June i6, 1919 Sulphates Affecting Plant Growth and Composition 91 



Hall, Brenchley, and Underwood (lo) at the Rothamsted Experiment 

 Station, in some experimental work in support of the theory of the direct 

 nutrition of plants by fertilizers, found that wheat and barley showed 

 parallel growth in the soil, in the soil extracts, and in artificial solutions 

 of the same phosphorus-pentoxid (P2O5) and potassium-oxid (KjO) con- 

 tent. The soil solutions corresponded to the natural drainage water, 

 depending upon the past fertilizing treatment and present composition of 

 the soil. The growth in extracts from poorly fertilized soils could be 

 made equal by direct addition of suitable phosphate and potassium 

 salts. Boiling did not affect the nutritive value of the solutions, and the 

 diffusion of the nutrient solution over particles of sand did not interfere 

 with the growth, although proper aeration of the roots was found to be 

 essential. 



By growing the plants on sand the possibility of the sulphates acting 

 on minerals in the soil would be eliminated, and boiling the soil extract 

 would destroy the bacteria originally in the solution. So in these experi- 

 ments, if an increase in growth is observed in the soil pots from the appli- 

 cation of sulphur fertilizer, and a corresponding increase is also obtained 

 in the sand pots containing soil extract to which sulphur had been added, 

 this same order of growth in the soil and sand would indicate in all 

 probability that sulphur had acted directly in promoting the growth. 



The object of this experiment was to make a study of the influence of 

 an available supply of sulphates on the early growth of the plants and 

 determine whether the elemental sulphur was capable also of supplying 

 the necessary sulphates; to see what effect sulphates would have on the 

 nitrogen content of the plant and if beneficial results are obtained whether 

 the sulphur acted directly as a plant food in producing them. 



EXPERIMENTAL WORK 



The pots used were ordinary clay flowerpots which had been paraffined 

 on the inside, and each contained about 700 gm. of soil. The sand was 

 of a fine quality, obtained from Eimer and Amend. It was washed with 

 dilute hydorchloric acid until no potassium, phorphorus, or sulphur was 

 detected in the acid extract. Larger pots were not used on account of 

 the beginning of this type of experiment, the number of pots needed and 

 the individual attention required. The growing period was about two 

 months with the exception of the oats which were allowed to ripen. The 

 seed was sown on March 15, and the work was carried on in the green- 

 house. At the end of a month the plants were thinned out so that there 

 were 10 clover plants, 6 oat plants, and 3 rape plants per pot. At this 

 time the sulphur and nitrogen were determined in the clover plants 

 taken from soil A, The clover and rape were cut on June i, the dry 

 weight taken, and the total sulphur and nitrogen determined. Twenty- 

 five cc. of nutrient solutions containing compounds as given in the state- 

 ment on p. 90 were added daily to each pot after growth had started. 



