Shermin and I have a number of ongoing themes in our discussions. One of them is about sustainable agriculture and how many people can our planet actually support. The latter question has a caveat of course: the answer depends on which technology one would use for growing food. I would surely think that the Earth would support more people if we grew food using conventional (i.e., not sustainable) methods compared to organic. But how much more? Twice as much? Ten times as much?
A recent paper in the journal Nature called “Comparing the yields of organic and conventional agriculture” (free full version available here) by Seufert, Ramankutty and Jonathan Foley (see his TED talk, by the way) offers some insight into the answers. The paper presents the results of a meta-analysis of comparisons of yields between conventional and organic farms. The main result is that organic farms generally have a lower yield, but how much lower depends on the details. For example, vegetables give about 30% lower yield in organic farms than in conventional farms, whereas fruits give pretty much identical yields. Another interesting observation is that, if one compares farms with “best management practices” (not very well defined what this means though) in both types of farms, organic give about 13% less yield than conventional. So, not bad at all!
One interesting likely explanation for the poorer performance of organic systems is that these systems are nitrogen limited whereas conventional systems are not. This means that, when you increase the input of nitrogen into the organic system (e.g., by dumping more fertilizer), its performance goes up. Not the case for a conventional system. The reason why nitrogen is limiting in organic systems is probably because it is released slower from decaying organic matter than is necessary for plant growth.
In short, this article give some clues as to how to optimize food production and gives some hope that organic systems will in the future be able to provide a large fraction of necessary food supply.