Usually the cheapest irrigation system would be what we call the irrigation by
gravity. That means that you would have a water source that is high enough and
can be led into the growing areas, and you just open the dike and this water ca
n flow easily in. And that is the best way and the cheapest. But that kind of t
hought is now very much limited, al-most has been developed already. And what w
e are doing now is to get a system coming from a big river, waterworks and so o
n. And from there they have to pump in.
But in my experience in Vietnam, and in Laos and in Cambodia we can see that ra
inwater harvesting by dry seeding, as I discussed, is perhaps the cheapest way.
Because usually the farmers, traditionally, wait for the rain to come, about o
ne month, to soften the soil before they plow. So that one month's water is was
ted. Of course it is not wasted, but it is used for softening the soil. But if
we harrow and plow right after the rain stops in the pre-vious season, when the
soil is still soft, the plow makes a dry fallow on the plowed soil, it will be
easy to break up those plowed layers when the rain has started. And at the sam
e time they sow the seeds. So the seed that time uses every drop of rain from t
he very be-ginning of the season. And it can grow. And if the fanner is careful
to manage the weeds during the dry season, the weeds will not be a problem whe
n the rain comes down. And by doing this we can get four to five tons of rice p
er hectare within that period when the farmer is waiting for the rain to soften
the soil, then plow and harrow and prepare the land, to just plant the main ri
ce crop. So this is one way, now is the second, have been increasing areas in V
ietnam. And we tried to introduce this in Laos, for example. In Laos and Cambod
ia, now still they wait for the rain come, then soften the soil, and they ploug
h it and they harrow, and then they transplant. But then, usually the rainy sea
son there is the monsoon, as you know. After one month of rain, or after two we
eks of rain, it stops rain-ing for a few weeks, sometimes even one month, we ha
ve this dry spell. It is during this dry spell that the just-planted rice will
die. Most of the hazard in Cambodia and in Laos, in their rice-production, is t
heir use of this very old technique. If it sits through the dry-seeding, the dr
y-seeded rice is not afraid of the drought, because the soil is granulated. So
the roots can find some water in the sub-soil, therefore dry-seeded rice can no
w be called the best technology in grain harvesting for rice growing.
The second question is the ground water depletion. Yes, yesterday we saw one sl
ide from Dr. Uchijima about the cycle of the water. So the water evaporates fro
m the oceans, and transpires from the land, become clouds, and then the clouds
will move in and give the rain. That rain will replenish the river and replenis
h the water. So that cycle will go around. However, if in one deep well, using
the water, they pump it too fast, the replen-ishment rate for the. will be less
, and then they will have to suffer from the lack of water at that ground water
. So the replenishing will come. Now in Bangkok, for example, the rate of extra
cting the water is so great because of the large population in that city, then
subsidence of the soil take place every year because of that, because they extr
act too much. They need to replenish it from some other sources, but the replen
ishment is low. So we have to be very careful in exploiting the ground water re
sources.
Now if industrialization would give some adverse effect on agricultural develop
ment, yes, you are right. But not only industrialization, but also urbanization
, these two go together.
