BP SodiCalc
About This calculator provides a platform to estimate the soil amendment requirement where a soil is found to be dispersive and the cumulative cost of dispersion is likely to exceed the cost of amendment. SodiCalc calculates the amendment rate and cost from soil chemical characteristics and supply costs supplied by the user and makes no assumptions about the profitability of the soil amelioration strategy.  The Cation Converter tab is a simple tool to restate cation concentrations provided as mg/kg as cmol(+)/kg required by Sodicalc.
General White cells  in the calculator can be edited or changed. Calculations are not saved on exit so if a record is required, print a copy when all input fields have been filled.
Soil pH Input the pH (CaCl2) from a soil test. In acid sodic soils lime and dolomite can be viable amendment options for soil dispersion.
Electrical Conductivity Input the EC (dS/m)  from a soil test. Use to calculate the Electrochemical Stability Index (ESI) of the sample. ESI helps understanding of the impact of  soil salinity on dipersion in clay soils, particuarly when related to very low soil salinity.
Individual cations Input the individual  exchangeable cation results (cmol (+)/kg)  from a soil test. Use the Cation Converter to change results as mg/kg to cmol(+)/kg.
Depth of soil to be treated Input the depth of soil to be ameliorated.
Soil bulk density Input the average soil bulk density for the soil layer to be ameliorated. Generally a value between 0.9 and 1.6.
Target ESP % Input target Exchangeable Sodium %, generally between 6 and 10 %.
Target EMP% Input target Exchangeable Magnesium %, generally between 20 and 30 %.
Target EKP% Input target Exchangeable Potassium %, generally between 4 and 8 %.
Product cost Input product purity and cost associated with the product purchase, handling, transport and spreading.
Estimate gypsum efficiency The rate of cation exchange of Na, K and Mg on charged surfaces by Ca is affected by the law of diminishing returns i.e  the efficiency of removal of Na, K and Mg decreases  the closer the starting and target % cation values.  The compulsive exchange rate  in this calculator is modified by this efficiency to reflect the ease of exchange as relate to starting and target ESP,EMP and EKP.
Output Calculated rates of gypsum, liming products or blends with the cost per area based on the range soil chemistry values and prices provided.
Disclaimer The evaluation and recommendation reports provided here are a guide only, and depend on representative samples being analysed and a reasonable  estaimate by the user of other inputs. Additionally environmental and managerial factors influence performannce therefore as suppliers of this decision support we do not accept any liability whatsoever arising from the application of recommendations, for any damage, loss or injury of any nature and the user takes these evaluations and recommendations on these terms. This recommendation is made in good faith, based on the best technical information available.
© Back Paddock Company 2018
BP Sodicalc                              
SOIL ANALYSIS RESULTS                                
Soil pH (CaCl2)                                  
EC (1:5 water)                                  
Ca (Exchangeable) (cmol/kg)                                
Mg (Exchangeable) (cmol/kg)                                
K (Exchangeable) (cmol/kg)                                
Na (Exchangeable) (cmol/kg)                              
Al (Exchangeable)  (cmol/kg)                                
Soil depth to be treated cm                                
Soil Bulk Density g/mm3                                
Effective CEC   (cmol/kg)                                
Electrochemical Stability Index                                  
New  ESI estimate                                  
Starting ECP %                                
Starting ESP %                                
Target ESP %                                
Sodium Difference  %                                
SodiumDifference  (cmol/kg)                                
Starting EMP %                                
Target EMP %                                
Magnesium Difference  %                                
Magnesium Difference  (cmol/kg)                                
Starting EKP %                                
Target EKP  %                                
Potassium Difference  %                                
PotassiumDifference  (cmol/kg)                                
Estimated Gypsum Efficiency                                  
Pure gypsum rate for sodium t/ha                                
Pure gypsum rate for magnesium t/ha                                
Pure gypsum rate for potassium t/ha                                
Total t/ha                                
Total Ca rate t/ha                                
Equivalent Ca rate as lime (unadjusted for pH) t/ha                                
GYPSUM (pH(CaCl2)>6.5) LIME (pH (CaCl2)<5.5) GYPSUM + LIME                     
Commercial Gypsum = t/ha Lime Rate t/ha Lime % Mix                      
Gypsum Purity = % Effective Neutralising Value   Gypsum % Mix                      
Product Cost $/t Product Cost $/t Lime Rate t/ha                    
Delivery Cost $/t Delivery Cost $/t Gypsum Rate t/ha                    
Cost Spread $/t Cost Spread $/t Combined Product Rate t/ha                    
GypsumTotal cost/t  $/t Total cost  $/t                          
      Est. Lime Efficiency % gypsum                          
Cost $/ha   Cost $/ha   Cost $/ha                      
© Back Paddock Company 2018                                    
Cation Converter    
  Input Output
Nutrient (ppm or mg /kg) (cmol(+)/kg
Ca % CEC  
Mg % CEC  
Na % CEC  
K % CEC  
Al % CEC  
Ca/Mg ratio  
© Back Paddock Company 2016