[Nagaoka (1903)] dealt with plots in the rice fields which had not been manured for the three previous years and which were then treated with manure at the rate of 100 kgm. ammonium sulphate, 100 kgm. potassium carbonate and 100 kgm. double superphosphate per hectare. Twelve series were worked in triplicate and received manganese sulphate in varying quantities, equivalent to 0–55 kgm. Mn2O3 per hectare, one set of three being left untreated. The cultivation was normal and the application of manganese was found to influence the yield of rice. 25 kgm. per hectare gave the best result and increased the harvest of grains by one-third; higher doses of Mn2O3 gave no better crop. The percentage of grain relative to the straw was also increased. The increase in both respects was evident all through the series from 10 to 55 kgm. Mn2O3 per hectare. The conclusion was reached that the application of this salt to soils poor in manganese would be a commercial advantage.

The next year ([1904]) the experiments were extended to observe the after effects of the initial doses of manganese sulphate. The harvest of grain was greatest in those plots that had received 30 kgm. Mn2O3 per hectare, while it was approached very closely by that from the plot with 25 kgm. Mn2O3, which had proved the best in the first year’s experiments. The maximum increase of yield over the unmanured plots in the first year was 37%, while in the second year it dropped to 16·9%.

[Asō (1904)] also obtained an increase of one-third in produce of grain when 25 kgm. Mn3O4 per hectare (as manganous chloride) was applied to rice. The development of the plants was improved and the treated plants flowered about four days before the untreated ones.

[Loew and Honda (1904)] grew Cryptomeria japonica in beds, treating the soil with various manures and with iron or manganese sulphate. The latter favoured increase in height, and within 11⁄2 years the cubic content of the trees had increased to double.

[Fukutome (1904)] grew flax in pot cultures, each pot containing 8 kgm. soil, to which was added ·4 gm. MnCl2 . 4H2O and ·4 gm. FeSO4 . 7H2O. This mixture had a marked effect on the growth of the flax, but the individual salts in doses of ·4 gm. per 8 kgm. soil had but little effect.

[Namba (1908)] applied manganese salts to onion plants in pots with a considerable measure of success. Pots containing 8 kgm. loamy soil were manured and received:

the manganese sulphate being applied in high dilution as top dressing. The bulbs and leaves were considerably stimulated by small doses of manganese sulphate, the best results being obtained from (2), which represents a manuring of 22 kgm. MnSO4 per hectare. An increase of the dose lessens the beneficial effect, as the toxic action begins to come into play. The actual figures obtained may prove of interest.

Wt. leaves Wt. bulbs Total weightBulbs & roots
& roots Absolute Relative leaves
gm.gm.gm.gm.
1.29·5 8·538·0100·0·28
2.38·022·560·5159·2·59
3.35·516·551·0134·2·46

[Uchiyama (1907)] carried on a variety of experiments with manganese sulphate on several plants on different soils, both in the field and in pots, and found that the compound exercised a favourable action in most cases when applied in appropriate quantities. In summarising his results he stated that both manganese and iron stimulate the development of plants, different plants varying in their susceptibility to the action. Sometimes a joint application of the two salts is the most beneficial, sometimes an individual application is the better, in which case manganese sulphate is generally better than ferric sulphate in its action. The stimulating action of manganese varies greatly with the character of the soil, and the mode of application also affects results. As a general rule the manganese acts best when applied as a top dressing rather than when added together with the manure. Further the stimulating action differs greatly with the nature and reaction of the manurial mixture. Uchiyama concludes that 20–50 kgm. per hectare of crystallised manganese sulphate is a good general amount to apply.