VALUE OF FERTILIZERS. 329 



be, that the guano is still the cheapest manure in the market, but 

 at any rate the price is higher than formerly while there has been 

 no corresponding advance in the price of produce in the markets 

 of the world." 



POTASH AS A MANURE. 



On land where fish, fish-scrap, or guano, has been used freely 

 for some years, and the crops exported from the farm, we may ex- 

 pect a relative deficiency of potash in the soil. In such a case, an 

 application of unleached ashes or potash-salts will be likely to 

 produce a decided benefit. 



Clay or loamy land is usually richer in potash than soils of a 

 more sandy or gravelly character. And on poor sandy land, the 

 use of fish or of guano, if the crops are all sold, will be soon likely 

 to prove of little benefit owing to a deficiency of potash in the soil. 

 They may produce good crops for a few years, but the larger the 

 crops produced and sold, the more would the soil become deficient 

 in potash. 



We have given the particulars of Lawes and Gilbert's experi- 

 ments on barley. Mr. Lawes at a late meeting in London, stated 

 that " he had grown 25 crops of barley one after the other with 

 nitrogen, either as ammonia or nitrate of soda, but without 

 potash, and that by the use of potash they had produced practically 

 no better result. This year (1877), for the first time, the potash 

 had failed a little, and they had now produced 10 or 12 bushels 

 more per acre with potash than without, showing that they were 

 coming to the end of the available potash in the soil. This year 

 (1877), they obtained 54 bushels of barley with potash, and 42 

 bushels without it. Of course, this was to be expected, and they 

 had expected it much sooner. The same with wheat ; he expected 

 the end would come in a few years, but they had now gone on be- 

 tween 30 and 40 years. When the end came they would not be 

 sorry, because then they would have the knowledge they wcro 

 seeking for." 



Dr. Vcelcker, at the same meeting remarked : " Many soils con- 

 tained from li- to 2 per cent of available potash, and a still larger 

 quantity locked up, in the shape of minerals, which only gradually 

 came into play ; but the quantity of potash carried off in crops 

 did not exceed 2 cwt. per acre, if so much. Now 0.1 per cent of 

 any constituent, calculated on a depth of six inches, was equiva- 

 lent to one ton per acre. Therefore, if a soil contained only 0.1 

 per cent of potash, a ton of potash might be carried off from a 



