8 Tlie Hidorij of a Meld newly laid down to Permanehi Gh-asS. 
mated to supply more pliosphorio acid than was removed in the 
crops ; and, taking the dung and artificial manures together, 
there was, taking the average of the whole period, nearly twice 
as much supplied in manure as removed in the crops. 
Lastly, as to the potash : — It was only over the second period, 
when the largest amount of artificial potash-manure was em- 
ployed, and when the hay crops had not reached their maximum, 
that the calculations show an excess of potash supplied in 
manure. Over the first period there was a considerable, and 
over the third period there was a slight, deficiency of supply. 
It is further of interest to observe that over neither period was 
the dung alone estimated to supply anything like the amount 
of potash removed in the crops; whilst oVer the whole period it 
did not supply two-thirds as much as was removed in the hay. 
Taking the whole period of 23 years, th&re is, in dung and 
artificial manures together, an average of only 2 lbs. more potash 
supplied per acre per annum than was taken off in crops. 
The calculations show, therefore, that the manures supplied 
considerably more nitrogen and phosphoric acid, but only about 
as much potash, as the crops removed. 
It is seen that the estimates for the whole period show an 
average of 58'2 lbs. of nitrogen, 15'5.1bs. of phosphoric acid, and 
02 -1 lbs. of potash, removed in the crops, per acre per annum. 
On this point it may be stated that the Rothamsted experiments 
on the continuous growth of grass without manure have shown 
that, in first crops of hay alone, more than 30 lbs. of nitrogen, 
and nearly 30 lbs. of potash, are, on the average, annually re- 
moved in the crops so grown for many years in succession on- 
the Rothamsted soil ; and it is to be supposed that something 
like these amounts would be available to the growing grass 
crops under consideration. 
Upon the whole, it may be concluded that, under the con- 
ditions of manuring provided, there would be accumulation 
within the soil both of nitrogen and phosphoric acid, though 
but little, if any, of potash. Indeed, the results afford a forcible 
illustration of how great is the exhaustion of potash when hay 
is sold, and how important it is that there should be adequate ' 
return either in dung or in artificial manures. 
It has to be borne in mind, however, that whilst neither 
phosphoric acid nor potash is subject to any appreciable or 
material loss by drainage, the nitrogen of manures is subject to 
such loss. In the case of artificial nitrogenous manures, such 
as ammonia-salts and nitrate of soda, the loss may sometimes 
be very considerable when they are applied to arable land, when 
there is no crop actively growing, and in wet seasons when 
