EN
The aim of the paper is to evaluate the effects of five agrotechnical factors on: a) mean root weight of sugar beet plants per plot and within-plot standard deviation of root weight, b) coefficient of determination for root weight of sugar beet plants by three independent variables x₁, x₂ and х₃ and standardised partial regression coefficients for those independent variables. The factors investigated in a 2⁵ factorial field experiment were: sowing date (A), harvest date (B), N rate (C), N application date (D) and division of N rate (E). Multiple linear regression analysis was carried out using plants from one row of 10 m length for each of 32 experimental plots. The independent variables were: xi - the state of plant development 30 days after sowing (measured by the number of leaves), x₂ - growing space per plant in a population, х₃ - coefficient of location, defined as the ratio of half the distance to its the nearest neighbour within the row to half the distance to its further neighbour within the row. A factorial analysis was carried out using the above parameters concerning a sugar beet population. It was proved that: 1) variation of root weight of sugar beet plants in a population was significantly larger for early sowing compared to late sowing and was larger for late harvest and higher N rate compared to the other levels of these factors, 2) the influence of development stage (x₁) on root weight was significantly larger for early sowing compared to late. A higher N rate increased the influence of the x₁ variable, 3) the effect of growing space (x₂) on root weight was larger for early sowing date and late harvest date, 4) the interactions between factors in a sugar beet population as presented in this paper are complicated and modified by agrotechnical factors and weather conditions, and should be further studied in other experiments.