REPORT OF THE CHEMIST. 161 



SESSIONAL PAPER No. 16 



In considering the foregoing- data, it would be well to keep constantly in mind 

 that in two very important features the season of 1900 was abnormal in the North- 

 west — an unusual drought in early summer and an exceptionally heavy rainfall in 

 the autumn months. Under these conditions, we may suppose the loss of nitrates 

 during the late autumn was greater than is ordinarily the case. 



Brandon. — Soil in fallow 1900. With certain minor fluctuations, which I think 

 may be accounted for in a large measure by the rainfall, the amount of nitrates keeps 

 up until the early part of September, when it rapidly falls, evidently owing to the 

 heavy rains already referred to, which washed the nitrates beneath the first 8 inches 

 of soil. It has already been remarked that the season of 1899 was more or less normal 

 in character, and it is probably from this fact that the soil in May possessed such a 

 fair amount of nitrates. The largest amount was obtained in the sample taken August 

 11, no doubt due chiefly to the moisture that fell the preceding month promoting 

 the nitrification process. 



On the soil cropped in 1900 we find, as might be expected, a falling-off after the 

 June sample was collected, due undoubtedly to the wheat crop making its draught upon 

 this nitrogenous food. 



Indian Head. — Soil in fallow 1900. This soil, probably owing to a very favour- 

 able physical condition, gave large amounts of nitrates throughout the sum- 

 mer, but these, as in the case of the Brandon soils, rapidly fell off during October 

 from the cause we have advanced. 



Soil in crop 1900. The soil, similarly, was richer in nitrates than the correspond- 

 ing Brandon sample, but in a general way showed the same falling-ofl' as the season 

 advanced, due to the crop's i«equirements. 



It is to be confessed that the present investigiation gives support to the view 

 that the nitrates are largely lost to the surface soil during the late autumn months, 

 hut whether this occurs in normal seasons to the extent here indicated is very doubt- 

 ful. Further work is necessary Jo determine this paint. It seems clear, however, 

 that fallowing encourages the development of the nitrates. 



FERTILIZERS. 



• MARL. 



This material consists essentially of carbonate of lime, but considerable amounts 

 of organic matter, sand and clay, frequently are present. It occurs in beds of 

 varying thicknesses in old lake and pond bottoms, ai.-^^ on the margins of many existing 

 bodies of water, showing their former extension. Usually it is overlaid with peat or 

 swamp muck. It has arisen from the breaking down of countless fresh-water shells, 

 many of which, however, still retain their form, and thus give the name shell marl to 

 the deposit. It is very widely distributed in Canada, samples from beds of marl from 

 almost every large area in the Dominion having been examined in our laboratories. 

 The better and purer marls of Ontario are now being largely used for cement- 

 making. 



Considered agriculturally, marl must be regarded rather as an amendment than 

 a fertilizer ; improving the tilth, neutralizing acidity and promoting nitrification, 

 are amongst its chief functions, though it has a distirct value as a supplier of lime (an 

 element of plant food) for soils deficient in that constituent. 



The application of marl is especially to be recommended for heavy, plastic clays, 

 for very light soils deficient in lime, and for those in which humus predominates. It 

 renders the tilth of the former mellower, allowing air to permeate the soil and the roots 

 to spread more easily ; its addition improves sandy soils, by making them heavier and 

 more retentive of moisture and fertilizing materials. In the slow oxidation of the 



16—11 



