Evaluation of the impact of tillage/cropping systems on soil microflora and week seedbank predation

Soil erosion and pesticide use are critical issues in sustainable agriculture. With a view to decreasing the amount of pesticides used for weed control, researchers assessed the impact of tillage, cropping systems and weed management regimes on seasonal and long-term weed and weed seedbank population dynamics, especially in Conservation Reserve Program land being returned to production. Background no-till make inappropriate use of herbicides because of the same knowledge void. The Conservation Reserve Program (CRP) Effect of tillage, cropping systems, and weed was established in 1986 as a voluntary promanagement on weed seedbank The fate of a gram to help reduce soil erosion and adjust weed seedbank is controlled by several facproduction of some agricultural commodities. tors, including seed germination, predation After ten years, farmers were allowed to put from vertebrates and invertebrates, and infec­ the land to other uses or to potentially re-enroll tion by soil microorganisms. Other factors in the program. In 1996, Iowa had more than include dormancy and loss of viability, which 2 million acres under CRP, and surveys indiare influenced by the physiological status of cate that 40 to 50 of the producers intend to the seed and the environmental conditions in return some of the land to row-crop producthe soil. tion. The southern one-third of the state has the largest area in CRP, while the central tier Predicting potential weed emergence is a funand the upper third have considerably less. damental need in the development of inteThus research on lands under CRP that may grated pest management and strategies for return to production is needed to determine weed control. If growers could predict the how to minimize environmental disruption composition and density of weed seedlings and contamination from cropping systems. that will emerge during a growing season, they could plan and implement appropriate When tillage systems are altered, an immedicontrol measures only when and where ate change in the crop-weed relationship ocnecessary. curs. Tillage systems influence weed seed germination rates and the efficacy of weed Crop and weed management programs are control tactics, thus affecting weed populaclosely linked and influence changes in the tions. This change is not fully understood and soil weed seedbank. Tillage systems influ­ likely represents a major impediment to the ence weed seed germination rates and herbi­ successful implementation of conservation tillcide efficacy, thus affecting future weed popu­ age systems. Growers may abandon no-till lations. Tillage also impacts the physical systems because of weed problems that occur location of the weed seedbank. due to a lack of knowledge about changes in weed ecology. Further, it is possible that Effect of set-aside on weed seedbank Surveys growers who are successful practitioners of of weeds present can provide quantitative Principal Investigator: M.D.K. Owen Agronomy Iowa State University Co-investigators: J. Felix Agronomy R. Hartzler Agronomy T. Loynachan Agronomy