The Microbiology of Farmyard Manure Decomposition in Soil I. Changes in the Microflora, and their Relation to Nitrification

Abstract

Decomposition experiments were carried out in the laboratory with different kinds of farmyard manure in various soils (sand and clay, acid and neutral). In neutral or slightly acid soil there was a very strong multiplication of bacteria and, to a smaller extent, of actinomycetes immediately after the addition of manure. This increase, which was especially marked when fresh straw was present in the manure, was sooner or later followed by a rather sudden decrease, which caused the numbers of bacteria gradually to approach those in the control soils. The actinomycetes were generally more abundant in the later stages of the process. This suggests that they may be especially active in the decomposition of the more resistant residues. The “numbers” of fungi were not affected by the addition of manure alone (except to a slight degree in strongly acid soil, where the bacteria seemed inactive), but the presence of fresh straw caused them to become active, especially in strongly acid soil, where their “numbers” remained at a very high level for a long time, this abundance of fungi consisting of both mycelium and spores.