62 MANAGEMENT OF THE FORCING-HOUSE. 



" i. Lettuce of good quality can be grown under glass 

 in an artificial soil such as we have described, with the use 

 of commercial fertilizers. We are not prepared to say at 

 present that its quality is as good as the best lettuce 

 grown in rich, natural soil. 



"2. A crop of forcing-house lettuce, raised as above 

 described, takes from the soil in roots and heads, per 

 1,000 heads, not less than : 



Grams. Pounds. Ounces. 



Nitrogen. . . .282.6 Equivalent to 3 15 Nitrate of soda 



Phosphoric acid 87.7 i 2 Dissolved bone black. 



Potash 621.0 " 2 10 Muriate of potash. 



"3. To supply this plant food to the soil under the 

 conditions of our experiment, it was necessary to add to 

 the soil the following quantities of fertilizers per 1,000 

 plants, or per 387 square feet, the area used in our ex- 

 periment for 1,000 plants : 



Pounds. Ounces. Costing, cents. 



Nitrate of soda 9 >3 25 



Dissolved bone black 2 15 4 



Muriate of potash 3 7 



36 



On the use of fresh stable manure. All experienced 

 gardeners place the greatest faith in old well-rotted stable 

 manure, and uniformly avoid fresh manure. A discus- 

 sion of the behavior of fresh manure in its relation to 

 nitrification is made in the Connecticut report which is 

 quoted above, and it seems to throw much light upon 

 the craft of g?rdeners. A somewhat full abstract of the 

 article is here given. It is known that when nitrogen 

 compounds, either in the form of nitrates or occurring in 

 organic matter in manures, are fully exposed to the air, 

 the nitrogen may be lost as gas by the action of certain 

 denitrifying microbes. It now seems probable that simi- 

 lar losses, though much less in amount, may be occasioned 

 in the soil by the use of fresh stable manure. Wagner 

 has found that the nitrogen of well-rotted stable manure 



