutrient in the soil decreases, the amount of that nutrient needed in the soil to produce a maximum yield (the soil nutrientrequirement) increases from a value determined by the magnitude of the yieldand the optimum percentage composition of the crop, to a constant value.”


•Bray “…as the mobility of a nutrient in the soil decreases, the amount of that nutrient needed in the soil to produce a maximum yield (the soil nutrientrequirement) increases from a value determined by the magnitude of the yieldand the optimum percentage composition of the crop, to a constant value.”



Soil Phosphate (P) or Potassium (K) Supply(soil test index)Soil Phosphate (P) or Potassium (K) Supply(soil test index)

100100

5050

7575

10 40 70 10010 40 70 100

Bray mobile nutrientBray mobile nutrient


•Bray

For a nutrient that is 100 % mobile in the soil (NO3-N ?)

Soil nutrient supply requirement = Yield X % nutrient in tissue

(Input requirement = harvest output or removal)

Idealized situation would be hydroponics nutrient supplying system (no soil-nutrient interaction)


•Bray

For a nutrient that is 100 % mobile in the soil (NO3-N ?)

Soil nutrient supply requirement = Yield X % nutrient in tissue

(Input requirement = harvest output or removal)

Idealized situation would be hydroponics nutrient supplying system (no soil-nutrient interaction)

What Happens to Applied What Happens to Applied Nitrogen Fertilizer?Nitrogen Fertilizer?


AMMONIUM AMMONIUM FERTILIZERSFERTILIZERS

NITRATENITRATENITROGENNITROGEN

SOIL M ICROORGANISMSSOIL M ICROORGANISMS

SOIL REACTIONSSOIL REACTIONS

AMMONIUMAMMONIUMNITROGENNITROGEN

SOIL ORGANICSOIL ORGANICMATTERMATTER



AMMONIUM AMMONIUM FERTILIZERSFERTILIZERSAMMONIUM AMMONIUM FERTILIZERSFERTILIZERS

NITRATENITROGENNITRATENITROGEN

SOIL MICROORGANISMS

SOIL MICROORGANISMS

SOIL REACTIONSSOIL REACTIONS

AMMONIUMNITROGENAMMONIUMNITROGEN

SOIL ORGANICMATTER

SOIL ORGANICMATTER

CROP UPTAKECROP UPTAKECROP UPTAKECROP UPTAKE

NH3NH3

Plant Growth and Soil Nutrient Supply RelationshipsPlant Growth and Soil Nutrient Supply Relationships

Wheat response to fertilizer NWheat response to fertilizer N

502 10-year average

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N Fertilizer (lb/acre)

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Bray mobile nutrient


•Bray


•Bray

Soil nutrient supply requirement = Yield X % nutrient in tissueSoil nutrient supply requirement = Yield X % nutrient in tissue

Bushel Wheat Requirement = (lb/bu) * % N = 60 * 2.2 % N (13 % C.P.) = 1.33 lb N/bushel

•Assumes –100 % efficiency in converting soil N to wheat grain N.– relatively constant N content

At 70 % efficiency, requirement is 1.33/.70 = 1.9 lb N/bu


•Assumes –100 % efficiency in converting soil N to wheat grain N.– relatively constant N content

At 70 % efficiency, requirement is 1.33/.70 = 1.9 lb N/bu


•Bray


•Bray


At 70 % efficiency and 13 % C.P., requirement is 1.33/.70 = 1.9 lb N/bu


At 100 % efficiency and 11 % C.P., requirement is 1.1/1 = 1.1 lb N/bu




At 100 % efficiency and 11 % C.P., requirement is 1.1/1 = 1.1 lb N/bu

Fate of Inorganic N in SoilsFate of Inorganic N in Soils

Nitrogen soil availabilityNitrogen soil availabilityNitrogen soil availabilityNitrogen soil availability

Source and fate of nitrate (NO3

-).Source and fate of nitrate (NO3

-).

NONO33--NONO33--

RainfallRainfall

NONO33--NONO33--

LeachingLeachingLeachingLeaching

NONO33--NONO33--

OO22 + NH + NH44++OO22 + NH + NH44++

NitrificationNitrificationNitrificationNitrification

HH+ + ++HH+ + ++

DenitrificationDenitrificationDenitrificationDenitrification

NN22O and NO and N22NN22O and NO and N22

- O- O22- O- O22

RainfallRainfall


NONO33--NONO33--



- O- O22- O- O22

NONO33--NONO33--


Source and fate of ammonium (NH4

+).Source and fate of ammonium (NH4

+).

CEC (-)CEC (-)CEC (-)CEC (-)

NHNH44++NHNH44++

Soil OrganicSoil OrganicMatter-NMatter-NSoil OrganicSoil OrganicMatter-NMatter-N

MineralizationMineralizationMineralizationMineralization

++OHOH--

++OHOH--

NHNH3 3 + + HH22OONHNH3 3 + + HH22OO

HH+ + ++HH+ + ++NONO33

--NONO33--

NONO33--NONO33--

OO22 + +OO22 + +

VolatilizationVolatilizationVolatilizationVolatilization

RainfallRainfall


NONO33--NONO33--



- O- O22- O- O22

NONO33--NONO33--


Source and fate of ammonium (NH4

+)Source and fate of ammonium (NH4

+)

CEC (-)CEC (-)CEC (-)CEC (-)

MineralizationMineralizationMineralizationMineralization

++OHOH--

++OHOH--

NHNH3 3 + + HH22OONHNH3 3 + + HH22OO

HH+ + ++HH+ + ++OO22 + +OO22 + +

VolatilizationVolatilizationVolatilizationVolatilization

Soil OrganicSoil OrganicMatter-NMatter-NSoil OrganicSoil OrganicMatter-NMatter-N

NHNH33NHNH33

NONO33--NONO33--

NONO33--NONO33--

NHNH44++NHNH44++

immobilizationimmobilizationimmobilizationimmobilization


•Bray –Current Oklahoma field practice


•Bray –Current Oklahoma field practice

Estimated yield in bu/acre (YG) * 2 lb N/bu =Estimated N requirement

Estimated N requirement - soil test NO3-N =Fertilizer N requirement.

Estimated topdress N = est.(Yield * %N) - preplant and soil N supplied

–sensor based goalEstimated topdress N =k sensed yield and

sensed % N

Estimated yield in bu/acre (YG) * 2 lb N/bu =Estimated N requirement

Estimated N requirement - soil test NO3-N =Fertilizer N requirement.

Estimated topdress N = est.(Yield * %N) - preplant and soil N supplied

–sensor based goalEstimated topdress N =k sensed yield and

sensed % N

Plant Growth and Soil Nutrient Supply RelationshipsPlant Growth and Soil Nutrient Supply RelationshipsN use efficiency = [100 (Nx - N0) grain N] / Nx appliedN use efficiency = [100 (Nx - N0) grain N] / Nx applied

Lahoma 502, 30-yr Averages

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Lahoma 502, 30-yr Averages

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Spatial Variability in Precision Agriculture What is it? What is it? – Precision n. The quality or state of being precise. Used or intended for precise.

Documents

population of production

fieldsspatial variability

agronomic units

soil properties

precision agriculturewhat

agronomic land use

soil productivity appropriate

free soil tests