salinity and plant growth

[K N and P J Harris]

Salts for -plant experiments
Epsom salts Magnesium sulphate. Interesting comparison to sodium 
chloride as the sulphate ion tends to be much less toxic. The carbonates 
and bicarbonates are a problem because the pH will be very different, 
this tends to be true for many of the metal salts like copper 
sulphate. Ammonium nitrate is a possible too. Shold be available from 
pharmacists or garden centre.More important to get a good range of 
concentrations than a huge range of compounds at very widely spaced 
concentrations. Don't forget to make sure you have enough repeats 
(replications) for a little simple statistics (ouch) and think very hard 
about the amounts of different salts you use for comparison. They should 
be equiosmotic or at least equimolar. Just straight percent by weight 
will not get you anywhere. Even worse, remember sodium chloride is 
completely ionised at low concentrations but not at high concentrations 
so the relationship of osmotic stress to concentration is NOT a straight 
line.
Good luck,
Dr Peter Harris,
Deoartment of Soil Science,
The University of Reading.UK.