244 IIUMUS HUMOGEN. 



first ex{X)sed to the weather for about two years. It is ver}" 

 obvious that peat is very deleterious to plant life ; this, because 

 of its acid nature. 



The highly antiseptic nature of peat is another of its re- 

 markable properties. A dead body recovered weeks after sub- 

 mergence in a peat bog will show little or no decomposition. This 

 shows that peat has very great power to inhilnt and even ijreveni: 

 l)acterial life processes. 



The gardener knows that he can safely use manure made 

 with peat provided it has been exposed long enough. This long 

 exposure to weather results in the acidity of the peat giving way 

 to a condition of neutrality or alkalinity, while the inhibitory 

 properties towards bacterial life have given place to an abilit}' to 

 support an intense bacterial activity. 



In its acid state, peat contains very little soluljle humus, but 

 after exposure it has become rich therein. ( 14) Bottomley. 

 prompted, apparently, by what happens during the weathering of 

 peat moss litter, experimented and found that this weathering- 

 process could be speeded up by saturating it with certain aerobic 

 bacteria. Peat that has been changed by these aerobes, steril- 

 ized, and then saturated with nitrogen-fixing organisms of the 

 groups B. Radicicola and Azotohacter, is the Bacterised Peat or 

 Humogen of Bottomley. Bottomley discovered Humogen during 

 a search for a suitable medium in which to convey cultures of 

 nitrogen fixing organisisms to the soil. 



Soil inoculation came to be practised as a result of Hellriegel 

 and Wilfarth's discovery of the nitrogen fixing bacteroids in 

 th'e nodules frequently found on the roots of legumes. These 

 bacteroids live in symbiosis with the plant, providing it with 

 more nitrogen than it requires in return for carbonaceous and 

 mineral food. Often, however, the roots of legumes are not 

 infected under field conditions. This may be due to the fact 

 that the biological conditions of the soil are such that the organ- 

 ism is unable to live in it, or it may be due to other causes. In 

 Norfolk it has long been the practice to grow legumes, especially 

 clovers and trefoils, before wheat. For Avheat, the dominant 

 plant food in England, is nitrogen. The Norfolk practice, al- 

 though much older than Agricultural Chemistry, is evidently 

 based on the foundation that the clover crop adds nitrogen to the 

 .soil, by reason of the bacteroids that live in symbiosis with it 

 on its roots. In the light of Bottomley's researches, however, 

 it would seem that there is also an additional reason, i.e.. that 

 the radicicola bacteria produce accessory plantfood substances. 

 As has already been stated, soil inoculation came to be prac- 

 tised sulxscf|uent to the discovery by Hellriegel and Wilfarth that 

 a legume whose roots were infected by the bacteria was not only 

 independent of soil nitrogen, .but added to the soil, on its decay, 

 the excess of nitrogen that had been gathered from the air for 

 the plant by the nodule bacteria. It is obvious that agricultural- 

 ists were high in the ho])e that i)rovided they grew legumes 



