Volunteer Glyphosate-Tolerant Corn Reduces Soil Water Storage and Winter Wheat Yields.

A common crop rotation in the west central Great Plains is no-till winter wheat-corn-fallow. Because most of the corn produced is herbicide-tolerant, volunteer corn in fallow is not controlled with glyphosate. This study evaluated the impact of volunteer corn on soil moisture storage in fallow and the succeeding winter wheat crop across three locations in western Kansas from 2008 to 2010. Volunteer corn reduced available soil water at wheat planting in 8 out of 9 site years. On average, available soil water was reduced by 2.54 cm for each 6,200 volunteer corn plants ha^-1. Volunteer corn water use reduced wheat tillers in half of the site years. Similarly, volunteer corn reduced wheat yields in half of the site years, and yields fell 67 kg ha^-1 for every 1,200 volunteer corn plants ha^-1. When wheat yields were above 4,700 kg ha^-1 or below 2,350 kg ha^-1, other factors affected wheat yield more than the preceding volunteer corn population or available soil water at wheat planting.