NOVELTY - Method for measuring algal biomass in biological soil crust, involves selecting well-developed algae crust, (b) crushing algal crust, (c) soaking the crust in distilled water and removing impurities, (d) adding algal suspension mixture to Erlenmeyer flask containing blue green (BG11) broth, transferring cultured suspension to storage tank and harvesting algae, (e) extracting chlorophyll from algae, measuring absorbance value and calculating the chlorophyll content, (f) selecting highest regression coefficients as standard curve, and (g) calculating the algal biomass.    USE - The method is useful for measuring algal biomass in biological soil crust (claimed).    ADVANTAGE - The method provides accurate result.    DETAILED DESCRIPTION - Method for measuring algal biomass in biological soil crust, involves (a)selecting well-developed algae crust, loading the algal crust into envelope using shovel, (b) crushing collected algal crust using 0.2 mm sieve, (c) soaking 20 g sieved algal crust in 50 ml distilled water, and allowing to stand for 20 minutes, placing the soaked algal crust in gauze, slowly adding distilled water and removing impurities in the sample, adding clean water to remaining algal suspension mixture, (d) adding 2-5 ml algal suspension mixture to Erlenmeyer flask containing 300 ml blue green (BG11) broth and rotating the flask at a speed of 140 revolutions per minute (rpm), preliminary training the culture in indoor by maintaining temperature at 25-30 degrees C for 7-10 days and light intensity at 550-650 Lux, transferring the preliminary cultured algal suspension to outdoor in 100 ml plastic storage tank, where each tank containing 60 mu l BG11 broth, cultivating 7-8 days under aerobic condition, harvesting cultivated algae, cooling and drying harvesting algae, (e) placing the dried algae in oven at 65 degrees C and grinding the dried algae into powder, polishing 0.005 g, 0.01 g, 0.05 g, 0.1 g, 0.5 g, 1 g, 2 g and 5 g algae powder thrice, weighing algae powder, adding weighed powder to 10 ml test tube containing extraction liquid, extracting chlorophyll a and b, using ethanol, acetone and water in a ratio of 4.5:4.5:1, closing the extracted chlorophyll using rubber stopper, and incubating at 45 degrees C for 24 hours, until algal powder becomes white, measuring absorbance value at wavelength of 645, 652 and 663 using UV spectrophotometer and calculating the chlorophyll content by mg/g Fw, (i) chlorophyll content a-(12.71, D663-2.59, D645) V/1000/m, (ii) chlorophyll content b-(22.88, D645-4.67, D663) V/1000/%mass, and (iii) chlorophyll content (20.29, D645+8.04, D663) V/1000/%mass, where m represents dried algal powder and V represent volume of extract, (f) selecting chlorophyll a and b with known algal biomass as highest regression coefficients as standard curve, and (g) calculating the algal biomass in crust based on standard curve.