yo Summary of Agricultural Experiments, [april, 



chemical factors which are of the greatest importance in governing 

 the proper growth of plants. 



Absorption of Manurial Constituents by Soils. (Bulletin Mensuel, 

 Ministere de V Agriculture, France. January, 1909.). — In the course of 

 some manurial experiments, conducted by Messrs. Rousseau and 

 Brioux, with sandy soils in the Auxerrois, the results of the application 

 of chemical fertilisers were found to vary considerably, and this varia- 

 tion was not always explained by differences between the soils in 

 chemical composition. The quantities of fertilising materials removed 

 by water passing through the soil were first ascertained, and this raised 

 the question of the mechanism of absorption and the influence of the 

 chemical and physical composition of the soil thereon. The question 

 of the distribution of phosphoric acid in the soil, and the absorption of 

 this material and of potash are specially dealt with. The soils were 

 light sands, of the Greensand formation, and were, generally speaking, 

 very poor in fertilising matter, but other soils were used for comparative 

 purposes. 



The experiments showed that, as is already recognised, certain 

 manurial constituents, such as nitrates, sulphates, chlorides, and lime, 

 are freely washed out by drainage water, while potash is retained, the 

 proportion removed depending on the original richness of the land 

 in potash and the quantity applied in manures. The loss of phosphoric 

 acid, the least soluble manurial constituent, was materially affected 

 by the presence of lime. One type of soil, very poor in lime, slightly 

 clayey, and fairly rich in phosphoric acid, gave very high proportions 

 of phosphoric acid in solution. This loss in solution was reduced to 

 less than half by the application of basic slag, at the rate of 8 cwt. per 

 acre, and almost stopped by a dressing of lime at the rate of one 

 ton per acre. It is concluded, therefore, that on sandy soils the appli- 

 cation of basic slag is to be preferred to super-phosphates. 



It was also found that the application of chemical manures to 

 soils of this type resulted in an appreciable quantity of silica being 

 dissolved. In dry periods this has a tendency to cement the surface 

 into a hard crust which, unless it is broken up by cultivation, prevents 

 the penetration of rain. 



It is suggested that a determination of the available constituents 

 of the soil that are soluble in weak acids, and in some cases the 

 examination of soil solutions, would often explain the results of field 

 trials, which cannot be understood from a mere analysis of the total 

 fertilising constituents. 



Manuring of Plants in Pots. (Bulletin Mensuel, Ministere de 

 V Agriculture, France. January, 1909.). — M. Petit, Professor at the 

 National School of Horticulture at Versailles, observes that from his 

 experiments it appears that nitrogenous manures are absolutely neces- 

 sary in pot culture, even when, as is the case in practical horticulture, 

 soil rich in organic matter is used. This is due to the small quantity 

 of earth available for the plants, the feeble nitrification, owing to 

 the earth being left undisturbed, combined with the washing out of 

 nitrates, which takes place to a minute extent each time the pots are 

 watered. In these experiments the best quantity of fertiliser to apply 

 was tested, nitrate of soda being used. The quantity producing the 



