Rao MylavarapuSoil & Water Science Department, IFAS

University of Florida

Optimum Yield or Optimum Yield or QualityQuality‘‘Optimum’ should Optimum’ should

ideally refer to ideally refer to economically and economically and environmentally environmentally sustainable returns sustainable returns

Existing Existing approaches have approaches have been been predominantly predominantly based on based on economicseconomics

Profit

No Soil TestingNo Soil Testing

Always FertilizeAlways Fertilize

Luxury Luxury

ConsumptionConsumption

Pollution Pollution

Potential HiPotential Hi

Treats soil as a Treats soil as a

bankbank

Calibrated Soil Calibrated Soil TestTest

Fertilizer Fertilizer amounts amounts adjusted for soil adjusted for soil contributioncontribution

Based on plant Based on plant need, not plant need, not plant uptakeuptake

Pollution Pollution Potential LowPotential Low

Fertilize the Fertilize the plant not the soilplant not the soil

Soil Categories & Extractants Soil Categories & Extractants for Floridafor FloridaAcid soils Acid soils - - Mehlich-1 Mehlich-1 (dilute double (dilute double

acid)acid)

-P, K, Ca, Mg, Cu, Zn, Mn-P, K, Ca, Mg, Cu, Zn, Mn

Calcareous soils Calcareous soils (pH (pH >> 7.4) - 7.4) - AB-DTPA AB-DTPA (Ammonium Bicarbonate-DTPA)(Ammonium Bicarbonate-DTPA)

-P only-P only

Organic soils Organic soils

--Water Water extraction for phosphorusextraction for phosphorus

--Acetic Acid Acetic Acid for K, Mg, Ca, Na, Sifor K, Mg, Ca, Na, Si

Field CalibrationField CalibrationAB-DTPA extraction procedure for AB-DTPA extraction procedure for

calcareous soils needs to be replaced calcareous soils needs to be replaced urgentlyurgently

-poor field calibration with the procedure -poor field calibration with the procedure severelyseverely

limits its applicabilitylimits its applicability-extremely high carbonate levels make -extremely high carbonate levels make calibration difficultcalibration difficult-background P concentration higher than -background P concentration higher than the critical limitthe critical limit-both commercial and urban horticultural -both commercial and urban horticultural operations lack a valid soil testoperations lack a valid soil test

Soil and plant diagnostics are complementary Soil and plant diagnostics are complementary and serve different purposes and serve different purposes

Tissue test does not completely replace a soil Tissue test does not completely replace a soil test test

Plant analysis is effective in monitoring in-Plant analysis is effective in monitoring in-season nutrient needs, especially of perennial season nutrient needs, especially of perennial cropscrops

The tissue tests confirm suspected nutrient The tissue tests confirm suspected nutrient deficiency symptoms, reveal hidden hunger deficiency symptoms, reveal hidden hunger and verify toxicitiesand verify toxicities

Nutrient deficiencies corrected through foliar Nutrient deficiencies corrected through foliar applications, although not always effectiveapplications, although not always effective

Leaf diagnosis shows nutrient status Leaf diagnosis shows nutrient status at the time of sampling reflecting soil at the time of sampling reflecting soil fertility status fertility status

Soil fertility status in turn is also Soil fertility status in turn is also determined by temperature, water, determined by temperature, water, management factors, nutrient balance, management factors, nutrient balance, etcetc

Leaf analysis has to be integrated with Leaf analysis has to be integrated with soil analysis for confirming the soil analysis for confirming the deficiency, sufficiency or toxicitydeficiency, sufficiency or toxicity

Complementary Soil & Complementary Soil & Tissue TestingTissue TestingTwo such new tests have been Two such new tests have been

developed and implementeddeveloped and implemented

- for Bahia pastures - for Bahia pastures

-for commercial Citrus -for commercial Citrus

In both tests, phosphorus requirement In both tests, phosphorus requirement and deficiency confirmation is and deficiency confirmation is determined by a combination of both determined by a combination of both soil and a plant tissue testsoil and a plant tissue test

Potential for a new protocol for Potential for a new protocol for Blueberries Blueberries

Plant Sap AnalysisPlant Sap Analysis

NIR Spectrophotometry NIR Spectrophotometry Technique providesTechnique provides

• routine soil analysisroutine soil analysis• decision supportdecision support• soil property classificationsoil property classification• soil survey and mappingsoil survey and mapping• precision agricultureprecision agriculture• diagnosis of soil problemsdiagnosis of soil problems• contaminated site characterization contaminated site characterization • input data for modelsinput data for models

Why Replace Wet Chemistry?Why Replace Wet Chemistry?

Soil Test Laboratory Soil Test Laboratory TechniquesTechniques

ReflectancReflectance e MeasuremMeasurementent

Signal Signal ProcessingProcessing

Statistical Statistical AnalysisAnalysis

ValidatioValidationn

CalibratiCalibrationon

InterpretatioInterpretation &n &RecommendRecommendationation

Previous WorkPrevious Work

Wavelength (nm)

500 1000 1500 2000 2500

log(1

/Reflecta

nce)

0.2

0.4

0.6

0.8

1.0

1.2

Alfisol Entisol Ultisol

WaterWater

PredictPredicted & ed & ValidatValidated Soil ed Soil PropertPropertiesies

Study 3 (on-going) Study 3 (on-going) A sample set consisting of 1,000 soil and A sample set consisting of 1,000 soil and

corresponding 1,000 tissue samples is corresponding 1,000 tissue samples is being collected from through out the being collected from through out the statestate

Commodities targeted- forages, Commodities targeted- forages, vegetables, peanuts, citrus (Ridge, vegetables, peanuts, citrus (Ridge, Flatwoods and Indian River)Flatwoods and Indian River)

Soil and leaf tissue reflectances will be Soil and leaf tissue reflectances will be correlatedcorrelated

A subset of soil samples was used to A subset of soil samples was used to determine the influence of multiple determine the influence of multiple moisture levelsmoisture levels

Soil texture will also be determined for a Soil texture will also be determined for a subset of soil samplessubset of soil samples

Mylavarapu, R.S., Schumann, A.W., Obreza, Mylavarapu, R.S., Schumann, A.W., Obreza, T.A., Cornejo, C. 2007. Rapid Soil & Tissue T.A., Cornejo, C. 2007. Rapid Soil & Tissue Analysis Techniques Using Near Infrared Analysis Techniques Using Near Infrared Reflectance Spectroscopy. FDACS Project Reflectance Spectroscopy. FDACS Project 61580, Annual Progress Report. 61580, Annual Progress Report.

ResultsResultsPLSR for P in PLSR for P in

DRY and DRY and MOIST soils MOIST soils samples samples respectivelyrespectively– Moist refers Moist refers

to samples as to samples as they arrive they arrive from the fieldfrom the field

– Dry samples Dry samples are oven dryare oven dry

Dry

Moist

Part A: Transport Potential Due to Site and Transport Characteristics

Site and Transport Characteristics

Phosphorus Transport Rating Value

Soil Erosion No Surface Outlet

0

<5T/Aa

15-10 T/A

210-15 T/A

4>15 T/A

8

Runoff Potential Very Low0

Low1

Medium2

High4

Very High8

Leaching Potential Very Low0

Low1

Medium2

High4

Very High8

Potential To Reach Water Body

Very Low0

Low1

Medium2

High4

Total for Part A: Site and Transportb

Part B: Transport Potential Due to Phosphorus Source Management

Phosphorus Source Management

Phosphorus Loss Rating Value

Fertility Index ValueSoil Fertility Index x 0.025( _____ ppm P x 2 x 0.025)c

P Application Source and Rate d

0.05 x ( _____ lbs P2O5) for fertilizer, manure or compost

0.015 x ( _____ lbs P2O5) for biosolids

0.10 x ( _____ lbs P2O5) for waste water

Application Method

NoSurface Outlet

Or Solids incorporated immediately or injected

Applied via irrigationOr Solids

incorporated within 1 day

of application

Solids incorporated

within 5 days of application e

Solids not incorporated within 5

days of application

0 2 4 6

Waste Water Application

0.20 x _____ acre inches/year

Total for Part B: Phosphorus Source

Multiply Part A x Part B

THE

FLORIDA

P

INDEX

PrioritiesPrioritiesDetermine the feasibility of complementary Determine the feasibility of complementary

soil and tissue analyses for phosphorus soil and tissue analyses for phosphorus management for perennial crops and management for perennial crops and landscape plants and grasseslandscape plants and grasses

Integrate recommendations for irrigation Integrate recommendations for irrigation management with nutrient management with nutrient recommendations for commercial recommendations for commercial horticultural cropshorticultural crops

Further develop VNIR techniques and Further develop VNIR techniques and continue field calibration for wider continue field calibration for wider diagnostic applicationsdiagnostic applications

Develop newer diagnostic techniques for Develop newer diagnostic techniques for environmental impact assessmentenvironmental impact assessment

Thank You!raom@ufl.edu