6 SOME ASPECTS OF THE INDIGO INDUSTRY IN BIHAR 
rises and remains at a fairly high level till October when it rapidly falls.4 
Of perhaps greater significance in this respect are the movements of the 
ground water. In the indigo areas of Bihar, the flow of the rivers is often 
checked during the monsoon by the rise of the level of the Ganges. As a 
result, the rivers overflow and the lowlying areas go under water. The rise 
in the level of the rivers is followed by a rise in the water-level of the wells. 
These movements of the river level and of the general ground water are illus- 
trated in the curves opposite (Plate IT) which represent the state of affairs 
of the river at Pusa and of one of the wells (about a quarter of a mile distant 
from the river bank) for the years, 1910, 1912, 1913 and 1914. This upward 
movement of the ground water, which must push in front of it the soil air 
from the deeper layers, occurs at a period when the general drainage of the 
country is checked and when the permeability of the surface soil is poor due 
to consolidation by heavy rain. We should expect, therefore, that the aeration 
of the soil will be at its lowest point during the second half of the ramy 
season. 
Briefly stated these are the conditions under which a tropical leguminous 
plant has to grow in Bihar. The range is wide. The crop is sown at the end 
of the rains in late September or early October, when the surface soil is suffi- 
ciently warm and moist for rapid germination. By the beginning of the cold 
weather in December, the plant is three or four inches high. Growth then 
ceases till March. After the rains set in towards the end of May or early in 
June, growth is exceedingly rapid and the first cut is taken at the end of June 
or early in July. The stumps shoot again and the second crop is harvested 
in late July or early August, followed, in good years, either by a final cut in 
September or by a crop of seed during the cold weather. After this, the 
stumps are dug out and the land is prepared for other crops. The original 
practice in Bihar was to raise the seed after at least two crops of leaf and at a 
period in the life-history of the plant when its vigour was at its lowest point. 
II]. Tue Cause or WILT. 
The earlier results relating to the cause of wilt of Java indigo were published 
in 1916,in Pusa Bulletin 67. Since that time, the subject has been investi- 
gated afresh but in much greater detail with the consequence that our former 
conclusions have been confirmed in all respects. Briefly stated, we have 
found that when the roots and nodules of an indigo plant have suffered exten- 
sive damage, wilt invariably results from any cause which interferes with 
. *It is possible that other deleterious substances beside carbon dioxide are produced in 
Bihar subsoils during the rainy season. ‘The subject needs further investigation. 
