82 BULLETIN 47!>, ('. S. DEPARTMENT OF AGRICULTURE. 



dampened, contains from 10 to 12 per cent of nitrogen and from 5 to 

 6 per cent of phosphoric acid. Both of these substances act rapidly. 



POTASH FERTILIZERS. 



For the introduction of potash two salts, kainite and carnal- 

 lite are good. These salts contain sulphuric acid and magnesia in 

 addition to potash. Their use, especially that of the kainite, must be 

 watched carefully, as the chloride easily corrodes the plants, so that 

 too great a quantity should be avoided, especially directly before 

 sowing or transplanting. Disregard of such precautions may lead 

 to the total destruction of the plants. The most practical method is 

 to mix the kainite in the compost heaps with the addition of lime, 

 thus neutralizing the effects of any chlorine that may be liberated. 



PHOSPHOBIC ACID FERTILIZERS. 



Bone meal and Thomas meal, also known as Thomas slag or basic 

 slag, may be used to supply the soil with phosphoric acid. Crude 

 dry bone meal contains from 20 to 22 per cent phosphoric acid and 

 from 4 to 5 per cent nitrogen. Thomas meal, a by-product in the 

 manufacture of steel, which is more generally used in European nur- 

 series, contains from 11 to 23 per cent of phosphoric acid and from 

 38 to 39 per cent of lime, besides iron, manganese, silicic acid, and 

 magnesia. Possible damage may arise from the use of Thomas meal 

 if it is applied just previous to planting the beds. 



LIME FERTILIZERS. 



Lime is not only an important plant substance found in all plant 

 ashes, but it has an important influence on the soil; it hastens the 

 disintegration as well as the decomposition of the organic sub- 

 stances, neutralizes the free acids which may be injurious to the 

 plants, such as humic and phosphoric, and makes the soil loose and 

 friable. Some of the other fertilizers mentioned, bone dust and 

 Thomas meal, contain lime, but with soil very deficient in lime a 

 heavier addition may be necessary. For this purpose burnt lime, 

 carbonate of lime, or marl may be used. 



The burnt or unslaked lime is the most effective form. It contains 

 from 90 to 95 per cent of lime and is generally used as part of a 

 compost. It may also be placed directly on the ground in small 

 heaps and then slaked by pouring over it one-third its weight in 

 water and covering with a layer of earth 3 or 4 inches thick. In 

 24 hours it will change to a fine powder and should then be spread 

 around and worked into the soil. 



The carbonate of lime is a natural product and is simply applied 

 in a pulverized state. When mixed with sand and clay it forms marl, 



