These have very little food value, but are useful as a soil conditioner if they are available in your area cheaply. They can be used at any time. This is an excellent improver for heavy soils. It should be forked in well and mixed intimately with soil particles. Gypsum is not usually expensive, and should be available from garden centres or agricultural dealers in your area.
Gypsum works in the same way as lime, but without raising the pH and making the soil more alkaline.
Lime and Gypsum work in the same way, but lime has a profound effect on soil pH. Lime can be used at any time of year, but is best in spring on light soils. This darkens the soil and makes it slightly earlier, because dark colours absorb heat better than light ones. Soot must not be used fresh, you must let it weather for at least six weeks before applying it to soil. Charcoal An expensive material which will also darken the soil. It is strongly alkaline and can raise the pH as lime does.