Effect of crop rotation on weed seed bank

Abstract

Knowledge of weed soil seed bank is of great importance for forecasting weediness for next years. Crop rotation and tillage are two primary practices that have an impact on soil seed bank. In our study, soil samples were taken in order to evaluate the size and species composition of the weed seed bank in the soil on plots under different growing systems: monoculture of corn of about 40 years, crop rotation of corn, wheat and soybeans with different variations of fertilization. Samples were collected during October, using probe (diameter 5 cm) in a layer of 15 cm. Four soil samples collected from 10 sampling points were taken from each of 7 plots. Seeds were extracted from the soil by washing and were determined and counted. Next year (during August) weediness (abundance and species composition) evaluated in the same plots. The weed seed bank was dominated by Chenopodium album, Amaranthus retroflexus, Datura stramonium, Sorghum halepense in all treatments. In the plots which were under wheat in the previous year, beside the listed species, seeds of species characteristic for grain crops were also present as dominant. The higher number of seeds was observed in treatments where manure was applied. In the unfertilized treatments the seed bank was higher and represented by a higher number of weed species than in other plots. Composition of weed species emerged in the next year were in accordance with results of seed bank analysis and the fact that the investigated plots were seeded to maize. In fact, the dominant species were those typical of row crops.