stance of the flesh of fish is enormously high as compared with ordinary 

 foods. It may be said to be, approximately, 75 per cent, of the water-free 

 substance. Some varieties of fish are taken alone for their oil product 

 and agricultural value. This is especially true of the menhaden, vast 

 quantities of which are annually br ought to land, and after being passed 

 through the oil factory are ground and distributed as fish scrap to the 

 manufacturers of fertilisers. The practice of using fish for fertilising pur- 

 poses is many centuries old ; bat until recent years the farmers residing 

 along the coast were the only ones receiving any benefit therefrom. At 

 the present time the nitrogenous elements taken from the sea find their 

 way to the gardens, truck lands, and fields of the interior. 



RELATION OF DIFFERENT CROPS TO FERMENTATIVE ACTIVITY. 



It is a well-established principle of farming that there are certain crops 

 •which cannot be grown continuously upon the same field, while in the 

 case of other crops almost an indefinite growth can be secured. Broadly, 

 it may be said that cereals can be grown upon the same field almost in- 

 definitely and without fertilisation. In such cases, the large crops of 

 cereals which are at first obtained rapidly diminish in quantity until they 

 reach a certain minimum limit, at which point they tend to remain, with 

 variations in yield due only to seasonal influences. On the other hand, 

 root crops of all kinds, and especially leguminous crops, do not continue 

 to flourish upon the some soil, even when liberally fertilised. The neces- 

 sity for rotation, therefore, is far greater in the latter class of crops than 

 with the cereals. It appears from the result of the s< ientific investiga- 

 tions attending this difference of behaviour that the relations of these two 

 classes of growing crops are different toward the soil ferments. In the 

 case of the cereals thejquantity of nitrogen which they require can be ob- 

 tained from humus, or other sources, with little effort. In the case of 

 the other class of crops, such as root crops and those of a leguminous 

 nature, it appears that the humus should be particularly rich in nitrogen, 

 and that when by the activity of the soil ferments the percentage of 

 nitrogen is reduced to a certain limit, there is no longer a possibility of a 

 sufficiently vigorous nitrification to meet the demands of the growing 

 vegetables. There is thus a scientific basis, as well as practical reasons, 

 for a frequent rotation of crops. Even in the case of cereals, which, as 

 mentioned above, can be grown with considerable success without rota- 

 tion, experience has shown that a change from one crop to another is 

 always beneficial. 



THE RELATION OF HUMUS TO SOIL FERMENTS. 



The term humus is applied to those constituents of the soil which have 

 been derived chiefly from the decay of vegetable matter. In this decay 

 the original structure of the vegetable has been entirely lost, and the resi- 

 due, in the form of a vegetable mould of a black or brownish colour, is 

 left distributed in the soil. In the processes of decay, the organic mat- 

 ter of the vegetable is converted largely into acids of the humic series, 

 and the nitrogenous principles of the plant become changed from an al- 

 buminoid to amore inert form, in which it ismore readily preserved. It 

 is this practically inert form of nitrogen on which the soil ferments exer- 

 cise their activity in preparing it for the uses of the plant. It has been 

 a commonly accepted theory in the past, especially since the time of 



