Lubricating oil should contain as much fat as possible, be clear from acid and mucus and form no sediment. Such is the crude rape-seed oil, and this is its principal use.
By-products.
Rape-seed cake is a valuable by-product of rape oil manufacture. The cake is broken by means of mills made for the purpose, where the cake passes between toothed steel cylinders. After breaking it may be ground into a fine meal in roller mills. This meal contains 9.23 per cent of oil and 5 per cent of nitrogen, which makes it a valuable feed, when it does not become rancid, and a valuable fertilizer at all times. It has been found that 85 per cent of the protein substances, 88 per cent of the fat sub stances, and 78 per cent of the non-nitrogenous substances in rape meal are digestible. While a valuable feed, rape-seed meal needs to be used in conjunction with other feeds, for when used exclu sively it forms flesh of a soft and flabby and wholly undesirable character.
The high percentage of nitrogen contained in the meal and the amount of phosphoric acid in the ash make rape-seed meal a very valuable fertilizer. Analyses have shown 6.82 per cent of the meal to be ash, and of the ash 32.7 per cent is phosphoric acid. Besides these two valuable soil constituents, the meal leaves a residue of organic matter to im prove the mechanical and water-holding properties of the soil. The 5 per cent of nitrogen contained in the rape cake is almost immediately available. In their experiments at Rothamsted, England, Lawes and Gilbert found that 70.9 per cent of the nitro gen in the rape-seed meal was utilized by the crop the season of application. In this it compared very favorably with nitrate of soda, of which 78.1 per
cent was found to be immediately available.
Value.
Grisdale, of the Ottawa Experimental Farm, esti mates the cost of growing an acre of rape at six dollars and ninety-five cents. The cost will, of course, vary with the locality, price of labor, and other factors. When care is taken, crops of 1,000 pounds of seed per acre are not uncommon. If sold at five cents per pound, the seed would bring fifty dollars per acre. Estimating the growing of the crop to cost ten dollars per acre, the rape would still give a net return of forty dollars per acre. This would surpass a crop of ninety bushels of oats per acre, taking into consideration the straw and the heavier soil-feeding of the rape. Rape may therefore prove a paying crop in some sections.
Literature.
Thomas Shaw, Forage Crops, Orange Judd Com pany, New York ; John Wrightson, Fallow and Fodder Crops. Chapman & Hall, London ; W. M. Hays. Rape Test of Varieties, Bulletin No. 46, Minnesota Experiment Station : A. S. Hitchcock, Rape as a Forage Crop, Farmers' Bulletin No. 164, United States Department of Agriculture ; John A. Craig. The Rape Crop, Its Growth and Value for Soiling and Fattening Sheep and Swine, Bulletin No. 58, Wisconsin Experiment Station ; Forage and Folders, Report, Kansas State Board of Agri culture, Quarter Ending March. 1900; J. H. Cris dale, The Rape I'lant : Its Culture, Use and Value, Bulletin No. 42, Central Experimental Farm, Ottawa, Canada ; The Book of Rothamsted Experi ments, Compiled by A. D. Hall, John Murray, London (1905); Wm. T. Brannt, Animal and Vege table Fats and Oils, Henry Carey Baird & Com pany, Philadelphia.