Il6 AGRICULTURAL BACTERIOLOGY. 



nitrate formation should therefore, if possible, be checked until 

 the denitrifying bacteria have ceased their growth. This ma}' 

 be accomplished, in part, by keeping the manure well packed 

 together so as to exclude air, for the nitrifying bacteria demand 

 a good supply of oxygen and will not produce nitrates in well- 

 compacted manure. 



In the use of manurial fertilizers it is necessary to bear in 

 mind that the advantage from the process comes from two 

 wholly different factors. The soil gains in fertility from the 

 actual food materials in the manure used, but it may also gain 

 an equal, and, in some cases, a greater advantage, from the 

 large quantities of bacteria thus inoculated into the soil ready 

 to produce further chemical transformations. But these bac- 

 teria may contain some of the species which cause a loss as 

 well as some that cause a gain of nitrates. To check the action 



of the former and to stimulate the action of the latter should 







be the aim of the proper use of manurial fertilizers. Anything 

 which teaches the farmer to accomplish this end brings him so 

 much nearer to the ideal condition of continued soil fertility. 



THE COMPOST HEAP. 



It is evident that in a compost heap there must be going on 

 a series of similar bacterial transformations. By proper means 

 the farmer may make use for his soil of almost any organic 

 material which contains nitrogen or the minerals needed for 

 his crops. Vegetable tissues of all sorts contain more or less 

 nitrogen and may readily be brought under the influence of 

 the bacteria which are able to reduce them to plant foods. A 

 valuable source of such material may be obtained from sea- 

 weeds, if they are at hand, or indeed any abundant vegetable 

 substances may thus be heaped into a mass, and, if this is 

 moistened sufficiently by rains, the bacteria are sure to work 

 within it, gradually transforming the nitrogens, and in the end 

 converting them into nitrates for plant food. Into his garbage 



