Vegetable Earth
or VEGETABLE MOULD. Soil largely mixed with humus or decayed remains of plants (see Humus). It is usually very dark, but the colour varies with the proportion of humus, and of the other constituents of the soil. Good Vegetable Mould may contain from 3 to 25 per cent. of humus, and is usually very fertile. A higher percentage of plant-remains is unfavourable, as organic acids are apt to be formed and to accumulate in the soil, to the detriment of most plants, though some species of wild plants prefer such a soil, e.g., several prefer peat, which consists of little but humus. To render such soils as contain excess of humus fertile, it is necessary to add certain manures or other substances to them in order to hasten the decay of the vegetable remains, and to bring them into a condition fit for the nutrition of the plants for which the ground is to be prepared. See also Humus.