Ratio of Increase in Crop to Ammonia supplied. 103 



increased the efficacy of the supplied nitrogen. The general 

 result is that, whilst it is essential that there should be & 

 liberal provision of mineral constituents, the amount of 

 produce is more dependent on the supply of available nitrogen 

 within the soil than of any other* constituent. 



QUANTITY OF AMMONIA EEQUIEED TO PEODUCE 

 AN INCEEASE OF ONE BUSHEL PEE ACEE IN 

 THE BAELEY CEOP. 



The third section of the report of experiments on the 

 continuous growth of barley for twenty years in succession 

 on the same land discusses the amount of ammonia in 

 manure (or its equivalent of nitrogen in other forms) 

 required to yield a given increase of grain (and its propor- 

 tion of straw) ; also how much the quantity will vary, 

 according to the amount applied per acre, to the supply of 

 mineral constituents, and to the characters of the seasons. 

 A comprehensive table is constructed to show the amount of 

 ammonia or of nitrogen in nitrate of soda, or in rape-cake, 

 or in farmyard manure, reckoned as ammonia required to 

 yield one bushel (521b.) of increase of barley grain, and its 

 proportion of straw, under a great variety of conditions of 

 manuring, and in each of the twenty seasons. In each case 

 increase is calculated over the produce on the corresponding 

 plot without nitrogenous manure, the increase on the nitrate 

 of soda and the farmyard manure plots being taken over the 

 mean unmanured produce. 



One example in detail will suffice to indicate the kind of 

 information deducible from the table, which is far too 

 extensive to reproduce. Five plots each received 2001b. 

 ammonia - salts per acre per annum for twenty years, 

 but in other respects were variously treated as follows : 

 (1) Without any mineral manure ; (2) with superphos- 

 phate ; (3) with sulphates of potash, soda, and magnesia ; 



