This document printed from the University
of Illinois Extension From the Fields at http://www.extension.uiuc.edu/rockfordcenter/
Two Topics of Great Concern Addressed at Agronomy Day at U of I
August 31, 2007
Jim Morrison
Extension Educator, Crop Systems
Rockford Center 417 Ware Ave, Suite #102
Rockford, IL 61107-6412
Phone: 815-397-7714
FAX: 815-397-8620 morrison@uiuc.edu
Two of the many topics discussed at the 51st Agronomy Day at the University of Illinois, Urbana-Champaign were managing for soybean cyst nematode and managing corn following corn. Here are a few major points from of those topics.
Soybean cyst nematode (SCN) has created a persistent and significant annual yield loss in many soybean fields. Eric Adee, agronomist at the University of Illinois Research and Demonstration Center at Monmouth reported that SCN can cause 10 bushel per acre or more yield loss with no visible symptoms. SCN resistant or moderately resistant varieties can recover some of that yield loss. Variety resistance information can be found at this web site: http://web.aces.uiuc.edu/VIPS/
Yields of resistant and moderately resistant varieties were 8.2 and 11.8 bushels per acre better, respectively, than the susceptible. Resistant varieties have a "carryover" benefit of reducing the SCN population.
An extra year between soybean crops increases soybean yield by 5 to 7 bushels per acre, and reduces the SCN population. Every 1,000 reduction in SCN egg numbers translates into a two bushel per acre or more increase in yield.
Emerson Nafziger, Extension agronomist, noted that if the demand for corn means increased corn acreage so that we have two-thirds corn and one-third soybean, then half of the corn crop will follow corn every year. Research at Urbana continues to show modestly higher yields for corn following soybean as compared to corn following corn.
A three year study at Urbana found second year corn yielded the same as continuous corn, and corn following soybean yielded a few bushels more, but the difference was not significant. Nafziger noted that second year corn does not face more problems than 5th or 10th year corn.
Despite claims that nitrogen starts to "recycle" so that nitrogen fertilizer rates decrease after several years of continuous corn, data from Urbana does not show such a pattern. The amount of nitrogen needed is correlated to corn following corn yield, but yield shows no trend over time.
A study on continuous corn at Urbana has shown little response to increasing levels of tillage (chisel vs. rip), extra fertilizer (including 100 more pounds of nitrogen), or higher plant populations (40,000 vs. 32,000 plants per acre).
Nafziger concluded by saying questions that remain to be answered include whether or not we can do less tillage, including strip-till, in corn following corn, and what effect removal of residue (for conversion to biofuel) might have on yields and soils in corn following corn. Responses to management are not consistently different in corn following corn compared to corn following soybean.
