26 



Or Agricultural Chemistry. 



In 1 847, with ammoniacal supply only, we have^ — 



On Plot 10a, 25| bushels of dressed corn and 2891 lbs. of straw. 

 On Plot I8fl, 32^ bushels of dressed corn and 3852 lbs. of straw, with 

 minerals added. 



In 1848, we have, — 



On Plot 10a.* 191 bushels of dressed corn and 2367 lbs. of straw. 

 On Plot 18a, 26f do. do. and 2935 lbs. do. 



In 1849, we have, — 



On Plot 10a, 32i bushels of dressed corn and 2854 lbs. of straw. 

 On Plot 18a, 32| do. do. and 3592 lbs. do. 



On Plot m, 33| do. do. and 3858 lbs. do. 



with minerals added to the two latter plots. 



In 1850, again with ammoniacal salts only, we have, — 

 On Plot 10a, 27 bushels of dressed com and 30S9 lbs. of straw. 

 And the minerals and ammonia give — 



On Plot 18a, 29f bushels of dressed corn and 3927 lbs. of straw. 

 OnPlotl7^29i do. do. and 4034 lbs. do. 



Thus it appears, then, that although Plot \0a, with ammo- 

 niacal salts only, has given every year a considerable increase be- 

 yond that of the unmanured plot, yet the ammoniacal salts thus 

 supplied were evidently much in excess over the minerals available 

 within the soil ; for in every case when minerals have been also 

 liberally supplied, w^e have in corn, straw, or both, a con- 

 siderably larger increase still. In 1849, indeed, the exces- 

 sively mineral-exhausted plot (10a) gives about the same quantity 

 of corn as those which had always a liberal provision of mineral 

 constituents. The straw, however, is deficient. 



The effect of mineral manures for the growth of wheat is then, 

 in these cases, clearly shown : — but what are the circumstances 

 under which this result is obtained ? It is only when, after taking 

 from the land the whole produce of a rotation without return, we 

 provide ammoniacal salts alone, in such quantity as to 3-ield crops 

 year after year larger than the average obtained in the county 

 under the ordinary course of rotation and home manuring ; and 

 the produce thus obtained by ammoniacal salts only, was very 

 nearly equal to that resulting from an annual supply of 1 4 tons of 

 farm-yard manure. We by no means suppose, however, that if 

 some cheap source of ammonia were discovered, we might with 



* The produce of this plot being so small, we had been disposed to suspect that 

 some mistake had arisen either during the harvest or at the time of threshing. It was 

 however observed that the crop in this season was particularly irregular and sickly- 

 where there was a deficiency of minerals ; but as the produce of this plot (lOa) was at 

 the following harvest (1849) considerably more than we should have anticipated, we 

 are disposed to believ^e that the result as stated for 1848 is probably correct, and that 

 the high rate of increase by ammoniacal salts alone, in 1849, was partly due to the 

 72on-exhaustion by the previous crop. ^ 



