What did the Nabateans grow?

You know how the internet is. Endless rabbit holes down which to lose oneself. Some questions answered. Others, not so much. New ones arise. Here’s an example. It all started with the Mosaic of the Seasons in the 5th century Byzantine church at Petra in Jordan. I visited the site last week and thought the agrobiodiversity-themed mosaics wonderful.

That got me thinking about Nabatean crops more generally. What did these people grow in the middle of the desert? Did it include the plants depicted in these mosaics? The Nabateans were known as spice (and incense) traders, but more as middlemen rather than actual producers. Why, indeed, did they find it necessary to grow anything at all in such a harsh environment? Couldn’t they have traded for everything they needed, sitting astride a major trade route from the East to Rome?

So I googled a bit, and it turns out there’s a book called Nabatean Agriculture. Or Al-Filahah al-Nabatiyah in fact, written by a 9th century Mesopotamian scholar called Ibn Wahshiyah. Unfortunately, though the Arabic text is online, I could not find anything that I could actually read on the contents of the book beyond that it includes “a wealth of knowledge on the preparation of basic foods from the agricultural products mentioned throughout the book.” Frustrating.

However, I did find an enormous amount on the sophisticated water management practices of the Nabateans, for example in the supporting document to Israel’s proposal for inscription of the “Desert Cities of the Negev” as a World Heritage Site. It’s a huge pdf, so watch out, but it does have great descriptions, starting on page 108, of the channels, damns and cisterns these communities built to save and manage water in a region with less that 100mm of annual rainfall. Some of these practices are in fact being revived. One consists of enigmatic piles of rocks called tuleilat el anab in Arabic, which means “grape mounds.” 1

They measure 1 m in diameter by 30 cm in height and in some places extend for several square kilometers. So it’s not just pleasure gardens we’re talking about. The prevailing view seems to be that the grape mounds were intended to enhance the flow of run-off water into agricultural terraces. Their name is the only clue to the crops grown by the Nabateans that I’ve been able to find 2, apart maybe for those mosaics. There must surely be some archaeobotanical evidence somewhere? More rabbit holes beckon.

Drought resistance: “it’s complicated”

In case anyone out there is still wondering why all those early promises of drought-resistant crop varieties have been so long arriving, Ford Denison has a wonderfully clear explanation. He takes as his starting point a 2004 paper about the development of Drysdale wheat, bred in Australia for water use efficiency. And he came to that in search of counterexamples to his default view.

I’m always skeptical when someone speculates that we could double crop yield just by increasing the expression of some newly discovered “drought-resistance gene.” My rationale is that mutants with greater expression of any given gene are simple enough to have arisen repeatedly over the course of evolution.

The question Denison asks of Drysdale wheat is whether the tradeoffs that in the past prevented the selection of greater productivity — for example the ability to withstand drought being penalized in average and wetter years — are no longer relevant.

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Rather than give away the answer, or attempt to summarize the key arguments, I just urge you to go and read the full post. I will, however, add a little tidbit I discovered all on my own (with Google’s help). You might think that naming a drought-resistant wheat Drysdale marks a marketing triumph. You would be wrong. It recalls Russell Drysdale, an Australian artist whose paintings of rural life in general and drought in particular captured the land and its people.

Tying up some Amman loose ends

You’ve been wondering about those as yet unanswered questions from the Amman conference, haven’t you? Ok, here goes.

Jose Cubero asked why there are no commercial faba bean hybrids. He had no answer. The yield gain is considerable. BTW, did you know that protein content in faba bean is not negatively correlated with yield potential, as is apparently the case in other pulses? And that you can have totally selfing varieties, with closed flowers? I need to learn more about this crop.

Raj Paroda asked if aeration might be the answer to decreasing methane emissions from paddies. Well, it’s possible. Work in Japan is showing that prolonged mid-season aeration can cut methane emissions down to zero. But what will this do to yield? And what will it cost? Of course, “[m]any rice varieties can be grown under much drier conditions than those traditionally employed, with big reductions on methane emission without any loss in yeild. Additionally, there is the great potential for improved varieties of rice, able to produce a much larger crop per area of rice paddy and so allow for a cut in the area of rice paddies, without a cut in rice production.” See? Even when it’s not about germplasm, it’s really about germaplasm.

Theib Oweis wondered whether we shouldn’t measure — and select for in breeding programmes, by implication — productivity on the basis of unit of water consumed rather than of land used. Indeed we should, certainly in the dry areas. Potatoes had the highest yield per cubic meter of water of the crops on his list, and olives the highest economic return per cubic meter of water. You can get 8 t/ha of wheat, but the highest water productivity is actually at 6 t/ha. You need 1000 kg of water to grow 1 kg of wheat. I could go on and on, he had lots of figures like this.

And would you believe it, Ken Street did indeed think of a better way of identifying germplasm for evaluation, and it’s called FIGS.

How many did you get?

Vote for innovative nutrition solutions

We had an email from Yvonna Tan alerting us to the Ashoka Changemakers competition for innovative solutions to improve nutrition. Yvonna wanted us to recommend her project to our readers, but we’re uncomfortable doing that. There are lots of great-sounding projects in the list, from fake goats to vegetable gardens. So while we’re greatful to Yvonna for poking us, we’ll leave you to choose the projects you want to support. You have to register, and that requires responding to an email, so it is a bit time-consuming. But the winning project gets $5000 so you might consider it time well spent. You have till 8 February.