434 
On the Continuous Growth of Wheat on the 
has received 16 applications of mineral manures, and 16 appli- 
cations of salts of ammonia. 
It is evident that an experiment of this description is well 
adapted to ascertain the unexhausted residue of a substance 
like salts of ammonia. During the first 8 years the two plots 
received different artificial manures, yielding a very similar 
produce. In the following table will be found the average 
produce of the mineral manures, and also of the salts of am- 
monia in periods of 8 years ; further, for comparison, is given 
the average produce of plot 5, where minerals alone have 
been employed. 
Table XXV. — Showing the Bushels of Dressed Geain and Total 
Produce (Corn and Straw) upon Plots 5, 17, and 18 ; 5 being 
Manured with Mixed Mineral Manures alone during the whole 
Period, and 17 and 18 receiving alternately Minerals and Salts 
of Ammonia, 
Plot 5, 
Mineral 
Manures 
every 
Year. 
Bushels 
per Acre 
Dressed 
Corn. 
Plots 
17 or 18, 
Mineral 
Manures 
only. 
Bushels 
per Acre 
Dressed 
Corn. 
Plots 
17 or 18, 
Salts of 
Ammonia 
only. 
Bushels 
per Acre 
Dressed 
Corn. 
Plot 5. 
Total 
Produce 
Corn and' 
Straw. 
Plots 
17 or 18. 
Minerals 
onlj'. 
Total 
Produce 
Corn and 
Straw. 
Plots 
17 or 18. 
Ammonia 
only. 
Total 
Produce 
Corn and 
Straw. 
8 years, 1852-1859 .. 
8 years, 18tJ0-18G7 .. 
8 years, 1868-1875 .. 
8 years, 1876-1883 .. 
19 
151 
14 
121 
18s 
ICi 
15 
32i 
28J 
27f 
3191 
2450 
2144 
1899 
3235 
2G96 
2404 
1869 
5938 
5297 
4781 
4930 
32 years, 1852-18G3 .. 
151 
30 
2421 
2551 
5237 
Looking at the bottom line — which gives the average of the 
whole period of 32 years — it will be seen that during the 
16 seasons in which plot 17 received salts of ammonia, and in 
the 16 seasons in which plot 18 received that substance, the 
average produce was 30 bushels per acre ; while the plot which 
during the alternate years received minerals only, yielded 
15|^ bushels ; or in other words, only a fraction of a bushel 
more than plot 5, which had received no ammonia during the 
whole period ! 
In the 400 lbs. of salts of ammonia it is estimated that 
86 lbs. of nitrogen are applied to an acre. 
The resources of the soil were evidently competent to furnish 
the nitrogen contained in 15 bushels of wheat, and its straw, as 
we obtained that produce on plot 5 which receives no ammonia. 
In the remaining 15 bushels and its straw, obtained by the 
application of the salts of ammonia, certainly less than 26 lbs. 
