Dear Paul Reed Hepperly ,

Thank you very much.

For pH 6 to 8 you can use phosphate buffers.

From pH 4 to 6 you can use acetate buffers.

The difference from 4 to 8 is about 10,000 based on the logarithmic scale of pH.

You might want to use cellulose pads, sand, vermiculite/perlite and soil as medium for the tests.

Use at least 4 seedloots of 50 to 100 seeds to get good mean separation.

Dear Paul Reed Hepperly ,

Thank you very much.