Documents: Special Interest: In The Kitchen:

Plants Producing Fertilizer & Beans

Some agricultural crops may be able to manufacture their own fertilizer; plus a few comments and suggestions on beans in the garden.
by Art Drysdale
by Art Drysdale


Art Drysdale, a life-long resident of Toronto and a horticulturist well known all across Canada, is now a resident of Parksville, British Columbia on Vancouver Island, just north of Nanaimo. He has reno-vated an old home and has a new garden there. His radio gardening vignettes are heard in south-western Ontario over radio station Easy 101 FM out of Tillsonburg at 2 PM weekdays.

Art also has his own website at

August 13, 2006

Growing in our garden this year are some new, annual (although may be considered perennial in some climates) Echium. I have not as yet identified them past the genus stage! Above are three shots of them—excellent performers! Below, the Pineapple lily (Eucomis comosa) also a good performer this year. This one is a bulb which we’ll likely try to over-winter in the ground with some extra mulch over it. Author photos.

“Crops could make their own fertilizer,” according to Michael Hopkin in an on-line issue of the journal Nature. “Crop researchers hope that staples such as wheat could be coaxed to produce nitrogen-processing roots.

“Plant geneticists have induced plants to form 'fertilizer factories' without the aid of bacteria that are normally crucial to the process. If the technology can be transferred to plants such as wheat or rice, industrial fertilization of these crops could be reduced or even abolished.

“When bacteria known as rhizobia enter the roots of a leguminous plant, such as a pea or bean, the plant develops lumps, or nodules, on its roots to house the microbes. The bacteria take nitrogen from the air and turn it into ammonia that feeds the plant.” Most high-school science students will remember this from their school days!

“Two research groups have now made legumes that produce nodules in the absence of rhizobia, potentially paving the way for crops that would not need to be treated with nitrogen fertilizer, but instead would rely on nitrogen-processing bacteria that are omnipresent in the soil to colonize their nodules.

“Fertilizing crops is inefficient and environmentally damaging, says Giles Oldroyd of the John Innes Centre in Norwich, UK, who led one of the research teams. Besides polluting waterways, chemical fertilizer production ac-counts for an estimated half of the fossil fuels burnt by agriculture.

“Nitrogen-fixing bacteria are a better way for plants to gain their nitrogen, Giles Oldroyd adds. Many farmers and gardeners alternate legumes such as broad beans or clover with their other crops. Traditional Latin American farmers plant beans alongside their maize.

“‘Cereals have a huge nitrogen demand. But legumes not only provide nitrogen for themselves, but also for other plants,’ says Giles Oldroyd. He and his colleagues are attempting to genetically engineer related plants such as tobacco and tomato to produce root nodules.

“Cereals have a huge nitrogen demand. But legumes not only provide nitrogen for themselves, but also for other plants. Nodule production is normally initiated when nitrogen-processing bacteria enter a plant's root cells. The plant senses the bacteria and its root cells grow to form a nodule. But the two research groups, Giles Oldroyd's team and a group led by Jens Stougaard of the University of Aarhus, Denmark, found that by mutating a gene that produces a cellular messenger called CCaMK, root cells can be converted into nodule-forming cells, even without the bacteria.

“The idea that a self-fertilizing facility could be set up in other crop plants has not yet been tested, although Giles Oldroyd says that his work on tobacco and tomato should reveal whether this occurs. There is no theoretical reason why it shouldn't work, he says. ‘We can make empty nodules, but the plant has to allow the bacteria to invade,’ he says. ‘But if legumes can do it, others should be able to as well.’

“The technology is in its infancy: ‘A number of key steps need to be achieved,’ Jens Stougaard warns. But he hopes that it could be used to make self-fertilizing versions of the world's main food staples: maize, wheat, barley and rice.”

* * *

While out and about in Parksville this week, a friend asked about beans, in general. She had, in the past, planted the Blue Lake cultivar, and this switched to Scarlet Runner.

Now, while the Scarlet Runner beans do have nice red flowers, which are really attractive, as far as the beans are concerned they are not near as good as far as I am concerned. The main difference is the fact there is about ten days’ difference in the time to maturity of the beans--Blue Lake is generally considered to produce beans in 55 days, whereas Scarlet Runner takes 65 days.

Green and yellow or wax beans, as well as the climbing varieties such as Blue Lake, are warm season plants, and that's why I suggest delaying planting them in the Spring until the weather finally warmed up. Now however, regardless of how many rows of beans you planted earlier, you should be considering planting a few more of each of your favourite varieties. They'll grow quickly during the Summer, and produce a crop in about six or seven weeks. Actually, the secret with many veggies, not just beans, but also lettuce and radish, is to sow small quantities of seed every two or three weeks, rather than a larger quantity just once.

While writing about beans, there is another important item about these plants of which many vegetable gardeners are not aware. There is a common disease that leaves the beans themselves with rust spots at maturity. This rust can be prevented quite easily by staying out of the bean patch, that is, not walking between the rows, when the plant foliage is at all damp. It seems this is what causes the rust to spread, so stay away from your bean plants when the foliage is wet from rain, watering or even morning dew.

And, if you like to pick nice clean bush beans that have not been splashed with mud from rain pelting the soil, tie up each row with a line of string running along both sides. This will support the plants and keep the beans them-selves from being excessively splashed. Of course, if you had used one of the bio¬degradable plastic mulches down between the rows when you planted your vegetable garden, you'd have no problem with soil-splashed vegetables! Keep these biodegradable mulches in mind for next year and enjoy the fruits of your harvest!

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