24 PLANT PRODUCTS 



bulky character. They are much appreciated by the Kentish 

 hopfarmers, and are particularly adapted for dry, gravel, 

 and chalk soils. They do not, however, decompose at all 

 readily in the soil, and their beneficial action is probably 

 quite as much physical as chemical. 



Damaged Cakes. — There are some cakes obtained by 

 pressing oil seeds which are not suited for cattle feeding. 

 To animals castor cake is distinctly poisonous and rape cake 

 is very bitter and distasteful. Further, some meals normally 

 of value for cattle feeding have become accidentally damaged 

 by fire, water, or mould. All of these materials come in 

 usefully as fertilizers for the soil. Part of their value de- 

 pends upon secondary effects, independent of the percentage 

 of nitrogen, which will vary from 4 to 7 per cent. Some of 

 the least edible, such as castor and rape, may very possibly 

 injure wireworms or other pests. I^inseed meal (see p. 136) is 

 stated to be eaten by wireworms, and then by swelling 

 inside them cause them to die. These materials decompose 

 fairly quickly in the soil. Mowha cake contains saponin 

 (see p. 145), and is used to remove earthworms from golf 

 greens. 



Meat Meal and Refuse from Meat Extract Works. 

 — These contain usually about 5 to 8 per cent, nitrogen, and 

 10 to 15 per cent, phosphoric acid. Their action in the soil 

 is very similar to fish and blood. The members of this group 

 of fertilizers stand midway in their action between " Chemical 

 Manures " and farmyard manure. 



REFERENCES TO SECTION I 



Russell, " Artificial Fertilisers, Their Present Use and Future Pros- 

 pects," /. Soc. Chem. Ind., 191 7, p. 250. 



Hendrick, "Field Trials with Nitrogenous Manuring,"/. Soc. Chem. 

 Ind., 1911, 523. 



Special Leaflet No. 57. Board of Agriculture. 



Vcelcker, /. Roy. Agric. Soc. Eng., 1904, 306; 1916, 244. 



Russell, " Manuring for Higher Crop Production," p. 7 (Camb. Univ. 

 Press). 



Hobsbaum and Grigioni, " Production of Nitrate of Soda in Chile," 

 /. Soc. Chem. Ind., 1917, p. 52. 



Kilbum Scott, " Production of Nitrates from Air, with special reference 

 to a New Electric Furnace," /. Soc. Chem. Ind., 1915, p. 113. "The 

 Manufacture of Nitrate of Ammonia," Chem. News, 19 17, p. 175. 



Lamb, "The Utilization of Condemned Army Boots," /. Soc. Chem. 

 Ind., 1917, p. 986. 



