RESPONSE OF CASSAVA (MANIHOT-ESCULENTA CRANTZ) TO POTASSIUM CONCENTRATION IN SOLUTION - CRITICAL POTASSIUM CONCENTRATIONS IN PLANTS GROWN WITH A CONSTANT OR VARIABLE POTASSIUM SUPPLY

Critical potassium concentrations were found to vary markedly with plant part sampled, cultivar, and method of plant culture. Youngest fully expanded leaves are suggested as a suitable index tissue for diagnostic plant analyses with cassava. Plants grown in flowing solution culture with a constant potassium supply had substantially higher critical potassium concentrations than plants grown by non-renewed solution culture methods in which the potassium concentration in the root environment decreased continuously with time. Plants grown at a range of constant potassium supplies and then transferred to zero potassium supply had critical concentrations intermediate between these extremes. The observed variation in critical potassium concentrations is discussed in relation to the interpretation of plant analysis data for field grown plants. © 1979.