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Background A significant source of greenhouse gas (GHG) emissions comes from the manufacture of synthetic nitrogen (N) fertilizers consumed in crop production processes. And the application of synthetic N fertilizers is recognized as the most important factor contributing to direct N2O emissions from agricultural soils. Based on statistical data and relevant literature, the GHG emissions associated with synthetic N manufacture and fertilization for wheat and maize in different provinces and agricultural regions of China were quantitatively evaluated in the present study. Results During the 2015–2017 period, the average application rates of synthetic N for wheat and maize in upland fields of China were 222 and 197 kg ha−1, respectively. The total consumption of synthetic N on wheat and maize was 12.63 Mt year−1. At the national scale, the GHG emissions associated with the manufacture of synthetic N fertilizers were estimated to be 41.44 and 59.71 Mt CO2-eq year−1 for wheat and maize in China, respectively. And the direct N2O emissions derived from synthetic N fertilization were estimated to be 35.82 and 69.44 Gg N2O year−1 for wheat and maize, respectively. In the main wheat-cultivating regions of China, area-scaled GHG emissions were higher for Inner Mongolia, Jiangsu and Xinjiang provinces. And for maize, Gansu, Xinjiang, Yunnan, Shannxi and Jiangsu provinces had higher area-scaled GHG emissions. Higher yield-scaled GHG emissions for wheat and maize mainly occured in Yunnan and Gansu provinces. Conclusions The manufacture and application of synthetic N fertilizers for wheat and maize in Chinese croplands is an important source of agricultural GHG emissions. The current study could provide a scientific basis for establishing an inventory of upland GHG emissions in China and developing appropriate mitigation strategies.

Much research has been devoted to investigating how water-extractable organic carbon (DOC) concentration and microbial activity regulate soil organic carbon (SOC) mineralization when soils are saturated with water. However, the relationships of DOC chemical structure and microbial community composition with SOC mineralization, as well as the relative contributions of microbial decomposers and their substrates on the mineralization rate have rarely been examined. In a laboratory experiment, we incubated two typical cropland soils (an Entisol and a Mollisol) of China for 360 days under submerged and non-submerged conditions, and we evaluated the concentration and chemical structure of soil DOC, soil microbial metabolic potential and community composition by using total C/N analysis, solution-state 1 H NMR, Biolog EcoPlates, and 16S rRNA amplicon sequencing, respectively. The results showed that submergence significantly increased DOC concentration ( P P P P P P P P P P > 0.05; Mollisol: SPC = 0.30, P P > 0.05; Mollisol: SPC = −0.45, P

The interactions between plants and nanomaterials (NMs) can shed light on the environmental consequences of nanotechnology. We used the major crop plant rice (Oryza sativa L.) to investigate the uptake of gold nanoparticles (GNPs) coated with either negatively or positively charged ligands, over a 5-day period, in the absence or presence of one of two amino acids, aspartic acid (Asp) or lysine (Lys), acting as components of rice root exudates. The presence of Asp or Lys influenced the uptake and distribution of GNPs in rice, which depended on the electrical interaction between the coated GNPs and each amino acid. When the electrical charge of the amino acid was the same as that of the surface ligand coated onto the GNPs, the GNPs could disperse well in nutrient solution, resulting in increased uptake of GNPs into rice tissue. The opposite was true where the charge on the surface ligand was different from that on the amino acid, resulting in agglomeration and reduced Au uptake into rice tissue. The behavior of GNPs in the hydroponic nutrient solution was monitored in terms of agglomeration, particle size distribution, and surface charge in the presence and absence of Asp or Lys, which depended strongly on the electrostatic interaction. Results from this study indicated that the species of root exudates must be taken into account in assessing the bioavailability of nanomaterials to plants.

Combinations of remediation technologies are needed to solve the problem of soil contamination in paddy rice, due to multiple potential toxic elements (PTEs). Two potential mitigation methods, water management and in-situ remediation by soil amendment, have been widely used in treatment of PTE-polluted paddy soil. However, the interactive relationship between soil amendment and water management, and its influence on the accumulation of PTEs in rice are poorly understood. Greenhouse pot experiments were conducted to examine the effects of phosphate amendment on Cd and Pb availability in soil and their influence on Cd and Pb uptake into rice, on Fe and P availability in soil, and on the alteration of Fe amount and compartment on root surface among different water management strategies. Results indicated that Cd and Pb content in the shoot and grain were significantly affected by the different water management strategies in nonamended soils, and followed the order: wetting irrigation > conventional irrigation > continuous flooding. The application of phosphate amendment significantly decreased the variations of Cd and Pb absorption in shoot and grain of rice among different water treatments. The reasons may be attributed to the enhancement of P availability and the decrease of Fe availability in soil, and the decreased variations of Fe2+/Fe3+ content in root coating after the application of phosphate amendment. These results suggested that the simultaneous use of phosphate amendment and continuous flooding to immobilize Cd and Pb, especially in acid paddy soils, should be avoided.

Tillage practice and residue management play important roles in N pool in soils. This study determined the impacts of tillage practice and residue management on crop yield. It also investigated the distribution, fractionation, and stratification of N at soil at depths ranging from 0 to 60 cm under wheat–maize cropping systems. Three treatments were established in 2009: no-tillage with straw removal for winter wheat and summer maize (NT), no-tillage with straw mulching for winter wheat and summer maize (NTS), no-tillage with straw mulching for summer maize and plow tillage with straw incorporation for winter wheat (NPTS). After 8 years, soil total nitrogen (TN) content in NTS was greater than in NT, but only in 0–10 cm layer. NPTS treatment increased TN content over NT and NTS in 10–20 cm layer by 18.0% and 13.9%, and by 16.8% and 18.1% in 20–30 cm layer, respectively. Particulate organic N, microbial biomass N and water-extractable organic N levels were the greatest in 0–10 cm layer under NTS treatment; and in 10–30 cm layer, the corresponding values were the highest under NPTS treatment. NPTS treatment could immobilize the mineral N in 10–30 cm layer, and reduced leaching losses into deeper soil layers (40–60 cm). Furthermore, total yield increased by 14.7% and 8.5% in NPTS treatment compared to NT and NTS treatments, respectively. These results indicate that NPTS is an effective and sustainable management practice, which will improve soil fertility, sustainable crop production, and environmental quality in low-productivity soils in central China.

Primary Korean pine(Pinus koraiensis) forest is climax community of Xiaoxing′an Mountains,in northeast of China.It has significant influence on regional ecology and hydrological environment.In order to investigate the canopy interception and allocation and evaluate forest hydrological function and benefit of virgin Korean pine forest quantitatively,positioning experiments were implemented during two rainy seasons of from 2010 to 2011 in Liangshui national nature reserve.Throughfall,stemflow and precipitation were measured and interception loss was subsequently calculated.On the basis of the observations of 21 rainfall events which collected from local weather station and forest stand respectively,we stimulated canopy interception process of virgin Korean pine forest in the Xiaoxing′an Mountains using the modified Gash model.The mesured values of total preciptation,througfall,stemflow,and canopy interception loss in virgin Korean pine forest of Xiaoxing′an Mountains were 514.1 mm,373.19 mm,8.02 mm,and 132.43 mm,respectively,during the study period.Throughfall and stemflow were all significantly positively correlated with precipitation(P0.01).The simulated values of throughfall,stemflow,and interception loss by modified Gash model were 370.91 mm,16.14 mm,and 130.07 mm respectively.Simulation value of throughfall was 2.28 mm lower than the actual value,with a relative error of 1.75%,while simulation value of stemflow was 8.12 mm higher than the measured value,with a relative error of 50.3%.The simulated value of canopy interception loss was 2.35 mm lower than the actual value,with a relative error of 1.81%.The stimulated values of throughfall and canopy interception corresponded well with measured values,while for stemflow,the simulated value was of great difference from measured value.Our findings reveal the Gash analytic model can be well applied to estimation of canopy interception loss of virgin Korean pine forest during rainy seasons in the Xiaoxing′an Mountains.