664 



PROCEEDINGS OF SECTION K. 



A similar series of observations was carried out in the spring of 

 1912 with the following results: — ■ 



It will again be observed that in every case except one (that at 

 Adavale, Parkes), an increase (varying from 3 in. to 19 in.), in the 

 depth of root penetration is shown due to the action of superphos- 

 phate. The result at Parkes can hardly be regarded as normal, 

 because the deepest roots on the unmanured plot were found grow- 

 ing in the track of a decayed tree-root, and it was noted at the time 

 that there was a much larger number of roots reaching down to 

 about 30 inches in the case of the manured plot than the other. 

 Besides, on new land in this district superphosphate has a much 

 less marked effect on plant growth generally than in the southern 

 portion of the wheat-belt. 



The most striking contrast was shown at Peckham, Narrandera, 

 especially at the time of the first observation. The second obser- 

 vation, for which I am indebted to Mr. Norman Forsyth, was made 

 after a long period of hot di-ying winds, and it was noteworthy 

 that the manured plot had suffered less from the drought than 

 the unmanured plot in spite of the wheat on the former having a 

 larger transpiring surface. On digging down to examine the roots 

 the reason for this was obvious; for, although the top 18 inches of 

 soil were almost completely dried out, there was still a considerable 

 amount of moisture below this right down to the depth of 3 feet. 

 The observations on this farm, which were made at adjacent spots 

 at an interval of a little over a month, also brougM out the point 

 noted in the previous year's experiment that the beneficial effect 

 of superphosphate on root development is greatest in the early 

 stage of growth. 



