Sunday, 28 February 2010

Oca Yield – Keeping up with Andean Peasants?

How do you judge if you are obtaining a reasonable yield from your Oca?  With most crops you can look over the fence to our neighbour's garden to see how you measure up, but none of my neighbours grow Oca.

So having looked at various quoted Oca yields (see down the page), I've done some calculations to allow comparison in garden-scale cultivation, based on growing on 4ft wide beds with 1ft wide paths. This means that each linear meter of bed occupies just over 1.5sq.m including access paths.

From a one-meter-run of 4ft wide bed, if you produce:-

  • 14.55kg – You equal the world-wide highest claimed oca yield (that I can find).
  • >6kg – You are up there with the white-coated men using select varieties, unlimited NPK, pesticides, irrigation, and often undisclosed, probably non-sustainable methods.
  • 3 - 6kg – You match modern commercial producers, e.g. in New Zealand.
  • 1.5 - 3kg – Good levels for traditional Andean peasant methods.
  • 0.75 - 1.5kg – A poor effort for a peasant.
  • < 0.75kg – Perhaps you are more cut out to be a hunter-gatherer.
This is quite encouraging to me, given that the above figures are for monocultures. I have been able to more than match the best peasants, but within a polyculture, so obtaining as a bonus, a similar weight of tomatoes, and a fair quantity of fast-maturing salad crops from the same ground.
With a monoculture system, planted at 6 plants per meter of bed, I'm confident I could achieve 6kg. But man cannot live by Oca alone.

Average 7-10, maximum 40 tonnes/hectare. 

5 tonnes/hectare (traditional Andean husbandry)
7-10 tonnes/hectare (commercial yields, Peru and New Zealand)
40 tonnes/hectare (experimental conditions)

Development of New Oca Lines in New Zealand. R.J. Martin, G.P. Savage, B.Deo, S.R.P. Hallow, P.J. Fletcher says:
Up to 20 tonnes/hectare (experimental).

Neglected Crops 1492 from a different perspective. J.E. Hernandez Bermejo, J. Leon says:
3-12 tonnes/hectare (average production, Peru). 97 tonnes/hectare (experimental selections and treatments)

Andean Tubers, C. Arizu and M. Tapia (CIP, Lima, Peru) says:
40-50 tonnes/hectare.

(1 tonne/ha = 0.1 kg/sq.m)

Friday, 19 February 2010

Free-Range Oca

Oca has demonstrated to me that it can look after itself without protection, special feeding, or formalised cultural methods. It can blot out competing weeds, and it has its own chemical defences against some pathogens and pest insects, and can possibly (pending trial) chemically inhibit the growth of competing plant neighbours. It can mix it with the big boys, and it's time it left the easy-life behind. No more pampering. No more chitting near the radiator. No more rubbing shoulders with frilly lettuce and F1 hybrids with Italian-sounding names.
It's high time Oca got on its bike and learned to make its own way in the meritocracy of My Other Allotment.

To explain things ... my Other Allotment is the antithesis of my first allotment. It is something like a developing edible forest gardenwithout the canopy layer. Plants are mostly either perennial, self-sown, or plant-replant tubers. Any form of cultivation, watering, or weeding is rare. Call it a sink-or-swim free-range low-input happy-accident ultimate polyculture garden if you like. Some vague order is maintained by mulching, and very occasional strategic guidance and weed removal.

Below: Wormwood, Japanese Wineberry, and Yacon, with volunteer Perpetual Spinach, red-leaved Beetroot, and tomatoes (at rear). Oca could compete here.

Below: I count at least 20 edible species in this corner of the plot. But there is still space to spare for Oca.

Below: Mulched soil surface with self-sown red orach, New-Zealand spinach, and red-veined sorrel. Oca could fit in to this niche.
Conventionally, root-crops do not mix well with perennials, because harvesting the root-crop  disturbs them. But I am going to release a few Oca in to this wild system, and see where it survives, and where the tubers can be got at without digging deep.  Absence of cultivation for several years, coupled with occasional mulching, has produced a high-organic-content layer on the surface, which will be easy to scratch through to collect tubers. Those that are missed will seed the following year's crop. At least that is the plan!

25/4/10 The soil has warmed up nicely, so today is planting day. Basically, I'm just finding gaps between existing plants, scooping out a depression with the spade, dropping in a sprouting tuber, and dumping a shovelful of rough garden compost on top. More mulch will be added during the season, and I'm hoping this will encourage the tubers to develop near the surface, making them easy to harvest. The photo below shows a planting in a bed that has been reworked this Spring. I'll be adding other plants – yacon, and mashua, – for an Andean tuberous hotch-potch, conveniently all harvested at the same time of year.

This trial will be ongoing. Come back to this post for regular updates.
And I'm keen to hear from anyone with experience of growing Oca in similar circumstances.

Above: 12/7/10 This view shows the same area. The Oca now have yacon, tuberous nasturtiums, broad beans, and yarrow as neighbours. There's been a prolonged dry hot period, and the Oca are showing signs of stress, though have still managed to put on good growth. Others located elsewhere with more shade and moisture look fresher and happier, but are not so large as these.

Sunday, 7 February 2010

Oca-centric aims for 2010

Deepest Winter - last year's successes are sauteed, or set aside for seed, the failures composted. It's time to look forward and decide on some plans for the coming season.

Last year answered some questions, at least partially, but it also raised a few.
  • There is the question of allelopathy. Oca probably exhibits an allelopathic effect on subsequent crops. If so, which crops are most affected, and how significant is the effect?  I need to grow a range of vegetable crops on last year's Oca bed, with a control to give comparison. Any understanding of allelopathy that can be gained is going to be useful in relation to bi-cropping and crop-rotation. For this trial go here.
  • The second question is how to increase the average size (as opposed to total weight) of tubers produced by Oca plants (improving my so-called Oca Productivity Index). Tuber thinning does not seem practical (or at least it is too fiddly and too much work).  The remaining possibility is to somehow prevent (or reduce the number of) stem tubers forming. I have a few ideas on how to do this that need to be tried out.
  • My third area of experimentation is going to look at whether Oca can be grown so that it looks after itself as part of a perennial plant guild - a kind of "wild and free, sink-or-swim" planting scheme. Productivity per-square-metre will be lower than more conventional cultural methods, but productivity per unit of inputs (work/other resources) is what matters here. For this trial go here.

I'd like to have another go at determining optimum harvest date, what with the first attempt being messed up by the unusually cold weather (see 2009 harvest results). But I don't have enough space to do that as well as the other trials above, so I will leave it for another year. If anyone else would like to repeat the experiment, I'd love to hear about it.