| Companies in the U.S. have started using corn (Zea mays L.) residue as feedstock for cellulosic ethanol production. However, concerns including field storage and removal methods effects on crop growth and development, soil health, and environmental quality have been raised. In the Midwest corn cob have being utilized as feedstock material for cellulosic ethanol production in addition to corn residue. Nevertheless, there are many management issues that need to be addressed in order to efficiently store and remove corn cob from the field with minimum damage to subsequent crops and soil health. The current practices include the storage of loose corn cob mixed with corn residue as piles and bales at the edge of harvested fields over winter for later use in ethanol production. The corn cob residue refers to the mixture of corn cob and corn stover in the loose and baled corn cob treatments used in this experiment. Unfavorable plant growth responses have been observed after storing corn cob residue in the field. The objectives of this study were 1) to investigate the effects of loose and baled corn cob residue storage methods and management practices on plant development and crop yield, 2) evaluate and understand the effects of both methods on soil health, and 3) determine the effects of different amounts of loose corn cob residue left after removal and management practices on greenhouse gas (CO2 and N2O) emission and management practices to mitigate such effects.;The study investigated two storage methods at two different sites that were established in fall of 2010. Trials ran through the fall 2012. The loose corn cob residue study was conducted at the Agronomy Research Farm at Iowa State University located near Ames, Iowa (AC site). The soil type is Canisteo silty clay loam (Fine-loamy, mixed, superactive, calcareous, mesic Typic Endoaquolls) and Harps loam (Loam, mixed, superactive, mesic Typic Calciaquolls). The treatments for the loose corn cob residue method consisted of two randomized tillage systems conventional tillage (CT) and no-tillage (NT), which represented the main treatment. Each tillage system was split into five corn cob residue treatments as Control, Removed Residue (7.5 cm applied in the fall and completely removed early spring), 2.5, 5.0, and 7.5 cm corn cob residue depths randomly assigned at each tillage treatment and replication. Then each corn cob residue treatment was split to receive four N fertilizer rates of 0, 90, 180, and 270 kg N ha -1 randomly assigned at each corn cob residue treatment and replication. The N fertilizer was 32% liquid UAN (NH4NO3), which was side-dressed and injected in May after planting using a spoke point injector. The AC site was planted on 6th May, 2011 and 14th May, 2012 using a 111 day maturity corn variety (P33W84) with a seeding density of 79,000 seeds ha-1.;The second study was established at a Northwest Iowa farmer's field near Emmetsburg and near the POET, Biorefinery plant (ENW site). The soil type is Clarion loam (Fine-loamy, mixed, superactive, mesic Typic Hapludolls). The ENW site used a square corn cob residue bale as a storage method, in which bales were placed in the field after harvest and stored over winter, but removed in the spring before planting. The main treatment consisted of corn cob residue left after bales removal: 1) Corn cob residue left after bales removal as a result of breakdown of bales if any, 2) corn cob residue completely cleaned or removed from each plot, and 3) the control treatment, where no bales were placed on plots. Each of the corn cob residue treatments were split into four N fertilizer rates of 0, 90, 180, and 270 kg N ha-1 and randomly assigned at each corn cob residue treatments. The different N fertilizer rates were hand applied using granular urea in May after planting. The ENW site was planted on 5th May, 2011 and 25th April, 2012 using a 111 day maturity corn variety (P0448AM1), with a seeding density of 89,000 seeds ha-1.;Field data collection and measurements for plant, soil, and other parameters were conducted at both sites on weekly, monthly, and seasonal basis. These measurements included plant growth and development parameters, soil physical, chemical, and biological properties such as, soil organic carbon (SOC), soil total nitrogen (STN), microbial biomass (MBC), soil pH, organic acids (only at the AC site), soil penetration resistance (SPR), water stable aggregates (WSA), soil bulk density (rhob), and soil water infiltration rate (Ir only at the AC site only). Also, measurements of greenhouse gas emission (CO2 and N2O) were monitored along with soil mineral N (NO3--N and NH4--N), soil temperature, and moisture at the AC site only. (Abstract shortened by UMI.). |
