22 ARTIFICIAL MANURES [CH. 



more slowly, out of animal or vegetable matter. It is not 

 necessary, therefore, to add the nitrogenous food in the form of 

 nitrates; other suitable combinations can be used, provided the 

 soil organisms can work. Fortunately soil organisms want exactly 

 the same soil conditions as plants, and if the soil is well cultivated, 

 and sufficiently supplied with lime and organic matter, so that it is 

 in a state favourable to plant growth, one can rest assured that it is 

 also favourable to soil organisms and the manufacturing process. 



But when conditions are not favourable to life, e.g. during very 

 cold weather in spring, it is not wise to rely on the soil organisms, 

 and in this case the nitrate should be supplied all ready for the 

 plant. 



The nitrogenous manures are: 



Nitrate of soda. This is ready for use by the plant without 

 undergoing any preliminary manufacturing process; it is, there- 

 fore, especially valuable in cold and wet conditions to ensure 

 an early start in growth, and thus it forms a good spring dressing 

 both for arable and grass land. When a young crop is suffering 

 through the attack of an insect pest, a dressing of about 1 cwt 

 per acre will help the plant to keep going, and to grow out of reach 

 of the pest. Again, in spring time, after a wet winter, when 

 wheat or winter oats are standing still and showing no signs of 

 moving, a dressing is often useful in making them start. 



It can be used for any crop : there is an idea that it is bad for 

 barley, but no direct evidence seems to be forthcoming : certainly 

 the Rothamsted barleys grown with nitrate of soda (and, of course, 

 the other necessary plant foods) give a good sample, and this 

 was also the case in the few Yorkshire trials that have been made 1 . 



Nitrate of soda is also useful for bulky leafy crops, such as 

 hay, cabbages, rape, kale, mangolds, etc. 



The disadvantage of nitrate of soda is that it injures the tilth 

 of heavy soils. This can be corrected by mixing it with equal 

 quantities of sulphate of ammonia. The mixture should be 

 applied immediately it is made. 



Nitrate of soda should be applied only as a top dressing after 

 the plant is up. One to two cwts per acre is a suitable dressing ; 

 larger quantities may give additional yields, but in peace time 

 1 Leeds Bull. No. 75, 1909. 



