62 T BIN ID AD AND TOBAGO B ULLE TIN. [X VIII. 2. 



mineral constituents of the cane are mostly available for return in the ash. 

 It is when the land is fairly treated in these respects, provided that root 

 disease can be safely ignored, that continuous cane cultivation is possible 

 Avithout exhausting the soil. The soil may in the hands of a capable 

 manager even continuously improve. 



21. There is a great deal of cane land in Trinidad that does not 

 appear to have had, in this sense, fair treatment. In these cases either 

 no pen manure or a very inadequate amount has been supplied, and 

 frequentlj' sulphate of ammonia has been used as a supposedly efficient 

 substitute. While this chemical has not the notorious effect of nitrate of 

 soda in directly destroying tilth, a similar result is reached if its use leads 

 to the omission of the organic matter on which the maintenance of 

 tilth largely depends. It has moreover a deleterious action of its 

 own which is set out in A. D. Hall's statement that on soils initially 

 poor in calcium carbonate the removal of this substance by sulphate of 

 ammonia soon induces a condition of actual sterility. Attempts are made 

 in Trinidad to correct by the application of lime the condition of 

 acidity thus produced, but this treatment to be certainly effective 

 should be carried out under scientific control on the lines of recent 

 work on this subject. 



22. The idea that the soil is a chemical mixture which can, be 

 sufficiently adjusted by adding more chemicals is now completely 

 discredited. An agricultural soil in good condition is a culture of living 

 organisms, mostly bacteria, on the action of which the maintenance of its 

 fertility depends. For this bacterial flora to thrive there are in addition 

 to moisture two requirements : (1) organic matter, which is supplied by 

 mulch, green dressing and pen manure, and (2) air, which gains access 

 through cultivation. How far some Trinidad fields are from this 

 condition is illustrated by cases I saw in which biological activity was 

 so reduced that buried trash and pen manure remained for a lengthy 

 jjeriod about as little changed as if soldered in a tin. And yet when 

 a field in this condition goes doM'n there is a tendency to attribute the 

 result entirely to froghopper. 



23. On the close-lying, stoneless, silt soils of the plain between the 

 Northern and Central Ranges the question of aeration appeared to me to 

 be of particular importance. A. Howard has recently demonstrated the 

 very great significance of aeration on soils of similar origin in India. 

 The feasibility of special measures for improvement in this direction, as 

 to which a suggestion will be made later, is a matter for experiment 

 to decide. 



24. Closely related to aeration is the question of drainage, the 

 importance of which seems to be generally appreciated, though local 

 difficulties in application have not alwaj's been overcome. It may be 

 pointed out that poor drainage is well known as a predisposing cause of 

 damage by root disease, operating like the conditions already described 

 by preventing the development of a desp and copious root system. 



25. A factor to which my attention was drawn, as contributing 

 seriously in some cases to bss of tilth, is the working of implements in 

 wet weather. It is important that this should be borne in mind, in 

 relation to the present movement towards increasing inipleu:ental 

 cultivation. I am convincad t'lat a gcod daal of liarm nip.y be dor.e by 



