Seedbank–plant relationships for 19 weed taxa in spring barley–red clover cropping systems

Abstract

The objective of this study was to examine the effects of crop rotation (spring barley monoculture vs. spring barley–red clover 2-yr rotation), tillage (moldboard plow, chisel plow, no-till), and weed management (intensive, moderate, minimum) on plant–seedbank relationships for 19 weed species. Plant and seedbank density data were collected over 4 yr and analyzed by analysis of variance and correlation analysis to confirm treatment effects on plant–seedbank relationships. The relative frequency (difference between aboveground and seedbank frequency) of many species was more influenced by rotation, whereas species density appeared regulated more by weed management than by other factors. Frequency data confirmed that very few species were ubiquitous over time or treatment, aboveground or in the seedbank. The perennial species, field horsetail, quackgrass, white clover, and perennial sowthistle were more frequent aboveground than in the seedbank. This was also observed for annuals such as common hempnettle, sun spurge, catchweed bedstraw, and annual grasses. Treatment effects on abundance were inconsistent aboveground and in the seedbank across time for 12 of 19 species. The seven species that showed more consistent treatment response for abundance were frequent species present in 50% of the plots both aboveground and in the seedbank. For most species, plant density was correlated with either the previous or current year seedbank, but correlations were rarely of the same magnitude and significance over the years. Common chickweed was the only species for which treatment effects on the plant–seedbank relationship were confirmed for all 4 yr. Correlations between midseason plant populations and subsequent seedbanks confirmed the role of residual populations in replenishing the seedbanks, including those of perennials like quackgrass and dandelion. Overall, plant–seedbank relationships were tenuous for many weed species and varied over time with cropping practices and environment.

The Selective Memory of Weed Seedbanks after 18 Years of Conservation Tillage

“…Consequently, the importance of such a weed species shift may not be apparent in seedbanks. Accordingly, the frequency of perennial species was 2 to 25 times greater in the in-crop weed communities than in the seedbanks between 1989 and 1992 (Légère et al 2005b). However, spring seedbanks did reveal the occurrence of perennial species.…”

“…Prolific species such as common lambsquarters and pigweeds contributed to tilled treatments, whereas yellow foxtail and field pennycress were dominant in NT seedbanks in 2006. However, neither of the latter two species had been affected by tillage in autumn seedbanks sampled in the early 1990s (Légère et al 2005b). This could suggest that selective factors (tillage but also crop production factors, herbicides, etc.)…”

Effect of Management of Sulfonylurea Resistant Stellaria media on Barley Yield

“…Even though the chickweed population did not affect barley yield during the year of the experiment, over the long term problems could arise, especially if less competitive, shorter, lodging sensitive, and slower growing crops are grown in the area without adequate weed management. Moreover, the chickweed seed bank was reported to respond directly to weed control treatments [23] and thus the species could increase so as to cause severe yield reductions if not managed properly.…”

Corn Tolerance to Weed Interference Varies with Preceding Crop

“…Clearly, this challenge is compounded when dealing with mature conservation tillage plots. In our case, each 20-yr-old tillage plot came with its own weed problems, actual and potential (Légère et al 2005). Seedbanks assessed in 2006, the year prior to the start of this study, were approximately 50 to 80% greater in no-till than in chisel or moldboard plow tillage treatments (Légère et al 2011a).…”