128 Commercial Gardening 



would thus become a medium in which the bacteria would exercise their 

 activity and virulence to the utmost. That is a far more simple and 

 expeditious method of inoculating the soil than cultivating the bacteria 

 in gelatine or powder. One crop of Broad Beans, French Beans, Clover, 

 or Peas would produce trillions upon trillions of nitrogen-fixing bacteria 

 to the acre in the top spit in the course of a season, and cultivators would 

 do well to bear this fact in mind. 



Denitrification. This is the term applied to denote that the nitrates 

 in the soil have become changed into free nitrogen. The nitrates thus 

 become lost. Denitrification is said to be due to certain bacteria, just as 

 the production of nitrates is due to other bacteria. Curiously enough, 

 some scientists say that if air is admitted to the soil nitrogen is set free 

 from the organic matter; and, on the other hand, if air is excluded, nitrogen 

 is set free from the nitrates; and in both cases it is lost. 



These views would appear to be mutually destructive. All good 

 cultivators know from experience the great advantages to their crops 

 arising from allowing a free circulation of air amongst the soil particles 

 and organic matter, and the more thoroughly these are mixed the better 

 the results. Growers of plants in pots always make a point of thoroughly 

 mixing the various ingredients of their special composts so as to secure 

 as much evenness or homogeneity as possible throughout. In field and 

 garden, however, this work, although possible, is rarely practised. And 

 it sometimes happens that enormous quantities of manure are dug or 

 ploughed into a soil which already contains a good and sufficient supply 

 of organic material. In such cases it is possible that, owing to the soil 

 being as it were surfeited or gorged with manure, certain bacteria attack 

 the organic material with the object of releasing the superfluous supply 

 of nitrogen. It has already been shown at p. 110 that even a soil that 

 has been unmanured for fifty years still has a fund of 2500 Ib. of nitrogen 

 to the acre at 9 in. deep just in the region where the nitrate-forming 

 bacteria are most numerous. 



In support of the view that overdosing the soil with manure may result 

 in the loss of nitrogen, the following experiments at Rothamsted may be 



quoted: 



I. PLOT 7; RECEIVING AMMONIUM SALTS (CONTAINING 

 86 LB. NITROGEN AND MINERALS) 



lb. per Acre. 



Nitrogen originally present in 1865 ('1170 per cent) ... 3034 

 Nitrogen supplied in manure, 1865-93 ... ... ... 2408 



Nitrogen supplied in rain, 1865-93 ... ... ... 140 



Nitrogen supplied in seed, 1865-93 ... ... ... 56 



Total nitrogen expected, 1893 5638 



Nitrogen removed in crops, 1865-93 ... ... ... 1932 



Nitrogen found in soil, 1893 (-1146 per cent) 2971 



Total nitrogen accounted for in 1893 4903 

 Leaving nitrogen unaccounted for ... ... ... 735 



5638 



