1912.] New Forms of Potash Manure. 102$ 



and in the Eifel district of Germany, there are masses, usually 

 volcanic in origin, of highly felspathic rocks containing up to 

 8 or 10 per cent, of potash in the form of double silicates. 



In forming an estimate of the value of a material as manure 

 it is not, -however, sufficient to have merely the percentage of 

 potash ; the condition in which that potash exists must be 

 known too. Potash in a soil or manure may be in either 

 of two forms. It may be in an available state in which the 

 plant can make use of it at once,' or it may be in such a 

 condition that years of "weathering" are necessary before 

 the plant can take it up. 



For instance, a clay soil will contain up to 2 per cent, or so 

 of potash (also mainly in the form of double silicates), but 

 this may become so slowly available for the use of the plants 

 that application of soluble potash manure may be necessary 

 to obtain maximum production from the soil. 



The potash manures usually employed — kainit, sulphate, 

 and muriate of potash — are soluble in water, and it is 

 assumed that plants can make use of these at once if required. 

 At the same time, owing to the absorbent properties of the soil, 

 there is little fear of loss through drainage. In the case of 

 the silicates referred to only a fraction of one per cent, of 

 the potash is soluble in water, or weak acid corresponding 

 to the dissolving power of the plant root, and the question 

 arises as to how far it will become available for the use of 

 crops in a reasonable time. 



A considerable number of experiments have been carried 

 out to test this point. Detailed reports and discussion of 

 results will be found, for instance, in the Transactions of the 

 Highland and Agricultural Society of Scotland, 1887; 

 Bulletin 104, Bureau of Plant Industry, U.S. Dept. of 

 Agriculture, published 1907; Mitt, der Landw. Ins. Univ. 

 Breslau, 191 1; K. Landtbr. Akad. Handl. och Tidskr, 49 

 (1910), No. 8 (abs. Exp. Station Record, U.S. Dept. of 

 Agri., Vol. xxv., No. 5); Deut. Landw. Presse, 38 (191 1), 

 No. 63. 



The results of these different experiments are to a great 

 extent contradictory and inconclusive, possibly owing to the 

 fact that the effect of a potash manure is seldom so clearly 

 marked as that of nitrogenous or phosphatic manures. In 



