Evaluation of Potential Organic Resources as Low Carbon-Emitting Soil Amendment in a Red Pepper Cultivated Soil

Application of soil organic matter (SOM) is one of the most important strategies to enhance soil quality and combat climate changes by mainly increasing soil carbon stocks in agriculture. However, there is still a lack of information on soil respiration rate and temperature sensitivity in soils amended with different organic amendments in red pepper cultivation soil. To evaluate effects of different organic resources on enhancing soil carbon (C) balance in red pepper cultivation soil, four different low-carbon organic amendments (red pepper residue, compost, rice hull biochar, and wood biochar) with different application levels (0, 5, 10, and 20 Mg d.w ha-1) were set on a laboratory experiment by investing soil respiration rate, Q10 value, and soil chemical properties including pH, total C, dissolved organic C, etc. This study showed that all organic amendments significantly increased soil C input, showing the highest mean value (49.8 mg C) in NPK+wood biochar treatment as followed by NPK+rice husk biochar (38.7 mg C) > NPK+red pepper residue (33.3 mg C) > NPK+compost (26.7 mg C). However, NPK+rice husk biochar showed C output, showing the lowest mean soil respiration rates (0.86 mg C) during the incubation as followed by NPK+compost (1.08 mg C) > NPK+wood biochar (1.13 mg C) > NPK+red pepper residue (2.70 mg C) during the experiment. The C balance was the highest in the NPK+wood biochar (48.7 mg ΔC) mainly due to increased C input as compared to low C output. This result might be due to having different chemical properties that possessed a more stable C source than easily degradable C in the biomass. As an indicator of temperature sensitivity, the Q10 value was the highest in NPK+red pepper residue treatment (1.38) that could be comparatively sensitive for SOM degradation with rising air temperature and then followed by NPK+compost (1.21) > NPK+wood biochar (1.19) > NPK+rice hull biochar (1.18). In conclusion, wood biochar application could be a better soil management strategy to increase soil C storage particularly in the greenhouse conditions, showing high temperature during the cultivation.Soil carbon input, output, and balance of different organic material application regimes at the different levels under laboratory-scale experiments. Treatment† OM application level (Mg ha-1) C input (A) (mg C) C output (B) (mg C) C balance‡ (A - B) (mg ΔC) NPK + R 5 14.3 k§ 0.71 c 13.5 j 10 28.5 g 2.66 b 25.8 g 20 57.0 c 4.74 a 52.3 c Mean 33.3 2.70 30.6 NPK + Com 5 11.5 l 0.47 c 11.0 k 10 22.9 h 1.05 c 21.9 h 20 45.8 d 1.72 bc 44.1 d Mean 26.7 1.08 25.7 NPK + RB 5 16.6 j 0.45 c 16.1 i 10 33.2 f 1.00 c 32.2 f 20 66.4 b 1.14 c 65.2 b Mean 38.7 0.86 37.9 NPK + WB 5 21.3 i 0.89 c 20.5 h 10 42.7 e 1.24 bc 41.5 e 20 85.4 a 1.25 bc 84.1 a Mean 49.8 1.13 48.7 Type (A) *** *** *** Level (B) *** *** *** A × B *** *** *** †Incubation temperature: 25°C; R: Red pepper residue; Com: Compost; RB: Rice hull biochar; WB: Wood biochar.‡C balance: C input (OM application level × C content) - C output (OM application soil - NPK soil respiration (0.24 g by urea)).§The different letter means a significant difference among the treatments (at p ≤ 0.05, Tukey’s test). The same letter indicates no significant differences among treatments. *, **, and *** donate significant differences at levels of p < 0.05, 0.01, and 0.001, respectively.