Weed seedbank dynamics and composition of northern Great Plains cropping systems
Harbuck, Kristin Suzanne Bates
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With a growing concern about sustainability of agricultural production systems, interest in integrated weed management systems has increased. Increasing the understanding of weed seedbank dynamics will improve efficiency of management. The objectives of this study were to 1) quantify weed seedbank dynamics in response to seed density and burial depth, 2) determine weed seedbank decay at varying seed densities and burial depths, 3) quantify weed seed predation in wheat and tilled fallow fields, and 4) characterize and compare weed seedbanks in organic and conventional no-tillage production fields. Objective 1 was carried out at Montana State University's Arthur H. Post Agronomy Farm. Seedbanks were established at four densities and two burial depths. Weekly seedling counts were taken for two consecutive growing seasons. Data indicated higher density seedbanks had lower proportions of emergence. Individual species responded differently to depth treatments. We concluded that management affecting seed density and depth will affect seedling emergence. Objective 2 was carried out in the same plots as objective 1. Seedbank samples were used to separate seeds.We found that all studied species declined to low levels over two years with little difference due to depth and density. Wild oat seeds were more germinable in buried treatments. We concluded that seedbanks of these species will decline quickly with lack of seed inputs. Objective 3 was carried out in four spring wheat and four tilled fallow fields at Montana State University's Arthur Post Agronomy Farm. Surface seed predation was measured at six times during the growing season for four weed species. We observed that predation levels did not differ between wheat and fallow fields for three of four species. We conclude that seed predation can represent an important loss in Montana. Objective 4 was carried out in spring wheat production fields near Big Sandy, Montana. Weed seedbanks were sampled along a range of aboveground weed diversity points over two years. Weed seedbank composition and characteristics did not differ between cropping systems, but did between years. We conclude that weed seedbank diversity and richness may vary based more upon yearly environmental factors than the management system.