SEEDBANK AND PLANT POPULATION CHANGES FOLLOWING CONSERVATION TILLAGE IN THE MARYLAND PIEDMONT AND COASTAL PLAIN

Abstract

Effects of conservation tillage were compared at two locations in the Maryland Piedmont and Coastal Plain following no-till planting of corn (Zea mays L.) and herbicide application in June, 1990. Field evaluations of broadleaf plant density, frequency, and dominance were made on plots with one year and five years of conservation tillage and on undisturbed plots. Seedbank composition was evaluated on the basis of bimonthly identification of seedlings which had germinated from soil samples removed from field plots and maintained in a greenhouse for one year. Within all treatments in the field, perennial broadleaf plants were generally dominant at the beginning of the growing season but their dominance decreased over time as annual broadleaf plants and grass became more important. Over the growing season perennial plants decreased in importance more in treated plots than in control plots. Similar trends were observed in the greenhouse as the number of germinating perennial broadleaf plants decreased rapidly in contrast to the number of germinating annual plants. Dandelion and Canada thistle were dominant perennial broadleaf plants in both field and greenhouse. Pennsylvania smartweed, smooth pigweed, chickweed, and henbit were dominant annual broadleaf plants. Grasses were the dominant plants on undisturbed control plots at both locations during August, September, and October. Also, grasses generally increased in dominance at both locations in all plots regardless of treatment.