I am using ArcGIS 10.3 basic desktop to interpolate GPS soil points and then create a lime prescription map. I can easily interpolate the points however when I use the field calculator to enter the target lime formula for the desired pHw level I get an error message of 99999 that says a field name was not found or there were unbalanced quotation marks. The formula was produced by a leading university and has been used in numerous types of software so I don't believe it is the problem.
I don't think ArcObjects will help as you have the same issue attempting to convert the formula to C#. It is not clear what field is to be calculated and what parameters are going into the existing formula.
As Darren points out, all of the values appear to be constants.
I'm not sure where you're getting your formula, but I've been looking for something similar online. It appears that this calculation is more complicated than a simple pH of the soil, as it varies due to soil type, soil buffering ability, relative neutralizing value of the lime applied, exchangeable acidity, residual lime credit, and various other complicated chemical factors. If you could give us a citation or some other reference, maybe we could help you find the calculation you need.
