EXPERIMENTS ON THE MIXED HERBAGE OF PERMANENT MEADOW. 301 
supposed to be due, in part at least, to the fact that plot 12 is earlier sheltered from 
the evening sun, and therefore the less liable to suffer in dry weather. After the 
experiments had been continued for 20 years, however, the soil of each of the plots 
was sampled, in three places, in each case six depths of nine inches, or in all a total 
depth of 54 inches, being taken ; and both the notes made on the sections of the soil 
and subsoil, and the percentages of nitrogen at the respective depths (determined by 
the soda lime method), lead to the conclusion that a considerable part, at any rate, of 
plot 12 must have been made ground, as the mould extended to a greater depth, and, 
as will be seen further on, the percentage of nitrogen in the lower layers was con¬ 
siderably higher than in the case of the other unmanured plot, and indeed higher than 
in that of most of the manured plots. After a careful consideration of the facts, it has 
been decided that the results obtained on plot 3 provide fairer standards with which 
to compare those yielded on the manured plots than would the mean indications of 
the two unmanured plots. Accordingly, all such comparisons, unless otherwise stated, 
have reference to the produce of the unmanured plot 3. 
The average annual decline in yield on plot 3, over the second 10 years compared 
with the first, amounted to nearly 300 lbs. of hay, to rather more than 4 lbs. of 
nitrogen, and to about 22-1- lbs. 0 f total mineral matter. The percentage decline 
over the second period was slightly greater in the nitrogen than in the hay, and 
greater in the mineral matter than in either. The analytical results will show that 
the deficiency was more or less in all of the mineral constituents ; but it was the 
more marked in the cases of the potass and the soda, the phosphoric and the sulphuric 
acids, and especially of the silica. 
It may be concluded that, apart from the influences of season, which were not 
without effect on the result, the reduction of produce on the continuous growth 
without manure was due, in part to deficiency of available nitrogen, but probably 
more still to that of an available supply of potass, of phosphoric acid, and of silica. 
Under these conditions of general want of luxuriance—of no marked predominance 
of either nitrogen or any special mineral constituent, favouring any particular species 
or families of plants—no artificial struggle was set up. The result wms a more 
complex herbage than on any of the manured plots. In other words, a greater 
number of species maintained a place. The proportion of the produce consisting 
of gramineous herbage was comparatively low ; that of the leguminous was fairly 
high ; but the most marked characteristic was the large number, and high proportion 
by weight, of the miscellaneous species. 
Under the infhjence of such great variety in the character and habit of growth of 
the plants composing the unmanured mixed herbage, accompanied it may be supposed 
with correspondingly varied powers of food-collection, we have a considerably greater 
annual assimilation of nitrogen, and of some of the most important mineral con¬ 
stituents, over a given area, than in an unmanured gramineous crop grown separately, 
on arable land, such as wheat or barley for example. The characteristic differences in 
