in Stackyard Fields Wobuni. 
7- 
cient amount of a soluble salt to produce 11 and 14 bushels of 
barley per acre. How much more may exist in the soil to be 
available for other crops having longer lives and a more powerful 
arrangement of roots it is impossible to say. It is, however, 
evident that the subject is one of great interest, bearing as 
it does upon the value of unexhausted manures, &c., and must 
be one of many others which science has to take in hand. 
In a lecture on root crops recently delivered by Dr. Gilbert 
at Cirencester, he pointed out that the use of nitrogenous 
manures was to increase the non-nitrogenous substances in our 
crops. He showed that in the field at Eothamsted which has 
long been under root crops, we obtained about 20 lbs. increase 
of sugar in our mangolds, for each pound of nitrogen which we 
apphed in manure. In cereal grain, starch is found in the 
seed, and not sugar, but it is quite possible that a similar cal- 
culation would show that the increase of starch obtained by the 
application of one pound of nitrogen would not differ very much 
from that of the sugar in the mangolds. 
The very large increase in the wheat, and the still larger 
increase in. the barley, by means of salts of ammonia and nitrate 
of soda alone, show how large must be the amount of mineral 
substances existing in the soil. We must not, however, infer 
from this that these crops remove the same amount of potash 
or phosphoric acid which is carried off by plants under ordinary 
circumstances. In some respects plants resemble man and 
animals : where food is abundant they take of the best, and 
sometimes more than they can make use of ; where it is scarce 
or of inferior quality they do the best they can with it. In 
some of our barley experiments, where nitrogen, phosphoric acid 
and potash, and the same amount of nitrogen and phosphoric 
acid without potash, have been applied for a number of years, 
the crop has been nearly the same in both instances ; but while 
the straw in one case contained 48 lbs. of potash, in the other 
it contained less than 7 lbs. Were it not for the economy of 
the plant, our soils, when constantly cropped without a suffi- 
cient supply of important manure ingredients, would be much 
sooner exhausted. 
Although the large increase in wheat and barley obtained in 
the Woburn experiments by the application of salts of ammonia 
and nitrate of soda cannot be obtained in the ordinary practice 
of farming, still it is quite certain that, by more careful attention 
to the various circumstances necessary to insure success, a much 
larger yield of crop from a given quantity of manure is quite 
possible. Now that we have in several counties important ex- 
periments carried out under the superintendence of practical 
farmers, we may expect a much more rapid diffusion of know- 
