Effects of Crop and Weed Management on Density and Vertical Distribution of Weed Seeds in Soil
- Melinda L. Hoffman ,
- Micheal D. K. Owen and
- Douglas D. Buhler
Cultural practices used for crop management can influence numbers of weed seeds in the soil seed bank. This paper reports results of field experiments conducted for 6 yr to examine changes in weed seed numbers due to management practices. We evaluated the effect of tillage, herbicide application, and interrow cultivation on weed seed numbers in a soybean [Giycine max (L.) Merr.l/corn (Zea mays L.) rotation and in continuous corn. Treatment effects on weed seed numbers were more repetitive in soybean/corn than continuous corn. Foxtails (Setaria spp.) were the weed class most affected by treatments. Weed seeds were uniformly distributed among sampling depths in conventional tillage and concentrated near the soil surface in reduced tillage and no-tillage. We expected weed seeds to become more numerous in the top 5 cm of soil as tillage was reduced. Tillage, as a main effect, rarely influenced weed seed numbers; therefore, we inferred that weed seed losses at the surface must have increased in reduced-tillage plots. Seed numbers were uniform among soil depths if herbicides were broadcast, but differed if herbicides were banded or omitted, due to increased seed deposition at the surface. Tillage affected vertical distribution of seeds, while the quantity of weed seeds in the top 5 cm of soil was regulated by weed control practices. This indicates that reducing weed seed deposition could be helpful for maintaining weed seeds in reduced-tillage systems at numbers similar to those of intensively tilled systems.
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