1919] SOILS — FERTILIZERS. 427 



merit careful consideration at the present time of the utilization of our liberal 

 supply of sodium salts as economic supplements to a limited amount of 

 potassium. 



Relation of sulphates to plant growth and composition, H. G. Miller {Jour. 

 Afff. Research [U. S.], 17 {1919}, Ao. 3, pp. 87-102, pis. -'/).— lu this contribution 

 from the Oregon Experiment Station it is reported that " pot experiments to 

 show the effect of sulphur fertilizers — namely, sodium sulphate, calcium sul- 

 phate, and sulphur on red clover, rape, and oats were carried on with three 

 different soils, including one with a high sulphur content, one that did not re- 

 spond to elemental sulphur in the field, and one that did. 



" To eliminate the sulphur compounds acting upon the insoluble plant food 

 and soil organisms these plants were also grown on sand receiving the sterilized 

 soil extract, and certain pots received the additional sulphur fertilizers as the 

 soil. Sodium sulphate and calcium sulphate were added daily in solution form. 

 The elemental sulphur was mixed with the soil and calcium carbonate at the 

 time of sowing the seed. Sodium nitrate solution was added daily to eliminate 

 available nitrogen as a limiting factor of growth, and also to determine what 

 effect sulphates would have on nitrogen assimilation by the plant. The plants 

 were grown for two and one-half months, and the dry weights of the tops were 

 recorded. The total sulphur and nitrogen was determined in the majority of 

 cases. 



"Addition of suli)hate and elemental sulphur enhanced the growth of the 

 plants grown in pots in the greenhouse. The corresponding increases obtained 

 on the soil extracts indicated that sulphur acted directly in promoting this 

 growth. The great increase in the nitrogen content of the clover grown on the 

 soil where sulphates had been added is the result in all probability of the 

 sulphates stimulating the action of the legume bacteria. Sulphates caused in- 

 creased root development and number of nodules on the clover grown in the 

 soil pots." 



A list of references to literature on the subjct is given. 



Available fertilizer from smelter by-products, P. J. O'Gaka {Proc. Wash. 

 Irrig. Inst., 5 {1917), pp. 102-110). — Experiments on the effects of sulphur 

 dioxid on alkali soil and on crops showed that " (1) the water solubility of 

 the alkali was lowered; (2) there was a reduction in carbonate; (3) there 

 was an increase in sulphate; (4) there was an increase in available potash; 

 (5) crops fumigated daily throughout their period of growth with sulphur 

 dioxid in concentrations just below the toxic limit . . . showed either a 

 slight gain, or at least no loss in total vegetable matter produced, as compared 

 with check plats grown under identical conditions but not treated with 

 sulphur dioxid; (6) the sulphur content of the plants was increased." 



Field experiments with field and truck crops in which elemental sulphur 

 was added at the rate of 400 lbs. and sulphuric acid at the rate of 2,172 lbs. 

 per acre showed that as compared with imtreated soils in check plats, the 

 water solubility of the alkali was reduced about 20 per cent, while the avail- 

 ability of potash and phosphorus were increased approximately 20 per cent. 

 The treated soils showed an increase in sulphate content, a decrease in car- 

 bonate content, and an increase in all crops grown. 



*' One of the striking effects of sulphur and sulphuric acid treatment of soils 

 on the soil microorganisms is the decided and consistent increase in total 

 bacteria as determined by the plate method. Under certain conditions in a 

 period of three weeks the sulphur and sulphuric-acid-treated plats showed 50 

 per cent more microorganisms than did the imtreated checks. The sulphur 

 plats in general showed a greater increase in the number of organisms than 

 did the sulphuric-acid-treated soils ... In general the sulphur-treated plats 



