for Twenty Years in succession on the same Land. 
283 
As without manure, so with farmyard manure, over whichever 
period the wheat is averaged, the barley gives a considerably 
greater quantity of corn, but considerably less straw, than the 
wheat. Of total jiroduce, however, when the wheat is averaged 
over the whole 28 years, the barley gives (over 20 years) an 
average annual excess of 222 lbs. over the wheat ; when the first 
20 years of wheat is taken the excess of barley is 342 lbs. per 
acre per annum ; but when both wheat and barley are taken over 
the same 20 years (in the case of the wheat after 8 preceding 
years of the same manuring and cropping), the barley gives a 
slight average annual deficiency of total produce, namely, 
131 lbs.* 
From these facts it may be concluded that, excepting differences 
due to season, or other incidental causes, a given amount of farm- 
yard manure annually applied to a given soil will, when averaged 
over a sufficient period, yield identical amounts of total produce 
of the autumn-sown and autumn-manured wheat, and of the 
spring-sown and spring-manured barley. 
The practice of applying 14 tons of farmyard manure per 
acre, per annum, is, it is true, as unusual as that of growing 
either wheat or barley so many years in succession on the same 
land. Nevertheless, the results of such an experiment are of 
much interest. They may be briefly summarised as follows : — 
With the great accumulation of constituents within the soil, the 
produce of both crops is higher in the later than in the earlier 
years ; much more corn, but much less straw, was obtained with 
the spring-sown and spring-manured barley, than with the autumn- 
sown and autumn-manured wheat ; but the two crops gave almost 
identical amounts of average annual total produce (corn and straw 
together). Notwithstanding that the dung supplied several times, 
as much nitrogen, and more of all other constituents, its produce 
seldom exceeded that of some of the artificial mixtures of mineral 
manure and ammonia-salts, or nitrate of soda. 
Lastly in regard to the effects of the farmyard manure, attention 
has been called (pp. 139-141 and 151) to the influence of the 
accumulated matter on the physical condition of the soil, in- 
creasing its porosity, enabling it to retain more moisture, and 
rendering the crop much less liable to injury from adverse 
climatic conditions, and especially from drought. Future experi- 
* The general result is the same whether the acreage produce of the two crops 
be compared, as above, or only the increase of produce by manure; and as in 
adopting the increase as the basis of comparison, the diminution of produce with- 
out manure (which moreover was different for the two crops) would be a necessary 
element affecting the ailculation, it is concluded that, for the purpose in view, 
the comparison of the produce of the two crops is less open to objection than that 
of the increase. 
