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Gao D.C.,Hunan Agricultural University | Gao D.C.,Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use | Gao D.C.,Hunan University | Gao D.C.,National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization | And 18 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2015

Farmland soils are the important source of greenhouse gases emissions, so it plays an important role for slowdown of the climate change by reducing the emissions of greenhouse gases from farmland soils. Because of high carbon content and carbon stability of biochar, and its influence on regulation of soil structure and microorganism, biochar has the important effect on increasing of soil carbon accumulation and reducing of the greenhouse emissions. However, biochar is setting up with high or low addition amount currently, possess a big blind area, and few reports are involved in effecting of biochar on reducing effectiveness of comprehensive greenhouse. Simulation experiment indoor of soil column was conducted in this experiment, and adding 0% (0 t/hm2), 0.5% (5 t/hm2), 2% (20 t/hm2), 4%(40 t/hm2), 6%(60 t/hm2), 8%(80 t/hm2) biochar (the biochar was prepared by pyrolyzing corn straw at 500-550 °C under oxygen limited condition) into red dryland land of Southern China under urea application condition (300 kg/hm2), and using static chamber/gas chromatograph techniques to collect and determine the CO2, CH4, N2O fluxes. The results showed that CO2 emission was significantly increased by biochar application during simulation experiment indoor of soil column, and the relationship between addition amount of biochar and emission amount of CO2 meet the linear equation: y=12.591x+235.02 (R2=0.834, n=24). The CH4 emission was almost inhibited and the N2O flux was significantly decreased when biochar addition ratio was above 2% (including 2%), and the comprehensive greenhouse effective of CH4and N2O were significantly decreased, and the decreased range was bigger when the ratio reached 4%. But N2O emission was significantly accelerated by adding small amount of biochar(0.5%), and no significant effective of reducing the comprehensive greenhouse. The apparent decomposition rate of biochar decreased as the increasing of biochar addition, indicating that the higher biochar addition with the more carbon accumulated in soil. As a conclusion, recommended applying amount of biochar is 20 t/hm2 in agricultural production, which has a better effect both on carbon fixation and reduction. © 2015, Ecological Society of China. All rights reserved.

Gao D.,Hunan Agricultural University | Gao D.,Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use | Gao D.,Hunan University | Gao D.,National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization | And 18 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2014

Excessive application of nitrogen fertilizer in agricultural soils is considered as a main cause of ecological problems such as nitrogen leaching, which has become an important limitation to improving nitrogen use efficiency in agricultural production. Because of its physical, chemical, and biological stability, biochar when applied to soils can play a key role in nutrient cycling, potentially affecting nitrogen retention and improving soil fertility. However, experimental results were variable and dependent on the experimental set-up, soil properties, and fertilizer application rates and biochar were set up at the high and low levels, which possess a big blind area. A laboratory experiment was conducted to investigate the effects of biochar additions on dynamic changes of nitrogen under artificial rainfall conditions by adding 0, 0.5%, 2%, 4%, 6%, and 8% biochar (the biochar was prepared by pyrolyzing corn straw at 500-550°C under oxygen limited condition) into soil columns collected from red dryland of southern China under urea application condition (300 kg/hm2). The results showed that the speed of leaching of NO3 - and total nitrogen was delayed by biochar applications. Compared with urea application treatment, the total nitrogen and NH4 + contents in leachate were significantly decreased by 4.02% and 8.93% when ≥2% biochar was applied into soil, and the NO3 - contents of leachate was obviously decreased by 3.23%-11.87% when the biochar ratio reached 4%. But there was no significant effect of adding small amount of biochar (such as 0.5%) on N leaching compared with urea application treatment. Leaching losses of NO3 - had been found to be highest because the NO3 - was mobile, and may not be taken up by plants. NO3 - leaching amount accounted for 84%-90% of the total nitrogen leaching amount, while NH4 + leaching only accounted for 0.4%-2%; The total nitrogen content of different soil layers in each treatment was similar regardless of the fertilization and biochar applications. While the total nitrogen contents in soils were markedly different among the treatments. Compared with urea application treatment, the content of soil total nitrogen was significantly increased by 4.62% to 10.62% when biochar addition was ≥2%, and the relationship between addition amounts of biochar (x) and the content of soil total nitrogen (y) followed an index equation: y=1.6e0.0845x (R2=0.99, n=24). The results above suggested that biochar could be used as a potential additive for nutrient retention in order to increase the utilization efficiency of chemical fertilizers. In conclusion, biochar additions could decrease the leaching amount of NH4 +, NO3 - and total nitrogen and partly increased the concentration of soil total nitrogen. However, the low biochar addition had no significant effects on reducing nitrogen leaching and increasing soil total nitrogen content. Therefore, the purpose to obviously decrease nitrogen leaching and increase the content of soil total nitrogen could be realized only when biochar addition was above 2% in dryland soil. Nonetheless, the effect of biochar addition on reducing soil nitrogen leaching needs to be further verified before biochar can be applied to agricultural fields on a large scale.

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