Question from Anne: I am still in the planning stages of my herb garden and need to get the soil ready first. We are reclaiming land from an overgrowth of Wattle trees and I have been told that the Wattle trees deplete the soil of phosphate.
Is there a way that I can increase the phosphate levels in the soil? Perhaps a plant / herb that I can grow as a green manure and dig in? Specific plants that I can add to my compost heap?
Answer: Most South African soils lack phosphate – the root maker or root nutrient. Plants can’t ‘manufacture’ phosphate, they can only utilize and ‘bind’ (or recycle) that which is available. Comfrey is a good example of a plant that can ‘bind’ soil phosphate
I recommend you first correct the problem by working a natural organic phosphate source such as blood and bone meal and/or well composted horse manure into your soil. If you are not too finicky about chemical fertilizers an application of super phosphate will also do the trick.
Once you’ve done that you can apply topdressings of bone meal and grow some comfrey which you can add to the compost heap or use to make your own liquid fertilizer.