82 CROP GROWING AND CROP FEEDING 



ened, change the volatile carbonate of ammonia to the less volatile sulphate 

 and thus retain it in the manure. A more efficient agent for this purpose, 

 that can be mixed with the manure, but should not be used under the animals, 

 is kainit, or the low grade crude sulphate of potash. The large amount of 

 salt it contains helps to keep the manure moist, and it has the same effect of 

 replacing the carbonate of ammonia with the sulphate and at the same time 

 adding potash, which is usually deficient in the manure in proportion to its ni- 

 trogenous content. Years ago in the southeastern part of Virginia, where 

 there are extensive deposits of plaster rock and also extensive salt deposits, 

 the salt manufacturers got up what was known as the Holston mixture, made 

 of plaster, ashes and salt, and this mixture for a long time had a great reputa- 

 tion in Virginia. Its beneficial effects on crops were largely due to the ashes, 

 and, on some soils, to the plaster, while the salt, though not a fertilizer at all, 

 may have had some effect in the solution of matters of value in the soil. As a 

 rule, where a farm is cultivated in a good rotation and lime is used in connec- 

 tion with the growing of clover there will be little or no use for the plaster, 

 unless it may be in a section where plaster is a remarkably cheap article, and 

 even then it could hardly take the place of lime. 



GAS HOUSE LIME. 



Near the. city gas houses this lime is commonly offered so cheaply that 

 farmers are tempted to use it on their land. We have seen some disastrous 

 results from the use of this lime as it is freshly brought from the gas works. 

 It contains, while fresh, sulphides that are positively poisonous to plant life, 

 and while it may be used with some good effect after a long exposure to the 

 air, even the small percentage of nitrogen it contains in the form of sulphate 

 of ammonia may be positively harmful, so that while it contains a good per- 

 centage of lime, we cannot advise its use. Far better pay a reasonable price 

 for fresh quick lime than have the gas house lime for the hauling. 



SULPHATE OF LIME AS A WASTE PRODUCT. 



Sometimes the manufacturers of fertilizers, in order to make a more con- 

 centrated article of superphosphate, remove a portion of the sulphate of lime, 

 which contains a small percentage of phosphoric acid. This has been sold 

 at about the price of common plaster, and when in a good mechanical condi- 

 tion it is a good substitute for plaster. One manufacturer offers this under 

 the name of "stable dust/' and recommends it for sprinkling manure to pre- 

 vent the formation of the volatile carbonate of ammonia and a consequent 

 loss of nitrogen. Of its proper use in this we have already written. 



