0 (the soil which forms) the top layer of ground in which plants grow
1 the layer of earth in which plants grow:
rich topsoil
Pure declines in nutrient stocks, and losses of topsoil and soil-physical structures are therefore parallels to the distinction between renewable and exhaustible resources.
Seeds were then germinated in a shadecloth 'nursery' (4% full daylight), in trays 5 cm deep filled with forest topsoil.
Tubs were filled with sandy secondary forest topsoil over 5 cm of coarse gravel.
The importance of nutrient input from litterfall to nutrient availability in the topsoil was particularly evident in the case of calcium and phosphorus.
High evapotranspiration rates in these climatic zones bring salts in the soil solution to the topsoil where the salts accumulate after water is evaporated.
When topsoil depth declines to 25 cm, productivity falls by about 75 per cent.
In fields with deep topsoils, the transitional period occurs between years 25 and 30.
As the topsoil was removed, leaching increased by 40 per cent, on average, over the 30-year time horizon.
