150 



THE GARDENER'S ASSISTANT. 



of conservers of soil nitrogen, while arable land 

 from which most of the soil is carted away will 

 be placed at the opposite end of the scale. 



The following table illustrates the amount of 

 nitrogen and of organic matter, both per acre and 

 in parts per hundred, in various soils and moulds, 



reckoning the top 9 inches of dry soil in each 

 case to weigh approximately the following: — 



Arable soil, 

 Pasture soil, 

 Leaf -mould, 

 Peat-mould, 



3,000,000 lbs. per acre 

 2,250,000 lbs. 

 1,500,000 lbs. „ 

 1,000,000 lbs. „ 



Table showing the amounts of Nitrogen and of Organic Matter in various Soils, in quantities per cent and per acre. 





Per Cent. 



Per Acre. 



Nitrogen. 



Organic 

 Matter 



Nitrogen. 



Organic 

 Matter. 



Arable land, Rothamsted, 



Old pasture land, ,, ... 



Old kitchen-garden, ,, 



per cent. 

 0-106 

 0-247 

 0-510 



per cent. 

 1-12 

 3-38 



lbs. 



3,195 



5,558 



11,475 



lbs. 

 33,450 

 76,050 



Prairie land, Niverville, Manitoba, .. 

 ,, Brandon, ,, 

 ,, Selkirk, ,, 

 ,, Winnipeg, ,, 



0-261 

 0-187 

 0-618 

 0-428 



3 42 

 2-66 

 7-58 

 5-21 



5,873 



4,208 



13,905 



9,630 



76,950 



59,850 



170,550 



117,225 



Black soil, Russia, 

 Forest-mould, ,, 



0-607 

 0-450 



7-00 

 8-46 



13,658 

 6,750 



157,500 

 126,900 



Leaf -mould No. 1, France, ... 



Leaf-mould No. 2, ,, 



Peat-mould, ,, 

 Heath-mould, Ghent 



5-00 



5-87 



5-00 



11-65 



17-00 

 9-53 



18-80 

 64-00 



7,500 



8,805 



5,000 



11,650 



85,000 

 141,950 

 188,000 

 640,000 



An inspection of these figures will show how 

 enormously the different soils vary in richness 

 of nitrogen and organic matter, and hence in 

 fertility and power of providing nutriment to 

 plants. 



In a peat-bog we find the conditions most 

 favourable for the accumulation of organic 

 matter. The Sphagnum and other bog plants 

 cover the surface with a perennial growth, 

 which supplies annually a large residue of dead 

 vegetable matter; while the soil being water- 

 logged, and necessarily free from carbonate of 

 calcium, the oxidation of this vegetable residue 

 is reduced to a minimum. 



In fertile meadows and prairie lands we have 

 conditions much more favourable to oxidation. 

 The soil here is not water-logged, but fairly 

 well aerated, and oxidizing agents, both animal 

 and vegetable, are abundantly present. The 

 land being, however, always covered by a thick 

 vegetable growth, considerable accumulations 

 of organic matter may take place in the soil, 

 though never to the extent observed in a peat- 

 bog. 



Turning now to arable land, we find that the 

 conditions have become so favourable to oxida- 

 tion that loss rather than gain of soil nitrogen 

 is probably the general rule. Oxidation is here 

 greatly assisted by the operations of tillage, 

 and by the fact that the land lies in a state of 



fallow during a considerable part of most years. 

 In such soils large quantities of nitric acid are 

 produced, which may be washed out by winter 

 rains and lost. As all arable land was once 

 pasture or forest, the loss of nitrogen and of 

 organic matter that has occurred during culti- 

 vation is obvious. 



The rapid oxidation of organic matter which 

 occurs under tillage means the production of a 

 large amount of available plant -food. The 

 nitrates produced, though liable to be lost by 

 drainage, are also equally capable of yielding 

 valuable crops, and the skill of the gardener is 

 displayed in so arranging his methods of culture 

 that the nitrates shall be a source of profit 

 instead of loss. 



Soils suitable for Azalea Culture. — It may be 

 of interest and value, before passing on to 

 discuss the subject of manures, to give some ac- 

 count of investigations by Georges Truffaut on 

 the growth and culture of Azalea indica. In 

 dealing with the history of the Azalea he says 

 that the culture of the Azalea has widely 

 extended during the last thirty years, the centre 

 of production in France being Versailles, whence 

 the nurserymen annually send more than 100,000 

 plants into the market, and even this does not 

 satisfy the increasing demand. In fact, as the 

 horticultural trade cannot find in France a 

 sufficient quantity of these plants, they are 



