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The next crop revolution?

Biochar touted as key soil management component

July 2, 2010
By Larry Kershner/Farm News news editor

BOONE When David Laird, standing in a corn test plot, said Tuesday evening that biochar not only repaired damaged soils for crop production, but was also a key component in long term crop sustainability in fertile soils, a murmur rolled through the listeners.

He pressed on.

"The idea of the biochar is to maintain soil quality, while maintaining yield."

Article Photos

An unidentified conference attendee takes pictures of the pit dug to show the soil profile where biochar and dairy manure was disced into damaged soil in a test plot designed to show how it can help restore depleted soil.

Laird was speaking at Iowa State University's BioCentury Research Center, near Boone. Hen was talking to a group of field tour attendees, who have also been attending an international biochar conference in Ames.

This conference is a multiday event where the science, practice, and understanding of biochar were advanced. Conference literature claimed that biochar exists at the intersection of agriculture, climate science and energy, acting as a soil amendment and an agent for carbon sequestration.

According to www.answerbag.com: "Biochar provides places for micro flora to grow and also holds water and nutrients that can be available for plants. When mixed with soil, the result is terra preta."

Fact Box

Biochar:

-noun. A fine-grained charcoal high in organic carbon and largely resistant to decomposition.

As a soil amendment, biochar significantly increases the efficiency of, and reduces the need for, traditional chemical fertilizers, while greatly enhancing crop yields.

Source: reference.com

In the corn test plot, plant growth and yield were being monitored based on the amount of biochar incorporated into the soil, along with the removal of field residue. The trial is trying to indicate if residue removal - for biofuel production, for example will not deprive soil of the nutrients gained from residue breakdown, if biochar can substitute that loss.

The test plants that were the tallest had biochar incorporated, at a rate of 4.4 tons per acre, with 90 to 100 percent of residue removed. Whether that computes into more corn in grain cart this fall is yet to be determined, he noted.

Laird said the taller corn was evidence that the plants were not competing with the residue for nitrogen. "Now that's the short term view," Laird cautioned his listeners. The long term considerations of leaving more residue behind at harvest includes erosion control in times of heavy rain while plants are small and early-season weed control that residue provides between rows.

The 24-acre parcel contained 28 plots, 24 with biochar incorporated in 2007, Laird said. The plots include cover crop applications and corn planted with both no-till and conventional tillage methods.

Laird said there are plans to incorporate more biochar this fall. "For long term sustainability, it becomes necessary to apply additional carbon because you are harvesting the forage."

To dramatically show what biochar can accomplish for a field, Laird introduced the tour attendees to a small parcel of corn planted in a totally depleted soil. The spot was near U.S. Highway 30, where the Iowa Department of Transportation took the topsoil for construction when widening the highway.

A 16-row corn plot was planted into the poor soil. A three-row wide segment was mixed with biochar, at a rate equal to 30 tons per acre, Laird said, along with some dairy manure.

These three rows were twice as big, almost five feet tall, and a lush green color. The other rows farther away from the biochar-manure-soil mix were stunted and light green by comparison.

He said biochar is applicable for redemption of sandy, depleted, eroded or damaged soils. He said there is also application for urban areas where bulldozers have compacted the topsoil.

"We anticipated seeing benefits (of biochar) in depleted soils," Laird said, "But we're seeing that in better quality soils, biochar becomes a component in maintaining a sustainable system."

To be used, biochar should be incorporated into the soil of a garden or farm field. It should be mixed in gently so as to prevent killing worms. Biochar could make-up five percent to 10 percent of the soil when the job is done, but it should not all be mixed in at once. Two or three years of adding smaller amounts seem to work better.

Once the biochar is in the soil, there should be little need to till. There should also be reduced fertilizer requirements, although phosphorus, potassium and trace minerals may need to be added periodically.

Other plots

Other test plots on Tuesday night's tour, included looking at switchgrass, being grown for biofuel and biochar sources and understanding when is best time for harvesting. ISU agronomists Emily Heaton and Danielle Wilson, explained that the plot is watching how the grass responds to harvesting at five different intervals of the growing season.

They said that it is already understood that the grass should wait until fall, when most of the nitrogen has receded into the lower third of the plant.

"The more nitrogen that is extracted with the bio-oil," Wilson said, "the more expensive it is to remove it from the oil."

Matt Liebman, an ISU professor of agronomy, and Renae Diettzel, who is working on her PhD in carbon sequestration, explained how they are looking at native prairie grasses, grown for biomass production, in both fertilized and unfertilized plots. They are monitoring, among other things, when nutrients move from soil to plant and back again, as well as the carbon the plants sequester and the quality of rain water runoff.

Liebman said there is more root development in the unfertilized field than in the fertilized. He explained that the fertilized plants don't have to work as hard for nutrients as its unfertilized counterpart.

However, he noted, that because the unfertilized stand has shorter, thicker stalks, they stand better against high winds with less lodging than the fertilized stand.

Matt Helmers, an associate professor in ag engineering at ISU, showed the well monitoring system that tracks and records the amount of runoff from each of the different plots, as well as the trace elements, such as nitrates, that are carried in the water.

Contact Larry Kershner at (515) 573-2141, Ext. 453, or by e-mail at kersh@farm-news.com.

 
 

 

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