Laboratory Methods

METHODS OF ANALYSIS - SOIL

Analysis  Method Code  Method Summary  
Aluminium  ICP9  Soil dried (40oc) and ground (<2mm), aluminium extraction by 1:10 soil/1M KCl solution, tumbled for one hour, centrifuged, filtered and measured by AAS.   
Ammonium Nitrogen  AMMONIUM_N  Soil dried (40oc) and ground (<2mm), ammonium extraction by 1:5 soil/2M KCl and 0/05M H2SO4, tumbled for one hour, centrifuged and measured by automated colorimetric analysis.  
Boron  ICP7  Soil dried (40oc) and ground (<2mm), boron extraction by 1:2 soil/hot 0.01M CaCl2 solution, refluxed for 30 minutes, centrifuged, filtered and measured by ICP-AES.  
Buffer pH  BPH  Soil dried (40oc) and ground (<2mm), extraction by 1:1:1, soil/water/Mehlich buffer, stirred, stand one hour measured by combination electrode.   
Chloride  SNO3CL  Soil dried (40oc) and ground (<2mm), chloride extraction by 1:5 soil/water solution, tumbled for one hour, centrifuged, filtered and measured by automated colorimetric analysis.  
Colour  PHYS  Visual assessment of soil colour against Munsell colour chart.   
Dispersion  PHYS2  Visual assessment of the behaviour of soil aggregate in water, dispersion of aggregate graded after two and twenty hours.   
Electrical Conductivity  PH  Soil dried (40oc) and ground (<2mm), 1:5 soil/water solution, tumbled for one hour and solution measured for electrical conductivity.   
Exchangeable Cations  ICP8  Soil dried (40oc) and ground (<2mm), exchangeable cations (Ca, Mg, Na, K) extracted by 1:10 soil/ammonium acetate (pH 7.0) solution, tumbled for half hour, centrifuged, filtered and measured by ICP-AES.   
Nitrate Nitrogen  SNO3CL  Soil dried (40oc) and ground (<2mm), nitrate extracted by 1:5 soil/water solution, tumbled for one hour, centrifuged, filtered and measured by automated colourimetric analysis.   
Mechlich III  SMEHL3  Soil dried (40oc) and ground (<2mm), extraction by 1:10 soil/Mechlich III solution, shaken for 5 minutes, centrifuged, filtered and measured by ICP-AES.   
Moisture (Percentage)  MOIST  Soil water content is calculated by weight of water lost after drying (105oc), result is expressed as percentage moisture.   
Organic Carbon (Walkley Black)  UV1  Soil dried (40oc) and ground (<2mm), carbon extraction by H2SO4 and Na2Cr2O7, centrifuged, filtered and measured by UV-VIS colorimetric analysis.   
PH (1:5 water)  PH  Soil dried (40oc) and ground (<2mm), aluminium extraction by 1:5 soil/water solution, tumbled for one hour and solution measured by combination electrode.   
PH (1:5 CaCl2)  PH  Soil dried (40oc) and ground (<2mm), aluminium extraction by 1:5 soil/water solution, tumbled for one hour and solution measured by combination electrode after the addition of 0.5 ml 1M CaCl2 solution.   
Potassium (Colwell)  COL_K  Soil dried (40oc) and ground (<2mm), potassium extraction by 1:100 soil/0.5M sodium bicarbonate (pH 8.5) solution, tumbled for 16 hours, centrifuged, filtered and measured by AAS   
Potassium (Nitric)  ICP11  Soil dried (40oc) and ground (<2mm), potassium extraction by 0.65:50 soil/1M HNO3 solution, boiled for thirty minutes, cooled, centrifuged, filtered and measured by ICP-AES.   
Phosphorus (Colwell)  COL_P  Soil dried (40oc) and ground (<2mm), phosphorus extraction by 1:100 soil/0.5M KCl sodium bicarbonate (pH 8.5) solution, tumbled for 16 hours, centrifuged, filtered and measured by auomated colorimetric analysis.   
Phosphorus (Bray)  BRAY_P  Soil dried (40oc) and ground (<2mm), phosphorus extraction by 1:7 soil/0.03M NH4F/0.025M HCl solution, shaken for 60 seconds, centrifuged, filtered and measured by automated colorimetric analysis.   
Phosphorus (Lactate)  SLACTP  Soil dried (40oc) and ground (<2mm), phosphorus extraction by 1:50 soil/0.02M C6H10CaO6 solution, shaken for 90 minutes, centrifuged, and measured by UV-Vis colorimetric analysis.   
Phosphorus (BSES)  BSES_P  Soil dried (40oc) and ground (<2mm), phosphorus extraction by 1:200 soil/0.005M H2SO4 solution, tumbled for 16 hours, centrifuged, filtered and measured by automated colorimetric analysis.   
Phosphorus (Olsen)  OLS_P  Soil dried (40oc) and ground (<2mm), phosphorus extraction by 1:20 soil/0.5M NaHCO3 (pH 8.5) solution, tumbled for 30 minutes, centrifuged, filtered and measured by automated colorimetric analysis.   
Phosphorus Buffer Index (PBI)  PBI  Soil dried (40oc) and ground (<2mm), phosphorus extraction by 1:10 soil/1M CaCl2 solution, 100mg/L phosphorus addition, tumble for 17 hours, centrifuged, filtered and measured by ICP-AES.   
Sand, Silt, Clay (%)  SANSILCLAY  Soil dried (40oc) and ground (<2mm), sand, silt and clay separation by Calgon solution, stirred and shaken; silt and clay measured by hydrometer, sand by sieve analysis.   
Silicon (BSES)  BSES_P  Soil dried (40oc) and ground (<2mm), silicon extraction by 1:200 soil/0.005M H2SO4 solution, tumbled for 16 hours, centrifuged, and measured by automated colorimetric analysis.   
Silicon (CaCl2)  BSESSI  Soil dried (40oc) and ground (<2mm), silicon extraction by 1:10 soil/0.01M CaCl2 solution, tumbled for 16 hours, centrifuged, and measured by automated colorimetric analysis.   
Slaking  PHYS2  Visual assessment of the behaviour of soil aggregate in water measured after two hours.   
Sulphur (KCl)  ICP2  Soil dried (40oc) and ground (<2mm), sulphur extraction by 3:20 soil/0.25M KCl solution, heated (40oc) for 3 hours, centrifuged, filtered and measured by ICP-AES.   
Sulphur (MCP)  ICP12  Soil dried (40oc) and ground (<2mm), sulphur extraction by 1:5 soil/0.01M Ca(H2PO4)2 solution, tumbled for 16 hours, centrifuged, filtered and measured by ICP-AES.   
Texture  PHYS  Field texture techniques of Northcote.   
Total Nitrogen (Kjeldahl)  STOT  Soil dried (40oc) and ground (<2mm), nitrogen digestion by 1:50 soil/H2SO4 and selenium oxide, potassium sulphate, boiled for 4 hours, cooled, centrifuged, filtered and measured by automated colorimetric analysis.   
Total Phosphorus (Kjeldahl)  STOT1  Soil dried (40oc) and ground (<2mm), phosphorus digestion by 1:50 soil/H2SO4 and selenium oxide, potassium sulphate, boiled for 4 hours, cooled, centrifuged, filtered and measured by automated colorimetric analysis.   
Trace Elements (DTPA)  ICP6  Soil dried (40oc) and ground (<2mm), zinc, copper, iron, manganese trace element extraction by 1:2 soil/DTPA solution triethanolamine/CaCl2 two-hour tumble, centrifuged, filtered and measured by ICP-AES.   
Zinc (HCl)  ICP10  Soil dried (40oc) and ground (<2mm), zinc extraction by 1:10 soil/0.1M HCl solution, tumbled for one hour, centrifuged, filtered and measured by ICP-AES.   

CALCULATIONS - SOIL

Cation exchange capacity  Sum of Calcium, Magnesium, Sodium, Potassium and Aluminium if analysed (meq/100 grams).    
Calcium/Magnesium ratio  Calcium/Magnesium    
Aluminium saturation  Aluminium (meq/100 grams)*100 / Cation exchange capacity (meq/100 grams)    
Exchangeable sodium percentage (ESP)  Sodium (meq/100 grams)*100 / Cation exchange capacity (meq/100 grams)    
Electrical conductivity of saturated extract  Calculation based on electrical conductivity (EC 1:5) and soil texture class.    
Phosphorus Buffer Index (PBI)  PBI = Ps(mg P/kg) + Colwell P (mg P/kg) / c(mg P/L), where c is the concentration of solution P in mg P/L and Ps is the amount of P absorbed by the soil in mg P/kg.    

METHOD OF ANALYSIS - PLANT

Analysis  Method Code  Method Summary   
Chloride  PNO3CL  Plant tissue sample dried and ground, chloride extraction by 1:250 plant tissue/water solution, boiled for one hour, cooled, centrifuged and measured by automated colorimetric analysis.   
Nitrate  PNO3CL  Plant tissue sample dried and ground, nitrate extraction by 1:250 plant tissue/water solution, boiled for one hour, cooled, centrifuged and measured by automated colorimetric analysis.   
Total Nitrogen  UV2  Plant tissue sample dried and ground, total nitrogen digestion by concentrated H2SO4 and Selenium catalyst, centrifuged and measured by automated colorimetric analysis.   
Total Elements  ICP4  Plant tissue sample dried and ground, total elements (Al, B, Ca, Cu, Fe, K, Mg, Mn, Na, P, S, Zn) digested by concentrated HNO3, centrifuged and measured by ICP-AES.  

CALCULATIONS - PLANT

Nitrogen/Phosphorus ratio  Nitrogen/Phosphorus    
Nitrogen/Sulphur ratio  Nitrogen/Sulphur    
Nitrogen/Potassium  Nitrogen/Potassium   

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