156 Commercial Gardening 



in 1872 to 289,000 tons in 1906, and more than one-half the quantity is 

 obtained from gasworks. 



Sulphate of ammonia is neither an acid nor an alkaline manure; it is 

 a neutral substance, and when added to the soil causes a loss of calcareous 

 or chalky food (see p. 161.) 



Nitrolim or Calcium Cyanamide. This manure has recently come 

 into prominence as a nitrogenous fertilizer. It is obtained from calcium 

 carbide, so much used for acetylene gas. When this is heated to 1000 C. 

 the nitrogen from the atmosphere combines with it and forms about 60 

 per cent of calcium cyanamide. This contains 20 per cent of nitrogen, 

 the remainder being 24 per cent quicklime, 10 per cent carbon, and 15 per 

 cent of various mineral oxides. In appearance nitrolim resembles basic 

 slag, being a dark -grey finely powdered substance. In action it is some- 

 what similar to sulphate of ammonia, and is much slower in its action than 

 nitrate of soda. 



5. PHOSPHATIC MANURES 



Phosphatic manures are derived from various sources, and are valuable 

 because they induce the earlier production of flowers and fruits. They 

 are mainly useful for the supply of phosphoric acid, which is an ingredient 

 of every part of a plant, and exists in considerable quantities in some, such 

 as the Cauliflower, the Radish, Peas, and Beans. There are fair supplies of 

 phosphoric acid in the soil, as much as 2750 Ib. to the acre being recorded 

 at Rothamsted in a field that had not been manured for fifty years. As 

 already stated, from 20 to 125 Ib. of phosphoric acid per acre is a sufficient 

 supply for most crops. These quantities may be liberated by deep cultiva- 

 tion and the addition of stable manure, and by the judicious application 

 of some of the following "artificials", chiefly remarkable for their phos- 

 phates. 



Bones. The use of bones as a manure dates from the earliest times, 

 and has become more extensive than ever. Between 45,000 and 60,000 tons 

 of bones in various forms have been imported annually in recent years from 

 the East Indies, the Argentine, Brazil, Morocco, Egypt, and the Continent. 

 In addition to this it is computed that about 60,000 tons of bones are also 

 available annually in the United Kingdom. This would bring the manurial 

 consumption of bones up to about 100,000 tons per annum. 



In a natural state bones are crushed into various sizes, and in the form 

 of bone meal are very popular with gardeners. A ton of bone ash contains 

 from 800 to 900 Ib. of phosphates; while 1 ton of dissolved bones, and 

 1 ton of steamed bones contains from 300 to 600 Ib. of phosphates. Bone 

 flour is also a valuable phosphatic manure, containing over 300 Ib. of phos- 

 phates in 1 ton, and also yielding up a small quantity of nitrogen. Dis- 

 solved bones also yield up even a larger supply of nitrogen. 



Superphosphate. This is one of the most popular phosphatic manures. 



