Seed bank characterization and emergence of a weed community in a moldboard plow system

Abstract

Field experiments were conducted in 1992 and 1993 to characterize the weed seed bank, to determine the influence of moldboard plowing and secondary soil disturbance on the emergence pattern of weeds, and to measure weed seed bank depletion by emergence in a long-term moldboard plow corn cropping system. Viable seeds of common lambsquarters, redroot pigweed, and each of 10 other species accounted for about 85, about 9, and less than 1%, respectively, of the total weed species in the seed bank. A negative binomial distribution described the spatial distribution of viable seeds of 10 species, but not of common lambsquarters or of redroot pigweed. Decreased density of seeds among species was associated with increased aggregation. Secondary soil disturbance increased the rate and magnitude of common lambs quarters emergence in 1992 but did not influence emergence in 1993. Secondary soil disturbance did not influence the magnitude and rate of emergence of redroot pigweed or velvetleaf. Whereas cumulative growing degree days from April through July were similar between years, the amount of rainfall was about 50% less in 1992 than in 1993. Secondary soil disturbance may have increased common lambsquarters emergence by increasing the availability of soil moisture and improving conditions for seed germination during the dry year. Even though seed bank depletion by seedling emergence was relatively low for all species, secondary soil disturbance in creased seed bank depletion of common lambsquarters and redroot pigweed about 7- and 3-fold, respectively, in 1992. Seasonal variation in the amount of rainfall may have influenced the effect of soil disturbance on emergence and seed bank depletion of common lambsquarters, which is the most abundant species in the weed community.

Phenological and demographic behaviour of an exotic invasive weed in agroecosystems

“…The total soil surface area sampled was 98.72 cm 2 per quadrat. Following Dessaint et al (1990) and Mulugeta and Stoltenberg (1997), soil core samples were stored for 2 weeks in the PVC cores at 4°C with the aim to prevent seed germination. Later, the samples were water-cleaned and the organic fraction, containing velvetleaf seeds, placed in aluminium trays in the greenhouse.…”

“…Lindquist (1995) suggested a competition for light so that the late velvetleaf seedlings would be more affected due to a great canopy closure than to the present plant density. (Mulugeta and Stoltenberg 1997). Cumulative emergence was described by y ¼ 7.519 ln x ) 28.892.…”

“…A similar logarithmic function was established by Mulugeta and Stoltenberg (1997), but our data showed an earlier and greater emergence for the same cumulated GDD in comparison with those American populations. In all cases, emergence was nearly complete after 380 GDD.…”

Vertical distribution, size and composition of the weed seedbank under various tillage and herbicide treatments in a sequence of industrial crops

“…These results are in accordance with previous studies, which indicated that the seedbank is composed of a few dominant weed species; Amaranthus spp. was always one of the dominant species (Mulugeta & Stoltenberg, 1997b; Bàrberi et al. , 1998a; Dorado et al.…”

Competition between Lolium perenne and Digitaria sanguinalis: Ecological consequences for harbouring an endosymbiotic fungus

“…However, when dissecting the competitive interactions between plants with markedly different life history strategies additional measures may be useful. Competition from weeds is, largely, a function of seed bank dynamics (Panetta & James 1999;Forcella et al 1997;Mulugeta & Stoltenberg 1997) and annual grasses are no exception in this regard. In our study, D. sanguinalis seed production mirrored aboveground biomass production with more seed being produced by D. sanguinalis when competing with endophyte infected L. perenne.…”