riverat if your soil is alkaline you can acidify it with peat moss or manures and fish emulsions etc. Even if you add iron to the soil if you are alkaline the plants will still not be able to absorb the added iron {ferrous sulphite) Ive never had this problem myself but have been using natural fertilizers like magnesium sulphate and barn lime for years also with as much compost as I can produce! I also have layer hens so my soil is well balanced, of course with out realizing exactly why, until moreless explained it to me! Knowledge is powerful ingredient in the garden!