Seed Bank Characterization and Emergence of a Weed Community in a Moldboard Plow System

D. Mulugeta and D. E. Stoltenberg

Field experiments were conducted in 1992 and 1993 to characterize the weed seed bank, determine the influence of moldboard plowing and secondary soil disturbance on emergence pattern of weeds, and 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 ten other species accounted for about 85, 9, and less than 1%, respectively, of the total weed species seed bank. A negative binomial distribution described the spatial distribution of viable seeds of ten species, but not common lambsquarters or redroot pigweed. Decreased density of seeds among species was associated with increased aggregation. Secondary soil disturbance increased the rate and magnitude of common lambsquarters emergence in 1992, but did not influence emergence in 1993. Secondary soil disturbance did not influence the magnitude and rate of redroot pigweed or velvetleaf emergence. Whereas cumulative growing degree days from April through July were similar between years, the amount of rainfall was about 50% less in 1992 than 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 increased 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, the most abundant species in the weed community.

Weed Sci. 45:54-60 (1997)