Viable Seeds Variation in an Area with Hilly Relief in Moderate Climate Agrophytocenoses

As climate conditions and agricultural technologies change, the soil seed bank may increase or decrease, which may affect the species composition and abundance of weeds in crops. The research was carried out in order to evaluate the influence of hillside parts on the number of viable seeds during different seasons (spring and autumn) in agrophytocenoses, which differ in the duration of the land’s covering with plants. Soil samples have been taken out in spring and autumn at the summit, midslope, and footslope of the hill. The time of the soil sample collection and covering of agrophytocenoses had a significant effect on soil seed numbers. In autumn, the average seed amount in the soil was higher by 6.38% than in spring. The largest seed number (in spring and autumn) was evaluated in the soil of cereal–grass crop rotation with a 2.0- and 6.9-times higher seed amount compared to the rotation with a row crop and permanent grassland. During the years, hill parts had a significant effect on the seed bank in autumn. In spring, the viable seeds comprised 67.10%, and in autumn, they comprised 65.33% of the total seed number. Significantly, the highest percentage of viable seeds was estimated in the footslope of the hill. This can be related to more favorable microclimatic conditions and higher soil moisture at the footslope, where more fertile soil and organic matter naturally accumulate, creating better conditions for seed viability preservation.