A MODIFIED HYDROPNEUMO-ELUTRIATION APPARATUS FOR QUANTITATIVE ROOT SEPARATION FROM LARGE SOIL CORE SAMPLES

An apparatus was designed to separate roots automatically from large soil samples (>20 kg). The apparatus (1.50 m height) was constructed of polyvinyl chloride pipes (diameter = 100 mm). The roots were separated from soil mineral particles at the base of the apparatus by a high energetic hydrovortex, and then transfered to a 200-mu m sieve by a flow of water and small air bubbles. The inlet flow of both water and air were ajusted to obtain roots similar to those separated by hand (control). The statistical analysis indicated that 7 out of 42 tested pairs of water and air flows gave results not significantly different from the control. The inlet water flow is fixed to 3 L/min and the air inlet to 100 units for routine analysis. The washing cycle is completed in 5 minutes for 200 g of soil, but for larger soil samples, it could be extended over several hours after evacuating the mineral particules from the base of the apparatus.