No. 6. DEPARTMENT OF AGRICULTURE. 497 



First. Those immediately available. 

 Second. Those ver}^ quickly available. 

 Third. Those slowly available. 



Of the first class Sodium nitrate^ or Chili saltpeter, is the chief 

 representative, although not the only one as will be shown a little 

 later. Sodium nitrate has its nitrogen in such a form that the plant 

 can take it up and use it in making plant tissue and seeds, just as 

 soon as the nitrate dissolves in water, and that is as soon as it ap- 

 plied to the soil. This form of nitrogen is immediately available, and 

 all of it is available at once. The sodium nitrate of commerce, con- 

 taining 15-16 per cent, of nitrogen, is made by solution and crystal- 

 lization of an impure material called ''caliche'' which is mined in 

 large quantities from a liigh, dry plateau of Chili. The theory of 

 its formation is that nitrifying bacteria — those bacteria which make 

 nitrates in the soil — acted on large quantities of decaying vegetation 

 which grew ages ago in the mountains above this arid plain. The 

 base supplied in this case was sodium, so there was formed sodium 

 nitrate instead of calcium nitrate, as would be the case in our own 

 soils. Eains washed the sodium nitrate so formed down into the 

 desert where the water evaporated, leaving the nitrates to accumu- 

 late. 



Of the second class Ammonium sulphate is the principal represen- 

 tative. This material jiossihly can be used by the corn plant just as 

 it is, and is hence immediately available, but for most crops certainly 

 it must first be changed by bacteria to nitrates. This process is very 

 rapid, for in the change of complex organic matter to nitrates, the 

 formation of ammonia is the first step, and the liardest step. The 

 rest of the process is easy and rapid. Consequently the nitrogen of 

 ammonium sulphate is very quickly made available to plants. 



Ammonium sulphate is made principally from the ammonia given 

 off in the making of coal gas or coke. The ammonia is absorbed by 

 sulphuric acid, and crj-stallized out. It contains 19-20 per cent, of 

 nitrogen. Every coke oven can be equipped with the apparatus 

 to make ammonium sulphate at very little expense, relatively speak- 

 ing, and the product will more than pay for the expense of the re- 

 torts. 



The third class comprises those substances containing nitrogen in 

 complex organic forms which have to undergo decay and bacterial 

 change in the soil before plants can make use of their nitrogen. In 

 many cases the decay is very slow, that is, the initial decay and change 

 to ammonia is slow. Of these very slow acting fertilizers, — these 

 inert nitrogen carriers, — Doctor Frear has told you, and stated how 

 they can ])e made more quickly available — I refer to leather, hO'Ofs, 

 hair, gartage tankage, peat and so forth. 



Other forms which are quicker acting are dried 'blood, containing 

 10-14 per cent, of nitrogen; psh scrap, 7-9 per cent, nitrogen and 6-8 

 per cent, phosphoric acid; tankage, refuse from slaughter houses, not 

 garbage tankage, containing 5-20 per cent, nitrogen and 1-14 per cent, 

 phosjjhoric acid; perhaps there might be mentioned cottonseed meal 

 and linseed meal, running about 5 per cent, nitrogen. These last 

 products, however, are better fed to stock and the manure applied to 

 the land. 



32—6—1^^11 



