Yield response of continuous corn to residue removal, tillage, and nitrogen rate

Removing corn residue for use as biofuel may require adjustments in tillage systems and nitrogen rates. Research was conducted at DeKalb, Monmouth, Urbana, and Perry, Illinois to examine the response of three residue removal rates (full, partial, and none) and two tillage treatments (no-till and conventional (chisel) tillage) to four N rates (60,120, 180, and 240 lb N/acre) for five years, with years three through five examined here. Removing all of the residue raised yields in eight of the twelve site-years under no-till, but not when plots were tilled. At high N rates, there was not a significant difference in yields between conventional tillage and no-till in six of the twelve site-years tested when averaged across residue treatments. However, in the remaining six site-years, conventional tillage yielded significantly more than no-till in five of them, by an average of 12 bu/acre. When averaged from 2008 to 2010 across locations, conventional tillage yielded 12 bu/acre more than no-till under high N rates. Removing all or part of the residue increased yields by 10 bu/acre across years and tillage treatments. No-till with no residue removed yielded an average of 24 bu/acre less than all other residue-tillage treatment combinations at high N rates. No-till with partial residue removal yielded 17 bu/acre more than no-till with no residue removal, but was still significantly lower than the other 4 treatment combinations. Under conventional tillage, all three residue treatments showed a similar response to N rates across years, with yields increasing as more N was applied, and reaching a plateau between 150 and 200 lb N/acre at most locations. Under no-till, full and partial residue removal showed a very similar response to N rates as conventional tillage, but no residue removed required more than 200 lb N/acre to achieve maximum yields at every location except Urbana. This study suggests that the effects of residue removal depend on the tillage system in place. Removing residue increased yields in no-till, but decreased them in conventional tillage