Managing Continuous Corn for Yield and Soil Productivity

145 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008.With recent transition from the corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] (CS) rotation to continuous corn (CC) in the Midwestern U.S., there is a need to understand how this transition will affect soil organic matter (SOM). Soil samples were collected following corn from three locations after 8 yr of CC and CS rotations. Soil organic C (SOC) and total N after 8 yr were greater with CC than with the CS rotation, but only at one location where the relatively fine-textured soil and cool climate limited decay and allowed differences to develop between rotations. Both phases of the CS rotation were present each year in this study, and soil samples were also collected following soybean in attempt to identify how SOM is affected by the previous crop. At the one location where crop-derived C returned to the soil over the 8 yr of this study was similar between both phases of the CS rotation, SOC and the soil C/N ratio were greater following corn. Thus, when comparing SOC or the soil C/N ratio among rotations, the previous crop in each rotation at the time of soil sampling should be the same. Corn residue remaining after grain harvest may be used for ethanol production in the future, and corn residue may preferentially be harvested from fields where corn is grown continuously. Field experiments were conducted in Illinois to determine how residue removal and tillage system affect the response of CC to N fertilization. Across four N fertilizer rates and five Mollisol environments with abundant rainfall, grain yield with no till improved as residue removal increased, and equaled that of the chisel plow tillage system when all residue was removed. Across tillage systems in these environments, the response of grain yield to N fertilization was similar when all or half of the residue was removed. Residue removal also reduced the economically optimum N fertilizer rate without affecting yield potential. However, producers that harvest corn residue will need to be conscious about how much residue they return to the soil in order to protect against soil erosion and loss of SOM.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD