Guideline for soil sampling &Processing

Ermias Betemariam (e.betemariam@cgiar.org) Keith Shepherd

13 April 2015Kampala

ContextOutline

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• Context

• Sampling

• Field work

• Lab work

Context• Soil comes to the global agenda:

– Sustainable intensification took soil as a x-cutting

– Global Environmental Benefits - land degradation and soils are among the priority global benefits (GEF/UNCCD)

• Increasing demand for soil data at fine spatial resolution

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High spatial variability of SOC can rise sevenfold when scaling up from point sample to landscape scales, resulting in high uncertainties in calculations of SOC stocks. This hinders the ability to accurately measure changes in stocks at scales relevant to emissions trading schemes (Hobley and Willgoose, 2010)

• Land productivity is key to feed the world• Land degradation remains a global challenge and reducing/reversing land

degradation is a development/research priority• Soil comes to the global agenda: sustainable intensification • Global Environmental Benefits - land degradation and soils are among the priority

global benefits (GEF/UNCCD)

Context

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Soil nutrient balance• Inputs

– Litter, roots, branches

• Outputs

• Autotrophic respiration: roots

• Heterotrophic respiration: CO2

respiration of soil organisms that use dead plant matter as a food source

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Guidelines

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Remote sensing for carbon monitoring

Consistent field protocol

Soil spectroscopyCoupling with remote sensingPrevalence, Risk factors, Digital

mapping

Sentinel sites Randomized sampling schemes

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No. District No of EAs No. of Farms No of soil samples

1 Serere 15 180 360

2 Sironko 15 180 360

3Iganga and Mayuge 45 540 1080

Total 75 900 1800

How many samples

Field navigation

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Plot layout

Plots are laid out with four subplots (Y- frame)

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Field workPreparation for field work• Proper preparation before going to the field • Collate existing information (e.g. soil map)• Train staff and pilot all procedures• Prepare logistics in terms of transport, etc.

Collecting field samples• Locate the predetermined sample location• Take composite soil samples from 4 points using

auger• Collect any associated data required (e.g. land

management)

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Field work- composite samples

Field work- Texture analysis

Soil sampling

Field soil data collection Soil sample to be send to the lab for processing

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Sample processing

• Drying• Crashing• Sieving

– 50 gm for spectral analysis= all samples– 750 gm soil for reference analysis = 10% of of the total samples

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Soil Infrared Spectroscopy

Rapid Low cost Reproducible Predicts many soil functional properties

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10 50 100 150 200 2500

2000

4000

6000 NIR spectroscopyThermal oxidationSample preparationSoil sampling

Number of samples

Co

st (

US

D)

Personnel Others0

3

6

9

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15NIR spectroscopy Thermal oxidationSample preparation Soil sampling

Co

st p

er

sam

ple

(U

SD

)

Cost –error analysis

0 500 1000 15000

2000

4000

6000

8000 Thermal oxidationNIR spectroscopy

Number of samples

Cost

(USD

)

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

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

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

Cost –error analysis

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Things to be careful [2]

Proper labeling

Avoid contamination

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Properly locate your plots/sites

Ermias Betemariam | Hands-on soil infrared spectroscopy training course | Nairobi | Nov. 12, 2013 | 19

Preliminary results from Ethiopia

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Preliminary results from Ethiopia

• More research on cost-effective measurement tools• Reduce uncertainties in measurements- error propagates• Develop national capacities, networking and partnership • Enable decision makers have clear understanding of soil status and trends

Finally…

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