91 



The results in general were not as marked as in 1922 when, 

 however, a different soil was used. But the results are in each 

 case in the same direction and tend to show that lead as chloride 

 will be toxic, and almost entirely destroy a crop at a concentration 

 of .50 per cent. It was noticed after removal of the soil from the 

 pots at the close of the experiment that, with the higher concen- 

 trations, viz., .50 per cent, and 1 per cent., a deposit of metallic 



lead formed round the edge of the soil on the inside of the pots. 



• 



(b) Uranium Compounds. 



In 1919, experiments had been made with ores stated to be 

 11 radio-active," but no benefit was found from their use. As the 

 activity of these ores was believed to be dependent upon the 

 presence of compounds of uranium, experiments were made with 

 salts of this metal. Wheat was used, and the soil was from 

 Lansome Field. The oxide (as sodium diuranate) and uranyl 

 chloride, sulphate and nitrate were tried, each concentration 

 supplying .05 per cent, and .10 per cent, respectively of uranium. 

 The quantities were mixed with the whole of the soil in each pot, 

 these being filled on December 19th-20th ? 1922, and sown with 

 wheat on December 23rd. 



Germination was quicker with the untreated pots. The 

 poorest lots were those with the chloride and sulphate. About 

 the end of April the treated pots improved. The absence of sun 

 in May prevented any marked change, except that in some cases 

 — chiefly with the sulphate and chloride — one or two plants 

 developed abnormally. The wheat was cut on August 13th, and 

 the comparative results obtained were : — 



With the doubtful exception of the .1 per cent, dose of sodium 

 diuranate, uranium had no good effect, and in most forms it was 

 actually harmful. 



2. Green-manuring Experiments. 



New interest having been aroused in the subject of green- 

 manuring, it was decided to revert to the experiments at the 

 Woburn Pot-culture Station which had been previously carried on 

 in conjuncion with the Field Experiments, but which had been 

 temporarily suspended. 



Briefly to recapitulate, field experiments conducted on Lan- 

 some Field since 1895, and on Stackyard Field since 1911, had 

 shown that, without exception, better cereal crops (both of wheat 



