252 ARTIFICIAL MANURES [chap. 



must remain dry ; should rain come the sulphate of 

 ammonia dissolves, washes down into the lawn, and 

 fertilises weeds and grass alike. A more effective plan 

 is to choose a fine morning and put a pinch of sulphate 

 of ammonia into the crown of the plantains and other 

 flat-leaved weeds. 



Nitrate of soda is a substance obtained from certain 

 extensive natural deposits in Chili, and has been 

 brought to this country since about 1835. It forms a 

 grey or pinkish soluble salt which easily picks up water 

 from damp air, and will even pass into a liquid state 

 when left to itself. It is not retained in any way by the 

 soil, and is most commonly employed as a top-dressing. 

 Since it has to undergo no change but can feed the 

 plant directly, it is the most active of all fertilisers, and 

 is particularly effective in forcing on a plant into very 

 rapid growth. Because of its immediate availability, it 

 is also a specially valuable manure in early spring, when 

 the natural processes producing ammonia and nitrates 

 are so slowed down by the cold, that even in rich soils 

 the plant is not obtaining sufficient nitrogenous food. 

 Thus, nitrate of soda is particularly useful to the 

 market gardener who needs to force on his crops rapidly 

 or to get them growing specially early, and very large 

 quantities are thus employed with profit. Nitrate of 

 soda is particularly valuable as a top-dressing for wheat 

 and maize, for grass land that is being laid up for hay, 

 for mangolds, and for cabbages. On heavy soils it often 

 forms an unsatisfactory manure, because it leaves the 

 land in a state of bad tilth, very wet and sticky after 

 rain, and then drying into hard clods. In such cases a 

 mixture of equal parts of sulphate of ammonia and 

 nitrate of soda is even more effective than either separ- 

 ately, and does not interfere with the texture of the soil. 

 It is because of this bad effect upon the tilth that 



