The field research was carried out in the years 1998–2000 in farm Bezek near Chełm, a part of Agricultural University in Lublin. The experimental field was situated on light and sandy clay soil. The phosphorus content in soil was high, in potassium medium, in magnesium low. Humus contents was 1.2%. The purpose of this work was to determine the influence of conventional and ploughless tillage system in crop rotation: potato – spring barley – winter rye upon air dry weight roots and content of some macroelements in roots of potato in two differentiated fertilization and plant protection levels on light soil. Root mass was determined before harvest by means of a steel cylinder of 400 cm2 down to 30 cm, dividing them into the following layers: 0–10 cm, 10–20 cm, 20–30 cm. The roots were rinsed with running water with about 1 mm diameter mesh sieve, then dried and weighed. It was stated that potato accumulated a significantly higher air dry mass of roots (81.4%) in 0–10 cm surface layer on light soil than the deeper layers. Cultivation systems and chemicalization levels do not significantly differentiate the mass of root. It was confirmed that intensive fertilization and plant protection levels increases dry matter of potato roots. Content of phosphorus, potassium and magnesium in potato roots was higher on the treatment with ploughing soil cultivation in comparison witch ploughless tillage. Intensive chemical level increases the content of total nitrogen, phosphorus, potassium and magnesium in the roots of potato in comparison with the basic level.