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Ray R. WeilUniversity of Maryland
Test Plants                                Test Soil     • Petiole/stem              Visually assess                   sap...
Talk to the farmer• What’s the  problem?• What was done?• What was applied?• Trust but verify
In-field variability         What makes the “good           spots” so good?Can we make the whole fieldas good as the “good...
Terrace catches water in Ethiopia
Furrow-irrigated maize in MalawipH 4.8,                       pH 5.4,Labile C 400 mg/kg            Labile C 660 mg/kg
One source of variability.                    Farmer shows me how he incorporates                      manure: Trust but v...
Test Soil•   pH / EC•   Nutrients•   Physical tests•   Signs of life
Collecting surface soil composite sampleusing farmer tools.
 Soil Chemical Properties of surface soil  (composite sample) Chemical Properties of soil profile (mini-pits) Physical ...
My current field tool box of soil andplant testing materials ~ $1600.
EC meter:                                               $20                               pH meter: $35            NO3 met...
Range : 0.05 to 1.0 dS/m                                                                  0.55                          EC...
EC, pH andNO3 metersalso used forwater that maybe used forirrigation
In a smallholder’s farmyard
 1: 1 soil: water slurry   Soil pHH2O   Soil electrical conductivity Add calcium chloride to EC to > 2.5   Soil pHCaC...
Nitrate-NpHw in the field usingbottled drinking wateris comparable tostandard lab pHw.
Nitrate-NSoil NO3-N in field using general purpose HoribaNO3 meter is comparable to standard lab NO3-Nextraction only for ...
$0.18 glass                   “cuvette” &                   Rx vessel                       P reagent                     ...
6.0                                                                  70                                                   ...
For:•Soil pHCaCl2•Delta pH (pH H2O - pHCaCl2)•Salt extractable nitrate, sulfate and potassium
Clear sample after settling Muddy sample after stirring
Clear vs. muddy samples for K and NO3 meters                                70                                            ...
 1: 10 soil: Mehlich3 extraction solution   Mehlich3 extractable K+                                    Tests for P and S...
Labile carbon (indicative of SOM, degradation)2.5 g dry soil in 20 mL 0.02 M KMnO4 (method of Weil, 2003)
 Earthworms and channels Termites, ants and nests Dung beetles and other fauna Plant roots, nodules, mycorrhizae Fung...
 Flat-tip pH meter on  moistened soil Direct-reading EC probe  inserted into moistened soil• Presence of free carbonates...
Example of soil profile limitations:Guambeh brothers, Nimba County, Liberia
Guambeh brothers farm in Nimba, Liberia           “Poor”    “Good            area     ” area
Test Plants•   Petiole/stem sap•   Foliar symptoms•   Cut open stem•   Dig up roots
Farmer used urea and DAP
Good quality                          garlic pressColorimeter for           ($18.00)PO4                  Ion specific mete...
0.54 reading                          1.99 reading = 12 ppm S in vial                       = 48 ppm S in vial= 240 ppm S ...
S = 240 ppm                              S = 960 ppmN = 53                                   N = 530K = 6500              ...
Future farmers in Ethiopian finger millet field
Simple quantitative and qualitative field test for diagnosis of small holder farm problems
Simple quantitative and qualitative field test for diagnosis of small holder farm problems
Simple quantitative and qualitative field test for diagnosis of small holder farm problems
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Simple quantitative and qualitative field test for diagnosis of small holder farm problems

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Discussion of how field diagnosis can be conducted using a kit of modern but simple to use instruments

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Simple quantitative and qualitative field test for diagnosis of small holder farm problems

  1. 1. Ray R. WeilUniversity of Maryland
  2. 2. Test Plants Test Soil • Petiole/stem Visually assess sap Field • pH / EC • FoliarTalk to the variability • Nutrients symptomsFarmer • Crop growth • Physical • Cut open• Trust but • Soil colors tests stem verify • Topography • Dig up roots
  3. 3. Talk to the farmer• What’s the problem?• What was done?• What was applied?• Trust but verify
  4. 4. In-field variability What makes the “good spots” so good?Can we make the whole fieldas good as the “good spots? Maize field in Tigray
  5. 5. Terrace catches water in Ethiopia
  6. 6. Furrow-irrigated maize in MalawipH 4.8, pH 5.4,Labile C 400 mg/kg Labile C 660 mg/kg
  7. 7. One source of variability. Farmer shows me how he incorporates manure: Trust but verify
  8. 8. Test Soil• pH / EC• Nutrients• Physical tests• Signs of life
  9. 9. Collecting surface soil composite sampleusing farmer tools.
  10. 10.  Soil Chemical Properties of surface soil (composite sample) Chemical Properties of soil profile (mini-pits) Physical soil properties Biological soil properties
  11. 11. My current field tool box of soil andplant testing materials ~ $1600.
  12. 12. EC meter: $20 pH meter: $35 NO3 meter: $350 $0.50 bottle drinking waterAnd “on the ground”
  13. 13. Range : 0.05 to 1.0 dS/m 0.55 EC of 1:1 soil:water suspension, dS/m 0.50Often indicative of 0.45general fertility level 0.40in humid region soils. 0.35 EC relates to fertility 0.30 SOIL 0.25 Tropept- ter 0.20 Ustult-fal 0.15 0.10 0.05 0 50 100 150 Sum (K + + NO 3-), mg/ kg soil
  14. 14. EC, pH andNO3 metersalso used forwater that maybe used forirrigation
  15. 15. In a smallholder’s farmyard
  16. 16.  1: 1 soil: water slurry  Soil pHH2O  Soil electrical conductivity Add calcium chloride to EC to > 2.5  Soil pHCaCl2  Delta pH (pH H2O - pHCaCl2  CaCl2 extractable nitrate-N (ion specific meter)  CaCl2 exchangeable K+ ions (ion specific meter)  CaCl2 extractable Sulfate-S (turbidity with BaCl2)  CaCl2 extractable phosphate-P (colorimeter)
  17. 17. Nitrate-NpHw in the field usingbottled drinking wateris comparable tostandard lab pHw.
  18. 18. Nitrate-NSoil NO3-N in field using general purpose HoribaNO3 meter is comparable to standard lab NO3-Nextraction only for samples with > 15 mg /L.
  19. 19. $0.18 glass “cuvette” & Rx vessel P reagent packets $0.26 per sample $50 colorimeter programmed for PO4 to 0.01 ppm. $15 balance good to 0.01gOut of the rain in my “no-star hotel”
  20. 20. 6.0 70 60 pH w N03--N or K+ , mg/kg soil 5.5 pH CaCl2 50pHw- or pHCaCl2 40 5.0 30 NO3_N 20 4.5 K+ 10 4.0 0 Tropept- ter Ustult-fal Tropept- ter Ustult-fal SOIL SOIL
  21. 21. For:•Soil pHCaCl2•Delta pH (pH H2O - pHCaCl2)•Salt extractable nitrate, sulfate and potassium
  22. 22. Clear sample after settling Muddy sample after stirring
  23. 23. Clear vs. muddy samples for K and NO3 meters 70 70 NO3-N using clear solution, mg/L 60 K NO3K+ using clear solution, mg/L 60 50 50 40 40 30 SOIL SOIL Tropept- ter 30 20 Ustult-fal Tropept- ter Ustult-fal 20 10 0 10 0 10 20 30 40 50 60 70 10 20 30 40 50 60 70 K+ using muddy suspension, mg/L NO 3-N using muddy suspension, mg/L
  24. 24.  1: 10 soil: Mehlich3 extraction solution  Mehlich3 extractable K+ Tests for P and S use  Mehlich3 extractable PO4 2- light beam and so require filtering.  Mehlich3 extractable SO4-S
  25. 25. Labile carbon (indicative of SOM, degradation)2.5 g dry soil in 20 mL 0.02 M KMnO4 (method of Weil, 2003)
  26. 26.  Earthworms and channels Termites, ants and nests Dung beetles and other fauna Plant roots, nodules, mycorrhizae Fungal mycelium /fruiting bodies. Bio-interpretation of nitrate and labile C tests
  27. 27.  Flat-tip pH meter on moistened soil Direct-reading EC probe inserted into moistened soil• Presence of free carbonates (10% HCl drops)• Reduced iron (α-α diperidil)• Mn oxides (H2O2 drops)• Physical observations (e.g. water, density, colors, nodules)
  28. 28. Example of soil profile limitations:Guambeh brothers, Nimba County, Liberia
  29. 29. Guambeh brothers farm in Nimba, Liberia “Poor” “Good area ” area
  30. 30. Test Plants• Petiole/stem sap• Foliar symptoms• Cut open stem• Dig up roots
  31. 31. Farmer used urea and DAP
  32. 32. Good quality garlic pressColorimeter for ($18.00)PO4 Ion specific meters for K+ and NO3-N
  33. 33. 0.54 reading 1.99 reading = 12 ppm S in vial = 48 ppm S in vial= 240 ppm S in sap = 960 ppm S in sap
  34. 34. S = 240 ppm S = 960 ppmN = 53 N = 530K = 6500 K = 6680P = 21 ppm P = 9 ppm Farmer used urea and DAP
  35. 35. Future farmers in Ethiopian finger millet field

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