SCIENCE BULLETIN, No. 



Thus the highly interesting problem of accounting for the diversity in 

 the action of the phosphatic fertiliser is presented. 



The investigation of which the results are here submitted, deals with 

 one important factor entering into the problem, viz., the soil constitution. 

 The scheme of work was devised by Professor Watt, 'of the University of 

 Svdney, and the work carried out in the University laboratory. 



With regard to previous literature dealing with the effect of superphos- 

 phate 011 the wheat yield, there is but little available dealing with New 

 South Wales conditions. Experiments have been conducted by the 

 Department of Agriculture, and the results published from time to time 

 in The Agricultural Gazette of New South Wales; these publications are 

 well summarised in the article quoted at the commencement of this paper. 



1 Fall (" Fertilisers and Manures," pages 139 and 140) calls attention to 

 the stimulating effect of the fertiliser on root development. " The action of 

 phosphoric acid on the plant is not confined to its ripening effect; it 

 stimulates the early development of the young seedling to a remarkable 



extent It may also go to explain the extraordinary results of 



quite small dressings of phosphoric acid upon soils in Southern Australia, 

 where a manuring with half a cwt. per acre or even less of superphosphate 

 has been found sometimes to double the yield of cereals. On analysis the 

 soils are not rich, but they show no such signal deficiency in phosphoric 

 acid as would account for the action of the manure; it seems much more 

 likely that in a semi-arid country where the whole success of the crop 

 depends on the roots getting quickly down to the cooler and moister sub- 

 soil, the stimulating action of the phosphoric acid upon the young roots 

 becomes of the greatest value." 



In a paper read before the Australian Association for the Advancement 

 of Science this year, Professor Watt presented facts which bear out this 

 contention as regards New South Wales conditions. 



Little, however, seems to have been done in the direction of accounting 

 for the variation in the effect of the fertiliser in different parts of the 

 wheat belt. Mr. A. H. E. McDonald, Inspector of Agriculture for the 

 North- Western Division, states : " Possibly the greater temperatures of 

 the north and the summer rains may be partly responsible for the failure 

 of the soil to respond to fertilisers. Probably these conditions would be 

 more favourable to the liberation of inert plant-food material. The season 

 is almost a month earlier than that of the south; that is, the crops are ripe 

 nearly a month earlier than they are in Kiverina. Last year (1011) I 

 started harvesting at Moree 011 llth October. I feel sure, however, that 

 nearly all the wheat land in the north-west is very rich; the presence cf 

 varied vegetation and especially many legumes, indicates that." 



In a consideration of the problem it would appear to be of fundamental 

 importance to know something of the amount and the state of " avail- 

 ability " of the phosphates present in the wheat soils. While realising 

 that a chemical analysis is of itself insufficient as a means of judging the 



