collecting the dirt on soils: advancements in plot-level soil testing and implications for...

Collecting the Dirt on Soils:Advancements in Plot-Level Soil Testing and Implications for Agricultural Statistics

http://www.worldagroforestry.org/research/land-health

Ermias Betemariam ([email protected])

Sydney Gourlay Keith Shepherd



Context

2Ermias Betemariam| ISI2005 2015, | Rio de Janeiro| July 2015|

Innovations in Agricultural Statistics

• Administrative data is often seen as methodologically flawed and

lacks credibility

• Lack of consistent, good quality data on soil health

• Data collection methods

• The role of technology

• What works in developing countries?

Context (2)


Methodological improvements in smallholder agricultural statistics for decision making

http://www.csa.gov.et/index.php/component/content/article/14-survey-reports/123-latest-national-statistics-abstract





Objectives

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Improving measurements of agricultural productivity by combining household level and soil fertility data

• Develop soil-plant spectral analytical methods and diagnostic tools for rapid, low cost and reliable assessment of soil samples using light (Technology)

• Demonstrate applicability of integrating scientific method of soil quality assessment along with the socio-economic panel data

Ermias Betemariam| ISI2005 2015, | Rio de Janeiro| July 2015|

Field data


3661 soil samples collected from three agro-ecologica zones

• Household socio-economic data• Subjective assessment of soil quality

• Soil sampling• Objective assessment of soil quality

Lab analyses

Ermias Betemariam| ISI2005 2015, | Rio de Janeiro| July 2015| 6

Laser Diffraction Particle Size Analysis(LDPSA)

Total X-ray Fluorescence spectroscopy (TXRF) for elemental analysis

FT Diffuse reflectance MIR Alpha MIR spectrometer

Instrumentation Dispersive VNIRFT-NIR FT-MIR

Handheld NIR/MIR

•Portable•Repeatability?•External service•No validation

•Benchtop•Repeatability•Self serviceable•Validation in-built•ISO compliant•Industry proven•Multipurpose

•Benchtop•Repeatability•No gas purging•Some servicing•Robotic•Validation in-built•ISO compliant•Outperforms NIR

•Handheld•Sample

homogeneity?•Variable

moisture?•Repeatability?•Still expensive•Rapidly

developing•Need to prepare

by developing soil reference libraries

Working on Rural labs


Lab analyses (2)

Why infrared spectroscopy?

Rapid Low cost Reproducible Predicts many soil functional properties


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Land Health applicationsAfrica Soil Spectroscopy Lab Network

EthioSIS 97 Sentinel sites


MIR- reflectance

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Mid-infrared spectroscopy strongly predicts soil properties


MIR- reflectance

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Objective vs subjective soil quality measurements

Farmers use soil texture and color to describe soil qualities

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Soil carbon and pH values



SOC (95% CI): 3.18 - 3.30%

pH(95% CI): 6.28 - 6.34

14



Soil quality indicators

USDA: http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/health/assessment/?cid=stelprdb1237387

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Subjective soil quality assessment poorly correlated to the scientific output

Science: about 17% of the soils have SOC < 2% but only 5%= poor soils

Local respondents identified only 5% of the as poor soils



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Age Sex Literacy



Age class, sex, and literacy did not significantly influence the subjectiveGrading of soil quality

Farmers better identify poor and not-poor soils but not “Fair soils” that future Questions should consider

10 50 100 150 200 2500

2000

4000

6000NIR spectroscopyThermal oxidationSample preparation

Number of samples

Ca

rbo

n m

ea

surm

en

t co

st (

US

D)

Pers...

Oth

ers0

3

6

9

12

15 NIR spectroscopyThermal oxidationSample preparation

Ca

rbo

n m

ea

sure

me

nt

cost

pe

r sa

mp

le (

US

D)

Cost –error analysis

0 500 1000 15000

2000

4000

6000

8000Thermal oxidation

Number of samples

Carb

on m

easu

rem

ent

cost

(USD

)Comparisons of costs of measuring SOC using a commercial lab and NIR

CostIR is cheaper (<~ 56%) than combustion method for large number of samples

ThroughputCombustion ~ 30-60 samples/dayNIR ~ 350 samples/dayMIR ~ 1000/day


Surveillance science Land health metrics

Consistent field protocol

Soil spectroscopyCoupling with remote sensing

Sentinel sites Randomized sampling schemes


AfSIS: Soil functional propertiesFrom polygon-based to probabilistic mapping

+

Probability of observingcultivation

Current lime requirement ? ~ min [prob(pH < 5.5), prob(cult)]

Probability topsoil pH < 5.5 ... very acid soils

Grid-based probabilistic maps increases the reliability of the map and its power to be combined with other data sources (remote sensing & terrain data)

(Walsh, 2013)

=

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Data sources

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• More research on cost-effective measurement tools- the future is bright• Subjective and objective measurement results do not much well• It was possible to integrate soil health measurement into the panel

household survey• Enhancing our understanding of household attributes, land management

practices and soil health management• Enable decision makers have clear understanding of soil status and trends

Finally…

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Smart data - Smart decisions

[email protected]: www.worldagroforestrycentre.org

collecting the dirt on soils: advancements in plot-level soil testing and implications for...

Science

soil texture

soil carbon

soil qualities

soil fertility data

soil reference libraries

plotlevel soil testing

good quality data

field data