Just to catch you up, this week we're focusing on Rosario Costa Cabral, one of the world's more inspiring farmers.
Talking Plants community member Julian Blackwood recently asked a number of in-depth questions that were beyond the scope of the NPR Amazon story. I thought I'd post his q's (edited for clarity) with answers provided by Columbia U. ecologist Miguel Pinedo-Vasquez, who is an expert in Amazonian biodiversity and has known Rosario for a decade.
Q: Since (Rosario farms on) tidal land, presumably the water is somewhat saline? Or is it backed-up fresh river water that floods her land twice a day?
A: The water is not saline. The fresh water of the Amazon actually extends far into the sea.
Q: If the flood-tolerant pepper plant anecdote was accurate, it raises the interesting question of how that particularly valuable gene combination for flood tolerance (if that's what it is) is maintained in a partly cross-pollinating crop.
A: Well, the flood threat (and natural selection) is constant as is the human selection process. So presumably if cross-pollination does occur, any non-tolerant plants that might result are quickly eliminated. But I also saw that Dona Raimunda (Rosario's mother) seems to do some hand pollination with some vegetables; she shakes the flower of onions onto other onions. She says that way she gets better bulbs. How and where she learned this I don't know.
Q: The reference to distributing cassava "seeds" (of her improved selection) presumably meant the usual stem cuttings used for clonal propagation - as cassava is cross-pollinated. But the really big question is exactly what land was she actually farming when you visited?
A: When Rosario and her family came to Mazagao they could not bring cuttings but rather seeds (although as you point out, reproduction by cuttings is the usual process). The family had been dispossessed from their farm and were not sure when and where they would plant again. Any cuttings would have probably died. She also apparently distributed seeds not cuttings; people try out the seeds on their own land, select on their own. On her own land she plants her own cuttings.
Q: I understand Rosario's farming on logged-over land. She is probably planting gaps in various glades, cropping them until soil fertility or pest build-up drives her to a new plot (similar to traditional "shifting" cultivation). Let's hope she changes plots regularly so that the soil is not exhausted to the point where only tertiary scrub can regenerate (her planting of local tree species was good news).
A: Rosario is indeed planting in gaps and she moves annuals and semi-perennials around every few years to other parts of her landholding. Of course many of her crops are actually perennials and are native trees. The problem with fertility loss in the floodplain is not nearly as great as you might have in an upland site. The twice-daily tides carry and deposit nutrients and the flooding (both tidal and seasonal) probably helps keep down some pests.