514 Report of Experiments icitli different Manures 
required), so that the estimation of the quantity of haj to which i 
corresponded is necessarily a matter of calculation merely. The 
plan adopted was — to fold sheep on each plot, the number depend- 
ing upon the amount of grass ; to move the hurdles day by day as 
required ; to note the time taken to consume the produce ; and 
then to estimate, approximately, the amount of hay to which the 
consumed grass was equivalent, on the assumption that each, 
sheep would, on the average, consume grass equal to IG lbs. of 
hay per head per week. Such an estimate, though only approxi- 
mative, still affords a very useful indication of the relative, if not 
the actual, amounts of after-grass of the respective plots. In 
1860 and 1862 it was so eaten off twice, but in each of the other 
years only once. 
It will be obvious that, as the animals would return to the 
land by far the larger proportion of both the mineral constituents 
and the nitrogen of the produce, to ser^ve as manure for the first 
crop of the succeeding season, and so on each year, the amounts 
of hay estimated as above described cannot be added to the 
actual amounts of the first crop, and the sum reckoned as the 
annual yield on the respective plots. The latter would, however, 
it is true, be somewhat higher than the amount of first crop hay 
alone. 
Judging from the relative amounts of first-crop hay where 
the mineral constituents would probably be in relatively large 
amount (without manure, with purely mineral manure, or with 
farmyard manure, for example), and where, therefore, the produce 
would be the more directly limited bv the conditions of season, 
it would be concluded that these were the least favourable in 1859, 
more so in 1860, and still more favourable, and about equally so, 
in 1861 and 1862. Judging, in the same wa}', from the esti- 
mated amounts of hay corresponding to the after-grass, it would 
appear that the period of its growth was the most favourable in 
1860, and nearly equally so in 1862 (these being the two years 
in which the produce was eaten off twice), that it was somewhat 
less favourable in 1861, and less so still in 1859. But it is 
obvious that the influence of accumulation, or of non-exhaustion 
of previous manuring, as well as that of season, has to be taken 
into account as affecting the produce in one year compared with 
another. The less the exhaustion of the more active manurial 
constituents by the growth of the first crop, the greater will be 
the accumulation for the after-growth, though their activity will 
greatly depend on the climatic conditions. And, again, varia- 
tions in the amount of after-grass will affect the amount of 
manure left by the animals on the surface of the land, to be 
washed in and serve for the first crop of the succeeding year ; 
though it will be obvious that any effects of such variation will 
