chowold2

有草覆蓋的泥土的確很難改善，我見過有人將整塊草坪清起，再用新12吋topsoil換去舊泥，好大工程

chowold2

Garden lime usually use to sweeten the soil (soil acidity is reduced and alkalinity increased).
And the clay soils or alkaline soils is high in pH. If adding more lime to the clay soil will only make it worst. The best way to make improvement to the clay soil is adding more sand and organic compost to it.

chowold2

If you already have an existing lawn, you will need to apply organic matter by a process called top dressing.  Top dressing is generally performed once or maybe twice a year in some cases. When topdressing you apply a thin layer of organic matter over your grass. Applying a layer of 1/4 inch to 1/2 inch thick usually works best depending on the mowed height of the grass. Up to 1 inch may work for grasses maintained at 3 or more inches. If you completely cover the grass with compost photosynthesis may be hindered and the grass will suffer. It is usually a temporary affect.