Organic matter thoroughly decomposed is carbon, and has the various effects ascribed to this substance on p. 79.
Organic matter in process of decay produces carbonic acid, and sometimes ammonia in the soil; also its decay causes heat.
Organic matter containing nitrogen, such as animal substances, etc., furnish ammonia, and other nitrogenous substances to the roots of plants.
FOOTNOTES:
[Q] Produce.
[R] By absorbing and retaining, we mean taking up and holding.
[S] Nitrates are compounds of nitric acid (which consists of nitrogen and oxygen), and alkaline substances. Thus nitrate of potash (saltpetre), is composed of nitric acid and potash: nitrate of soda (cubical nitre), of nitric acid and soda.