The density of A. artemisiifolia varied in the experimental field in 2009. The number of plants was between 4–44 m2. The fresh biomass weight of A. artemisiifolia varied between 30.0–271.2 g m-2 within the area, the dry biomass weight of ragweed was between 5.6–56.9 g m-2. In the present experiment, a correlation was found between the density and the dry weight of A. artemisiifolia (y=-0.0551x2+2.6403x–5.0876; r=0.7426; n=22; p<0.01; n=30). Based on this correlation, it can be stated that the biomass production of ragweed was growing parallel with the plant number of young ragweed. Its maximum was at the value of 24. Following that point, biomass production did not grow any further, but started to fall. This phenomenon showed that within the ragweed population strong intraspecific competition might have appeared under the conditions of our experiment. The AL-K2O content of soil varied between 118.7–445.50 mg kg-1, and the AL-P2O5 content was also in the range of 135.0–1933.6 mg kg-1 in the sample area. Like in 2009, there was a correlation between the density and fresh weight of A. artemisiifolia in 2014 (y=0.2306x+0.4191; r=0.7475; p<0.01; n=30). The average density was 12.7 pieces m-2 (0–41 pieces m-2), fresh biomass weight varied between 1–79 g m-2, dry biomass weight varied between 0.05–8.75 g m-2. The AL-K2O content of soil varied between 107–242 mg kg-1, and the AL-P2O5 content was in the range of 143–1544 mg kg-1. On the basis of organic matter content of the soil the nitrogen supply was medium on 67% and low on 33% of the sample points (MÉM NAK 1979). According to our results the phosphorus supply was high and the potassium supply was medium level. The year of 2014 was wetter (877 mm) as there was 270 mm more precipitation mcompared to 2009 (608 mm).
There was no mathematically proved relationship between the soil properties and density or biomass of ragweed neither in 2009 nor in 2014. Our results on the biomass, density and green water of ragweed provide useful data for the management of ragweed on arable lands.