More on that drip irrigation thing I Nibbled yesterday. David Zetland, the aquablogger sans pareil, has blogged a bit about this. On the PNAS paper, he had this to say:
Water has to go somewhere, and drip irrigation just controls that flow. Be a good cost-accountant and find out where else it goes. (There are losers and gainers on an individual basis, but society as a whole should just try to maximize overall benefit from water.)
I’m puzzled by “society as a whole”. Is that some overweening society, or just the outcome of individual actions?
An earlier post, in response to an email, revealed that Zetland, like me, had always though that drip would be more “efficient,” but that there are many factors that come into play.
It’s all about cost and benefit. When water is cheaper, it’s not too important to conserve it, but expensive water doesn’t necessarily mean that the “best” irrigation method is the one that uses the least water. (Although drip-irrigated rice uses less water, it also has a lower yield.)
So, it’s complex. Now, there’s a surprise. Wouldn’t it be nice if there were some decision-making tool that could tell the grower which system would provide the most crop per drop, taking into account, of course, the cost per drop?
And in related news, Reuters reports that Iraq plans to revive 2.5 million hectares of agricultural land by “sucking out the salt”. I’m not sure I understand the project fully. It seems to involve “pumping out the groundwater beneath the soil over several years”. Then what? Natural rainfall replenishes the groundwater? We shall see, but it sounds like a huge undertaking with no guarantees of success or even a reasonable return.
OK, so irrigation isn’t really about agrobiodiversity, but one can use agricultural biodiversity to take advantage of what water is available, and that’s a good enough reason to post.