214 On Permanent and Temporary Meadows and Pastures. 
to the acre, whilst the plot without manure gave 2662-6 lbs. to 
the acre; a difference of 2136"31bs., which would not pay for 
the quantity of farmyard-manure employed. Doubtless, it 
might be said, that the quantity of farmyard-manure was ex- 
cessive, and, according to the rule I have laid down, it ought to 
have been restricted to 9'87 tons per acre, which would be five 
times the weight of the hay actually produced. But, supposing 
that with such a reduction the return had been the same, it is 
still clear that the additional quantity produced would not have 
paid for the manure, and that it would have been more econo- 
mical to omit the manure altogether. 
Messrs. Lawes and Gilbert continued these experiments for 
13 3'ears, without any further addition of farmyard-manure. 
During the 5 years which followed the omission of the farm- 
yard-manure, the return was maintained at the constant level of 
an annual average of 4841"7 lbs. to the acre ; but in the 7 years 
which followed, it fell to an average of 2541*3 lbs. The 
general average over 20 years for this piece of ground, which 
had received annually during 8 years 13*47 tons of farmyard- 
manure to the acre, which would be an average of 5*575 tons 
a year throughout the duration of the experiment, has been 
4126*3 lbs. per acre, only exceeding, by 172 lbs., the field 
which had only received mineral manure, and by 1845*6 lbs. 
the return of the unmanured field. Thus Messrs. Lawes and 
Gilbert arrived at the following conclusions : — 
" In conclusion, of all the useful elements which farmyard- 
manure contains, it is the nitrogen which is the least profitable 
for the cultivation of grass-lands : assimilable with difficulty, 
it accumulates in the soil, and ends by forming a residue easy 
to estimate, but of extraordinarily slow action. The result of 
this is, that the agricultural value of nitrogen is less in farmyard- 
manure than in soluble manures such as sulphate of ammonia, 
nitrate of soda, &c." 
Certain Organic Manures. — If farmyard-manure, the complete 
manure, par excellence, is not economical for grass-lands, what 
shall I say of the many manures, indefinitely variable in com- 
position, and daily puffed by those who seek to palm off on 
agriculture, to their own advantage, the refuse of industries 
which can be turned to no other account? It is useless to 
examine in detail these various manures. The requirements 
of grass-lands having now been pointed out, it will be easy to 
recognise the value of any manure from its analysis. 
Artificially -loatcred Grass-lands. — As yet I have only referred 
to grass-land that is watered solely by the rain. This is the 
case with all temporary, and with a large number of permanent 
grass-lands. But there are also large extents of grass-land 
