it so often leads low-income nations into an agricultural development cul-de-sac.
Absolutely, hence my repugnance for the usual comparative advantage argument put forward by those who have a Groundnut or other "colonial crop" scheme to sell. Ploughing up virgin Asian steppe for biofuels sounds a bit like that to me.
From the agronomic point of view, I'm not sure about potatoes v maize. Monocultures are bad. Lighter soils are preferred for potatoes because tilling and harvesting are thus easier. The same soils dry faster, so may call for irrigation. Potatoes need considerable amounts of nitrogen, and in these soils + irrigation, that means N will leach down into the aquifer with pesticides. That's off the top of my head, however, no source.
Eurostat gives 2006 EU 27 potato production as 2.25 Mha at an average yield of 25 t/ha.
Wikipedia gives the energy content of the two, per 100 g, as Potato 320 kJ, Maize 360 kJ. So, roughly, maize = (potato x 0.9).
25 x 0.9 = 22.5 t/ha compared to 6.8 t/ha grain maize!
But I think soil requirements are more stringent than for maize, and maize is much easier to store and handle, making it already industry's favourite. Oh, and is there a potato lobby with any clout?
And without that energy input, there's no way that get 6+t/h. Either you intercrop with a nitrogen fixing legume, and then you are growing the maize in hills rather than flat rows, and the productivity per plant can be good, but the spacing kills the 6+t/h. Or you deplete the nitrogen, and the yield per plant plummets.
Meanwhile, intercropping potatoes in hilled rows with truck gardening crops you can get more than 10 t/h with a rotation.
Certainly, competing in oil-fed agriculture, potatoes are at a disadvantage to maize, but that may be a temporary state of affairs that will pass. I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.
In petro-farming, maize does call for more nitrogen fertiliser than potatoes. (On the order of, roughly, 300-400 kg/ha N for maize with yields above 10t/ha, while 200 kg/ha N is "enough" for potatoes). While tilling/harvesting will call for more energy in potato culture than maize, particularly with the advent of low- or no-till methods for sowing maize.
In petro-farming, maize does call for more nitrogen fertiliser than potatoes. (On the order of, roughly, 300-400 kg/ha N for maize with yields above 10t/ha, while 200 kg/ha N is "enough" for potatoes)
And then translate that to energy yield per hectare over energy cost of nitrogen fertiliser per hectare ... on the above:
22.5 t/ha compared to 6.8 t/ha grain maize!
that is: 44 kg N-fertilizer / ton maize yield for maize 9 kg N-fertilizer / ton maize-equivalent yield for potatoes I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.
The numbers were the industrial farming ones above, not the kind of hand-worked fields that lie behind in the latest Arc of the Sun diary ... for discussion of targets in the medium term time-frame in the EU or US, industrial farming has to be assumed, though possibly with marginal movement in the direction of sustainability. I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.
