DETERMINATION OF CRITICAL POTASSIUM CONCENTRATION IN YOUNG TOMATO PLANTS USING A NUTRIENT INTERRUPTION TECHNIQUE

A new method suggested by Burns (1992) was used to estimate critical p otassium (K) concentration in young tomato plants. A nutrient interrup tion experiment was conducted including only two treatments (+K and -K ). Plants were successively harvested to measure yield and K concentra tion. This data was used to explore the relationship between the fract ion of maximum growth rates and K concentration of plants suffering de ficiency. The critical concentration was determined from this relation ship. The new method provides a value for assessment of plant nutrient status which is well adjusted to the requirement of the plants with r egard to maximisation of yield and has advantages compared to the wide ly applied method recommended by Ulrich and Hills (1990). Problems tha t arose were discussed and advantages and disadvantages of the new pro cedure were pointed out.