Spatial Variability in Spatial Variability in Precision AgriculturePrecision Agriculture

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 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?

Precision 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.

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”

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

What causes field delineation.– Natural boundaries.

Rivers Rock out-crops

– Political boundaries. Roads Survey units

– Land ownership Consolidation

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

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

Soil acidity and Oklahoma Soil acidity and Oklahoma rainfallrainfall

Usually acidic

                                                                           

                                           

Usually not acidic

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

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

050

100150200250300

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

Soil Te

st P

C.V. = 54

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 FertilizationPreviousPrevious GrainGrain Normal FertilizationNormal Fertilization Soil Test ResultsSoil Test Results

AcresAcres Soil TestSoil Test YieldYield NN PP22OO55 KK22OO pHpH NN PP KKSurSur SubSub

86*86* 19811981 3535 100100 4646 4.54.5 2424 5454 106106 445445118*118* 19811981 2525 100100 4646 4.94.9 5353 108108 8888 411411

30*30* 19891989 3434 100100 4646 5.15.1 4444 4343 7575 37737765*65* 2626 100100 4646 4.44.4 115115 118118 159159 7527525050 19811981 2929 100100 4646 5.55.5 00 7070 4444 551551

*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

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

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 1pH=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

Terrace 3Terrace 3pH=5.4pH=5.4BI = 6.8BI = 6.8N = 20N = 20P = 31P = 31K = 522K = 522

Terrace 4Terrace 4pH=5.5pH=5.5BI = 6.7BI = 6.7N = 12N = 12P = 32P = 32K = 423K = 423

Terrace 5Terrace 5pH=4.6pH=4.6BI = 6.8BI = 6.8N = 16N = 16P = 65P = 65K = 310K = 310

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

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

STP 1996, EFAW

0102030405060708090

100

Feet North

Soil

Test

P

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