查看更多>>摘要：Empirical research indicates that heightened soil nitrogen availability can potentially diminish microbial decomposition of soil organic carbon(SOC).Nevertheless,the relationship between SOC turnover response to N addition and soil depth remains unclear.In this study,soils under varying N fertilizer application rates were sampled up to 100 cm deep to examine the contribution of both new and old carbon to SOC across different soil depths,using a coupled carbon and nitrogen isotopic approach.The SOC turnover time for the plot receiving low N addition(250 kg·ha-1·yr-1 N)was about 20-40 years.Conversely,the plot receiving high N(450 kg·ha-1.yr1 N)had a longer SOC turnover time than the low N plot,reaching about 100 years in the upper 10-20 cm layer.The rise in SOC over the entire profile with low N addition primarily resulted from an increase in the upper soil(0-40 cm)whereas with high N addition,the increase was mainly from greater SOC in the deeper soil(40-100 cm).Throughout the entire soil layer,the proportion of new organic carbon derived from maize C4 plant sources was higher in plots treated with a low N rate than those treated with a high N rate.This implies that,in contrast to low N addition agricultural practices,high N addition predominantly enhances the soil potential for fixing SOC by transporting organic matter from surface soils to deeper layers characterized by more stable properties.This research offers a unique insight into the dynamics of deep carbon under increased N deposition,thereby aiding in the formulation of policies for soil carbon management.
Robiul Islam RUBELLin WEISalman ALANAZIAbdulkarim ALDEKHAIL...
326-343页
查看更多>>摘要：Nitrogen(N)fertilizers in agriculture suffer losses by volatilization of N to the air,surface runoff and leaching into the soil,resulting in low N use efficiency(NUE)(＜50％)and raising severe environmental pollutions.Controlled-release nitrogen fertilizers(CRNFs)can control the release of N nutrients to NUE in crop production.Different methods were used to develop new CRNFs.However,different CRNF technologies are still underdeveloped due to inadequate controlling on N releasing time and/or unsustainable diffusion.The study on the influences of CRNF processing parameters on microbial conditions are lacking when the CRNFs composed of various bio-ingredients such as biochar,composts,and biowaste.The complexity of processing methods,material biodegradability,and other physical properties make current CRNFs of questionable value in agricultural production.This research aims to develop a novel biochar-compost-based controlled-release urea fertilizer(BCRUF)to preserve microbial properties carried by the compost.The BCRUF was synthesized by pelletizing the 50:50(dry,wt/wt)mixture of biochar and compost.BCRUF was loaded with urea and then spray-coated with polylactic acid(PLA).The releasing time of two types of BCRUFs,coated and uncoated with PLA,for 80％of N release in water was up to 6 h at three different temperatures(4,23,and 40 ℃),compared to conventional urea fertilizer and commercial environmentally smart N(ESN)fertilizer.The releasing time of coated BCRUF for 80％N release in soil was up to 192 h(8 days).Fourier-transform infrared spectroscopy(FTIR)analysis revealed that no new functional groups were found in the release solution,indicating no new chemical hazards generated.The differential scanning calorimetry(DSC)tests also verified that its thermal stability could be up to 160 ℃.The microbe populations in the BCRUF pellets were reduced after the pelleting and drying processes in BCRUF fabrication,but a few bacteria can endure in the air-drying process.BCRUF pellets soaked in water for 4 days retained some bacteria.The BCRUF showed very promising characteristics to improve NUE and sustainability in agricultural production.
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