674 PROCEEDINGS OF SECTION K. 



Agdell Field, at Rothamstead. A most pertinent question was, 

 ' ' Why is it that nitrogenous fertilizers are not required in the 

 "V'ictorian wheat areas, whilst pliospliatic manures are even more 

 effective here than in Europe." Would Whitney and Cameron 

 contend that ammonium salts are required to neutralize toxins in 

 American, but not in Australian soils? Moreover, among the 

 many obvious reasons why nitrogenous fertilizers are not required 

 in Australia is the fact, as proved by departmental experiments, 

 that nitrification is twice as active in Victorian wheat areas as at 

 Rothamstead. The toxin theory would, therefore, appear to be 

 superfluous when we can account for the facts in a more rational 

 manner. With regard to the effect of phosphates on root develop- 

 ment, there was a limit to the amount of superphosphate which 

 could be profitably applied in a dry season. In soils rich in lime 

 there was less danger in applying heavy dressings of superphos- 

 phate than in soils deficient in this ingredient. The heavy dress- 

 ings tended to greatly increase stock-carrying capacity. In pre- 

 paring mallee land for cultivation, the best results were always 

 obtained in places where a good burn took place. This has an in- 

 teresting bearing on Dr. Greig-Smith's theory. 



Dr. Heber Green said that four years ago he had visited most 

 of the leading agricultural colleges and universities in America, 

 and had found that nine-tenths of the agricultural investigators 

 there were entirely opposed to the conclusions of Milton Whitney 

 and his staff at the Soils Bureau at Washington. He deprecated 

 the looseness of expression involved when we talked of plant roots 

 searching for water as if they were sentient beings, who could 

 detect the presence of water at a distance, and could organize an 

 advance in its direction. Obviously any such directive growth of a 

 root must be due to unequal osmotic pressures on either side of it 

 causing the root to develop most on the side where the optimum 

 conditions of osmotic pressure, &c., were most nearly realized. 

 Similar considerations must apply to the distribution of plant food 

 in the soil, and will explain tlTe peculiarities of root growth in- 

 stanced by Mr. Gabriel. The question as to whether superphos- 

 phate should be planted with the seed or below it, as in the duplex 

 drill, is answered by deciding at what stage in the growth of the 

 root it is most profitable to give it a " lift." 



Dr. Patterson thought that when small quantities of super- 

 phosphate were used, they should be planted with the seed, and 

 larger quantities proportionately lower than it. 



Mr. Cheel quoted cases in which Ziereae, planted around a 

 dead cicada, had developed a large crop of fruits, and out of a 

 number of sweet peas planted in virgin soil at Hill-to]) only one 

 had developed; this one had received a little farmyard iranure. 



