An individual amoeba cell can live independently, slurping up bacteria in the soil. When the food is gone, it joins with its comrades, forming a sluglike organism about half a centimeter long that can wriggle to greener pastures… Once there, the slug becomes a stalk with a fruiting body—a tiny globe on top that releases spores, each spawning a single amoeba—to start the cycle all over again.

(Science Now even has a video of this process.)

But researchers at Rice University have discovered (and published yesterday in the journal Nature) another amazing attribute of this slimy eukaryote—some of them farm.

Some ants, termites and damselfish farm fungus or algae, but Dicty is an amoeba, a single-celled life form. Its crop? Bacteria.

Debra Brock, a graduate student at Rice, took 35 wild amoebae and found that one-third of them carried bacteria in their spores. She placed the spores (both those with and without bacteria) into sterile dishes and sure enough found that those with the bacteria seeded the dish. From Discover’s Ed Yong:

By seeding the dish with their bacterial cargo, they had a ready source of food. If the spores didn’t have any bacteria, the amoebae hatched to find a famine awaiting them. Very few completed their life cycle.

And it wasn’t just in sterile environments, says New Scientist:

Farmers even beat non-farmers on Petri dishes inoculated with natural soil bacteria, which suggests that the bacteria they store are better food.

Ms. Brock is quoted in the New York Times:

In a situation where they find a food source they don’t like and they’re carrying the bacteria they’d like to eat, the farmers can grow it for themselves. And they harvest; they don’t eat all of it, but they save some.

Voilà! Amoebic Agriculture!

Why don’t all of the amoebae farm? How long have they been farming? More research is needed in Dicty’s evolutionary tale to find out.

The aphids really do no harm to the plants; farmers have simply found that people won’t purchase lettuce with the bugs on them.

Organic lettuce growers can’t use the pesticides but also need aphid-free lettuce to bring to market. Many have discovered a way to grow the lettuce and keep the population of aphids in check without chemicals. The key? Other insects.

Since Erik is an entomologist, insects are right up his alley. When he got into the bug business, he knew he wanted to do something useful, not just theoretical. Enter agriculture. As a grad student, he studied insects in cotton fields and vineyards. Now he’s leading a study in lettuce fields.

Did you know 75% of the lettuce consumed in the US is grown nearby in the Salinas Valley? That makes the commute easy for Erik.

Turns out that a certain fly, the syrphid fly (aka hover fly), loves to eat aphids when it’s in the larval stage. When the fly larva is first born, it will eat about two aphids a day. But much like the very hungry caterpillar, as it grows, it will eat more and more, upwards of 100 aphids each day.

So to get rid of one bug on the lettuce, the farmers need to attract another. Adult syrphid flies love to eat the pollen and nectar from flowers. Organic lettuce farmers only need to give up a little lettuce land for flowers to bring the flies to their fields. Hopefully, the flies will come, lay their eggs on the lettuce field and their larvae will get to work ridding the field of the aphids.

Occasionally, this biological control strategy will fail. The flies won’t come, the larvae won’t eat the aphids in time or too many aphids will disappear, leaving the fly larvae nothing to feed on.  That’s where Erik comes in. He and his team are helping the farmers determine when, where and why the system works and doesn’t. As he says, “It’s just the science catching up to everyday life.” Hopefully his research will help more farmers adopt this natural pest control system.

(On a related note, today Seed Magazine begins a debate on sustainable agriculture. Check it out here.)

Creative Commons image by Beatriz Moisset

According to National Geographic, “By some estimates, it takes about 10 calories of fossil fuels to get each calorie of food from farm to fork in the American food system.” This has led some to explore whether there is a more sustainable way to maximize crop yield while minimizing costs.

Well, scientists from Iowa State University have found that if crops are rotated more—over a three or four year period—and include alfalfa or oats, the use of fossil fuels on the farm can be drastically reduced.  These results came from a six-year study and were published yesterday in the May/June edition of Agronomy Journal.

What they found is astonishing—between 2003 and 2008, nitrogen fertilizer inputs decreased 66% in the 3-year rotation and 78% in the 4-year rotation. Furthermore, herbicide use decreased 80% in the three-year rotation and 85% in the four-year rotation. Not only that, despite the reduction in energy input, corn and soybean yields matched or exceeded yields attained using the conventional system.

Organic farmers have already have adopted this method of crop rotation. According to Thaddeus Barsotti, co-owner of Capay Organic and Farm Fresh To You, “Crop rotation and specifically the planting of cover crops can increase soil fertility in lieu of the use of synthetic fertilizers, which require fossil fuels to produce. Our farm fertility program includes planting cover crops – such as vetch and alfalfa – and applying green waste compost to fields, both natural sources for inputting nitrogen into the soil for access by crops.”

The Iowa State researchers also used manure to reduce fossil fuel use. They “fed cows on corn, oats, and the hay from alfalfa, and then spread the cows’ manure back on the fields. This contributed to fossil fuel savings by further reducing the need for synthetic fertilizers to provide received key nutrients like potassium and phosphorous,” according to the National Geographic article.

Barsotti says, “We do not use manure on our farm but it is an important part of many soil fertility programs on diversified operations. I hope that conventional producers begin to look at ways to minimize their use of synthetic fertilizers and chemical inputs – unfortunately, big ag and fertilizer companies are not proponents of moderation. Studies like this one are important to show conventional producers that being a sustainable farming operation can also be financially viable and worthwhile.”

(More science news on conventional farming was published today, for more info, please click to read about Roundup resistance or methyl iodide pesticide use.)

Image by David N. Sundberg