AGRICULTURE AND RURAL ECONOMY. 555 



trition, yet retards their transformation, and thus saves them. 

 At any rate, it is evident that the facts which researches like 

 the above are bringing out may necessitate some changes in 

 the common ways of calculating nutritive values of foods. 



V. MANURES AND VEGETABLE PRODUCTION. 



The ways to restore the fertility of the soil occupy more of 

 the thought of the farmers of our older states to-day than any 

 other subject connected with their farming. The main ques- 

 tion concerns the sources, nature, and effects of manures. In- 

 side this, the special subject of " commercial," " artificial," or 

 " chemical " fertilizers attracts the most attention. 



ARTIFICIAL FERTILIZERS. 



Continuous Use of Chemical Manures. Experiments of Messrs. 



Lawes and Gilbert. 



In a paper read before the Society of Arts, in London, 

 in December, 1877, Mr. Lawes summarized the results of 

 some of the famous Rothamsted field experiments as fol- 

 lows : 



" Permanent Grass. The application of artificial manures 

 alone, containing nitrogen, phosphoric acid, and potash, for 

 twenty-two years in succession, has given an average annual 

 crop of hay of nearly three tons per acre. Twice during the 

 period a second crop has been cut without further manuring; 

 and it has on each occasion yielded nearly two and a half 

 tons more. 



"Permanent Wheat. In like manner, artificial manures 

 used alone, supplying nitrogen, phosphoric acid, and potash, 

 have given an average, over twenty-five years, of thirty-six 

 and three -fourth bushels of dressed grain, and more than 

 two tons of straw per acre, per annum. The produce of the 

 present year was forty bushels of dressed grain, and two tons 

 fourteen hundred-weight of straw. No dung has been ap- 

 plied to this land for thirty-eight years. 



"Root Crops. In 1876, the produce of roots (mangels), 

 with artificial manure alone, containing nitrogen, phosphor- 

 ic acid, and potash, was twenty-two tons eleven hundred- 

 weight, and in the present year (1877) it has been twenty- 



