POTASH MANUKES 285 



price per unit, preference should perhaps be given to 

 it, but for most ordinary purposes there is probably very 

 little to choose between them. 



Soils Suitable -for Potash Manures. Clays and loamy 

 soils are usually fairly well supplied with potash, but 

 sandy, calcareous, and humus soils, are often deficient 

 in that ingredient. It would, however, be a mistake 

 to proceed upon the assumption that such is neces- 

 sarily and invariably the case. The question can only 

 be determined by experiment, and every farmer who 

 has not already done so, would be well advised to 

 make such a trial, as very surprising results are often 

 obtained. The presence of a certain amount of lime is 

 essential to the proper action of potash manures, and if 

 the soil does not contain enough, more should be added 

 before they are applied. It is sometimes found that 

 potash manures give a much better result on one side of 

 a hedge than on the other. In some cases the difference 

 has been traced to the presence of a larger proportion of 

 lime in one of the two soils which were in other respects 

 very similar. Lime reacts with the salts, liberating the 

 potash and soda, and forming calcium chloride and sul- 

 phate (p. 116). 



Crops which require Potash Manures. Potash manures 

 are generally suitable for all kinds of leguminous crops, 

 roots especially mangolds potatoes, and various garden 

 crops, e.g., carrots, onions, fruits, etc. For cereals and 

 grass they are not, as a rule, so necessary. The effect 

 of potash manures on grass lands is often more con- 

 spicuous in the improved quality of the herbage than in 

 the increased weight of crop. They are particularly 

 favourable to tho development of clovers which are often 

 lacking in the light land pastures. 



Application. Kainite is commonly used at the rate 

 of from 4 to 8 cwts. per acre, and other salts in like 



