As spring approaches and plans for the 2018 crop are finalized, growers will determine what crops to plant and plant crop rotation across their acres. When considering crop rotations and yields, many focus on continuous corn and the yield penalties associated with that practices. However, there is one possibly overlooked benefit of crop rotation: avoiding a soybean yield penalty.
In this recently published article, the University of Kentucky’s John Grove discusses soybean yields for first year and second year soybeans from 2009 to 2016. Grove’s research data shows an average yield penalty of 2.3 bushels per acre across that 7-year period, with some years being showing yield losses greater than 10 bushels per acre. In another article from No-Till Farmer, Greg Roth shows data that predicts a 4 to 6 bu/ac yield penalty for second year soybeans.
Yield loses from continuous soybeans (and other continuous crops) are usually associated with increased disease presence as well as pests. Diseases that can over-winter on crop residue can be more severe for second year soybeans, especially in no-till production systems. Soybean cyst nematode presence can also increase with continuous soybean production. Additionally, weeds that are difficult to control in soybeans (marestail, etc.) can spread and rob yield as well.
There are several things growers can do to manage risk in second year soybeans. Practices such as crop rotation, varietal selection, seeding rates, row widths, and tillage practices can be used to mitigate yield losses in soybeans. As growers look forward to the 2018 season, yield losses from continuous soybeans should be considered when determining acreage for crops to be produced.