Effect of soil amendments derived from agricultural biomass on rice yield and soil fertility in a paddy field of South Korea

The objective of this study was to compare the effects of biochar and straw applications on rice yield and soil fertility during a three-year period. The three treatment conditions were: BC (barley straw biochar 2,000 kg ha^-1), BS (barley straw 2,000 kg ha^-1), and BC+BS (barley straw biochar 1,000 kg ha^-1 + barley straw 1,000 kg ha^-1, respectively). Each treatment area was separated by an untreated control (CN) area. During the study, rice yields for CN, BC, BS, and BC+BS treatments ranged on average from 473 to 515, 497 to 532, 516 to 528, and 583 to 602 g m^-2, respectively. Among the treatments, the BC+BS treatment produced the highest average rice yield and the BC+BS rice yield was stable during the three-year study. The soil changes after the final rice harvesting were different in the BC and BS application areas. Soil bulk density and pH were improved in all treatments except the CN treatment when compared to those of raw soil. The SOC and TN content after BC application increased by 0.56 and 0.08 g kg^-1, respectively, compared to those of the CN soil, while those after BS and BC+BS application increased by 0.89-1.36 and 0.16-0.3 g kg^-1, respectively. The soil CEC values after BC, BS, and BC+BS treatment were 0.55, 0.37, and 0.49 cmol_c kg^-1 higher than those in the CN, respectively. Therefore, such an approach can reduce the application of inorganic fertilizer, thereby encouraging the development of sustainable organic agriculture.