Your excellent Gobar Times issue on rice
(January 15, 2004) relating to water requirements of rice has perhaps understated the
figure. I make it 20 tonnes of water as usually used to grow 1 kg of rice.
The figure for water requirement usually used by
irrigation engineers is 2,000 mm of water per crop. Yet the physiological needs of the
rice plant for optimum growth is about one fourth of this figure. Why then the other 1,500
When you work this out, it is clear that it is all used
as a component for 'weed-control'. Water is now rapidly becoming the most expensive
'herbicide'! It is used for softening the ground for ploughing (weed-control), and then
for mudding and levelling (for controlling weeds). It is then re-admitted gradually for
drowning competitive weeds while the young seedlings grow.
Sadly, none of the systems devised for 'Water Management'
have delved thus deeply into the actual and basic reasons for this excess water apart from
that needed for the growth (physiology) of the rice plant.
Those of us who have also worked (and farmed, ourselves)
on 'upland' or rain-fed rice (e.g. with Oryza glabberima in Africa) will know that
whether rice is grown from seed (rainfed) or laboriously transplanted (into puddle fields)
provides identical yields provided that the competing weeds are equally well managed. The
fact that 'weed-management' is the key to 'water-management' in the growing of rice,
appears consistently to have evaded rice scientists.
Nor is the use of chemicals (herbicides) the only
alternative, although these also work as well, but also other (natural?) techniques for
successfully managing the growth of weeds as in the systems very effectively used by
Masanobu Fukuoka in Japan. And also by many farmers of Africa who also manipulate shade
and fertility of other crops (some of them symbiotic with rice and others allelopathic
(toxic) to weeds). Other techniques include 'perennial rices' and 'rattooning rices' which
have proven far lower in cost.
But it is unlikely that these techniques will receive the
funding for R&D which goes into industrially and/or chemically based techniques. Now
should we forget that di-hydrogen-oxide is also a chemical, albeit one that flows from a
tap rather than from a bottle on a shelf. But that too will doubtless change, like
'bottled-water' and 'metered-water' which are now taking over.
Vidya-Jyothi Raw Wijewardene
Moratuwa University, Sri Lanka
We always enjoy Gobar Times,
which is very useful and helpful for our activities. The idea of a rice reporter (January
15, 2004) is also interesting. Our network groups also surveyed the rice culture in our
Ecology and Natural Resource Education Project, Kolkata