♦28 SCIENTIFIC REPORTS OF THE AGRICULTURAL RESEARCH 



Food Controller would allow it to be used. Messrs. 

 Reckitt state that it is difficult to express a precise opinion 

 as to its selling value, but it seems probable that it would 

 fetch about £20 per ton. 



VII. Occurrence of Infertility under Trees. 



It is well known that trees often give rise to infertile 

 patches in their neighbourhood. Several causes may co- 

 operate in this and the question has been discussed by 

 Mr. J. N. Sen in some detail, and a collection of data has 

 been obtained in Pusa which throw light on the question. 

 It is shown that several trees, especially the bamboo and 

 tamarind, bring about a concentration of soluble salts in 

 the upper layers of the soil in their neighbourhood, pro- 

 bably largely owing to transpiration. An examination of 

 good and bad soils in the neighbourhood of trees growing 

 in different areas showed that the good soils generally con- 

 tained less than 0-3 per cent, of soluble salts but that bad 

 soils often contained more than 0-5 per cent. The nature 

 of the soluble salts, however, greatly modifies their effect in 

 limiting fertility. 



VIII. Tobacco and Transpiration Ratio Experiments. 



Pot and field experiments were started last cold 

 weather to ascertain the effect of different manures on the 

 yield, .quality and nicotine content of tobacco plants and 

 to ascertain the effect of aeration on these. The work is 

 still in progress. 



The experiments referred to in last year's report on the 

 relation between transpiration by a plant and the assimi- 

 lation of plant material have been continued but not yet 

 completed. 



IX. Programme of Work. 



Major subjects. 



1. Continuation of the investigations into the amount 

 and nature of drainage water from fallow land and land 

 bearing crops. 



