| The application of biochar in agriculture ecosystems was attractive globally in the last decade.Researchers found that the addition of biochar to soil can enhance soil terrestrial carbon sequestration and greenhouse gases mitigation,improve soil quality,increase crop productivity and environmental remediation.However,the benefits of biochar in crop productivity and climate change mitigation varied due to the differences of factors such as biochar types,soil conditions and cropping systems.Therefore,it is necessary to further explicit the function of biochar in different agriculture systems,and the relationship between biochar's function and soil nutrient turnover.In this study,a rain-fed dry cropland and a rice-wheat rotation system were chose to evaluat the effects of biochar soil amendment on crop productivity,soil carbon sequestion and greenhouse gases mitigation in different agriculture systems.And on the other hands,meta-analysis was used to investigate the effect of biochar soil amendment on soil phosphorus availability,soil carbon and nitrogen turnover.This study aimed to provide a scientific guideline for the application of biochar in agriculture ecosystems regarding to climate change mitigation and crop productivity improvement.The main results were as follows:(1)Effect of biochar amendment on crop productivity and greenhouse gases emission in rainfed maize cropland.Maize productivity in rainfed croplands is constrained by low soil fertility and moisture insufficiency.The local conventional fertilization regime(CF)is unbalanced with too much nitrogen in proportion to both phosphorus and potassium,which has led to low fertilizer use efficiency and excessive greenhouse gases emissions.This study was conducted from May,2011 to October,2012 in Xinzhou city,Shanxi province,and the soil is a calcareous inceptisol,cultivated under one season of maize a year.And the two-year field experiment was conducted to assess whether a high yielding but low greenhouse gases emission system could be developed by the combination of balanced fertilization(BF)and biochar amendment in a rainfed farmland located in the Northern region of China and the persistence.Biochar was applied at rates of 0,20,and 40t ha-1,and combined with BF and CF.Of which the fertilizer input rate of BF was calculated based on the fertility level of the soil and nutrients requirement of the maize,In CF treatment,N fertilizer was applied at 432 kg N ha-1 with P at 69 kg P2O5 ha-1,For the BF treatment,N fertilizer was applied at 217 kg N ha-1 with P at145.5 kg P2O5 ha-1.Of which BF treatment decreased N input and increased P input.Six treatments were conducted in total.This study based on the results of the first season,which has been done by Wu(2010),the second season investigation was done here.Results show that,in the second maize growing season,both BF and biochar increased maize yield and partial nutrient productivity and decreased nitrous oxide(N2O)emission.Maize yield under BF was 23.7%greater than under CF,and the yield was 35.4%higher with C2 treatment than CO under BF.Meanwhile,both BF and biochar increased the partial nutrient productivity in the second maize growing season.Soil bulk density was decreased in the second season,and soil moisture content was increased both of the two season for biochar treatments.Soil N2O emissions of BF were less than half of CF due to a reduced N fertilizer application rate.Biochar amendment decreased N2O by more than 31%under CF,while it showed no significant difference under BF.Combined with the result of the first season,the ANONA analysis showed that BF and biochar had persistence effect on maize yield,partial nutrient productivity and greenhouse gases emission.BF was effective in maintaining a high maize yield and reducing N2O emission.If combined with biochar amendment,BF would be more effective for sustainable low carbon agriculture in rainfed areas.(2)Effect of biochar amendment on crop productivity and greenhouse gases emission in rice-wheat rotation agriculture system.This study was conducted from June,2014 to June,2015 in Changshu city,Jiangsu province,and the soil is a Gleyic Stagnic Anthrosol,and cultivated under rice-wheat rotation.In this study,two types of biochar produced from different pyrolysis temperature(MBC1:lower temperature biochar;MBC2:higher temperature biochar)were chose to investigate the effect of biochar on crop growth,greenhouse gases emission and soil nutrient retention in rice-wheat rotation agriculture system.The iochars were applied at 20t ha-1.In order to investigate biochar's effect on agronomic nitrogen efficiency,two fertilizer regimes were conducted,including without N fertilizer(NO)and with N fertizer(N1).The results showed that,after one year treatment,soil organic carbon were significantly increased with biochar amendmet,while only MBC2 increased soil total N content;and the decreasing of soil bulk density was greater with MBC1 treatment than MBC2;biochar amendment significantly increased soil available P and K content.There was no significant effect of biochar on both wheat and rice yield.While biochar showed the potential to increase the agronomic nitrogen use efficiency,and the increasing was greater with lower temperature produced biochar than higher temperature produced biochar.This study showed that the greenhouse gases emission in rice-wheat rotation system was mostly influenced by fertilization,especially N fertilizer input,while little influenced by biochar treatment.Biochar treatment showed no significant effect on greenhouse gases emission in rice growing season,while in the wheat season,soil CO2 emission showed a slight increase with biochar amendment,and no effect on CH4 and N2O emission.Therefore,the role of biochar in the rice-wheat rotation agriculture system were most performed in soil carbon sequestration,nutrient retention and nutrient use efficiency increasing.(3)Meta-analysis of the regulating effect of biochar on soil phosphorus availability.The objectives of this section was to quantify the effect of biochar amendment on soil P availability,and to identify the factors controlling soil P availability in terms of biochar properties and soil conditions.A meta-analysis was conducted using 132 publications published till December,2015.Results showed asignificant increase of soil P availability by 64.4%with biochar amendment,and this effect could persist for more than 2 years.While the increasing effect size varied with time of duration,experimental types,soil conditions and biochar production conditions.The greatest effect with regard to soil properties was obtained in lower SOC content(93.3%)and neutral pH(85.8%)soils.In terms of biochar production conditions,P availability was significantly difference between biochar feedstocks,manure biochar was best(179.9%),and crop residues(69.1%)and sludge biochar(68.7%)was better than wood biochar(40.7%);and the effect sizes were weaken along with the pyrolysis temperature increase.In further,the change of P availability was related to biochar properties of chemical composition,surface area,CEC and ash content.This paper explicit the effect of biochar amendment on soil P availability,and it will be helpful for a better understanding of biochar's performance in agriculture and to get a rational application in specified agriculture conditions.(4)The effect of biochar amendment on soil C and N turnover.A meta-analysis was conducted to investigate the effect of biochar amendment on soil C and N cycling related enzyme activity,and its influence factors.Six enzymes were selected which related to soil C and N cycling,and the literature was selected was conducted untill June,2016.The result showed that,for the six enzymes,only a-Glucosidase activity was significantly decreased,the activity of P-Glucosidase,?-Cellobiosidase and ?-Acetyl-glucosaminidase were significantly increased with biochar soil amendment.The combined C and N cycling related enzyme activity was significantly increased by 11.5%and 6.9%,respectivity,after biochar amendment.The between-group variability analysis showed that the effect of biochar on soil C cycling related enzyme activity was influenced by experimental type,application rate and soil properties of SOC,soil N and C:N ratio,as well as biochar conditions of feedstock and pyrolysis temperature.The increasing of C cycling related enzyme activity was observed after two years with once biochar application.Simultaneously,high SOC and N content lead to higher C acquisition enzyme activity effect size.There was no significant change for C cycling related enzyme activity between biochar types,while the effect size was weaken along with pyrolysis temperature increase.The change of soil N cycling related enzyme activity significantly rely on soil conditions of SOC,N and cropping system,no significant difference observed between biochar feedstocks and pyrolysis temperatures.N cycling enzyme activity was significantly increased with dry land cereal crops,while no effect for cash crops.The change was positive when soil SOC>30g kg-1 and soil N>2 g kg-1,while insignificant with other soil levels.Thus,biochar soil amendment can accelerate soil C and N turnover and this effect influenced by biochar and soil conditions.In conclusion,the functions of biochar in rain-fed dry cropland and rice-wheat rotation system was difference.In the rain-fed maize cropping system,biochar can increase crop yield,enhance the agronomic nutrient efficiency,and reduce soil N2O emission in rain-fed cropland,and biochar significantly increased soil water content.While in rice-wheat rotation system,biochar had no significant effect on yield,and showed little effect on greenhouse gases emission,but biochar can enhance soil carbon sequestration,and increase agronomic nitrogen use efficiency.In addition,biochar can increase soil P availability,and accelerate soil C and N cycle,increase C and N use efficiency,and the beneficial was limited by soil and biochar properties.Thus it is of great significance important to the sustainable low-carbon agriculture to choose the resonalable biochar application method between different agricultural systems.This study provided a scientific basis of biochar application in agriculture on carbon sequestration and GHGs mitigation,and on crop productivity improvement. |
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