Soybean root activity: Methodology definition

Root study techniques are labor intensive. Among the most frequently used methods are the trench or profile wall, block or monolith, needle board and hand auger. These techniques use destructive and direct root sampling. With the objective of adapting an evaluation methodology of soybean root activity based on Rubidium Nitrate, an experiment was carried out in Botucatu, SP, Brazil, in two phases: one in the field and the other in a greenhouse. Soybean plants were grown in 15 L pots. 25 DAE, 3 mL of Rubidium Nitrate solution was applied at 0, 0.5; 1.0 and 2.0 mg dm(-3), at a depth of 0.05 m in the middle of each pot. The plants shoot was collected and divided in stalk + petiole and leaf after 2, 4 and 6 days of RbNO3 application. In the field, portions of 3.0 mL RbNO3 were applied at depths of 0.05; 0.10; 0.20; 0.40 and 0.60 m. The plant shoot was collected 4 days after RbNO3 applications. No phytotoxicity of RbNO3 to soybean plants was observed. RbNO3 was efficient to determine root activity.