Enhancing the nutritional value of rice can improve the health of rice consumers. Grain amino acid content is an important nutritional component. This study was conducted to test the hypothesis that the application of earthworm castings could increase the grain amino acid content in rice. Results showed that total amino acid content in the grain of rice was significantly elevated by applying earthworm castings (17 kg m -2 ), with an average increase of 8% across four tested rice cultivars. Application of earthworm castings had no significant ef...