for Twenty Years in succession on the same Land. 311 
less soluble combinations, or both, during the winter*, that hence 
there is less active root-development in the upper and more 
highly nitrogenous layers of the soil in the spring, and that 
hence the barley is more rapidly exhausting the accumulated 
nitroffen of the surface-soil than the wheat. 
7. By nitrogenous manures alone (ammonia-salts or nitrate of 
soda) much more barley was obtained than by mineral manures 
alone ; the produce declined much less in the later years ; and, 
for 20 years in succession, even fair, though not large, crops were 
obtained. This result is a striking illustration of the mineral 
resources of such a soil ; and it shows that when in what may, in 
an agricultural sense, be called a corn-exhausted condition, it 
was deficient in available nitrogen relatively to available mineral 
constituents. 
8. By ammonia-salts and superphosphate of lime together, an 
average produce of more than 47 bushels of dressed corn, and more 
than cwts. of straw, or considerably more than the average 
barley crop of the country, was obtained over 20 years in suc- 
cession ; and the produce of corn increased, and that of straw in 
a less degree diminished, giving a higher total produce, during 
the later than the earlier years. Notwithstanding the great de- 
mand made upon the supplies of potass within the soil, by the 
growth of the crop for so many years by ammonia-salts and 
superphosphate without potass, the addition of salts of potass, 
soda and magnesia, gave no further increase of corn, and very 
little of straw and total produce. The potass-yielding capabi- 
lities of such a soil, and the beneficial effects of the use of 
superphosphate, with nitrogenous manures, for spring-sown corn 
crops, are here strikingly illustrated. 
9. When the same mixed mineral manure, and 200 lbs. of 
ammonia-salts, were applied per acre per annum for 20 years, 
in the autumn for wheat, and in the spring for barley, the 
barley gave more than one-half more corn, nearly one-sixth more 
straw, and nearly one-third more total produce, than the wheat. 
When the same mineral manure was used with a larger quantity 
of ammonia-salts, the result was still in favour of the barley, but 
in a less degree than with the smaller amount. 
10. After applying 400 lbs. of ammonia-salts per acre per 
annum to barley for 6 years, and then reducing the amount to 
200 lbs., the plots so treated gave, for 10 years in succession, 
more produce than those which had only received 200 lbs. 
annually from the commencement. It thus appears that the 
excessive supply of 400 lbs. had left a residue of nitrogen 
within the soil which was available for succeeding crops. 
11. The experiments on barley with nitrate of soda and 
ammonia-salts respectively, are not exactly comparable with one 
