156 



Journal of Agriculture, Victoria. 



[lo Mar., 1911. 



be communicated now, since they are complete for the past year, though 

 not entirely conclusive. 



It appears to have been generally concluded by different investigators, 

 that prolonged exposure to any intense form of these radiations is in- 

 jurious to the plant, and either retards its growth or ultimately kills it. 

 Jt appears, however, to be a general rule in plant physiology that, in such 

 cases, the same agency when applied in less intense or less concentrated 

 form will cause an acceleration of growth, or will stimulate the general' 

 vigour of the plant, sometimes to a surprising degree. This peculiarity 

 is very pronounced in the case of certain poisons, which when diluted below 

 lethal concentration, may stimulate the growth of a plant to as great an 

 extent as an addition of a food substance or of manure would do. 



Bearing in mind the fact that exposure to radio-activity of low concen- 

 tration appears in some cases to stimulate the growth of the plant, it ap- 

 peared of interest to determine whether the addition of small quantities 

 of radio-active minerals to the soil would sufficiently stimulate the growth 

 of such plants as wheat, for example, to make their u.se profitable on an 

 agricultural scale. Large deposits of radio-active rock have been found' 

 in Australia, and a large supply of finely ground and strongly radio-active 

 rock was obtained from a particular localitv. This was applied to different 

 plots singly, as well as in conjunction with superphosphate, and finely 

 ground phosphate rock. The plots were harvested at the end of November 

 before the grain was fully ripe, .so as to avoid possible loss by birds and 

 falling grain. 



The fact that all the plots were slightly attacked with the Corn Mildew 

 {Erysiphe graminis) shows that the presence of a radio-active mineral in 

 the soil affords no protection against the attacks of parasitic fungi. 



Apart from the addition of the radio-active mineral and mineral- 

 manure, the plots received exactly the same treatment, and all consisted of 

 the same soil of rather light loam with a clayey subsoil. The wheat was- 

 planted in equi-distant rows and the grains in each row at the same depth 

 and distance. In plots i, 2, 4, 5, 6, 7, 8, each .seed received a separately 

 measured do.se of the mineral or manure after planting, and was then 

 covered with soil. In plot 9 the mineral was drilled in, while, in plot 10, 

 it was placed immediately under each seed. Plot 3 was a control plot 

 to which no mineral or manure was added. The heads and straw were 

 harvested separately by hand and weighed. The plots were not all exactly 

 the same ai-ea, and the figures which follow beneath are estimated at the- 

 same area and number of plants. 



Plot. 



1 

 2 

 3 

 4 

 5 



6 

 7 

 8 

 9 

 10 



Amount Per Acre. 



1 cwt. Radio-active Minera,! . . ... 



2 cwt. Radio-active Mineral 

 Control (none) . . 



1 cwt. Phosphoric Rock . . 



1 cwt. Phosphoric Rock and f cwt. Radio-active 

 Mineral 



\ cwt. Superphosphate 



\ cwt. each Radio-active Mineral and Superphospliate 



2 cwt. Radio-active Mineral 



3 J cwt. Radio-active Mineral (drilled) 



1 cwt. Radio-active Miner..! immediately under seed 



Heads. 



Straw. 



