Effects Of Dissolved Organic Carbon In Bamboo Biochar On Greenhouse Gas Emissions And Soil Nutrients

Much research about effects of biochar on soil greenhouse gas emissions has been reported in recent years. However, these reports are rarely involved with dissolved organic carbon from the constituents of biochar. In this paper, the bamboo biochar is obtained by bamboo waste materials, and acquired washed bamboo biochar by washing the bamboo biochar using distilled water in many times so as to the content of DOC within biochar was less than 50 mg L-1. A pot experiment was installed, the treatments are control(CK), fertilizer(CKF), bamboo biochar(B), washed bamboo biochar(WB), fertilizer+bamboo biochar(BF), fertilizer + washed bamboo biochar(WBF) by using of paddy soil in order to explore the effects of dissolved organic carbon within bamboo biochar on greenhouse gas emissions and soil nutrients. The greenhouse gases of N2O, CH4 and CO2 emissions were monitored during a whole rice period, and the soil pH, nitrate, ammonium were also analysed in different times. After the rice harvest, the yield of straw, grain and soil properties were measured. All of these works was done to provide a basis for the mechanism of greenhouse gas emissions and the application of biochar. The main results are as follows.(1)The content of DOC in washed bamboo biochar was 46.0 mg-L"1 and significantly decreased compared with bamboo biochar, and the pH, K content and ash were also part of the decline; the content of C, N, P and S, BET surface area, total pore volume and average particle size in washed bamboo biochar was no change compared with bamboo biochar.(2)Effects of bamboo biochar and washed bamboo biochar on soil NO3--N, NH4+-N and pH for different time showed that ①compared with CKF, the content of soil NO3--N for the treatments of BF and WBF were significantly reduced on the 2th,14th,28th and 28th day after transplanting; similarly, soil NO3-N for B and WB were significantly reduced on the 2nd day compared with CK. while the seven day after transplanting, soil NO3-N content was significantly lower than CKF for WBF.②On the 2th and 84th day after transplanting, compared with the CK and CKF, the concentration of soil NH4+-N can be reduced, respectively, and on 7th and 14th day, compared with CKF, washed bamboo biochar significantly reduced soil NH4+-N; while on the 28th day, bamboo biochar and washed bamboo biochar, compared with CK, significantly reduced NH4+-N concentration. ③whether compared with CK or CKF, both of them can significantly increase soil pH within the monitoring time, and there was no significant between bamboo biochar and washed bamboo biochar; compared with the initial soil pH, the treatments of B, WB, BF and WBF increased by about 0.45,0.54,0.49 and 0.46, respectively. ④the content of soil DOC was significantly decreased by the addition of bamboo biochar and washed bamboo biochar compared with the treatment of CK and CKF on a whole rice period, and in this condition, soil DOC for washed bamboo biochar was decline compared with bamboo biochar.(3) Research of bamboo biochar and washed bamboo biochar on soil nutrients and rice yield showed that①whether the application of fertilizer or not, soil organic carbon and available potassium were significantly improved by addition of bamboo biochar and washed bamboo biochar, respectively, and the soil available potassium was significantly increased by bamboo biochar compared with washed bamboo biochar, the yield of rice straw for B and WB were improved by 12.69% and 15.59%, respectively, the yield of rice grain for WB was increased by 15.65% compared with CK; soil total N was improved by application of BF and WBF compared with CKF, the yield of rice straw and grain for B, WB, BF and WBF were increased by 18.69% and 33.07%,16.67% and 18.37%, respectively, and the improvement of washed bamboo biochar was better than bamboo biochar. In terms of nutrient uptake, the absorption of N and K from rice straw and grain for BF and WBF were improved compared with CKF, and the absorbed N from rice straw and grain in the latter was more than the former, the results of uptake K from straw for bamboo biochar was better than washed bamboo biochar; both of single application improved the amount of N and K from straw; the absorption N and P within grain for WB and WBF were enhanced compared the CK and CKF, respectively, except the P of WB. Other cases had not been significantly different for all treatments.(4)Research of bamboo biochar and washed bamboo biochar on N2O, CH4 and CO2 emissions showed that ①there are three peaks for N2O emission, followed by the first 10th, 21th and 70th day after transplanting. Compared with CK, the cumulative N2O emissions for B and WB were reduced by 19.08% and 32.97%, respectively, by 60.83% and 67.16% for BF and WBF compared with CKF, respectively. Some measures, bamboo biochar and washed bamboo boichar can decline the content of soil NO3--N、NH4+-N and DOC and improve soil total N, reduced N2O emissions, whether the application of fertilization or not, the DOC for washed bamboo biochar was lower than bamboo biochar, therefore, the treatments of WB and WBF were decrease by 17.17% and 16.17%, compared with B and BF, respectively. The lower DOC content within bamboo biochar is more conducive to suppress N2O emissions regardless of the fertilization. ②in terms for CH4 emissions, the rate also has two peaks after transplanting 28 and 70 days respectively. Compared with CK, the treatments of B and WB’significantly reduced cumulative emissions of CH4 by 65.45% and 69.30%, and by 64.32% and 84.37% for BF and WBF, compared with CKF, respectively. The DOC for washed bamboo biochar was lower than bamboo biochar, and washed bamboo biochar can be more significantly reduced the amount emissions of CH4 by 56.20%. Therefore, the lower DOC content within bamboo biochar is more conducive to suppress CH4 emissions under the condition of fertilization. ③With the growth of rice, the CO2 emission rate was continuously increased and the discharge rate appeared on the 70th day after transplanting. Compared with CKF, the cumulative CO2 emissions for BF can be reduced by 11.12%, other treatments had showed no significant, and the relationship soil DOC with CO2 emissions need further study.