54 The Rothamsted Wheat Experiments. 



QUANTITY OF AMMONIA REQUIRED TO PRODUCE 

 AN INCREASE OF ONE BUSHEL PER ACRE IN 

 THE WHEAT CROP. 



One important point remains for discussion. It con- 

 stitutes the subject of the fourth section of the report of the 

 first twenty years' experiments, and deals with the amount of 

 increased produce obtained for a given amount of ammonia 

 supplied in manure. The data are furnished in Table XI., 

 which shows the annual average amount of ammonia in 

 manure (or of nitrogen as nitrate, reckoned as ammonia) 

 that was required for the production of one bushel (of 601b.) 

 increase of wheat grain, with its proportion of straw, on 

 the most important plots, in two periods of six years each, 

 and in the total period of twelve years ; in two or three 

 cases there were some modifications made in the manures, 

 but, to avoid complicating the table, these are not introduced. 



Long before the expiration of the first twenty years of 

 the wheat experiments, the investigators published their 

 opinion, founded on experiment, that the grower might 

 assume, for practical purposes, that he would, on the average 

 of seasons, get one bushel of wheat and its proportion of 

 straw, beyond the produce of the soil and season, for each 

 51b. of ammonia applied in the manure for the crop. The 

 results shown in Table XI. confirm this opinion. 501b. of 

 ammonia, or its equivalent of nitrogen, would be supplied in 

 rather under 2cwt. of commercial sulphate of ammonia, or 

 in Ifcwt. of commercial muriate of ammonia, or in about 

 2|cwt. of genuine Peruvian guano, or in rather more than 

 2|cwt. of nitrate of soda. These amounts are more than are 

 usually employed in common practice for the wheat crop, and 

 most growers would consider double these quantities to be 

 very heavy, if not excessive, dressings. Assuming that the 

 results obtained by the use, per acre, of 501b. or lOOlb. of 

 ammonia (or their equivalent of nitrogen in nitrate of soda) 



