126 The Duration of the Action of Manures. 
crop has been taken, and compensation to that extent should be 
given to the outgoing tenant, always assuming that the soil is 
one needing phosphatic fertilisers so that the original expen- 
diture was justified. When phosphatic fertilisers are used on 
suitable grass land the scale of compensation should be even 
higher and should last for more than four years, because of the 
cumulative change wrought in the herbage as well as the actual 
phosphoric acid left behind. 
Conclusions. 
The facts already brought to light by the experiments upon 
the Little Hoos Field at Rothamsted may be summed up as 
follows. As regards farmyard manure we can distinguish 
between the nitrogenous compounds introduced by the con- 
sumption of cakes and other concentrated feeding stuffs, and 
the compounds derived from the straw and the undigested 
residues of such coarse foods as hay. The former Avill have an 
immediate effect on the first crop, and to a much smaller extend 
on the second crop, after which they disappear ; the latter 
compounds act slowly, do not Avaste, and have a measurable 
value for many years, though for practical purposes we may 
neglect their action after the fourth year. 
Among nitrogenous fertilisers ammonium compounds and 
nitrate of soda have no perceptible action after the first year ; 
Peruvian guano, rape cake, and similar fertilisers containing 
proteins leaA 7 e very little residue after the first year, and none 
after the second. On the other hand, nitrogenous fertilisers of 
the avooI, hair, bone class are sloAvly acting and non-wasting, 
their effect may be expected to persist for at least four years. & 
Phosphatic fertilisers, even Avhen soluble like superphosphate, 
do not Ayaste in the soil, and their residues continue to be effec- 
tive until they have been exhausted by the crops. 
To. one other point attention may be called, though it does 
not arise strictly out of these experiments. It is seen that the 
residues of active nitrogenous fertilisers are Avasted ; this Avastage 
takes place in the winter, for soils in the autumn after the crop 
has been removed become very rich in nitrates, which usually 
disappear before the spring. Hence, especially in rich soils, 
there will be a great economy if before the winter the land can 
be occupied by a rapidly groAving catch crop Avhich Avill convert 
these fugitive nitrates, &c., into insoluble plant material, after- 
wards ploughed in to become available for another crop. 
A. D. Hall, M.A., F.R.S. 
(Late of the Rothamsted Experimental Station.') 
Mostyn Load, 
Merton, S,W. 
