Run DMC

ResearchBlogging.orgI am painfully aware of the risk we run here at the Agricultural Biodiversity Weblog of becoming single-issue bores.1 To a hammer, everything is a nail. And if your thing is agrobiodiversity, you’ll naturally be tempted to think that every problem can be solved by the judicious application of an agrobiodiversity thwack. How refreshing it must be to occasionally think against the grain, and question your most cherished assumptions. That possibility is why — apart from my native contrariness — I so enjoyed a recent paper in Field Crops Research very appropriately entitled “Conservation agriculture and smallholder farming in Africa: The heretics’ view.”2 Even though it didn’t really have much to do with agricultural biodiversity.

Conservation agriculture (CA), or direct-seeding mulch-based cropping (DMC), is a package of crop management practices — basically, no mechanical soil disturbance, plus permanent organic soil cover, plus crop rotation3 — that is being forcefully promoted by numerous research and extension systems around the world, backed by various international agricultural development agencies, as the alternative to conventional practices. There was a world congress on it recently. Its main aim is to prevent soil degradation, in particular organic matter and nutrient depletion, and cut back on labour and other inputs, while of course maintaining or increasing yields and yield stability.

The problem, according to the paper, is that the evidence for these benefits is at best ambiguous, at least from Africa. In the mixed cropping systems of semi-arid Africa, the opportunity cost of retaining crop residues is often too high. Yields are likely to decline in the short term (though they may well rise in the long term). The labour burden on women may well increase, and overall it stays the same. Reduced tillage on its own has little effect on soil fertility. It is unclear whether CA allows reductions in fertilizer use. Increased soil biological activity under CA may in fact be detrimental to crop production. And so on. No wonder adoption has been limited in Africa. The only really sure thing is that DMC reduces soil erosion, and you see the benefits of that in the long term.

That may well be enough to warrant the use of CA in some “socio-ecological niches,” and CA proponents should be trying to identify what those might be, rather than pushing it as an all-purpose solution. It is no panacea, no silver bullet, the authors contend, piling on the cliches a bit. A lesson there for all one-issue bores. Not all problems are nails, even if all you have in your hand is a hammer. Now, what can us agricultural biodiversity bores learn from it?

  1. Risk? Becoming? You’re a bit further down that road than you seem to think, bud. Ed. []
  2. Giller, K., Witter, E., Corbeels, M., & Tittonell, P. (2009). Conservation agriculture and smallholder farming in Africa: The heretics’ view. Field Crops Research. DOI: 10.1016/j.fcr.2009.06.017. []
  3. Ha, you see, there is agrobiodiversity involved after all! Thwack! []

3 Replies to “Run DMC”

  1. I really enjoyed the post on conservation agriculture (and thanks Luigi for pointing it out and all the other interesting papers). I readily admit that I don’t know much about CA, but I have always wondered what that infatuation with non-tillage is all about. Anyone who ever tended to a plot of vegetables knows how loosening the soil stimulates plant growth and helps removing weeds. I am relieved to see that a meta-analysis gives some support to my long-held doubts about CA. Interestingly, there is a -presumably untranslatable- German term for crops that not only need tillage but repeated soil disturbance during cultivation, namely “Hackfrüchte” (incl. potatoes, beets, etc.).

  2. I actually heard an interesting perspective on this from an unexpected source recently. I was watching The Long Now video on Michael Pollan’s recent talk, and in the question section he said this:

    Well, when I think about the future I imagine a time where there will not be 1 agriculture system. Where there will be more than one. On a 50 year horizon I don’t see industrial agriculture vanishing. And I’m not even so sure that would be a good thing, for it to vanish. I think, you know, coming up with one solution is another form of monoculture thinking. And that we would make a mistake to throw all our eggs in one basket, whether it was pastured beef or organic agriculture or any number of different things. We need a resilient system, which is to say with many many different ways of doing the same thing.

    Monoculture thinking — but it is funny because most of the people I talk to who are Pollan adherents are quite mono in my experience.

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