Methods of Crop Production

Whether organic or no-till farming best minimizes the agricultural world’s carbon footprint is still up in the air.

Five years after one of the last research studies was completed on no-till farming by Rattan Lal, director of the Carbon Management and Sequestration at The Ohio State University, new results have been published in the Agronomy Journal that may or may not clear the fog from the plains of debate.

Michel Cavigelli, a research soil scientist at the Animal and Natural Resources Institute of the U.S. Department of Agriculture, was the lead scientist on the long-term cropping systems trial published in Agronomy that compares organic and no-till farming methods.

His preliminary results show that there is more carbon in the soil of no-till land than conventional-till land, which Cavigelli said is a “classic finding that many others have shown over the years.”

What surprised Cavigelli and his colleagues is that the organic farming plots tested contained more carbon in the soil than both no-till and conventional-till methods. No-till farming has long been thought to be superior to organic in carbon sequestration because of the undisturbed soil structure.

“I'm not an agronomist, and I'm not an expert, but I'm not surprised,” said David Cleverdon, owner of Kinnikinnick Farm, a certified organic farm in Calendonia, about 80 miles northwest of Chicago.

“Have you ever seen no-till?” he asked. “It's like magic, subtle things happen.”

But if the right balance of chemicals is not used, the “soil is killed by chemicals,” Cleverdon said.

Cavigelli attributes the increased carbon in organic plots to the tilling involved. It buries the crop residues, animal manures used for fertilization and cover crop residues into the soil, he explained, all of which contain carbon.

“Organic methods rely very heavily on cultivation, which moves a lot of carbon into the atmosphere,” said Jerry Hatfield, a proponent of no-till methods and the supervisory plant physiologist at the National Soil Tilth Research Laboratory in Iowa.

“No-till methods sequester the carbon – it decreases the emissions and increases the carbon in the soil,” said Lal. “It is good to have carbon in the soil – it improves the quality of the soil and agronomic production is increased.”

But with the new results in Cavigelli’s study, no-till advocates may have to re-think their stance.

It is true, Cavigelli said, that the cultivation and tilling involved in organic methods release carbon into the atmosphere.

But there is a difference between “new” carbon and “geological” carbon, Cavigelli explained. New carbon is good carbon that the organic method puts into the soil – carbon is naturally occurring in the atmosphere and an essential part of photosynthesis for the crops. This “new” carbon is naturally recycled through the plants and adds nutrients and sustainability to the land.

“Geo” carbons, such as fossil reserves, are carbons that are naturally occurring below the ocean and soil – “stuff that nobody has had access to until they started pulling it out of the ground,” said Cavigelli.

He said that what should be scrutinized is the use of “geo” carbon, such as the fossil fuels that are used to run the tractors that are used for the tillage of organic plots.

His research group has not yet done the calculations on the how much carbon is  going into the soil or the carbon release.

The debate about which type of farming is best for the environment might come down to which system releases the most carbon emissions into the atmosphere, hastening the effects of global warming and a less sustainable method of farming.

Cavigelli does not foresee farmers making the transition away from organic farming, even if no-till methods come out on top when the debate is concluded. Even though no-till methods produce up to 15 percent more yield than organic practices, Cavigelli said, organic farmers end up with better profits because of the high demand for organic products.

No-till is currently incompatible with organic methods on a large scale, due to weed control issues. No-till uses pesticides and herbicides to control weeds, organic avoids them.

Although a combined organic/no-till method is being researched fairly extensively by soil and weed scientists, Cavigelli said, there are still very few no-till organic farmers now.

“It’s doable,” said Cavigelli, “but there are some serious challenges because of weeds.”

There is much lower soil erosion in no-till than organic, but organic practices minimize pesticide run-off.

It comes down to an “evaluation call,” said Cavigelli.

In the end, Cavigelli would not state his opinion as to which was better for the environment.

Neither did Lal, but he is excited about the idea of combining no-till and organic and the possibilities of weed control innovation.

Hatfield supports no-till because farmers end up with “an improved system in terms of promoting a healthier plant system.”

Cleverdon said that no-till is better because it leaves a smaller carbon footprint, "You don't have to make as many passes over the field."

But he also said that comparing the two is “like apples and oranges.”