The Duration of the Action of Manures. 119 
We have been much gratified by the reception already given 
to our earlier Tables, and we can but hope that the present 
revision and extension of them will be found of real benefit 
and will meet with general acceptance. 
J. Augustus Voelcker, 
A. D. Hall. 
[Copies of this article will be obtainable in pamphlet form at the Society’s 
House, 16 Bedford Square, London, W.C., through any bookseller, or of Mr. John 
Murray, 50a Albemarle Street, London, W. Price one shilling. Half price to 
Members on application to the Society only.] 
THE DURATION OF THE ACTION OF 
. MANURES. 
HOW long the action of a manure may be expected to last in the 
soil is a question of considerable scientific interest, and also of 
immediate practical importance, since an outgoing tenant is 
entitled to compensation for any added fertility he may have 
left in the land for the benefit of his successor. 
The obvious answer would be that of simple arithmetic ; 
the manure contains so many pounds of nitrogen, phosphoric 
acid, and potash ; one or more crops are grown after its appli- 
cation, each containing a certain amount of these constituents ; 
the difference, if any, calculated on the same scale of prices 
should then represent the value of the residue in the soil. 
We cannot, however, work along these lines ; too many other 
factors than the crop withdrawals come into play. The nitrogen 
compounds in the manure in particular are subject to various 
losses of an incalculable nature — some of them are exceedingly 
stable, persist in the soil, and slowly become available to the 
plant ; others change rapidly into ammonia and nitrates, and 
if they are not utilised by the crop are then liable to be washed 
out of the soil or destroyed by bacterial action. At Rothamsted 
the experiments have fully demonstrated that no part of the 
ammonia or nitrates applied as manure and not utilised by the 
the crop persists through the winter for the benefit of the 
succeeding crop. On the lighter soil at Woburn there is a 
small residue, the amount of which depends upon the winter 
rainfall and temperature. Phosphatic manures are less subject 
to loss ; they cannot be destroyed, and washing on ordinary 
soils is negligible. For example, at Rothamsted the whole of 
the unused phosphoric acid applied as superphosphate over a 
period of half a century still remains in the top nine inches of 
