The effect of flooding and residue incorporation on soil chemistry, germination and seedling growth

Anaerobic soil conditions created during flood events may alter soil chemistry. Increased concentrations of phenolic compounds and decreased soil inorganic nitrogen may occur, with subsequent negative effects on seed germination and seedling growth. We investigated these relationships under greenhouse conditions using simulated floods with stagnant, flowing or intermittent flood waters. These flood experiments were followed by germination tests using Virginia wild rye (Elymus virginicus L.) seeds; shoot growth was also evaluated. Flowing and stagnant flood water resulted in significantly lower soil nitrate levels than intermittent flood waters. Ammonium and polyphenolic levels, however, were greatest under the stagnant flood treatment. Germination and shoot growth decreased with increased soil polyphenolics. Polyphenolic levels explained about 17% of the variation in germination and 18% of the variation in shoot growth. These results suggest that flooding may affect subsequent regrowth of floodplain vegetation due to changes in soil chemical properties. However, further study is needed to determine if flooding affects soil polyphenolics and inorganic nitrogen under actual field conditions and to identify the types of polyphenolics formed and their possible effects on seed germination and root growth.