Manure replacing synthetic fertilizer improves crop yield sustainability and reduces carbon footprint under winter wheat-summer maize cropping system.

Manure replacing synthetic fertilizer is a viable practice to ensure crop yield and increase soil organic carbon (SOC), but its impact on greenhouse gas (GHG) emissions is inconsistent, thus remains its effect on CF unclear. In this study, a 7-year field experiment was conducted to assess the impact of replacing synthetic fertilizer with manure on crop productivity, SOC sequestration, GHG emissions and crop CF under winter wheat-summer maize cropping system. Five treatments were involved: synthetic nitrogen, phosphorus, and potassium fertilizer (NPK) and 25%, 50%, 75%, and 100% of manure replacing synthetic N (25%M, 50%M, 75%M, and 100%M). Compared with NPK treatment, 25%M and 50%M treatments maintained annual yield (winter wheat plus summer maize) and sustainable yield index (SYI), but 75%M and 100%M treatments significantly decreased annual yield, and 100%M treatment also significantly reduced annual SYI. The SOC content exhibited a significant increasing trend over years in all treatments. After 7 years, SOC storage in manure treatments increased by 3.06-11.82 Mg ha-1 relative to NPK treatment. Manure treatments reduced annual GHG emissions by 14%-60% over NPK treatment. The CF of the cropping system ranged from 0.16 to 0.39 kg CO2 eq kg-1 of grain without considering SOC sequestration, in which the CF of manure treatments lowered by 18%-58% relative to NPK treatment. When SOC sequestration was involved in, the CF varied from -0.39 to 0.37 kg CO2 eq kg-1 of grain, manure treatments significantly reduced the CF by 22%-208% over NPK treatment. It was concluded that replacing 50% of synthetic fertilizer with manure was a sound option for achieving high crop yield and SYI but low CF under the tested cropping system.

Estimating changes of forest carbon storage in China for 70 years (1949-2018).

In the realm of forest resource inventory and monitoring, stand-level biomass carbon models are especially crucial. In China, their importance is underscored as they form the bedrock for estimating national and international forest carbon storage. This study, based on the data from 52,700 permanent plots in the 9th National Forest Inventory (NFI) of China, was directed towards developing these models. After computing biomass and carbon storage per hectare using specific tree models for 34 species groups, we devised robust volume-derived biomass and carbon storage models for 20 forest types. The application of these models and historical data reveals notably a decline in China's forest carbon storage to 4.90Pg by the late 1970s due to aggressive forest exploitation. However, subsequent conservation and afforestation campaigns have affected a recovery, culminating in a storage of 8.69Pg by the 9th NFI. Over the past 40 years, China's forest carbon storage has surged by 3.79Pg, split between natural forests (2.25Pg) and planted forests (1.54Pg). In benchmarking against three pre-existing models, we discerned discernible biases, underscoring the need for larger modeling sample sizes. Overall, our models stand as a monumental stride in accurately gauging forest carbon storage fluctuations in China, both regionally and nationally.

Prokaryotic expression of the V protein of the peste des petits ruminants virus and development of an indirect ELISA.

In this study, we recombinantly expressed the V protein of the peste des petits ruminants virus (PPRV) and evaluated its diagnostic value for PPRV infection using an indirect ELISA (i-ELISA). The optimal concentration of the coated antigen of V protein was 15 ng/well at a serum dilution of 1:400, and the optimal positive threshold value was 0.233. A cross-reactivity assay showed that the V protein-based i-ELISA was specific to PPRV with consistent reproducibility and showed a specificity of 82.6% and a sensitivity of 100% with a virus neutralization test. Using the recombinant V protein as an antigen in ELISA is useful for seroepidemiological studies of PPRV infections.

The First Genomic Analysis of Visna/Maedi Virus Isolates in China.

Visna/Maedi virus (VMV) is a neglected pathogen that damages sheep and goats' nervous and respiratory systems. The virus was discovered 80 years ago and has been endemic in China for nearly four decades; nevertheless, there is little information regarding Chinese isolates' genotypes and genomic characteristics. In this study, the proviral DNA of strains isolated in 1985 and 1994 were extracted, and the proviral DNA was subjected to Illumina sequencing combined with Sanger sequencing of poor coverage regions. The results showed that the two isolates were clustered with genotype A2 and shared 78.3%-89.1% similarity to reference VMV genome sequences, with the highest similarity (88.7%-89.1%) to the USA strain USMARC-200212120-r (accession no. MT993908.1) and lowest similarity (78.3%-78.5%) to the Italian strain SRLV009 (accession no. MG554409.1). A maximum-likelihood tree showed that the Chinese VMV strains and the USA strain 1150 (accession no. MH916859.1) comprise a monophyletic group with a short tree branch. Our data filled the gap in genomic analysis and viral evolution in Chinese VMV strains, and would be benefit China's source-tracing and eradication program development in China.

[Effects of Stalk Incorporation on Soil Carbon Sequestration, Nitrous Oxide Emissions, and Global Warming Potential of a Winter Wheat-Summer Maize Field in Guanzhong Plain].

The net greenhouse gas emissions from upland soils, as indicated by global warming potential (GWP), mainly depend on the soil carbon sequestration and nitrous oxide (N2O) emissions. The annual changes in surface (0-20 cm) soil organic carbon (SOC) content from 2010 to 2017 and the N2O emissions from 2014 to 2017 were measured within a long-term fertilization experiment. The objective was to quantify the effect of stalk incorporation on the soil carbon sequestration, annual N2O emissions, and GWP of a winter wheat-summer maize field in the Guanzhong Plain. The field experiment included three treatments:conventional fertilization (CF), conventional fertilization plus maize stalks (CFS), and an unfertilized control (CK). The CF and CFS treatments received the same amount of urea per year, with nitrogen (N) input at 165 kg·hm-2 and 188 kg·hm-2 in the winter wheat season and summer maize season, respectively. The CF treatment retained the stubbles (about 10 cm above ground) when harvesting the winter wheat and summer maize crops. The CFS treatment retained the same wheat stubbles and all maize stalks (containing approximately 40 kg·hm-2 of N). The CK treatment was unfertilized throughout the year, with the stubble management the same as that in the CF treatment. The results showed that the CK treatment displayed few changes in SOC content and low N2O emissions, with GWP varying from 0.04 to 0.11 t·(hm2·a)-1. The SOC contents in the CF and CFS treatments increased linearly with the fertilization years (P<0.001), and their SOC sequestration rates were 0.69 t·(hm2·a)-1 and 0.97 t·(hm2·a)-1, respectively. The N2O emissions from the CF and CFS treatments varied from 1.65 to 5.36 kg·(hm2·a)-1 and from 3.08 to 7.73 kg·(hm2·a)-1, respectively. The annual N2O emissions from the CFS treatment were 43%-94% higher than those from the CF treatment, whereas the difference was only significant between 2015 and 2016 (P<0.05). The GWP of the CF and CFS treatments varied from -1.95 to -0.28 t·(hm2·a)-1 and from -2.59 to -0.35 t·(hm2·a)-1, respectively. The cumulative GWP of the CFS treatment was 42% lower than that of the CF treatment between 2014 and 2017. In summary, the studied winter wheat-summer maize field acted as a sink of greenhouse gases under the conventional fertilization regime. The stalk incorporation further favored greenhouse gas mitigation despite the trade-offs between SOC sequestration and N2O emissions.

Retrospective genomic analysis of the first Lumpy skin disease virus outbreak in China (2019).

Lumpy skin disease caused by Lumpy skin disease virus (LSDV) is a severe systemic disease affecting cattle and other ruminants. Lumpy skin disease was first reported in northwest China in August 2019 and has severely threatened the cattle breeding industry in China. However, there have been limited genomic studies of LSDV from the first outbreak and its subsequent epidemics. This study aims to characterize the comparative genomic evolution of the LSDV strain from the first outbreak in China. The etiological agent was isolated in a Madin-Darby bovine kidney cell culture and subsequently identified by PCR and Sanger sequencing of six selected genes. The genome sequence was determined using Illumina sequencing and analyzed through genome alignment and phylogenetic tree. The results showed that all six genes were successfully amplified and genetically clustered into LSDV. The virus presented the highest homology to strain China/GD01/2020, which shared 100% identities among 150 open reading frames (ORFs), and 97.1-99.7% identities among additional 6 ORFs. Bayesian inference tree analysis revealed that the virus shared a common ancestor with LSDV strains from China and Vietnam. The study provides an additional genomic data for LSDV tracking and control in China and neighboring countries.

Prevalence of Hepatitis E Virus (HEV) in Feral and Farmed Wild Boars in Xinjiang, Northwest China.

Hepatitis E virus (HEV) causes infections in humans and a wide range of animal hosts. Wild boar is an important natural reservoir of HEV genotypes 3−6 (HEV-3−HEV-6), but comparative analysis of HEV infections in both feral and farmed wild boars remains limited. In this study, samples from 599 wild boars were collected during 2017−2020, including 121 feral wild boars (collected 121 fecal, 121 serum, and 89 liver samples) and 478 farmed wild boars (collected 478 fecal and 478 serum samples). The presence of anti-HEV IgG antibodies were detected by the HEV-IgG enzyme-linked immunosorbent assay (ELISA) kit. HEV RNA was detected by reverse transcription polymerase chain reaction (RT-PCR), targeting the partial ORF1 genes from fecal and liver samples, and the obtained genes were further genotyped by phylogenetic analysis. The results showed that 76.2% (95% CI 72.1−79.9) of farmed wild boars tested anti-HEV IgG seropositive, higher than that in feral wild boars (42.1%, 95% CI 33.2−51.5, p < 0.001). HEV seropositivity increased with age. Wild boar HEV infection presented a significant geographical difference (p < 0.001), but not between sex (p = 0.656) and age (p = 0.347). HEV RNA in fecal samples was detected in 13 (2.2%, 95% CI 1.2−3.7) out of 599 wild boars: 0.8% (95% CI 0.0−4.5, 1/121) of feral wild boars and 2.5% (95% CI 1.3−4.3, 12/478) of farmed wild boars. Phylogenetic analysis showed that all these viruses belonged to genotype HEV-4, and further grouped into sub-genotypes HEV-4a, HEV-4d, and HEV-4h, of which HEV-4a was first discovered in the wild boar populations in China. Our results suggested that farms could be a setting for amplification of HEV. The risk of HEV zoonotic transmission via rearing and consumption of farmed wild boars should be further assessed.

Bipolar electrode ratiometric electrochemiluminescence biosensing analysis based on boron nitride quantum dots and biological release system.

In this article, we developed a novel ECL ratiometry on a closed bipolar electrode (BPE) for the sensitively and accurately detection of miRNA-21. High quantum yield and low toxicity BNQDs was synthesized and coated at BPE cathode as an ECL emitter, while the anode of BPE was calibrated via another ECL material, Ir(df-ppy)2(pic) (Firpic). The electron neutrality at both ends of the BPE electrically coupled the reactions on each pole of the BPE. Therefore, one electrochemical sensing reaction could be quantified at one end of the BPE. By the hybridization of target miRNA-21 and hairpin, the glucose blocked in MSNs by the hairpin was released and reacted with glucose oxidase (GOD) to generate H2O2, thereby reducing the ECL signal of the cathode BNQDs/K2S2O8 system and promoting ECL signal of anode Firpic/TPrA. Further, the G-quadruplex formed by unreacted hairpin bases consumed H2O2, which not only recovered the ECL of BNQDs, but also further improved the ECL emission of Firpic. Therefore, the concentration of miRNA-21 could be measured by the ECL ratio of BNQDs and Firpic. The data showed that the detection limit was 10-15 M (S/N = 3) with the linear range of 10-15 M to 10-9 M. The strategy of the BPE-ECL ratio method based on BNQDs showed a good prospect in clinical application.

Partial-film mulch returns the same gains in yield and water use efficiency as full-film mulch with reduced cost and lower pollution: a meta-analysis.

BACKGROUND: Plastic film mulch is widely used to improve crop yield and water use efficiency (WUE, yield per unit evapotranspiration) in semi-arid regions. It is commonly applied as partial-film mulch (PM: at least 50% soil cover) or full-film mulch (FM: complete soil cover). The PM has lower economic and environmental cost; hence it would be a superior technology provided it delivers similar gains in yield and WUE in relation to FM. RESULTS: To solve contradictory results from individual studies, we compared FM and PM in a meta-analysis of 100 studies with 1881 comparisons (685 for wheat; 1196 for maize). Compared with bare ground, FM and PM both increased yield of wheat (20-26%) and maize (37-52%), and WUE of wheat (16-20%) and maize (38-48%), with statistically undistinguishable differences between PM and FM. The increases in crop yield and WUE were stronger at elevation > 1000 m, with annual precipitation<400 mm, and on loess soil, especially for maize. CONCLUSIONS: We concluded that partial-film mulch could replace full-film mulch to return similar yield and WUE improvement, with reduced cost and environmental pollution. © 2021 Society of Chemical Industry.

Long-term fertilization affects functional soil organic carbon protection mechanisms in a profile of Chinese loess plateau soil.

Crop productivity and soil health are limited by organic carbon (OC), however, the variations in the mechanisms of SOC preservation in a complete soil profile subjected to long-term fertilization remains unclear. The objective of the study was to examined the content and profile distribution of the distinctive SOC protection mechanisms on a complete profile (0-100 cm) of Eumorthic Anthrosols in Northwest China after 23 years of chemical and manure fertilization. The soil was fractionated by combined physical-chemical and density floatation techniques. Throughout the profile, significant variations were observed among fractions. In the topsoil (0-20 and 20-40 cm), mineral coupling with the fertilization of manure (MNPK) enhanced total SOC content and recorded for 29% of SOC in the 0-20 and 20-40 cm layers. Moreover, MNPK increased the SOC content of the unprotected cPOC fraction by 60.9% and 61.5% in the 0-20 and 20-40 cm layer, while SOC content was low in the subsoil layers (40-60, 60-80 and 80-100 cm, respectively) compared with the control (C). The highest OC under MNPK in physically protected micro-aggregates (µagg) (6.36 and 6.06 g C kg-1), and occluded particulate organic carbon (iPOC) (1.41 and 1.29 g C kg-1) was found in the topsoil layers. The unprotected cPOC fraction was the greatest C accumulating fraction in the topsoil layers, followed by µagg and H-µSilt fractions in the soil profile, implying that these fractions were the most sensitive to the fertilization treatments. Overall, the unprotected, physically protected, and physico-chemically protected fractions were the dominant fractions for the sequestration of carbon across fertilization treatments and soil layers.

Seroprevalence of Five Zoonotic Pathogens in Wild Ruminants in Xinjiang, Northwest China.

Wild ruminants are at risk for zoonotic pathogen infection as a result of interactions with domestic animals and humans. One way to assess the level of a wild ruminant disease in a population is to determine the seroprevalence of the pathogen of interest. The objective of this study was to determine the seroprevalence of five zoonotic pathogens in wild ruminants in Xinjiang, Northwest China. In 2009 and 2011-2015, 258 wild ruminant sera samples were collected from various species. Samples were obtained from 30 Siberian ibexes, 94 goitered gazelles, 6 Tibetan antelopes, 32 argali sheep, 16 roe deer, 20 blue sheep, 56 red deer, and 4 wild yaks, in 10 regions of Xinjiang. Samples were tested using antibodies against Brucella spp., Chlamydophila abortus, Coxiella burnetii, Toxoplasma gondii, and West Nile virus. Seropositivity was detected for all five pathogens, with detection rates of Brucella spp., C. abortus, C. burnetii, T. gondii, and West Nile virus of 2.3% (95% confidence interval [CI], 0.5-4.2%), 6.2% (95% CI, 3.3-9.1%), 7.8% (95% CI, 4.5-11.0%), 2.3% (95% CI, 0.5-4.2%), and 0.8% (95% CI, 0-1.8%), respectively. The level of pathogens differed for different species and different regions. The results indicate that seropositivity to zoonotic pathogens is common among wild ruminants in Xinjiang, Northwest China, with C. burnetii and C. abortus detected at the highest levels. This study provides a baseline for future assessment of spillover events.

Effect of organic amendments on yield-scaled N2O emissions from winter wheat-summer maize cropping systems in Northwest China.

The effect of dairy manure amendments to agricultural soil on the yield-scaled nitrous oxide (N2O) emissions remains unclear. We hypothesize that an optimum ratio of dairy manure to synthetic fertilizers leads to large nitrogen use efficiency (NUE) and small yield-scaled N2O emissions. The aims of this study were to (1) quantify the variations in the crop yields and N2O emissions from winter wheat-summer maize cropping systems in Northwest China, (2) determine the responses of the NUE and yield-scaled N2O emission to the ratio of organic materials to synthetic fertilizers, and (3) evaluate the relationship between the NUE and yield-scaled N2O emissions. Field measurements were conducted within long- and short-term fertilization experiments between the years of 2014 and 2016. Treatments included synthetic fertilizers, synthetic fertilizers plus crop residues, and synthetic fertilizers plus dairy manure at both sites. The annual grain yields and N2O emissions varied from 13.3 to 18.0 Mg ha-1 and from 1.3 to 3.6 kg N ha-1, respectively, across the treatments. The yield-scaled N2O emissions related negatively to the NUE, suggesting that agronomic aims of improving NUE are an effective approach to mitigate N2O emissions. The ratio of organic materials to synthetic fertilizers was not a significant limit on the NUE and yield-scaled N2O emissions. We conclude that organic amendments appeared to play a minor influence on the promotion of the NUE and N2O mitigation.

Crop yield and N2O emission affected by long-term organic manure substitution fertilizer under winter wheat-summer maize cropping system.

Application of organic manure combined with synthetic fertilizer can maintain crop yield and improve soil fertility, but the long-term effects of substituting different proportions of synthetic fertilizers with organic manure on N2O emission remain unclear. In this study, field experiments and DNDC model simulations were used to study the long-term effects of substituting synthetic fertilizers with organic manure on crop yield and N2O emission. The field experiment was conducted at Guanzhong Plain, northern China, under a wheat-maize cropping system. Six treatments were included: no fertilization (CK); synthetic nitrogen (N), phosphorus (P) and potassium (K) fertilizers (NPK); and 25%, 50%, 75% and 100% of the synthetic N substituted by dairy manure (25%M, 50%M, 75%M, and 100%M), respectively. The DNDC model was calibrated using the field data from the NPK treatment from 2014 to 2017 and was validated for the other treatments. The results showed that the DNDC model can successfully simulate the crop yield (e.g. nRMSE < 5%) and annual N2O emission (nRMSE < 20%). In addition, a 30-year simulation found that organic manure substitution treatments could maintain wheat yield well, and the yield variation between different years was small. However, relative to the NPK treatment, the maize yields for the first 6 and 7 years were lower under 50%M and 75%M, and under 100%M maize yields were reduced for the first 15 years. The long-term simulation showed that N2O emission of fertilized treatment had an increasing trend over time, especially the 75%M treatment where the N2O emission was higher than that of NPK treatment after 25 years of fertilization. The annual mean N2O emission under different treatments was, in decreasing order, NPK > 25%M > 50%M > 75%M > 100%M > CK. The yield-scale N2O emission and emission factor were highest for the NPK treatment. Considering crop yield, yield stability and N2O emission, substitution of 25% synthetic fertilizer by organic manure can simultaneously ensure crop productivity and environmental protection under the tested environment.

Does animal manure application improve soil aggregation? Insights from nine long-term fertilization experiments.

Manure application is widely recognized as a method of improving soil structure and soil fertility due to additional organic matter and nutrient inputs. However, the salinity of animal manure may have a detrimental effect on soil aggregation. The objective of this study was to determine the effects of long-term animal manure application on soil aggregation, binding agents (soil organic carbon, SOC and glomalin-related soil protein, GRSP), and dispersing agents (e.g., Na+) and their relationships based on nine long-term fertilization experiments (12 to 39 yr) across China. The two red soil experiments (Qiyang, QY and Jinxian, JX) and one paddy soil experiment in Jinxian (JX-P) were conducted in southern China (precipitation above 1200 mm yr-1), whereas the other six experiments were established in semi-humid or arid regions in China with precipitation in the range of 500-900 mm yr-1. Each experiment included three treatments as follows: no fertilization (Control), inorganic fertilizer (NP or NPK), and a combination of inorganic fertilizer and animal manure (NPM or NPKM). Long-term animal manure application not only significantly increased the biological binding agents (i.e., SOC and GRSP) in the nine experiments but also considerably increased the dispersing agents (i.e., exchangeable Na+) (P < 0.05), except for the paddy soil experiment. Consequently, soil aggregate stability increased after animal manure application in three experimental sites in southern China but not in the experimental sites in northern China. Aggregate stability had a positive relationship with SOC and GRSP in the experimental sites in southern China (P < 0.01) but a negative relationship with exchangeable Na+ in the experimental sites in northern China (P < 0.05). The Na+ accumulation in soils was negatively related to mean annual precipitation (P < 0.001). Our study demonstrates that the long-term application of animal manure may degrade soil structure via the Na+ accumulation.

[Effect of Long-term Dairy Manure Amendment on N2O and NO Emissions from Summer Maize-Winter Wheat Cropping Systems].

Annual nitrous oxide (N2O) and nitric oxide (NO) emissions were measured within a 27 year fertilization experiment in Guanzhong Plain. Gas samples were collected using static chambers from June 2017 to June 2018. The primary objectives of this study were to quantify the variations in N2O and NO emissions and evaluate the effect of manure amendment on gas losses. Three treatments were set up in the field using a completely random block design. The control treatment (CK) remained unfertilized throughout the year. The synthetic fertilizers (NPK) and NPK plus dairy manure (NPKM) treatments received an annual nitrogen (N) input at a rate of 353 kg·hm-2. In the summer maize season, the NPK and NPKM treatments received urea as a N source at 188 kg·hm-2. In the winter wheat season, the NPK treatments received urea at 165 kg·hm-2. The NPKM treatment received the same amount of N as the NPK treatment but with 30% from urea and 70% from dairy manure. The results showed that N2O and NO emissions from the CK treatment were consistently low during the experimental period. Large emission peaks were captured in the NPK and NPKM treatments, mostly responding to fertilizer application and irrigation. The largest N2O and NO peaks were up to 103.0 g·(hm2·d)-1 and 71.0 g·(hm2·d)-1, respectively, and both occurred in the NPKM treatment during the summer maize season. The NO/N2O ratio was negatively related to soil water-filled pore space (P<0.01) at soil temperatures above 20℃ for the NPK and NPKM treatments, indicating the regulatory effect of soil temperature and water content on gas fluxes. Annual N2O emissions from the CK, NPK, and NPKM treatments were 0.21 kg·hm-2, 2.32 kg·hm-2, and 2.15 kg·hm-2, respectively, with a non-significant difference between the NPK and NPKM treatments (P=0.74). Annual NO emissions from the CK, NPK, and NPKM treatments were 0.23 kg·hm-2, 0.80 kg·hm-2, and 1.46 kg·hm-2, respectively, with a significant difference between the NPK and NPKM treatments (P<0.05). We concluded that long-term dairy manure amendment did not influence N2O emissions but increased NO emissions.

[Effect of Long-term Organic Amendments on Nitric Oxide Emissions from the Summer Maize-Winter Wheat Cropping System in Guanzhong Plain].

Agricultural soil is a significant source of nitric oxide (NO). The primary aim of this study was to quantify the effect of long-term organic amendments on NO emissions from the summer maize-winter wheat cropping system in Guanzhong Plain. NO fluxes were regularly measured by the static chamber method for one year (June 2016 to June 2017). Field experiments included four fertilizer treatments that commenced in 1990. The control (CK, 0 kg·hm-2) treatment was unfertilized throughout the years. The fertilized treatments were synthetic fertilizer (NPK, 165 kg·hm-2), synthetic fertilizer plus maize stalk (NPKS, (165+40) kg·hm-2), and synthetic fertilizer plus dairy manure (NPKM, (50+115) kg·hm-2) during the winter wheat season. They were fertilized with synthetic fertilizer (188 kg·hm-2) during the summer maize season. The results showed small NO emission [<12.2 g·(hm2·d)-1] from the CK treatment within the experimental period. Large NO fluxes [up to 112.0 g·(hm2·d)-1 in NPK treatment] were captured following sowing and fertilization during the summer maize season and following fertilization during the winter wheat season for all fertilized treatments. Annual NO emissions and direct emission factors ranged from 0.13 to 0.57 kg·hm-2 and from 0.04% to 0.12%, respectively. Annual NO emissions from the NPKS and NPKM treatments were 17.6% lower and 68.0% (P<0.05) larger than those from the NPK treatment, respectively. Seasonal NO emissions from the NPKS and NPKM treatments were 41.1%-60.0% (P<0.05) lower than those from the NPK treatment during the winter wheat season, indicating that organic amendments reduced NO emissions. Seasonal NO emissions from the NPKS and NPKM treatments were 25.2%-292.1% (P<0.05) larger than that from the NPK treatment during the summer maize season, mostly due to the positive effect of soil organic matter content on NO emissions.

[Effect of Organic Manure Substitution of Synthetic Nitrogen on Crop Yield and N2O Emission in the Winter Wheat-Summer Maize Rotation System].

Controlling agricultural greenhouse gas emissions, such as N2O, is important in mitigating global climate warming. Through monitoring the dynamics of N2O emission fluxes, we investigated the effect of organic nitrogen (N) substitution of synthetic N on N2O emissions and the yield of winter wheat and summer maize in the Guanzhong Plain of Shaanxi Province, China. The study involved six treatments, consisting of no fertilizer (CK), synthetic N, phosphorus (P), and potassium (K) fertilizers alone (NPK), 75% NPK+25% organic N through manure (25%M), 50% NPK+50% organic N (50%M), 25% NPK+75% organic N (75%M), 100% organic N (100%M). The results showed that the peak value of the N2O emission flux appeared after fertilization, rainfall, and irrigation. In the wheat season, the emission flux of N2O varied from -1.33 to 144.2 µg·(m2·h)-1, with the highest peak value in the NPK treatment. In the maize season, the emission flux of N2O varied from 88.2 to 1800.1 µg·(m2·h)-1, and the 50%M treatment showed the highest peak value. The range in the total amount of N2O emissions from the different treatments in the wheat-maize rotation system was 429.8-2632.1 g·hm-2, and the amount for the treatments decreased in order as follows:50%M > 25%M > NPK > 75%M > 100%M > CK. The yields of wheat, maize, or wheat plus maize were significantly higher in the fertilized treatments compared to the CK. Organic substitution treatments significantly increased wheat yield by 26.1% to 50.0% relative to the NPK treatment. While the maize yield in 50%M and 75%M treatments was similar to that in the NPK treatment, the 25%M and 100%M treatments showed significantly lower yields than with the NPK treatment. The total yield of wheat plus maize varied from 9166 to 17496 kg·hm-2, of which total yield was significantly higher with 50%M and 75%M compared to NPK. Overall, the 75%M treatment is the best measure to guarantee crop yield and to reduce N2O emissions in the wheat-maize rotation system based on a one year study in the Guanzhong plain of Shaanxi Province.

Effect of straw mulch and seeding rate on the harvest index, yield and water use efficiency of winter wheat.

Straw mulching has been used to improve water use efficiency (WUE, yield per unit evapotranspiration) in the Loess Plateau of China, but the seeding rate may need to be adjusted from conventional practice. We tested the three-way interaction between seeding rate, soil management (conventional tillage and straw mulching) and seasons. Wheat yield ranged from 2851 to 6981 kg ha-1 and WUE from 5.3 to 16.2 kg ha-1 mm-1. Generally, soil water storage was higher and soil temperature was lower under straw mulching than under conventional practice. Evapotranspiration was higher under straw mulching. Yield was significantly affected by the interaction between straw mulching and season. Conventional practice showed significantly higher mean harvest index (HI), yield, and WUE than straw mulching in favorable seasons. However, yield was significantly higher under mulching than under conventional tillage in very dry season. Seeding rate had no effect on yield, but low seeding rate increased HI compared to high seeding rate. It is concluded that low seeding rate would be suitable for straw mulching.

Trade-off between soil organic carbon sequestration and nitrous oxide emissions from winter wheat-summer maize rotations: Implications of a 25-year fertilization experiment in Northwestern China.

The primary aims of this study were to (i) quantify the variations in nitrous oxide (N2O) emissions and soil organic carbon (SOC) sequestration rates under winter wheat-summer maize cropping systems in Guanzhong Plain and (ii) evaluate the impact of organic amendments on greenhouse gas mitigation over a long-term period. We measured N2O fluxes during the maize season in 2015 under four fertilizer regimes in a long-term fertilization experiment. Soil was treated with only synthetic fertilizers in the maize season and with synthetic fertilizers, synthetic fertilizers plus crop residues and synthetic fertilizers plus low and high levels of dairy manure in the winter wheat season from 1990. The SOC content (0-20cm) was collected annually at the same site between 1990 and 2015. Synthesis of our measurements and previous observations (between 2000 and 2009) within the investigated agricultural landscape revealed that cumulative N2O emissions increased with the SOC content following natural logarithm models during both the maize and winter wheat seasons (r2>0.77, p<0.001), implying a trade-off between N2O emissions and SOC sequestration. The SOC content increased under all fertilizer regimes, and the dynamics were well fitted by the linear and logistic regression models (r2>0.74, p<0.001), indicating that all the fertilizer treatments in this study sequestered SOC. By applying these regression models, we estimated that the two manure-amended treatments accumulated a negative global warming potential (ranging from -1.9 to -12.9tCO2-equivalentha-1) over the past 25years. However, this benefit would most likely be offset by high N2O emissions at saturated SOC levels before 2020. Our estimates suggest that organic amendments may not be efficient for greenhouse gas mitigation in Guanzhong Plain over a long-term period. We recommend efforts to inhibit N2O production via denitrification as being critical to resolving the conflict between SOC sequestration and N2O emissions.

The seroprevalence of Mycobacterium avium subspecies paratuberculosis in dairy cattle in Xinjiang, Northwest China.

BACKGROUND: Mycobacterium avium subspecies paratuberculosis (MAP) causes chronic, wasting, and progressive enteritis in cattle, bringing significant economic losses in livestock industries. MAP has spread worldwide mainly due to movement of animals. The objective of this study was to determine the MAP seroprevalence in cattle in the Xinjiang Uygur Autonomous Region, Northwest China, and evaluate the difference between intensive farming herds (cattle number in a herd is more than 200, and the cattle cannot have access to pasture) and free-range herds (the cattle are bred by individual households, a herd is defined as the cattle are bred in a village or town in this study). RESULTS: A total of 3157 serum specimens were collected from 42 herds in nine different regions. This included 1481 specimens from 18 intensive farming herds in four regions and 1676 specimens from 24 free-range herds in six regions. Antibody against MAP was tested with commercial ELISA test kits. The results showed that the overall apparent prevalence was 4.8% (95% CI, 4.1 to 5.6%) at animal level, and 50.0% (21/42) at herd level. The apparent prevalence in intensive farming herds and free-range herds were 9.5% (141/1481) and 0.7% (11/1676) at the animal-level, 88.9%(16/18) and 20.8% (5/24) at herd level, respectively, with a significant statistical difference between these two farming modes (p < 0.01). Cattle in intensive farming herds had a relatively higher risk to be infected with MAP than those in free-range herds (RR = 14.4). CONCLUSION: This study demonstrates that apparent prevalence of MAP infection in dairy cattle differs with farming modes at the animal level and herd level, and farming density could be an important risk factor associated with the presence of MAP infected cattle. This study provides important epidemiological data for bovine MAP control in Xinjiang, Northwest China.