302 HOW CROPS FEED. 
It is seen that the ammonia-salts gave about one-fourth 
less crop than the nitrate of potash. The potash doubt- 
less contributed somewhat to this difference. 
The author began some experiments on this point in 
1861, which turned out unsatisfactorily on account of the 
want of light in the apartment. In a number of these, 
buckwheat, sown in a weathered feldspathic sand, was ma- 
nured with equal quantities of nitrogen, potash, lime, 
phosphoric acid, sulphuric acid, and chlorine, the nitrogen 
being presented in one instance in form of nitrate of potash, 
in the others as an ammonia-salt—sulphate, muriate, phos- 
phate, or oxalate. 
Although the plants failed to mature, from the cause 
above mentioned, the experiments plainly indicated the 
inferiority of ammonia as compared with nitric acid. 
Explanations of this fact are not difficult to suggest. 
The most reasonable one is, perhaps, to be found in the 
circumstance that clayey matters (which existed in the 
soil under consideration) “fix” ammonia, 7. e., convert it 
into a comparatively insoluble compound, so that the 
plant may not be able to appropriate it all. 
On the other hand, Hellriegel (Ann. d. Landw., VIL, 
53, u. VIIL, 119) got a better yield of clover in artificial 
soil with sulphate of ammonia and phosphate of ammonia 
than with nitrate of ammonia or nitrate of soda, the quan- 
tity of nitrogen being in all cases the same. 
As Sachs and Knop developed the method of Water- 
Culture, it was found Ly the latter that ammonia-salts did 
not effectively replace nitrates. The same conclusion was 
arrived at by Stohmann, in 1861 and 1863 (Henneberg’s 
Journ., 1862, 1, and 1864, 65), and by Rautenberg and 
Kiihn, in 1863 (Henneberg’s Journ., 1864, 107), who ex- 
perimented with sal-ammoniac, as well as by Birner and 
Lucanus, in 1864 (Vs. St, VIIL, 152), who employed 
sulphate and phosphate of ammonia. 
The cause of failure lay doubtless in the fact, first noticed 
