Soot contains some ammonia, and as this is in the form of a sulphate, it is not volatile, and consequently does not evaporate when the soot is applied as a top dressing, which is the almost universal custom.
GREEN CROPS.
What plants are most used as green crops?
What office is performed by the roots of green crops?
How do such manures increase the organic matter of soils?
Green crops, to plow under, are in many places largely raised, and are always beneficial. The plants most used for this purpose, in our country, are clover, buckwheat, and peas. These plants have very long roots, which they send deep in the soil, to draw up mineral matter for their support. This mineral matter is deposited in the plant. The leaves and roots receive carbonic acid and ammonia from the air, and from water. In this manner they obtain their carbon. When the crop is turned under the soil, it decomposes, and the carbon, as well as the mineral ingredients obtained from the subsoil, are deposited in the surface soil, and become of use to succeeding crops. The hollow stalks of the buckwheat and pea, serve as tubes, in the soil, for the passage of air, and thus, in heavy soils, give a much needed circulation of atmospheric fertilizers.
What office is performed by the straw of the buckwheat and pea?
What treatment may be substituted for the use of green crops?
Which course should be adopted in high farming?
Why is the use of green crops preferable in ordinary cultivation?