CONTRIBUTIONS FROM THE WISLEY LABORATORY. 305 



CONTRIBUTIONS FROM THE WISLEY LABORATORY. 



XXIX. — Report on Experiments with Bacterized Peat 

 or Humogen. 



By F. J. Chittenden, F.L.S. 



In the late autumn of 191 3 the Council requested me to carry 

 out some tests of Professor Bottomley's bacterized peat in order to 

 see how far the claims which had been put forward with regard to it 

 were justified. The following is an account of these tests. 



A . — Nature of the Peat. 



The term peat as used by the gardener in reference to material 

 employed in making potting composts is a generic one, but it does not 

 as a rule connote the peat from which the material under trial is pre- 

 pared. This raw material is peat -moss litter as sold for bedding horses 

 in stables, and consists almost entirely of dried Sphagnum, altered 

 somewhat through its submergence in bog water, and a certain amount 

 of fibre derived probably from heaths and similar plants which grow 

 on the surface of sphagnum bogs. It is not in its raw state used in 

 gardening operations except to a very limited extent. It consists 

 almost entirely of organic matter, the ash in the dry peat being only 

 I -37 per cent. It is brown in colour, and a water extract is decidedly 

 acid in reaction. Its most characteristic property is its relatively 

 enormous absorptive capacity, which has led to its use as an absorbent 

 of urine in stables and in a more recent state in the making of 

 molascuit and similar cattle foods, and in making surgical bandages. 

 Its chemical composition is undoubtedly very complex, and it 

 apparently contains some organic compound which is to some extent 

 detrimental to the growth of ordinary plants, though this bad effect is 

 not always very noticeable, as will be seen. 



Professor Bottomley tells us that this complex raw material is 

 treated in three stages in order to produce the bacterized peat. " First, 

 the raw peat is moistened with a culture solution of the special ' humat- 

 ing ' bacteria, and the mass kept at a constant temperature for a week 

 or ten days ; during this time the bacteria act on certain organic 

 constituents of the peat, and gradually convert a large amount of 

 the humic acid present into soluble humates ; second, the humating 

 bacteria, having done their work, are destroyed by sterilizing the peat 

 by live steam ; third, the sterilized peat is treated with a mixed 

 culture of nitrogen-fixing organisms — Azotobacter chroococcum and 



