14 BULLETIN 42, U. S. DEPARTMENT OF AGRICULTURE. 
growth 3 per cent. With 30 parts per million, manganese oxidation 
was increased 48 per cent and growth 19 per cent. With 50 parts 
per million, manganese oxidation was increased 45 per cent and 
growth 12 per cent. 
Subsequent experiments with other poor soils were made, the results 
of which are similar to the one recorded above. One of these tests was 
with a poor clay loam from Maryland. Manganese sulphate was 
added to the soil extract in amounts of 10, 30, and 50 parts per 
million. There was considerable improvement in growth and an 
increase in the oxidizing power of the plants following the manganese 
treatment. The relative growth was for the untreated 100; manga- 
nese 10 parts per million, 132; manganese 30 parts per million, 111; 
and manganese 50 parts per million, 105. The relative oxidation was, 
respectively, 100, 133, 133, and 160. 
A similar test was made with a sample of poor Collington sandy 
loam. The manganese was added at the rate of 20 parts per million, 
manganese in the form of chloride, sulphate, nitrate, carbonate, and 
dioxide being used. The results of the action of these various com- 
pounds on this soil extract are shown in Table V. The experiment was 
made from November 22 to December 6. 
Table V. — Effect of Truing anese (20 parts per million) on growth and oxidation of wheat 
in extracts of poor Collington sandy loam. ( Untreated extract = 100.) 
Treatment. 
Relative 
Relative 
growth. 
oxidation. 
100 
100 
96 
102 
102 
100 
110 
280 
108 
233 
110 
271 
Extract untreated. . . . 
Extract + MnCl 2 
Extract 4- MnS0 4 .... 
Extract + Mn(N0 3 ) 2 . 
Extract + HnC0 3 ... 
Extract -*- Mn0 2 
The chloride and sulphate showed practically no increase in oxida- 
tion or in growth in this soil solution. The other salts of manganese 
increased oxidation considerably and also the growth. Where the 
nitrate was used, oxidation was increased 180 per cent and growth 10 
per cent. With the carbonate, oxidation was increased 133 per cent 
and growth 8 per cent. With dioxide, oxidation was increased 171 
per cent and growth 10 per cent. 
The effect of manganese on an extremely poor lawn soil is reported 
in the next experiment. The soil used was very unproductive. The 
natural vegetation is stunted and attempts at lawn making had failed. 
The water extract of this soil is a poor medium for plant growth, but 
is much improved by treatment with carbon black, which acts as an 
absorbent. A chemical examination of the soil showed it to contain 
dihydroxystearic acid and picoline carboxylic acid, both of which are 
harmful to plants. 
