PROCEEDINGS OF SECTION K. 657 



Vol. IV., p. 1; and Vol. V., p. 1), in which are given methods of 

 determining the constants, specific pore space (the free space per 

 unit volume of soil), permeability to water and air, and capillary 

 co-efiicient. It would be of very great interest to determine the 

 extent to which the addition of fertilizers or soluble salts affect 

 these constants. 



Influence of Fertilizers on Soil-Oxidation, 



Another direction in which fertilizing substances can function 

 in other ways than as plant-food is in the promotion of oxidation 

 in soils. 



M. X. Sullivan and Reid (Journ. Ind. and Eng. Ghem., 1911, 

 Vol. 3, page 25) have shown that the oxidizing power of soils is in- 

 creased by the presence of water up to the optimum, and by the 

 common fertilizing substances, also by salts of iron, manganese, 

 lime, and magnesia, especially when simple organic hydroxyacids 

 are present. They find that soil-oxidation is comparable with the 

 same process in plants and animals, and that it is greater in surface 

 than in subsoil, and greater in fertile than in barren soils. 



O. Schreiner and H. S. Reed (Bui. 56, Bureau of Soils, U.S. 

 Dept. Agric.) showed that calcium salts, phosphates, and nitrates, 

 increase the oxidizing power of plant roots, whilst potassium salts 

 tend to retard it. (See also Schreiner, Sullivan and Reid, Bull. 

 73, Bureau of Soils, U.S. Dept. Agric). 



In addition to these many cases of conditions existing in the soil 

 favorable or unfavorable to plant development, and independent of 

 the supply of plant food, there are the better known instances of 

 soil infertility shortly reviewed in the Agricultural Gazette of New 

 South Wales (Vol. 21, p. 434), some of which are removed by 

 proper manuring and some unaflFected by manures. 



Catalytic Fertilizers or Plant Stimulants. 



There are also a large number of compounds whose presence in 

 minute quantities appears to have very often a quite remarkable 

 effect upon plant growth. These substances cannot be regarded 

 as fertilizers in the ordinary sense. Some of them are of rare oc- 

 currence in the soil, or occur only in minute quantities; many of 

 them are distinctly injurious in any large quantity. We are quite 

 in the dark as to their precise function, and the name " catalytic " 

 has been given to them for want of a better. 



H. Ost found small quantities of fluorine to be always present 

 in a number of healthy leaves which he examined. 



Aso, Oscar Loew, Ampola, and others show that small quanti- 

 ties of fluorine have a stimulating effect on many plants. Iodine 

 also has been shown to stimulate the growth of plants when in small 

 quantities. Oscar Loew and the Japanese chemists who have done 



