18 



almost all other cases there is a strong tendency for the subsoi j 

 to be stiffer than the topsoil in rainy districts, and this tendency 

 will be likely to have the most pronounced effect in these 

 districts, where the rainfall is medium and not very excessive 

 say from sixty to eighty inches. Apart from occasional deep cultiva- 

 tion or really on account of constant cultivation to the same depth 

 there results a hard layer at a distance from the surface varying 

 with the depth of the cultivation, This layer is known in 

 England as "pan," in America as a " plowsole." In many cases in 

 already exists before the land is cultivated at all, owing simply it 

 the effect of the rain washing the fine particles into the subsoil 

 but the stiffer the soil the more liable such a " pan " layer is to be 

 found. So hard does this sometimes get in the arid districts of 

 America, that in order to break it up dynamite is regularly used 

 and were the weather always dry in Assam as it is in the cold 

 weather, I know gardens where this would be almost the only 

 method of breaking it up here. The effect of such a hard "pan" 

 is to prevent the roots descending, and hence to keep them in the 

 surface layer of the soil, which means that their range for water is 

 restricted, as well as their range for food, Figures I & II (repeated 

 from my report to the Indian Tea Association on Red Rust in Tea) 

 show this condition of things exceedingly well. Hence plants on 

 land like this are starved for want of water, and also ultimately for 

 want of food ; are subject to drought and yet feel the evil effect of 

 excess of rain ; and are, in consequence of these things, subject to 

 blights of many kinds, of which the worst is probably Red Rust, 

 though these are the conditions, in Assam at any rate, under which 

 Red Spider is seen in its most serious. form. Further such a "pan " 

 becomes the cause of the retention of a very large amount of stand- 

 ing water in the subsoil which is not required, and causes this subsoil 

 to be non-aerated, to become rapidly sour, and from every point of 

 view unfit for the penetration of the delicate tea roots. 



SUBSOIL DRAINAGE. 



Since, however, subsoil root development is necessary for the 

 culture of luxuriant tea (except in few exceptional cases which 

 hardly concern us here and now), by some means or other this hard 

 " pan " must be got rid of, partially at any rate, where it exists, and 

 prevented from forming where it has not been yet produced. As I 



