SUMMARYAt the research farm of the Swedish University of Agricultural Sciences, Uppsala, above- and belowground production and changes with time in root length, mean root radius and root surface area of spring oilseed rape were studied during the growing seasons 1987 and 1990. In both years, the highest root growth rate was recorded during the stem elongation phase, and the highest shoot growth rate during flowering. The root: shoot ratio decreased throughout the whole period of root sampling, from 0·64 to 0·16, during the cool and wet first year. In the warmer and drier second year, the ratio increased to a maximum of 0·72 when flowering started, and thereafter decreased. More than 80% of the root dry matter was found in the topsoil. Roots were longer and thinner in the dry and warm 1990 than in the wet and cool 1987. Maximum root length was c. 4·9 km/m2 in 1990, and mean root radius varied between 01 and 0·7 mm. Increases in root surface area during periods of root growth were due to increased root length rather than to increased mean root radius.

No abstract

Concentrations and amounts of macro-nutrients (N, P, K, Ca, Mg, S) in shoots, vegetative and generative plant parts in B. napus and 5, juncea and nutrient inflow per unit root length in B. napus were studied in a field experiment at Uppsala, Sweden. Concentrations in vegetative plant parts were, except for Ca in B. napus, highest at the beginning of the season, and N and K were higher in B. napus than in B. juncea. The higher N concentration in vegetative parts (leaves, stems and pods) in B. napus was probably due to differences in growth pattern between the species. Seed concentrations of N, P, Ca, Mg and, most pronounced of all, S were higher in B. juncea. Nutrient amounts were, with the exception of K, throughout the season higher in B. juncea than in B. napus due to a higher dry matter production. Nutrient inflow per unit root length in B. napus was highest during the rosette stage for all nutrients. During flowering, the inflow decreased for N and K and increased for P and Ca. After root growth had stopped, no net inflow of K and S was found and inflow rates of other nutrients were at very low levels.

Oilseed rape was grown under irrigated conditions at equal plant density per unit area in PVC cylinders of 1 m length with different diameter (0.11, 0.16 and 0.20m). The influence of soil volume, expressed as cylinder diameter, was found not to be significant on root dry weight, root length, root surface area or the shoot: root ratio. However, a significant influence was found on shoot and seed dry weights. It was concluded that cylinders with a length of 1 m and a diameter of a minimum of 0.11 m are appropriate for the study of container‐grown root systems.