THE Errect oF MANGANESE COMPOUNDS ON SOILS AND PLANTS 397 
The addition of manganese sulfate to the soil resulted in a positive 
stimulation in the ammonifying power. The addition of calcium ecar- 
bonate resulted in a greater stimulation than that caused by the manga- 
nese alone. The stimulation of the manganese is not so great in alkaline 
soil as in soil deficient in calctum. This is as would be expected, for the 
solubility of the manganese is decreased. 
Nitrification.— To the soil used for nitrification tests, 220 parts per 
million of nitrogen in the form of ammonium sulfate was added. The 
calculated quantities of solutions of manganese and ammonium sulfate 
were mixed, and were added to the soil in the culture bottles together 
with sufficient water to bring the soil to a moisture content of 25 per cent 
(dry basis). The cultures were incubated for four weeks. At the end 
of this time the extracts and determinations were made as described, 
and the results, expressed as parts of nitrates per million parts of dry 
soil, are given in tables 17 and 18. The experimental error of this deter- 
TABLE 17. Errect or MANGANESE SULFATE ON NITRIFICATION OF AMMONIUM SULFATE 
IN DuNnxKIRK Sitt Loam 
(Cultures incubated for thirty days) 
Nitrates, 
average of 
Parts per million of manganese added 4 cultures Relative 
(parts per amounts 
million 
of soil) 
De cc oca nde eee ete El APRS tie Rclact nae Sta ai aren hese ae eee 234 100 
LO Ran tee i ea aaron) Sc iehs etic Sty mee 236 101 
DD. oncc56 80d dO GE Se ce eae ene Re wee tae 252 108 
3) EE eich ccacecnurs poet eddy SRR gee Bon, WE ep ae 197 84 
5D) ow edicid he Cee ee eee Sig aa ees AY Oe ak ey Ee 156 67 
WG ss ose a0 nek GALISS DE AOS Cte ACEI TRE ae AER en SEL TEL 136 58 
Ci) PR ae ee NEES. be gras heya vibe saayis pusysey see peas Se be | 122 52 
mination is large, and the data given in the tables indicate that manganese 
sulfate in low concentrations did not affect the nitrifying power of the 
soil. In soils containing larger amounts of manganese, however, the 
nitrification was checked. 
