Thank you, thank you very much, Dr, Uchijima, for your excellent and very
inter esting speech. Now we have still flfteen minutes for discussion. and
please giv e your comments wlth your ques-tions, if you have any.
Question 1 (Hon. P.J. Kurien, MP, INDIA):
Dr. Uchijima, thank you for your very nice presentation. Of course, it was more
technical. But I would like to ask one question. In your presentation you have
shown that due to salinization the area which has been damaged, the irrigated
area that has been damaged, is maximum in India, it comes to 20% of the total.
Could you explain to us why it hap-pened, and what Is the rationale of arriving
at such data?
Dr. Uchijima:
Let me respond to the question. This has to do with the soil salinization, as h
as been stated, in the arid and semi-arid areas. If you irrigate, salinization
is a problem you cannot avoid, it is bound to come. That is the case with the n
orthern part of China, the In]and of China, many parts of the former USSR, and
in the United States, and also the western Aslan regions and Africa. In the upl
ands of the semi-arid areas the salinization problem cannot be avoided. As I sa
id, in contrast to rivers which have enough precipitation, rivers of the arid a
nd semi-arid areas contain a lot of salt in their water, and when this water of
high salt content is irrigated to the fields, and as you know, water escapes i
nto the atmos-phere through the plants and through the land surface, and thus a
great amount of salt is retained in the land surface layer, increasing the sal
inity of the ground. As the salinity goes up beneath the land surface, there wi
ll be less and less water that the plants can ab-sorb from the soil. So in term
s of food production and increase in food yields, they are all receiving a very
detrimental effect from the salinization. In order to avoid this problem of sa
linlzation, according to rough calculation, for the wheat production for one he
ctare, it is said that you need three thousand tons of water. But you have to d
ouble that amount, you have to apply six thousand tons of water to go through t
he crop fields to leach the salt from the ground. And then where we are going t
o discharge the leached water, it has a very high salinity, and this indeed is
a very big challenge in resolving the soil salinization problem. In India you h
ave a very high figure, twenty percent. And the graph I showed you that was car
ried in the magazine "Science in the United States, I borrowed that graph from
"Science", and they warned that in India, China, Pakistan, in the United States
, and in the former USSR, soil salinization is becoming a very major issue.
