THE CONTENT OF MAJOR NUTRIENTS IN DRY-MATTER OF SUGAR-BEET ROOT AND LEAF IN THE 1ST YEAR OF VEGETATION

In the course of 13 or 16 years, respectively, the method of inorganic analyses has been applied to study the dynamics Of changes in total n itrogen, phosphorus and potassium and their distribution in leaves and roots of sugar beet in the first year of vegetation. From the aspect of exploitation of these analyses referred to fertilizing and nutritio n of sugar beet, an attention was paid in particular to the total vari ability of contents of these elements in different stages of growth an d development of plants. As follows from Figs 1 and 2, nitrogen conten t is varying during ontogenesis both in leaves and roots. If this is f luctuating from 4.6 to 5.3 % in the leaf at the beginning. of May, in the roots this is ranging from 2.3 to 33 % in the same period. Nitroge n content is falling to a certain degree in both organs due to gradual growth of sugar beet plant. In the following period its average value is not changing much. The pattern of changes in phosphorus content in dry matter of leaves and roots, as dependent on growth and developmen t stages, is on Figs 3 and 4. Phosphorus concentration in leaf dry mat ter is falling umbiguously gradually and regularly from the highest va lues taken on the 16th day from emergence to the lowest ones at the en d of vegetation. Phosphorus content is stabilizing in the leaf on the value 0,3 % towards the end of vegetation. Changes in potassium conten t as apparent in different organs of sugar beet are shown on Figs 5 an d 6. It clearly follows from the elements studied up to now in leaf dr y matter that potassium takes the largest proportion contained in dry matter. The highest potassium concentration in leaves can be seen in y oung leaves intensively growing (Fig. 5) where maximum value is near t o 10 %. A strong year's variability in the root particularly in this e lement is apparent at the beginning of May (ranging from 2.7 to 9.0 %) . The results showed that an important factor influencing the uptake o f major nutrients is the stage of ontogenetic development of sugar bee t and is associated with the function of these elements in metabolism. The above-mentioned studies of concentrations of major elements compr ised in leaf dry matter are important from the aspect of exploitation of leaf diagnostics in regulation of sugar beet nutrition during ontog enesis, in particular in May (on the onset of the 5th and the 6th leav es formation) or on the 120th day from emergence, respectively.