June 2, 1923 
Effect of Manganese on Plant Growth 
783 
in decreased yields; however, upon neutralizing the acidity in the soil 
by the addition of calcium carbonate the plots receiving manganese 
produced very marked increases in yields, thus showing that the reaction 
of the soil is an important factor in determining whether or not an 
application of manganese sulphate will exert a beneficial effect on plant 
growth. 
Funchess {4) has obtained data which tend to show that some acid 
soils contain soluble salts of manganese. He also offers the suggestion 
that the toxic effect associated with soil acidity may be due in part to 
soluble salts of this element. He describes experiments with acid soils 
that contained soluble salts of manganese and were toxic to the growth 
of plants. He found that the toxic effect of the soil was destroyed after 
neutralization with calcium hydroxid. 
In 1920 Olaru (7) published results showing the effect of manganese on 
some of the more important microorganisms concerned with nitrogen 
transformations in soils and leguminous plants. With pure cultures 
of Bacillus radiocicola, Azotohacter chroococcum, Clostridium pasteurianum, 
and Micrococcus ureae and with concentrations of manganese sulphate 
varying from zero to 10 mgm. per liter he obtained a marked stimulation 
in the functions of each of these organisms. The maximum stimulation 
appears to have been obtained with concentrations of about i mgm. of 
manganese per liter. He therefore concludes that the small amount of 
manganese occurring in the soil serves a very useful function with respect 
to the organisms concerned in nitrogen transformation. 
Robinson (ii) has determined the manganese content of 26 different 
and representative soil types in this country. The maximum amount 
found in any soil was 0.51 per cent, the minimum 0.01 per cent, and the 
average 0.20 per cent of MnO, respectively. Various other reports 
concerning the amount of manganese contained in the soils of this and 
other countries will average approximately o.io per cent of this element, 
which is as much as the phosphorus and sulphur contained in soils that 
produce average yields of field crops. 
In the foregoing review it has been the aim of the author to refer to 
those contributions on the subject which contain the more modern views 
concerning the probable function of manganese in its relation to agri¬ 
culture. 
The purpose of this investigation was, first, to show the effect of 
increased concentrations of manganese sulphate on the growth of plants 
in certain soils, and, secondly, to determine definitely if manganese is an 
essential element in the plant economy. 
EXPERIMENTAL DATA 
Citation {4) is a contribution whose data indicate that soluble salts of 
manganese are associated with and may in part be responsible for the 
toxicity of acid soils. To obtain further data on this subject, a series of 
experiments was planned in which plants were grown in acid and in 
neutralized portions of the same soil to which were added equal and grad¬ 
uated amounts of manganese sulphate. The soils selected for the experi¬ 
ments were not only acid but were lacking in capacity to produce good 
crops without the addition of certain plant nutrients. 
43323—23-4 
