DIFFERENT KINDS OF MANURE. 313 



Muriate of ammonia contains 31 per cent of ammonia =25| of 

 nitrogen. 



Nitrate of soda contains 16 2 / 5 per cent of nitrogen. 



Nitrate of potash, 13f per cent of nitrogen. 



From these figures you can ascertain, when you know the price 

 of each, which is the cheapest source of nitrogen. 



" True," said I, " but it must be understood that these figures re- 

 present the composition of a pure article. The commercial sul- 

 phate of ammonia, and nitrate of soda, would usually contain 10 

 per cent of impurities. Lawes and Gilbert, who have certainly had 

 much experience, and doubtless get the best commercial articles, 

 state that a mixture of equal parts sulphate and muriate of ammo- 

 nia contains about 25 per cent of ammonia. According to the fig- 

 ures given by the Doctor, the mixture would contain, if pure, over 

 28 per cent of ammonia. In other words, 00 Ibs. of the pure article 

 contains as much as 100 Ibs. of the commercial article." 



As to whether it is better, when you can buy nitrogen at the 

 same price in nitrate of soda as you can in sulphate of ammonia, 

 to use the one or the other will depend on circumstances. The 

 nitrogen exists as nitric acid in the nitrate of soda, and as ammo- 

 nia in the sulphate of ammonia. But there are good reasons to 

 believe that before ammonia is used by the plants it is converted 

 into nitric acid. If, therefore, we could apply the nitrate just 

 where it is wanted by the growing crop, and when there is rain 

 enough to thoroughly distribute it through the soil to the depth of 

 six or eight inches, there can. be little doubt that the nitrate, in 

 proportion to the nitrogen, would have a quicker and better effect 

 than the sulphate of ammonia. 



"There is another point to be considered," said the Doctor. 

 " Nitric acid is much more easily washed out of the soil than am- 

 monia. More or less of the ammonia enters into chemical com- 

 bination with portions of the soil, and may be retained for months 

 or years." 



When we use nitrate of soda, we run the risk of losing more or 

 less of it from leaching, while if we use ammonia, we lose, for the 

 time being, more or less of it from its becoming locked up in in- 

 soluble combinations in the soil. For spring crops, such as barley 

 or oats, or spring wheat, or for a meadow or lawn, or for top- 

 dressing winter-wheat in the spring, the nitrate of soda, provided 

 it is sown early enough, or at any time in the spring, just previous 

 to a heavy rain, is likely to produce a better effect than the sulphate 

 of ammonia. But for sowing in the autumn on winter-wheat the 

 ammonia is to be preferred. 

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