42 



answer to this question, we take the average produce of the 

 second ten years, 1887-96, of the dunged plots, so that the 

 effect of the residues of the manure may be included in the 

 result. The average produce of wheat on plot 116, receiving 

 each year the manure from 188 Ibs. of nitrogen as food and 

 litter, is during this period 27*8 bushels ; while 41 Ibs. of 

 nitrogen as nitrate of soda, employed with phosphates and 

 potash, have yielded during the same season 30-1 bushels. On 

 the corresponding plots in the barley field, the dung has yielded 

 89*9 bushels, and the nitrate 41*1. In both these cases the 

 nitrogen of the food when converted into manure produces 

 less than one-quarter the effect of the nitrogen in the form of 

 nitrate of soda. The farmyard manure in these experiments 

 is favourably circumstanced, for being of high quality and 

 well rotted, only a small quantity, 7 to 8 tons, is applied every 

 year. Half the quantity of dung applied for ten years on 

 plot 106 gave only 21-7 bushels of wheat, and 30*5 bushels of 

 barley ; there appears therefore to be no reason to regard the 

 larger application of dung as excessive. 



We may approach the same question in another way. On 

 plot lla, as already mentioned (p. 17), the manure furnished 

 by 188 Ibs. of nitrogen as food and litter was applied for five 

 years (six in the case of the barley experiments), and during 

 the rest of the twenty years the land was left unmanured. 

 We have already calculated (p. 19) the quantity of corn 

 produced by the residue of the farmyard manure during the 

 latter unmanured period ; we can add this subsequent yield to 

 that given in the years when the manure was actually applied, 

 and thus arrive at the maximum produce which the manure 

 was capable of producing. 



In the wheat experiment we have the manure from 940 Ibs. 

 of nitrogen in food and litter producing an increase of 24-5 

 bushels during the five years of its application, and an addi- 

 tional 25*6 bushels during the thirteen following years, after 

 which the effect ceased. We thus have 940 Ibs. of nitrogen 

 giving an increased produce of 50-1 bushels, or 1,000 Ibs. pro- 

 ducing 53 bushels. On plot 6, receiving nitrate of soda and 

 ash constituents, we have on an average of twenty years 

 1,000 Ibs. of nitrogen producing 322 bushels. The nitrogen 

 of the food when converted into farmyard manure had thus 



