Renner, K. A., S. J. Halstead, and K. L. Gross
Presented at the All Scientist Meeting (1998-07-21 to 1998-07-22 )
The weed seed bank in agroecosystems is the primary source of weed infestations each year. Tillage, crop rotation, and herbicide use influence the persistence, vertical distribution, species composition, and abundance of seeds in the weed seed bank. The seed bank at the LTER agroecosystem site was measured at site initiation in 1988 and then measured in 1990, 1993, and 1996 in each of the seven cropping systems imposed in 1989. In 1988 there was an average of 1873 seeds m-2 , with common lambsquarters (Chenopodium album L.) and fall panicum (Panicum dichotomiflorum Michx.) the co-dominant weed species in the seed bank. By 1990 the distribution and number of weed seeds was dependent on cropping system. The mean number of weed seeds m-2 was 67340 in the successional treatment, 23470 in alfalfa, and 5000 seeds m-2 or less in the other five cropping systems that included a corn-soybean rotation in no-tillage and conventional tillage with herbicide inputs, a corn-soybean-wheat rotation with low or no chemical inputs, and in Populus trees. From 1990 to 1996 the weed seed bank decreased in the successional community, and remained below 2000 seeds m-2 in Populus. The number of annual grass seeds in the alfalfa treatment was greatest the year following alfalfa seeding. Common lambsquarters and annual grass seeds increased in the conventional tillage and no-tillage corn-soybean rotation from 1990 to 1996 but the total weed seed bank in these two systems was less than the total seed bank in the low input system. Common lambsquarters and common chickweed (Stellaria media (L.) Vill.) were the co-dominant weed species in the seed bank in the low and no chemical input systems.Return to Contents
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