Abstract: To resolve the problems of hardening of heavy clay and low fertility in upland red soils in Jiangxi Province, a field experiment was conducted to study the effects of low doses of biochar on fertility and production of upland red soils. The experiment included three doses of biochar: 0, 758 and 1515 kg·hm^-2·a^-1 (denoted as CK, BC1 and BC2, respectively). The results showed that, compared with CK, soil bulk density under BC1 and BC2 treatments decreased by 0.57%-2.05% and 0.87%-4.88%, soil pH increased by 2.51%-13.66% and 8%-12%, and soil cation exchange capacity increased by 3.73%-6.45% and 4.91%-7.13% in 0-60 cm, respectively. Application of low doses of biochar is beneficial to increasing the contents of organic carbon and N, P, and K in upland red soils, and the contents of organic carbon, total K and soil available K increased with increasing the dose of biochar. The crop yields under BC1 and BC2 treatments increased by 19.08% and 23.68% in 2013, and 18.01% and 22.98% in 2014, respectively. Therefore, application of low doses of biochar shows great prospects in increasing agricultural production by improving physical and chemical properties, nutrient utilization efficiency of upland red soils, and soil fertility. From the viewpoint of comprehensive input/output, continuous application of lowdose biochar exhibits more practical values and prospects.

Key words: drought stress, transfer, isoflavone, synthesis, soybean