In Illinois, researchers realize that biomass feedstocks will need to come from many different sources, including crop residues, forest residues, and municipal waste, for example, said Marty Williams, a University of Illinois crop scientist and ecologist with the USDA-Agricultural Research Service. The use of double-cropping systems—a winter annual biomass crop is grown then harvested in the spring, followed by a summer annual crop—has been suggested as an additional option.
Knowing that many large-seeded vegetables in the Midwest must be planted later than agronomic crops into warmer soils, Williams was interested in the possibility of developing a bioenergy feedstock/vegetable double-cropping system. He explained that no such system had been developed and tested yet.
Field trials were conducted over three environments. During the study, Williams compared crop productivity and weed communities in four different pumpkin production systems, varying in tillage, cover crop, and bioenergy feedstock/pumpkin double-cropping. A fall-planted rye (Secale cereale) mix was used as the biomass feedstock.
Interestingly, the researchers saw pumpkin yields in the double-cropping system were comparable to conventional pumpkin production. However, the biomass feedstock also yielded an average of 4.4 tons per acre of dry biomass prior to pumpkin planting. “We saw a theoretical yield of 349 gallons of ethanol per acre, and a higher farm gate value than typical pumpkin production,” Williams said.