The purpose of the study conducted in 2005-2006 in Kruszyn Krajeński near Bydgoszcz was to determine the root mass of millet cultural varieties Gierczyckie and Jagna and the vertical distribution of the roots in a very light soil under sprinkling irrigation and diverse nitrogen fertilization. The mass and distribution of roots in the soil depended on sprinkling irrigation and nitrogen fertilization. Sprinkling irrigation contributed to an increase in the root mass of Gierczyckie and Jagna varieties by 11 and 53% respectively; it also promoted root growth in the upper soil layer. Nitrogen fertilization significantly increased the root mass of millet, where the highest increase was observed in Gierczyckie variety for nitrogen fertilization doses 80 and 120 kg·ha^-1 (increase by 80 and 52%), while in Jagna variety for nitrogen fertilization doses 40 and 80 kg·ha^-1 (increase by 43 and 51%). Sprinkling irrigation increases the ratio of P : K index, which defines the relation between grain yield (P) and root mass (K), whereas nitrogen fertilization decreases this ratio.

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