Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/26/2004
Publication Date: 1/26/2004
Citation: Anderson, R.L. 2004. A paradox with herbicide resistance, tillage, and semiarid crop production. In: Proceedings, No-Till on the Plains Conference. Jan 26-28, 2004, Salina, Kansas. p. 18-24. Interpretive Summary: Herbicides have enabled producers to reduce or eliminate the need for tillage to control weeds. However, with resistant weeds developing, producers are asking if occasional tillage could replace some herbicide applications. The paper summarizes the impact of tillage with the sweep plow on weed community dynamics in a semiarid region. Tillage favors weeds by burying the weed seeds in soil, thus protecting seeds from environmental extremes. Seed longevity in soil is two to five-fold longer if seeds are buried compared with seed remaining on the soil surface. Consequently, more weed seedlings establish within crops. Tilling before planting crops leads to more weeds after planting. Producers may have to increase herbicide inputs to control weeds during the crop season. Another consequence of tillage in seimarid climates is that crop yield is reduced, sometimes approaching 35% less yield. With this interaction between tillage and weed dynamics, producers can gain more advantages in managing resistance with crop diversity and rotating herbicides than by tilling.
Technical Abstract: Maintaining crop residues on the soil surface has changed cropping practices in the Central Great Plains. Where previously winter wheat-fallow was the prevalent rotation, producers now grow warm-season crops in sequence with winter wheat and fallow. Controlling weeds during fallow with herbicides eliminates the need for tillage, thus conserving more crop residues. However, producers are considering sub-surface tillage as an option to manage herbicide-resistant weeds. We reviewed the impact of sub-surface tillage with the sweep plow on weed dynamics and crop growth compared with no-till systems. Cropping systems studies show that rotations can be designed to reduce weed community density several-fold; tillage lessens this rotational effect by burying weed seeds and prolonging their survival in soil. Crop residues on the soil surface reduce weed seedling establishment in no-till systems, but tillage eliminates this effect. Crops also yield less after tillage compared with no-till in this semiarid climate. Tillage may help in managing herbicide resistance, but it also may increase weed density as well as reduce crop yield.