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Alkaline phosphatase (ALP), which was encoded by bacterial phoD genes, hydrolyzes organic phosphorus (P) into dissolved phosphorus in soils and is therefore vital for absorbing phosphorus (P) in vegetation. However, the unreasonable application of chemical fertilizer will inhibit this process of dissolving phosphorus. Until now, although the fact that straw is the optimal C source has been recognized, its impact on phoD-harboring bacteria under decreasing chemical fertilizer is not clear. A field experiment was established with chemical fertilizer only (F) and the gradient inorganic fertilizer reduction with straw: inorganic fertilizer with straw (FS), 70% inorganic fertilizer with straw (0.7FS), 60% inorganic fertilizer with straw (0.6FS), and 50% inorganic fertilizer with straw (0.5FS). Mixed treatments received equal amounts of straw. Integrated high-throughput absolute abundance quantification (iHAAQ) was used to investigate the phoD bacterial community structure. From the correlation between the plant-total P of three vegetables and microbial variables, only the plant-total P of chili was significantly related to ALP and the abundance of phoD gene. Although the total vegetable yield was significantly increased by the addition of straw, no correlation with ALP and phoD bacterial community was found. In addition, the abundance of the phoD bacterial community and the levels of ALP activity were both higher in a regime featuring 70% inorganic fertilization with straw (0.7FS), but the ability of phoD bacteria ALP release was strongly activated in a regime featuring 50% inorganic fertilization with straw (0.5FS). Distance-based redundancy analysis (db-RDA) indicated that the community of phoD bacteria clustered four groups and suggested that a number of soil factors played key roles in shaping the entire phoD bacterial community, including soil organic carbon, total nitrogen, available phosphorus, Ca2+-Ex, and total potassium. The correlation between the absolute abundance of ALP-regulating bacteria and ALP activity suggests that Amycolatopsis may predominantly account for ALP activity, especially in the 0.5FS regime. In the reduction of chemical fertilizer, the straw substitution did not reshape the structure of the phoD bacterial community but strongly activated phoD bacteria to release ALP.

Soil microorganisms have an important influence on the transformation of soil nutrients. As functional genes encoding phosphatase

The aim of the study was to understand the impact of biochar and straw return on soil aggregates and organic carbon for soil improvement of the newly cultivated purple soil dry slope land in the Three Gorges Reservoir area. In this study, a field test was used to set five treatment pairs with regards to soil aggregate composition and organic carbon distribution:no fertilization(CK), conventional fertilization(NPK), optimized fertilization(GNPK), chemical fertilizer reduction combined with straw(RSD), and chemical fertilizer reduction combined with biochar(BC). The results showed that fertilization can improve the level of soil fertility, especially with the RSD and BC treatments. The soil aggregates of each fertilization treatment were0.25 mm in size. Compared with the CK, each treatment significantly increased the aggregate content of 0.5-5 mm particles, and the values of MWD, GMD, and

The purple soil sloping field is the main cultivated land type in the Three Gorges area, and the soil fertility directly determines crop yield. In order to explore the effects of different fertilization treatments on the soil organic carbon content at different slope positions, field experiments were carried out at the Three Gorges Reservoir Test Station of Chengdu Institute of Mountain and Disasters, Chinese Academy of Sciences. A total of five treatments were set up:no fertilization(CK), conventional fertilization(T

The partial substitution of mineral fertilizers with straw in agricultural soils could help to control soil acidification, reduce the risk of eutrophication from agricultural runoff, and increase the utilization efficiency of straw. However, the effects of such coupled practices on greenhouse gas (GHG) emissions and production yields in vegetable fields are not clear. Therefore, the objectives of this study were to (1) understand methane (CH4) and nitrous oxide (N2O) emissions in response to the same amounts of straw return with varied amounts of mineral fertilizers, and (2) to identify a solution which could better coordinate GHG emissions, vegetable production yield, and the utilization of agricultural straw following disposal. We conducted four-season (lettuce-cabbage-chili-lettuce) vegetable cultivation for 1 year using a control treatment (CT), mineral fertilization only (F), and four mineral fertilization treatments plus maize straw (FS, 0.7FS, 0.6FS, and 0.5FS). We then examined seasonal changes of CH4 and N2O fluxes, CH4 and N2O cumulative emissions, soil organic carbon (SOC), nitrate nitrogen (NO3−-N) and ammonium nitrogen (NH4+-N) content, vegetable yields, global warming potential (GWP), greenhouse gas intensity (GHGI), and N2O emission factors (EF). Compared to the F treatment, the application of maize straw increased the N2O flux significantly in the FS, 0.7FS, 0.6FS, and 0.5FS treatments. In treatments with added straw, the reduced application of mineral fertilizer led to a reduction in the cumulative N2O emission; this was due to the reduced content of NO3−-N content. The lowest CH4 flux and cumulative CH4 emission were observed in the 0.7FS treatment; this may be due to a form of competitive oxidation between CH4 and NH4+-N from urea. Furthermore, the application of maize straw in combination with a full dose of mineral fertilizers led to high GWP and GHGI values, which showed increases of 88.7% and 78.8%, respectively, in comparison with the F treatment. When taking SOC storage variations into account, which were caused by straw decomposition during cultivation, we identified a negative net GHGI (NGHGI) value (− 0.0448 kg CO2-eq kg−1 yield) in the 0.7FS treatment. This indicated that the NGHGI had decreased by 116.2% relative to the F treatment when based on similar vegetable yields. Straw combined with 70% mineral fertilizer led to better GHG emissions and vegetable yield when taking into account the carbon sequestration and decomposition caused by the addition of straw.

The characteristics of dissolved organic carbon loss with different fertilization treatments were examined to derive the best nutrient management method for sloping farmland in the Three Gorges Reservoir area where maintaining the soil carbon balance and reducing environmental pollution caused by carbon loss is crucial. Experimental runoff plots were set up at the Experimental Station for Soil and Water Conservation and Environmental Research in the Three Gorges Reservoir Region, Chinese Academy of Sciences, involving the following five treatments:No fertilization (CK), conventional fertilization (conventional), optimum fertilization (optimum), biochar combined with 85% optimum fertilizer (biochar), and straw combined with 85% optimum fertilizer (straw). The effects of the five treatments on runoff flux, sediment yield, and soil organic carbon flux were monitored and evaluated. Results show that:①Subsurface flow accounted for 52.84%-92.23% of the runoff (both surface and subsurface flow) and the loss flux of dissolved organic carbon (DOC) in the subsurface accounted for 43.64%-87.35% of the total loss flux. Thus, in this sloping farmland, subsurface flow was the main pathway of runoff and dominated dissolved organic carbon transport. ②Compared with the optimum treatment, straw treatment reduced the surface runoff flux, sediment yield, surface loss flux of DOC, and loss flux of organic carbon in the sediment by 30.39%, 39.41%, 28.71%, and 23.97%, respectively, but increased the subsurface runoff flux and loss flux of DOC. Compared with the optimum treatment, the biochar treatment significantly increased the surface and subsurface runoff flux, sediment yield, loss flux of DOC in the surface and subsurface, and the loss flux of organic carbon in the sediment. ③The loss flux of DOC accounted for 99.31%-99.94% of the loss flux of soil organic carbon, and DOC was the major species of organic carbon in the organic carbon loss in this type of sloping farmland. The loss flux of DOC under the different fertilization treatments was ranked biocharoptimumstrawconventionalCK. ④Compared to the optimum treatment, the straw treatment and biochar treatment increased the soil organic carbon (SOC) content by 95.79% and 32.16%, respectively. Based on these results, straw combined with 85% of optimum fertilizer is the best nutrient management method for this sloping farmland as it can reduce surface runoff flux, sediment yield, and the loss flux of soil organic carbon while increasing the soil organic carbon content.

In order to understand the characteristics of soil nitrogen and phosphorus loss under different land use patterns in the small watershed of the Three Gorges Reservoir area and provide a scientific basis for the prevention and control of agricultural non-point source pollution, a field test method was used to study the paddy fields and drought in the small Shipanqiu Watershed in the Three Gorges Reservoir area. The characteristics of different runoff concentrations and the fluxes of nitrogen and phosphorus in surface runoff under the five land use schemes of paddy filed, slope land, woodlands, citrus orchards, and vegetable land. The results show that the annual total nitrogen loss followed the order of paddy field[17.73 kg·(hm

In order to explore biochar fertilizer addition, two types of industrial wastes (YM) and lees (JZ) and agricultural waste corn stover (JG) were used as the raw materials to make biochar, and the biochar was modified to make smoke-modified biochar (M-YM). The culture test method was used to study the law of ammonia volatilization and phosphorus fixation over a certain period of time with the different fertilizer ratios of the four biochars. We aimed to provide a scientific basis for the agricultural utilization of biochar. The results show that:① The cumulative volatilization and volatilization rate of ammonia of the four kinds of biochar with different fertilizer ratios were as follows:A1A2A3 (A1:2.25 g urea; A2:2.25g urea +2.25 g chlorination potassium; A3:2.25 g urea +2.25 g potassium dihydrogen phosphate). The addition of potassium chloride and potassium dihydrogen phosphate in urea reduced ammonia volatilization, and the cumulative ammonia volatilization and volatilization rate of different biochars under all chemical fertilizer ratios was JZM-YMYMJG; ② The amount of phosphorus by biochars fixation under the B1, B2, and B3 treatments (B1:0.4 g potassium dihydrogen phosphate; B2:0.4 g potassium dihydrogen phosphate +0.3 g urea; B3:0.4 g potassium dihydrogen phosphate +0.3 g potassium chloride) all increased and then decreased. Then, the fixation amount of phosphorus not significantly changed in period from 30th to 60th day. Among four biochar, the fixation rate of phosphorus was the highest under the B1 treatment.With the ratios of B1, B2, and B3 fertilizers, the order of the fixation rate of the four biochars to phosphorus was:M-YMYMJGJZ. Therefore, in order to reduce the volatilization of ammonia in nitrogen fertilizers in agricultural fertilization, potassium chloride and potassium dihydrogen phosphate can be added to urea. At the same time, in the fixation of phosphorus, increasing the particle size of biochar may weaken the phosphorous fixation ability.

The reduction in chemical fertilizers combined with organic fertilizers is a national strategy to achieve environmental friendliness and maintain the quality of cultivated land. It is of great significance for the prevention and control of soil pollution and the sustainable development of agriculture. In this study, purple soil and sloping land in the Three Gorges Reservoir area was studied. The field experiment method was used to study the control, conventional fertilization, optimized fertilization, biochar (fertilizer combined with biochar), and straw under rapeseed/corn rotation mode. The effects of five treatments on soil nitrogen/phosphorus form, crop nitrogen and phosphorus content, fertilizer utilization rate, and crop yield were studied in the field (fertilizer reduction combined with straw returning). The results showed that the soil ammonium nitrogen content was the highest in the rapeseed season, which was 4.51 mg·kg

This study seeks to clarify the effect of biochar application on nitrogen loss patterns and flux in purple arid sloping land, so as to provide a scientific basis for improving the quality of farmland and reducing the risk of agricultural non-point source pollution in purple arid sloping land. The effects of four treatments on surface runoff and soil nitrogen loss patterns and fluxes in purple arid sloping land were studied by field experiments, including no fertilization (control), conventional fertilization, optimized fertilization, and biochar (fertilizer reduction and biochar application). The results showed that:① Of the fertilization treatments, the total runoff of conventional treatment was the highest at 16133 L·a

To clarify the response of a nitrogen-related microbial community and function to different vegetation types in subtropical forest, soil samples were collected for analysis from the topsoil of five vegetation types in the Jinyun Mountain National Nature Reserve, i.e., coniferous forest, broadleaf forest, mixed broadleaf-coniferous forest

The purple soil sloping field is considered as the main source of sediment and non-point source pollution in the Three Gorges Reservoir area. To prevent and control the non-point source pollution, it is indispensable to explore the characteristics of nitrogen loss in the overland flow and interflow of purple soil sloping field in Three Gorges Reservoir area. The purple soil sloping runoff plots, located in the Shibaozhai Experimental Station of Chengdu Institute of Chinese Academy of Sciences in Zhongxian County, Chongqing, were studied. The experiment included no fertilization treatment (CK), traditional fertilization treatment (T

The ecosystem respiration and temperature sensitivity (

Phytolith-occluded organic carbon (PhytOC) is a form of long-term storage of soil organic carbon, which is of great significance for soil carbon sequestration. Taking six land use patterns in southwest China as the research object, including coniferous and broad-leaved mixed forest, bamboo forest, orchard, dry land, paddy field, and grassland, we compare the distribution of the PhytOC content under the different land use patterns in different depth sections of 0-20, 20-40, 40-60, and 60-100 cm. In addition, we estimate the storage of phytOC and analyze the carbon sequestration characteristics of the terrestrial ecosystems. According to the results, the soil organic carbon and phytolith mean content in the bamboo forest were the highest in the soil profile, at 16.75 g·kg

Studies have shown that the addition of biochar to agricultural soils has the potential to mitigate climate change by decreasing nitrous oxide (N2O) emissions resulting from denitrification. Rice paddy field soils have been known to have strong denitrifying activity, but the response of microbes to biochar for weakening denitrification in rice paddy field soils is not well known. In this work, compared with the chemical fertilizer alone, the chemical fertilizer + 20 t hm−2 biochar fertilizer slightly decreased denitrifying the nitrite reductase activity (S-NiR) and N2O emission without statistic difference, whereas the chemical fertilizer + 40 t hm−2 biochar significantly boosted them. The abundance of nir-denitrifiers contributed to S-NiR and N2O emission, especially nirS-denitrifiers, rather than the variation of community structure. Pearson correlation analysis showed that NO2−-N was a key factor for controlling the abundance of nir-denitrifiers, S-NiR and N2O emission. The biochar addition fertilization treatments strongly shaped the community structure of nirK-denitrifiers, while the community structure of nirS-denitrifiers remained relatively stable. In addition, Paracoccus and Sinorhizobium were revealed to be as the predominant lineage of nirS- and nirK-containing denitrifiers, respectively. Distance-based redundancy analysis (db-RDA) showed that changes in the nir-denitrifier community structure were significantly related to soil organic carbon, NO3−-N, and total phosphorus. Our findings suggest that, although the nirS- and nirK-denitrifiers are both controlling nitrite reductase, their responses to biochar addition fertilization treatments showed significant discrepancies of diversity, abundance, and contribution to N2O and S-NiR in a paddy soil.

This study was intended to explore the distribution and stability of soil aggregates and the organic carbon for different forest types and to provide a scientific basis for the efficient management of soil carbon pools in subtropical forest ecosystems. Four subtropical forest types, including bamboo forest, broad-leaf forest, coniferous forest, and a mixed coniferous and broad-leaf forest on Jinyun Mountain (Chongqing Municipality), were selected as research subjects to explore the distribution of soil aggregates and organic carbon in different layers (depths of 0-20, 20-40, 40-60, and 60-100 cm). The results showed:The content of2 mm aggregates and mean weight diameter (MWD), geometric mean diameter (GMD), and0.25 mm aggregate content (

Biochar addition can reduce methane (CH4) emissions from paddy soils while the mechanisms involved are not entirely clear. Here, we studied the effect of biochar addition on CH4 emissions, and the abundance and community composition of methanogens and methanotrophs over two rice cultivation seasons. The experiment had the following five treatments: control (CK), chemical fertilizer application only (BC0), and 0.5% (w/w) (BC1), 1% (BC2), and 2% of biochar applied with chemical fertilizers (BC3). The season-wide CH4 emissions were decreased (P

Nitrogen (N) and phosphorus (P) loss in runoffs has been a serious problem in China due to the amount of chemical fertilizer currently applied to farmland. Biochar has been used as a soil amendment for increasing nutrient retention, water holding capacity, and crop yield. However, little is known about the influence of biochar on the runoff erosion from both surface flow and subsurface flow, especially in sloping regions. Experimental runoff plots were, therefore, set up on Entisols in a sloping farmland, involving four treatments: control (CT), conventional NPK fertilization (CF, based on local practices), optimum NPK fertilization (OF, based on the recommendation from local agriculture committee), and biochar combined with 85% of optimum NPK fertilizer (BF). The effects of the four treatments on the runoff fluxes, sediment yields and the runoff coefficients, as well as the N (ammonium (NH4+), nitrate (NO3−) and total N (TN)) and P (phosphate (PO43-), total P (TP), dissolved TP (DTP), particulate P (PP)) losses via both surface runoff (i.e., surface flow, 0–20 cm, ploughed layer) and subsurface runoff (i.e., subsurface flow, 20–60 cm, non-ploughed layer) were all monitored and evaluated from April 2018 to September 2019. Results show that, in this sloping farmland, subsurface flow was the main process of runoff and dominated N transport, but surface flow dominated P transport. The three fertilization treatments reduced the runoff erosion by surface flow, while increasing it from subsurface flow (p

The nirS gene encodes nitrite reductase (NIR) and participates in the denitrification of inorganic nitrogen (N) in soils. Although the gene is important in the global cycling of N, little is known about the responses of nirS-denitrifier communities to the substitution of chemical fertilizer by organic materials. Therefore, a field experiment in a vegetable soil was established with only chemical fertilizer (F) and four partially substituted organic materials treatments: straw (SF), mushroom dregs (MF), biochar (BF), and cattle manure (CF). All treatments received equal amounts of total nitrogen, phosphorus, and potassium. Integrated high-throughput absolute abundance quantification (iHAAQ) was used to quantify the abundance of the nirS gene in denitrifier communities. The relations among NIR activity, N fractions and other soil properties were also evaluated. Compared with the F treatment, the substitution with organic materials increased the diversity but reduced the absolute abundance of the nirS gene, particularly in the SF treatment (P

How to address improving degraded soil has become an increased concern for agricultural production. Biomass ash is used for remediation of degraded soil and improvement in soil structure. To investigate the responses of aggregate stability and soil consistency by biomass ash and other amendments, a pot experiment with a degraded soil and seven treatments including a control (CK), no fertilizer or amendment; only N-P-K fertilizer (F); N-P-K fertilizer with lime (FL), lime and zeolite (FLZ), biomass ash (FBA), biological fertilizer (FBF) and peat ash (FPA), respectively, were conducted. Stability of soil aggregate, water-holding capacity, and soil consistency was analyzed within a lettuce-water spinach-lettuce planting system. Results showed that amendment additions significantly raised the fractions of >0.25 mm soil aggregate. Applications of biomass ash reduced the percentage of aggregate destruction (PAD) by 45.07%-59.97% and reduced the value of fractal dimension (D) by 1.79–2.16 during whole cultivation period, indicating the stability of soil aggregates. Soil organic matter (SOM) plays a key role in soil consistency because of significant relationship between SOM and soil consistency indicators including plastic limit (PL), liquid limit (LL), plasticity index (PI) and liquidity index (LI). While, hydrodynamic characters and potential low clay content occurred in the soil treated with biomass ash during high moisture conditions. These findings suggest that the application of biomass ash improved the stability of soil aggregate, which improved the structural stability of degraded soil but may pose a risk to soil erosion by water force.

Partially substituting chemical fertilizer with organic manure can aid in the disposal of agricultural wastes via recycling into agricultural land, reduce chemical fertilizer application, and influence nitrogen (N) transformation. However, relatively few studies have investigated the association between soil physicochemical properties, denitrifier communities and N2O emission after short-term substitution of organic manure in vegetable fields. We conducted a short-term vegetable field experiment which included one control treatment (CT, no fertilizer) and three fertilization treatments containing equal amount of total N, phosphorus and potassium (CF, chemical fertilizer only; CMR, chemical fertilizer plus mushroom residue; COM, chemical fertilizer plus cattle manure). The results showed that partial substitution of chemical fertilizer with organic manure greatly increased cumulative N2O emissions, N2O emission factors and yield-scaled N2O emissions by 122-203%, 238-600% and 128-181%, respectively. Compared with the CF treatment, short-term substitution with organic manure reduced the abundance of nirS- and nosZ-type denitrifiers, and increased that of nirK-type denitrifiers. Modeling indicated that nirS abundance, together with soil available N, NIR activity, nirK abundance, SOC, NH4+, and NO3- were the primary factors associated with cumulative N2O emissions. The denitrifier community composition of the CF- treated soil was separated from that of soils treated with CMR and COM, and was primarily influenced by soil NH4+ concentration. NIR activity showed a significant correlation with denitrifier community composition. Overall, short-term substitution of chemical fertilizer with cattle manure (lower C/N ratio) reduced the abundance of nirS- and nosZ-type denitrifiers, but stimulated N2O emission.

The effect of biochar application on the net ecosystem carbon budget (NECB) and the mechanism controlling methane (CH4) emission in paddy soils under vegetable–rice rotations are poorly understood. A 2-year field experiment was conducted with three treatments: control (no fertilizer or biochar application), chemical fertilizer (BC0) and biochar plus chemical fertilizer application (BC1) to analyze greenhouse gas (GHG) fluxes, soil organic carbon (SOC) content, as well as the abundance and community structure of methanogens and methanotrophs in a vegetable–rice rotation. Biochar addition (BC1) did not affect the yield, or the emission of total CH4 or nitrous oxide (N2O) but significantly increased carbon dioxide (CO2) emission as compared to BC0 in the vegetable season. Rice yield in BC1 was 14.1 % higher than in the control but was lower than in BC0 because of lower available nutrients in BC1 than in BC0. During the rice season, cumulative CH4 emission under BC1 was increased by 2.65 times as compared with BC0 (P

Despite numerous studies of the effects of biochar amendments on soil greenhouse gas (GHG) emissions in recent years, the intrinsic temperature sensitivity of GHG emissions in biochar-amended soils is still not clear. In order to investigate the effects of biochar on the thermal activation of GHG emissions, the GHG emissions and their activation energies (Ea) were analyzed in a rice-lettuce rotation microcosm experiment. The experiment had five treatments: control (CK), chemical fertilizers (NPK), and three biochar application rates that are equivalent to 10 Mg ha−1 biochar (BC10), 20 Mg ha−1 biochar (BC20) and 40 Mg ha−1 biochar (BC40). The study showed that biochar treatments reduced CO2 and N2O emissions by lowering their Ea compared with the NPK treatment in the rice cultivation season. The biochar amendment treatments significantly reduced N2O cumulative emissions by 55.2–72.9% compared with the NPK treatment in the lettuce cultivation season largely due to the thermally deactivated impact of soil temperature on N2O emissions. Microbial biomass carbon was increased in the lower rates of biochar amendment in both crop cultivation seasons. These findings suggest that biochar amendment of soil has the potential to decrease the positive and increase the negative Ea of GHG emissions, with the implication of mitigating GHG emissions from cropland soils that would otherwise be increased by applying chemical fertilizers in the context of rising global temperature. Production of biochar from agricultural wastes, which is a method of cleaner production, and its application to the soil shows its potential for reducing GHG emissions by changing the thermal activation of the emissions during rice–lettuce crop rotation.

The effects of different straw and biochar applications on the carbon balance of a farmland ecosystem were studied under a rape-maize rotation planting system. The study explored impact of straw and biochar addition on soil carbon sequestration. A field experiment was carried out at the National Monitor Station of Soil Fertility and Fertilizer Efficiency of Purple Soils (Chongqing, China). Five treatments, i.e., control (CK, no organic material), straw only (CS), straw and microorganism (CSD), half straw and half biochar (CSBC), and biochar only (BC), were applied.

In this study the effects of tillage methods (rice-winter paddy field conventional farming, CF; rice-winter paddy field combing ridge with no-tillage, RNT1; rice-wheat or rape combing ridge with no-tillage, RNT2; rice-wheat or rape conventional paddy-upland rotation tillage, CR) on purple soil profile of different forms of inorganic phosphorus distribution characteristics were investigated in a long-term experimental site established in 1990, Chongqing City, China. The results showed that compared to the status before the experiment, the total phosphorus, available phosphorus and various morphologies of inorganic phosphorus all increased to a certain degree in the soils with different long-term tillage treatments,and the contents of different forms of inorganic phosphorus in soil size ranked as RNT2CFCRRNT1. Except that the contents of Fe-P in the lower layer were higher than those in the upper layer, contents of Ca

The aim of this work is to understand the effects of straw and biochar return in soil on the content, distribution, stability, and relative contribution rate of organic carbon for soil aggregates, which could be used to better understanding the stability of the soil carbon pool and the protection mechanisms under straw and biochar return. In this study, a field experiment was conducted to study the effects of straw and biochar return on soil aggregates and carbon sequestration characteristics in a rape-maize rotation planting system. Five treatments, including a control (no organic material added, CK), straw (CS), straw and microorganism (CSD), Biochar (BC), half straw and half biochar (CSBC), were used. The results indicated that ① Straw and biochar could improve the content of soil organic carbon, and the BC and CSBC treatments increased it by 16.88-17.37 g·kg

In order to better understand the effect of reduced phosphorus fertilizer and combining organic fertilizers on phosphorus loss of purple soil sloping field, three rainfall-runoff events were monitored using field runoff observation method in the purple soil sloping field in 2014. There were six treatments in this research, including optimized fertilization (P), optimized fertilization+pig manure application (MP), optimized fertilization+straw return (SP), optimized fertilization which was reduced by 20%+pig manure application (MDP), optimized fertilization which was reduced by 20%+straw return (SDP), without phosphate (P0). The results indicated that the interflow was the main pathway of runoff for purple soil sloping field. The average contents of total phosphorus (TP) and the phosphorus loss load of overland flow were all much higher than those of the interflow. The overland flow was the main pathway of the phosphorus loss load for purple soil sloping field. Reduced phosphorus fertilizer and combining organic fertilizers had a significant reduction effect on phosphorus loss of purple soil sloping field. Compared with the treatment P, the average content of total phosphorus on SDP was reduced by 57% and that on MDP was reduced by 48% in the storm rainfall. Combining straw was better than pig manure. The average contents of the phosphorus loss load of typical rainfall changed between 0.01 and 0.26 kg·hm

With the increasingly serious impacts of NOx on environment, measures of controlling NOx are extremely necessary. Reburning technology has become a proven and effective method to control the emissions of NOx. In this paper, CFD software has been used to simulate the reburning process of South American coal (SAm) so as to study the effect of the reburning on the combustion in the furnace and NOx reduction. The result shows that, SAm reburning can reduce NOx emissions effectively, and removal rate of NOx reaches 50.63% with respect to the conventional combustion.

Flue gas of boiler is a kind of great potential waste heat resource. Relatively high temperature of exhaust has caused a vast waste of energy and serious environmental thermal pollutions. To make a full and reasonable use of the heat resource, a simplified single-tube heat exchanger is introduced in this paper. Dry air and wet air with different temperatures transfer heat with flue gas in the same model. And the results show that heat near the inner wall exchanges more violently than any other space in the heater. For dry air, the higher temperature of the air enters into the heater, the lower heat transfer effect of the heater. Heat exchange effect of the wet air with 0.03 mole fraction of water is more higher than that of dry air in this model.

In low-temperature SCR, corn straws pyrolysis carbon (CS) was prepared as a catalyst support and activated carbon (AC) was a comparison. Manganese (7 wt.%) was loaded respectively on this two supports (Mn/AC and Mn/CS). In 50°C~300°C SCR experiment, the highest NO conversion by using CS is 36.6 Vol.% at 300°C, while AC 37.9 Vol.% at 200°C. After loaded the manganese element, NO conversion increases with the temperature. At 300°C, Mn/AC has the highest NO conversion (81.9 Vol.%), while Mn/AC is 65.3 Vol.%. The sulfur resistance performance test shows that NO conversion decreases with the increasing of SO2 concentration. In the 400ppm SO2 fuel gas at 300°C, using Mn/CS, NO conversion reduces 16.7 Vol.%, however, using Mn/AC, it reduces 22.6 Vol.%. It is promising to apply biomass pyrolysis carbon modified catalyst.

Spiral tube exchanger is one of the most important heat transfer devices among the electric water boilers. In this paper, CFD software is introduced to simulate the process of the flow of the spiral tube exchanger. Cases with different inlet velocities of the cold water have been conducted and results show that, temperature increment of the cold water reaches 38.87 K, 20.21 K and 12.12 K with the inlet velocity of the cold water set as 0.05 m/s, 0.09 m/s and 0.13 m/s respectively.

In this paper, a tube electric furnace is used to process the co-combustion of biomass and crude oil in air atmosphere, the influence of the biomass mass fraction and the temperature on NO and SO2 emissions are analysed. Research shows that with the increasing addition ratio of biomass to crude oil, the amount of NO in per unit heat reduces. This tendency is more apparent at high temperatures. Compared with crude oil, the NO emission of 20% biomass mass fraction at 1100°C is reduced by 25.8% while 19.02% at 700°C. SO2 emission in per unit heat decreases with the increasing biomass mass fraction. This tendency is more apparent at low temperatures. Compared with crude oil The generation of SO2 of 20% biomass mass fraction can reduce 91.5% at 700°C while 36.7% at 1100°C.

The revamping project of turning coal-burning boiler into gas-fired boiler for urban heat supply in Tianjin causes high vapor content in flue gas, which has great influences on the day lighting of surrounding buildings. In this paper, CFD software is introduced to simulate the distributions of NOx, SO2 and vapor in space after leaving the chimney and their impacts on surrounding buildings with the effect of the atmosphere. Result shows that flue gas discharged from the chimney with the height of 30 m has significant impacts on the surrounding buildings.

Experiments of biomass char combustion in 10%O2/90%CO2, 21%O2/79%CO2, 10%O2/90%N2 and 21%O2/79%N2 atmospheres were performed in the fixed-bed reactor system at the temperature of 800°C-1200°C. The results show that at the same temperature, NO emission is higher in O2/N2 atmosphere than that in O2/CO2 atmosphere. The higher the O2 concentration is, the higher the NO yield is. As the temperature rises, the NO yield rises at first and then decreases at the same O2 concentration and atmosphere.

The method of selective catalytic reduction (SCR) to removal NOx is very mature. However, its initial investment and operation cost are still high, which limits the development of SCR technology. Low temperature SCR catalysts can significantly reduce the cost. Catalyst active component and its carrier is the key to the efficiency of denitration. This paper summarizes the research progress of noble metal catalyst of low temperature SCR.

Low temperature SCR method has caused concern for the scholars in recent years. This SCR unit can be installed downstream of the desulfurization and particulate control devices, which is conducive to match the existing boiler system. It can relief the poisoning and blocking of SO2 and dust, so as to extend the life of catalyst. This paper summarizes the research progress of molecular sieve catalyst of low temperature SCR.

The method of selective catalytic reduction (SCR) is now one of the mature applications of NOx removal technology, which has the higher denitration rate, less secondary pollution and lower cost. However, the active temperature of traditional SCR catalyst is usually in the temperature range of 300-400°C. This kind of installation leads to the reduction of catalyst activity, and the shortage of working life. The development of efficient and stable performance of catalyst at low temperature has become a key point in the research of SCR.This paper reviews the research progress of carbon catalyst of low temperature SCR. In addition, the future research work is discussed.

Eutrophication in the Three Gorges Reservoir has become a serious issue, and phosphorus (P) is the nutrient thought to be primarily responsible although there are few studies about P loss from the mostly sloping farmlands of the area. This work investigated the amounts and forms of P loss from 9 farmlands with the slopes of 4°, 9°, and 17° in a small watershed, Wangjiagou in Fuling District, Chongqing of China. The slope of the relationship between runoff and rainfall increased with field slope; i.e. , there was a significant interaction between the effects of rainfall and field slope on water export. For sediment export by surface runoff, there was no interaction between field slope and rainfall, and the intercept of the relationship between rainfall and sediment loss was significantly different for the 3 slopes. The main P loss was from sediments, regardless of slope. In the runoff water, particulate P was the largest P fraction, and its loss was greatest from the steepest land and least from the flattest. The release of total P and available P from sediments followed the same trend. The P loss during May to July in Wangjiagou was more than 60% of the annual total.

Precise control of the inclination and azimuth is of great significance for the efficient drilling of dynamic point-the-bit rotary steerable drilling tool. The design details of offsetting steerable mechanism for rotary steerable drilling tool based on inner and outer double eccentric rings are demonstrated in the paper. While drilling, the tool collar rotates and passes the torque and drilling pressure to the drill bit efficiently, and the stable platform mounted inside the collar is maintained geostationary by rotating it counter to collar rotation at the same frequency. And an offsetting steerable mechanism in the stable platform provides selectively and axially inclination to the collar by adjusting the relative position of the inner to the outer double eccentric rings. It is shown that the maximum oriented inclination can be reached as 1.0 degree flexibly for the presented structure.

The effect of different tillage systems on the size distribution of aggregates and organic carbon distribution and storage in different size aggregates in a Hydragric Anthrosol were studied in a long-term experiment in Chongqing, China. The experiment included three tillage treatments: conventional tillage with rotation of rice and winter fallow (CT-r) system, no-till and ridge culture with rotation of rice and rape (RT-rr) system, and conventional tillage with rotation of rice and rape (CT-rr) system. The results showed that the aggregates 0.02–0.25 mm in diameter accounted for the largest portion in each soil layer under all treatments. Compared with the CT-r system, in the 0–10 cm layer, the amount of aggregates > 0.02 mm was larger under the RT-rr system, but smaller under the CT-rr system. In the 0–20 cm layer, the organic carbon content of all fractions of aggregates was the highest under the RT-rr system and lowest under the CT-rr system. The total organic carbon content showed a positive linear relationship with the amount of aggregates with diameter ranging from 0.25 to 2 mm. The storage of organic carbon in all fractions of aggregates under the RT-rr system was higher than that under the CT-r system in the 0–20 cm layer, but in the 0–60 cm soil layer, there was no distinct difference. Under the CT-rr system, the storage of organic carbon in all fractions of aggregates was lower than that under the CT-r system; most of the newly lost organic carbon was from the aggregates 0.002–0.02 and 0.02–0.25 mm in diameter.