and Permanent Pasture. 
75 
act benejficlally upon vog;otatlon, are far better understood tlian 
those under which nitrates or salts of potash may be applied 
to the land with advantage. For this reason I instituted during 
the last five or six years numerous field-experiments, with the 
S})ecial view of affording to the practical farmer the means of 
judging for himself when he might with advantage employ 
potash-manures or nitrate of soda. 
In 1864 and 1865 my experiments were tried chiefly on light 
sandy soils, and having found potash efficacious when used in the 
shape of muriate or sul])hate of potash, and still more so when 
apj)lied to the land in conjunction with superphosphate of lime, I 
was anxious to ascertain whether the same beneficial effects which 
resulted from the use of potash-salts and phosphates on light soils 
would also manifest themselves on clay-land. In 1866 I conse- 
quently experimented upon heavy land with precisely the same 
manures which in previous years had given me a more or less 
favourable result on sandy soils ; but although several sets of ex- 
periments were tried in various parts of the country, no benefit 
whatever resulted from the application of salts of potash on heavy 
land either to roots or to clover-seeds. 
It is useless to record in detail all the failures, or rather nega- 
tive results, which were obtained with potash-manures on soils 
containing a considerable proportion of clay. I may, however, 
mention in particular that, at my suggestion, Mr. Robert Vallen- 
tine, of Burcott Lodge, Leighton Buzzard, applied salts of potash 
upon potatoes, mangolds, swedes, and clover, five years in succes- 
sion without Experiencing the slightest advantage from them, 
whether they were applied early or late in the season. Some of 
the experimental-fields at Burcott Lodge farm were decidedly 
stiff and retentive, in consequence of their containing much clay ; 
others were of a more friable character and poorer in clay ; but in 
neither case did potash do any good. It is evident, therefore, that 
either these soils contained naturally a sufficient amount of avail- 
able potash to meet all the requirements of the different crops 
experimented upon, or that by good management enough potash 
was restored to the land in the ordinary course of manuring and 
good farming to render the artificial supply of potash superfluous. 
This must not be supposed to be an exceptional case, for, as 
already mentioned, I have not as yet met with a single instance in 
which potash-salts produced any good effect on arable clay-land. 
Field-experiments, in order to be practically useful, should 
always be tried for a succession of years under as great a variety 
of conditions as regards soil, time and mode of application, and 
crops, as possible. It is further desirable to employ the same 
fertilising substances or their mixtures from year to year, and 
altogether to deviate as little as possible in succeeding years from 
