FIELD: analytical chemistry, ecology. SUBSTANCE: soil sample is treated with distilled water and calcium oxide is added at mass ratio soil : water : calcium oxide = 1:(4-5):(0.2-0.6), respectively. Then solution is filtered off and sulfamic acid, sodium hydrogen phosphate, starch and potassium iodide were added at mass ratio filtrate : sulfamic acid : sodium hydrogen phosphate : starch : potassium iodide = 1:(1.5 x 10-2 - 2.5 x 10-2):(0.8 x 10-2 - 1.2 x 10-2):(0.4 x 10-3 - 0.6 x 10-3):(0.5 x 10-2 - 0.7 x 10-2), respectively. Solution is kept for 15-20 min and subjected for photometry at wavelength 590 nm. EFFECT: express-analysis at field conditions. 2 tbl
