I 



BACTERIA AND PROTOZOA IN THE SOIL i5 



Life in the Soil 



And here we come to our second source of organic matter. 

 Garden soil is as teeming with hfe as is a great city. It is 

 recorded that Prince Bismarck once said to Lady Randolph 

 Churchill: "Have you ever sat on the grass and examined 

 it closely? There is enough life in one square yard to appal 

 you." 



It has always seemed to me a strange thing for the Prince 

 to have said. To begin with, throughout his long life he had 

 shown but an imperfect sympathy with the lower members 

 of the Animal Kingdom, and then, again, he was a man not 

 easily appalled ; but the saying is perfectly true. There are 

 millions of bacteria performing various functions. There are 

 millions of unicellular animals of an amoeboid and flagellate 

 nature creeping in and out the interstices of the soil. As a result 

 of 365 counts, made on consecutive days, of the bacteria and of 

 six different species of protozoa in a natural field soil, it became 

 clear that from day to day the numbers varied greatly, and that 

 this variation had no connexion with the weather. Fortnightly 

 averages showed certain seasonal changes, and the numbers 

 of both bacteria and protozoa are greatest towards the end of 

 November and smallest during February. The seasonal fluctu- 

 ations resemble those of many aquatic organisms and are in- 

 dependent of rain-fall and temperature. There is a noticeable 

 relationship between the numbers of certain Amoebae and of 

 the bacteria. More Ainoehae mean fewer bacteria. The former 

 eat the latter. 



It is easier to kill Ajnoehae than to kill bacteria. By an 

 accident at Rothamsted it was discovered that certain soil 

 heated to 98 degrees oxidizes more rapidly than normal 

 soil and in it bacteria were increasing at a more rapid rate 

 than usual. At the same time nitrates and ammonia in the 

 soil increased very much more rapidly. There is evidently 

 some living organism in the soil which consumes bacteria 

 and is destroyed at 98 degrees Fahrenheit while the bacteria 

 persist. By using such partially sterilized soil it is chiimed 

 that a crop of tomatoes which normally produced 32 to 35 

 tons per acre could be increased to 80 or 90 tons. 



