258 FERTILIZERS. 



abounds in the soil, it need not be added, though in its ordinary state, it is quite insoluble ; 

 but, by the use of lime, may we not always obtain it in sufficient quantity for use of vegetation, 

 without a special addition to the soil 1 and I think experience proves the economy of the use 

 of lime, and has a preference to Liebig's patent silicate of potash and soda, which has created 

 some noise, and has been recommended on the authority of his name. 



6. Of Mixed Saline Substances. 



I have spoken of the simple salts, as they have been used separately and alone. As plants 

 require several elementary bases, in combination with acids, it seems more agreeable to the 

 nature of the case to add mixtures of the salts of soda, potash and lime, as then the general 

 wants of vegetation will be far more likely to be met and supplied. Thus, if the sulphates of 

 lime, soda, magnesia and common salt, or the nitrates of potash and soda, with common salt 

 and gypsum, were mixed and used, the result would be better than the use of either singly. 

 There are various modes or proportions which may be observed in combining them, which will 

 meet the wants of the crops : these proportions may be determined by consulting the analyses 

 of the plants, which are given in books upon this subject. Indeed there is no other source 

 from whence our rules for the formation and application of fertilizers can be derived. These 

 mixtures may be used as top dressings, or they may be incorporated with the compost or ma- 

 nure heap. But in general these very soluble fertilizers, as the nitrates and sulphates of the 

 alkalies, are better adapted to growing crops, and to be used as top dressings. Top dressings 

 may be applied in two states, either in solution in water, or in powder, and sown broad cast. 

 For the former, the solution should be extremely dilute, scarcely or only slightly saline : in 

 the latter state the powders require intermixture with gypsum or ashes, in order to secure an 

 even distribution over the field, and also to prevent a concentrated effect upon the different 

 parts of it. When concentrated they have an effect which is described by the term burning — 

 a term expressive of the apparent action of too high a temperature. Instead of ashes, which 

 has been often recommended for mixing with saline matters, bone dust, when it is possible to 

 procure it, will be equally good or better than ashes, or if the ground mineral phosphate can 

 be procured, it will be quite as good as either. It is now ascertained that the latter may come 

 into use to a limited extent, as it is now proved to exist in veins in primary rocks. The mine- 

 ral called eupyrchroite, which I discovered at Crown Point, forms a vein varying in width from 

 two to six feet, and hence may furnish a large amount of native phosphate of lime, in the same 

 condition as it exists in the soil. This substance is less soluble than bone dust, and hence its 

 immediate effects may not be so striking as to arrest the attention of the farmer at once, yet it 

 will last longer and be more durable. Immediate effects are often desirable, and even neces- 

 sary, but when farmers have employed a fertilizer which is common in the constitution of all 

 plants, they need not regard the substance as wasted or lost, even though the first effects upon 

 his crops are not very striking. Thus common carbonate of lime, when sown upon his fields, 

 may not produce au increase in the value of his first crop, yet lime is one of the essential con- 

 stituents of all plants, and must exist in the soil : so especially the phosphate of lime is still 



