On the Gi'Oivth of Barley hy different Manures, S^-c. 519 



liere to do more than reiterate in a single sentence our assent to 

 the palpable truism, that if the mineral constituents of our crops 

 be deficient they must be supplied. We have on other occasions 

 (to say nothing of the present paper), so fully illustrated the 

 importance of keeping up a liberal provision in the soil of the 

 mineral constituents of our crops — and also so frequently shown 

 the usual circumstances of their removal or return, and the re- 

 quirements for their direct supply, under an ordinary course of 

 practical agriculture with rotation as it is — that we leave to the 

 judgment of the reader, the pervading insinuation in the paper 

 -above referred to, that in our views the essentialness of the supply 

 of the mineral constituents is ignored. 



The experiments quoted by Baron Liebig to show the propor- 

 tion of nitrogen recovered in the increase of crop to that supplied 

 in manure, were made upon hay. We hope to record our results 

 relating to that crop in an early paper. It will then be seen, 

 liow far facts relating to grass, when cut green, are applicable as 

 the foundation of conclusions regarding a ripened cereal grain. 

 On the present occasion we have only to show the proportion of 

 nitrogen recovered to that supplied in manure, in the experi- 

 ments on the growth of barley. 



AA^ere we to have attempted the direct determination of the 

 nitrogen in every separate stock of the different nitrogenous 

 manures used during the six years of the experiments in Hoos- 

 Field, and also in the corn and straw produced each year on 

 each of the 20 plots (making, as would be necessary, duplicate 

 analyses in each case), this would have involved from 500 to 

 600 such determinations ; a labour which we could not undertake. 

 As it is, the number of nitrogen analyses recorded in the follow- 

 ing Tables amounts to more than 100. 



The percentages of nitrogen in pure sulphate and muriate of 

 ammonia, and in nitrate of soda, are of course well known. As 

 these substances occur in commerce, however, a certain average 

 allowance has to be made for moisture and impurities. In 

 estimating the amounts of nitrogen supplied to the soil by their 

 use, we have made a deduction from the amounts they contain in 

 a state of purity, founded not on the analysis of each sample 

 actually employed, but on the experience of ourselves and others 

 as to the average composition of the commercial salts. The 

 exact amount of deduction thus made has been stated at page 488, 

 and it is more probably too high than too low. On this supposi- 

 tion the amounts of nitrogen we have supplied in manure will be 

 somewhat greater than has been assumed ; and in this case, the 

 numbers we arrive at to represent the proportion of the supplied 

 nitrogen, which is recovered in the immediate increase, will be 

 in a corresponding degree somewhat too high. The other 

 nitrogenous manure employed, namely, rape-cake, will, according 



2 M 2 



