MINERAL FERTILIZERS. 



75 



to planting. For this purpose, the seed is placed 

 in a tub of convenient size, thoroughly moistened 

 with water, the plaster added, and the whole well 

 stirred. As much as will adhere is dropped with 

 the seed. 



1 68. Gypsum, or plaster, has no caustic proper- 

 ties like quicklime and guano, and therefore seeds 

 are not injured by being placed in immediate contact 

 with it. The vigorous, healthy start which it gives 

 to the young plant is very desirable for both corn 

 and cotton, since weak, sickly plants are almost sure 

 to suffer from insects, or perish from other causes. 

 The noted English farmers, Lawes and Gilbert, found, 

 during four years, an average increase of nearly one 

 ton of hay per acre by the use of gypsum as compared 

 with adjoining land without gypsum. This is one of 

 the cheapest of fertilizers, and should be used by farm- 

 ers and planters who desire an increase of production 

 by a moderate outlay of money. It is not necessary 

 to mix gypsum with superphosphate, because, in the 

 process of making superphosphate from bones, cal- 

 cium sulphate, or gypsum, is always formed at the 

 same time, and constitutes a large part of the super- 

 phosphate. 



169. Common salt has been used as a manure 

 from very ancient times. It can be used with ad- 

 vantage only in small quantities, as a heavy applica- 

 tion destroys vegetation. Common salt, or sodium 

 chloride, consists of two elements, chlorine and so- 

 dium, and is a valuable addition to compost-heaps. 



