EFFECT OF NPK FERTILIZATION AND VEGETATIO N PERIOD ON THE MICROELEMENT CONTENT OF GRAIN-SORGHUM

Changes in the Fe, Mn, Yn, Cu, B and Na concentrations in the whole ab oveground part of grain sorghum in the course of the vegetation period were studied in a long-term fertilisation experiment on calcareous sa ndy soil. Plant samples were taken in the major developmental phases f rom an area of 0.35 m(2). Judging from the results obtained for the co ncentrations of the listed elements the following conclusions can be d rawn. The Fe, Mn and Zn contents rose during the vegetative phase of d evelopment, but exhibited a decline during the generative phase. The C u content decreased during the initial development phase and, after a temporary increase, at ripening. There was virtually no increase in bo ron during the vegetative phase, but it rose during the generative pha se. Na showed a slight reduction. At full maturity the largest quantit y of Zn was found in the grain, while the highest Fe, Mn, B and Na con tents were measured in the stems; the Cu content was much the same in the grain and stem yields. The effect of NPK, and particularly of phos phorus, was consistently seen in the development of the Zn content and in some cases in that of Mn and B contents in the vegetative organs. Diagnostic plant analysis in the 3-4 leaf stage showed a high Fe conte nt, a satisfactory Mn content, Door supplies of Cu and B and, in treat ments fertilised with phosphorus, poor supplies of Zn, based on foreig n limit values.