Triticale, a cross between rye and durum wheat, may join corn and soybeans in the Corn Belt crop rotations of the future. Iowa State University researchers are experimenting with triticale (pronounced tri-te-CAY-ley) and other crops to increase the total amount of biomass harvested in a year while addressing environmental concerns such as nitrates leaching into watersheds from heavily fertilized corn crops.
ISU agronomist Matthew Liebman is testing a system in which winter triticale is planted in the fall into soybean stubble. The triticale is cut for biomass when it is still green in early June, followed by a summer crop—either a short-season corn variety or a sorghum-Sudan grass hybrid—seeded directly into the triticale stubble. The triticale acts as a cover crop to prevent winter soil erosion and as a sponge to soak up nitrates. Triticale promises to be a low-input crop that requires little or no additional fertilizer and, because it grows so vigorously in the spring, little or no herbicides. As a biomass crop, triticale has reached its maximum vegetative growth by early June and can be harvested before it sets kernels, Liebman explains.
Trial plots throughout Iowa indicate the biomass yield for triticale should be between three and four tons of dry material per acre, Liebman says. With the triticale using the leachable nitrogen in the soil, a following corn crop will require more fertilizer than is usually applied following a soybean crop, he adds. Late-planted corn crops in the research trials produced grain yields between 125 and 175 bushels per acre, which is less than corn planted in April. The other summer crop option, sorghum-Sudan grass, is quite competitive with corn in the amount of biomass that is harvestable per acre, he says.
Using the U.S. DOE's estimated yields of 120 gallons of ethanol per dry ton of corn and 79 gallons of ethanol per dry ton of biomass, Liebman calculates that corn yields 500 to 600 gallons of ethanol per acre. Adding the ethanol yield from corn stover would increase that to 600 to 800 gallons per acre. The additional biomass from a winter triticale crop would boost the ethanol yield per acre between 725 and 900 gallons.
The calculated ethanol yields give an idea of the system's potential, although there are many issues to be worked out. Most cellulosic ethanol scenarios now being considered are based on dry feedstocks harvested after a killing frost and not a green, wet feedstock such as chopped triticale. Ensiling a green-chopped biomass crop may act as a preprocessing step for an enzymatic fermentation ethanol process. "We're waiting for similar advances on the engineering side to complement the advances in agronomy," Liebman says.
Along with the triticale trials, Liebman and his colleagues are evaluating a tropical legume as a potential nitrogen-fixing biomass crop. "In warmer regions of the United States, crotalaria can fix 150 to 200 pounds of nitrogen," he says. He's currently conducting studies to quantify the nitrogen-fixing performance in Iowa's growing conditions. While crotalaria doesn't produce as much dry matter per acre as corn stover or sorghum-Sudan grass, the ability to fix its own nitrogen may make it an attractive crop when compared with corn and its high-fertilizer requirements. "We haven't tested the system yet, but it's intriguing," Liebman says.
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