THE FARMER'S MAGAZINE. 



607 



obtain these large crops, he is approaching nearer and 

 nearer the limits at which they must cease." — Ibldi 

 p. 8i. 



Now, obviously, in these empbatical predictions is 

 implied this proposition — That whatsoever flush of fer- 

 tility may at first attend the use of highly nitrogenized 

 manurials, the inevitable consequence sooner or later 

 will be, a corresponding prostration of the productive 

 power of the soil in which they are used. 



Here, then, the question may be brought to a narrow 

 issue, namely this : Are there, or are there not, any 

 manifestations in the Rothamsted experiments, of a de- 

 creasing rate of yield consequent on the use of nitro- 

 genous manures? If yea, then must the experiments 

 be deemed to be confirmatory of Liebig's teaching. If 

 nay, then must the Rothamsted nitrogenous theory be 

 held to be corroborated as far as a set of trials confined 

 to one given soil and climate can yield conclusive evi- 

 dence on so very large a question. 



Now, the manner by which this important point may 

 be satisfactorily settled seems naturally to be, to divide 

 into equal parts the period of years involved in the ex- 

 perimenti", and then to examine whether the mean pro- 

 duce of the second division is greater or less than that 

 of the first. If unequivocally less, Liebig is right, and 

 his antagonists wrong ; if greater, then may the result 

 be deemed as militating against his dicta. 



Arrived at this point, we now at once refer to a 



diagram forming part of the experimentalists' paper of 



1856, vol. xvi. of the Royal Agricultural Journal, in 



which is tabulated each of the yearly products of wheat 



(both corn and straw) of that one of the trial plots 



designated Plot 10 a. In point of time, this instance 



comprised eleven consecutive years, ending with crop 



1855 ; and throughout this long period the soil received 



no dressing save nitrogenous salts (sulphate and muriate 



of ammonia), but in different quantities in different 



years. 



Table I. 



Corn & Straw. 



lbs. 

 During the entire period of eleven years, 

 the total produce was 49,875 



But divided into the quantities pro- 

 duced in the first and second halves 

 of the period, these stand thus : 



First period 26,031 



Second period 23,844 



Decrease in the second period.. 2,187 



Again, in a prior report of these experiments, given 

 in vol. xii. of the same Journal, data are given for show- 

 ing what the corn produce was, exclusive of straw, for 

 six years ending 1850 : 



Table II. Dressed Corn, 

 lbs. 

 It amounted altoirether to 10,728 



In the first three years the produce was,. 5,532 

 In the second three years 5,196 



Decrease. 



336 



Table III. 



From another plot (10 b) which, in eight years ending 

 1855, was ammoniacally manured — 



Corn and Straw. 



lbs. 



The total produce of corn and straw was. . 40,743 



In the first four years the produce was .. 20,927 

 In the second four years 19,816 



Decrease, 1,1 1 1 



But further, it has already been stated that during 

 the various years of each experimental series various 

 quantities of manure were administered. Of these 

 quantities the particulars are given for a number of 

 years sufficient to found any conclusions, as respects 

 only plot 10 A, already adverted to, the period being 

 the same six years ending 1860 spoken of before. 



Table IV. Dressed 



Manure. Com, 



lbs. lbs. 



Quantity of manure employed in the 



first three years 860 



Produce of corn, exclusive of straw, 



in the same period = 5,532 



Quantity of manure employed in 



the second three years 1,100 



Produce of corn, exclusive of straw . .. 5,196 



Increase of manure in second period 241 

 Decrease of produce in dressed corn 



336 



From this it appears that the decrease in the second 

 period occurred notwithstanding an increased use of 

 manure. 



Thus far the tendency of these results is to support 

 Liebig's assertion, that special manures of the nitro- 

 genous kind sooner or later produce an exhausted con- 

 dition of the soil ; and from the experiments in Wheat 

 nrou'ing, we now turn to the reported evidence of a 

 contemporaneous series of trials with Barley. 



Here the same procedure was followed as in the 

 wheat trials— that is to say, these experimental plots 

 were similarly tilled, but variously manured ; and the 

 following condensed table is so constructed as to exhibit 

 the productive results in dressed corn : 



