Weed seed rain, soil seedbanks, and seedling recruitment in no-tillage crop rotations

Abstract

Relationships among weed seed rain, soil seedbank, and seedling recruitment in no-tillage systems were studied from July 1993 to May 1996. Multiple regression analysis indicated that seedling recruitment of only six of the 25 weed species present was correlated with seed rain samples from the previous autumn, spring soil seedbank samples, or a combination of the two. However, seedling recruitment of the dominant annual grasses (yellow foxtail, giant foxtail, and fall panicum in Field 1–1994, Field 2–1995, and Field 3–1996, respectively) was related to seedbank populations or a combination of seedbank and seed rain densities. These grasses accounted for at least 32% of the emerged seedlings, 12 to 78% of the seedbank, and 16 to 77% of the seed rain. Seedling recruitment of large crabgrass and two broadleaf species, Virginia copperleaf and wild carrot, also were described by seedbank densities or a combination of seedbank and seed rain densities. However, both the broadleaf species were minor components of the cropping system, representing ≤ 4% of all seedlings. In each year, the sum of all weeds in the seedbank exceeded 1,300 seeds m−2 (0 to 10 cm deep). The fraction of the total seedbank that emerged each year ranged from 3 to 17%, but there was great variability among species. The aforementioned dominant grasses ranged in emergence from 3 to 25% of their seedbanks. Emergence of other species ranged from a low of 1% for common lambsquarters up to 41% for large crabgrass. Prediction of seedling recruitment from seed rain or seedbank densities was variable; however, combining both components improved the fit of regression describing seedling recruitment.

Seed-bank dynamics in the invasive plant,Ambrosia artemisiifoliaL.

“…The results obtained in field crops (12.2 -35.8%) were consistent with what was found previously for the species in similar habitat types, 6.8-38.2% (Forcella et al, 1992), 42% (Rothrock et al, 1993) and 15 -39% (Webster et al, 2003). The results obtained in field crops (12.2 -35.8%) were consistent with what was found previously for the species in similar habitat types, 6.8-38.2% (Forcella et al, 1992), 42% (Rothrock et al, 1993) and 15 -39% (Webster et al, 2003).…”

“…A. artemisiifolia forms a persistent soil seed bank (Thompson et al, 1997). The overall seed-bank densities of A. artemisiifolia in field-crop habitats have been analysed previously (Raynal and Bazzaz, 1973;Bigwood and Inouye, 1988;Gross, 1990;Rothrock et al, 1993;Webster et al, 2003). The seeds that do not germinate in spring re-enter dormancy due to secondary dormancy mechanisms (Bazzaz, 1970).…”

Weed Problems, Ecology, and Management Options in Conservation Agriculture: Issues and Perspectives

“…The seedbank study revealed a significant increase in the number of weed seeds and species, mainly of annual grasses such as Digitaria sanguinalis and Panicum dichotomiflorum, in CoT and NT (Menalled et al, 2001). Positive relationship was noted among weed seed rain (16-77%), seedbank (12-78%), and seedling recruitment (32% of the emerged seedlings) in NT for the annual grasses viz., yellow foxtail, giant foxtail, and fall panicum (Webster et al, 2003). Obviously weed species assembly in NT and CoT had assorted weed species, confirming the ability of seedbanks to buffer disturbances across a variety of cropping systems (Legere et al, 2005a).…”

Improving soil seed bank management

“…The natural variability of weed emergence is confounded by difficulties in studying the seed bank, as discussed above. Within a single seed bank quantification study, coefficients of variation for germination typically exceed 50% . Greenhouse studies of seedling emergence have been somewhat more accurate than field studies, however the artificial nature of the greenhouse challenges study of seed traits such as dormancy or community processes such as self‐thinning .…”