672 PROCEEDINGS OF SECTION K. 



DISCUSSION ON " SOIL FERTILITY." 



Mr. H. W. Potts specially emphasized the importance of depth 

 of root growth, as demonstra'ed by Professor Watt. 



Professor Cherry said that experiments with the " Duplex 

 Drill," which was designed to plant the fertilizer below the seed, 

 had given contradictory results. Neither lime nor ashes seemed to 

 completely neutralize toxins. He also raised the question in con- 

 nexion with Mr Musso's paper, as to which plants were the source 

 of the copper producing the colouration of parrots' plumage. 



Mr. Catton Grasby, with reference to points raised by Dr. Pat- 

 terson, explained that the presence of 2 to 3 per cent, of less 

 soluble phosphoric acid in commercial superphosphates was due to 

 purely business considerations. It was thought to be advisable 

 to accustom the public to a rather lower grade of material than 

 the best they could ordinarily put on the market, so as to leave a 

 margin in case of any difficulty in obtaining supplies of suitable 

 rock phosphate. The high salinity of certain South Australian 

 wines which had been condemned by the Government Analyst and 

 refused entry into Victoria, had subsequently been proved to be 

 due to a dry season and the high salt content of the soil of the 

 vineyard from which that particular vintage had come. 



Professor Watt agreed with Dr. Patterson that the chemical 

 analysis must not be overlooked. He was of opinion that Russell 

 and Hutchinson's conclusions might need to be modified, but he 

 did not think that Dr. Greig-Smith had so completely disproved 

 them as he appeared to claim. Had Dr. Greig-Smith tried a set 

 of experiments on ammonia production in garden soils treated with 

 toluene vapour similar to those carried out at Rothamstead ? He 

 himself (Professor Watt) was starting such a set at Sydney. He 

 did not think that agricere could be responsible for all the effects 

 found by Dr. Russell, who had, in his latest experiments, used 

 fcrmalin instead of fat solvents. Azoto-bacter had been obtained 

 by Dr. Hall in soils from the Transvaal, and other tropical 

 countries. 



Dr. Greig-Smith pointed out that in considering the action of 

 heat on soils, different results will be obtained according to the 

 moisture and other conditions under which that heat was applied. 

 He did not obtain any anti-toxins, and thought that the action of 

 fertilizers was due merely to their fertilizing value. Plant toxins 

 may not be the same as bacteria toxins, and the view held at 

 Rothamstead that toxins were absent from the soil did not seem 

 to be justified. Because work was done at Rothamstead, it was 

 not, therefore, perfect. Mistakes had been made there in the past, 

 and, in his opinion, Russell had used too high a temperature, and 

 had too completely sterilized the soils he had worked on. 



