In both the kinds of land we have been considering [i. e., classes of very fertile soil, rich in humus], we have supposed the humus to be mild, or ex… - Albrecht Daniel Thaer

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In both the kinds of land we have been considering [i. e., classes of very fertile soil, rich in humus], we have supposed the humus to be mild, or exempt from acidity. J Sour or acid humus totally destroys the fertility of a soil; sometimes, however, the soil contains so very small a portion of acidity that its fertility is very slightly diminished, and only with regard to some few plants. Barley crops become more and more scanty in proportion as the acidity is increased; but oats do not appear to be at all affected by it. Rye grown on such land is peculiarly liable to rust, and is easily laid or lodged. The grains of all the oereals become larger, but contain less farina. Grass which grows on these spots is, both in species and taste, less agreeable, and less suitable for cattle, than any other, although it yields a very considerable produce in hay. In fact, in exact proportion with the increase of acidity, is the decrease of the value of the soil...