AN IN-SITU TECHNIQUE FOR THE QUANTITATIVE DETERMINATION OF FERTILIZER PHOSPHORUS IN GROWING PLANTS

Abstract

A technique is presented which permits the quantitative estimation of fertilizer phosphorus in plants at any desired time during the growth cycle without harvesting the plants. The radioactivity of the growing plants was determined in situ by a thin-walled aluminum Geiger-Mueller tube assembly. The in-situ activity was found to be highly correlated with the fertilizer-phosphorus content (mg./pot) at any one stage of growth of oats (r = 0.975), corn (r = 0.966), and sugar beets (r = 0.813). The relationship between the in-situ activity and the fertilizer-phosphorus content varied with plant height. Regression equations are presented relating the fertilizer-phosphorus content to the in-situ activity and plant height. Correlation coefficients for the regression equations were 0.943, 0.914, and 0.902 for oats, corn, and sugar beets respectively. The coefficient of variation of the fertilizer-phosphorus content of sugar beets using the regression equation was 15.3 per cent, whereas that using the briquet technique was 16.1 per cent.