Because reduced tillage alters physical, biological and chemical properties of soil when compared with ploughed soil, it may also affect plant growth. The influence of continuous reduced tillage (deep loosening, shallow mulching) on the growth of sugar beet pants was studied in a field trial from 1993 to 1996. Dry matter production, leaf area index and growth rates were higher with reduced tillage in the spring, they then decreased in the summer and finally were lower compared with the ploughed treatment at harvest in October. This course was not affected by N fertilizer application. There was no difference in the net assimilation rate in summer. As a reason for better growth in reduced tillage in the spring, the higher root length density and the higher P and K supply in the upper soil layer in reduced tilled soil is considered. It is supposed that the decreased growth in the summer is caused by hormonal changes of the plants, due to the increase of mechanical impedance in the soil with reduced tillage.