The amount of potash removed by the different crops from the soil will be considered in a subsequent chapter. We need only say here that the class of crops which remove the largest quantity are the root crops, especially mangels. The loss is least in the case of the cereals. The amount of potash contained in the straw of cereals is about three times the amount of that removed in the grain. _Potash removed in Milk._ Lastly, we may refer to the potash removed in milk, which, on an average, may be taken at 10 lb. per annum for each cow. _Potash Manures._ Of potash manures the chief are the sulphate and the chloride, or, as it is commercially known, the "muriate." The chief source of potash manures are the Stassfurt deposits already referred to. Wood-ashes have also been used in large quantities in the past (chiefly as a potash manure), and in some parts of the world are still used. A considerable source of artificial potassic manures is the refuse manufacture of sugar-beet, such a large industry in Germany. Potash occurs as a constituent of certain other manures, more valuable for nitrogen and phosphoric acid, such as guano and dried blood. FOOTNOTES: [126] According to Boguslawski and Dittmar, the total amount of potash calculated as sulphate of potash in salt water equals 1141 x 10^{12} tons. [127] See Storer's 'Agricultural Chemistry,' vol. ii. p. 291. [128] See Appendix, Note I., p. 220. [129] See Appendix, Note II., p. 220. [130] According to Way, different samples of drainage waters were found only to contain from .00003 to .00031 per cent. APPENDIX TO CHAPTER VI. NOTE I. (p. 215). AMOUNT OF POTASH IN DIFFERENT MINERALS. Felspars-- Percentage of potash. (_a_) Orthoclase { 9.11 10.28 11.07 12.12 12.47 { 13.49 14.35 15.21 16.7 (_b_) Oligoclase 0.50 (_c_) Labradorite 0.33 Mica { 5.61 6.20 7.23 8.26 8.95 { 9.00 10.25 12.40 13.15 Amphibole 0.25 2.96 Pyroxene 0.34 2.48 Leucite 13.60 18.61 Zeolites 0.30 9.35 0.98 4.93 Stassfurt potash salts-- Per cent. (_a_) Polyhallite, _potassium sulphate_ 28 (_b_) Karnallite (KCl.MgCl_{2}6H_{20}), _potassium chloride_ 24 to 27 (_c_) Sylvin, pure _potassium chloride_. (_d_) Kainit (K_{2}SO_{4}MgSO_{4}MgCl_{2}6H_{2}O), _potassium sulphate_ 32 (_e_) Schoenite (K_{2}SO_{4}, MgSO_{4}, 6H_{2}O), pure _potassium magnesium sulphate_. NOTE II. (p. 217). The quantity of potash obtainable from various plants in the manufacture of potashes on a large scale is illustrated by the following statements. 1000 lb. of the following vegetative products yield the following quantities of potashes:--