Nitrification in acid soils

Abstract

Certain of the permanent grass plots at Rothamsted, which have been cut for hay and have received the same manurial treatment every year since 1856, of late years have declined in yield, and the herbage has assumed an unhealthy condition. The plots affected are those to which nitrogen in the form of a mixture of ammonium chloride and sulphate is applied; the one receiving the highest amount of ammonium salts now cariies a rank vegetation, consisting almost entirely of three species of grass - Holcus lanatus, Alopecurus pratensis , and Arrenatherum avenaceum - growing in coarse tufts with bare spaces between. The surface of these bare patches, which are spreading yearly, consists of a mat of peat-like decayed vegetation; a similar peaty formation is to be observed on the other plots receiving smaller amounts of ammonium salts. In determining the nitrifying power of a number of Rothamsted soils, Mr. S. F. Ashby observed that these grass soils failed to set up nitrification when small quantities were added to media suitable of the development of nitrates, indicating the comparative absence of the organisms causing nitrification. It was also noticed that the soil of these plots was distinctly acid, sufficiently so to redden blue litmus paper pressed against it in the moist state, a condition first observed by Voelcker to be set up by the long-continued uses of ammonium salts on the arable soils of the farm of the Royal Agricultural Society at Woburn.