Rice plants were cleaned (dust and soil removed) using deionized water, put in a 105 °C drying oven for 30 min, and then put in a 70 °C drying oven until the weight of the sample remained constant. Rice plants were then separated into four tissues (root, straw, husk, and brown rice), and ground using a stainless steel grinder (RT-02B, China). Crushed powder was passed through a 100 mesh sieve and kept in a cleaned polyethylene container before analysis. Rhizosphere soils were air-dried, crushed, and passed through a 10 mesh sieve to remove large debris, stones, and pebbles. The soils were ground to a powder with an agate mortar and pestle, sieved through a 100 mesh sieve, and kept in cleaned polyethylene containers for further analysis.