Guiding the landscape patterns evolution is the key to mitigating river water quality degradation

Consensus has emerged that landscape pattern evolution significantly impacts the river environment. However, there remains unclear how the landscape pattern evolves possible to achieve a balance between land resource use and water conservation. Thus, simulating future landscape patterns under different scenarios to predict river eutrophication level is critical to propose targeted landscape planning programs and alleviate river water quality degradation. Here, we coupled five water quality parameters (TOC, TN, NO3--N, NH4+-N, TP), collected from October 2020 to September 2021, to construct the river eutrophication index (EI) to assess river water quality. Meanwhile, based on redundancy analysis, patch-generating land use simulation model, and stepwise multiple linear regression model comprehensively analyze the Fengyu River watershed landscape patterns evolution and their impact on river eutrophication. Results indicated that current rivers reach eutrophic levels, and EI reaches 40.7. The landscape patterns explain 88.2 % of river eutrophication variation, while the LPI_Con metric is critical and individually explained 21.5 %. Furthermore, eutrophication in the watershed will increase in 2040 under the natural development (ND) scenario, and the EI will reach 44.4. In contrast, farmland protection (FP) scenarios and environmental protection (EP) scenarios contribute to mitigating eutrophication, the EI values are 38.2 and 38.1, respectively. The results provide a potential mechanistic explanation that river eutrophication is a consequence of unreasonable landscape pattern evolution. Guiding the landscape patterns evolution based on critical driver factors from a planning perspective is conducive to mitigating river water quality degradation.

Enhancing rice production sustainability and resilience via reactivating small water bodies for irrigation and drainage

Rice farming threatens freshwater resources, while also being increasingly vulnerable to drought due to climate change. Rice farming needs to become more sustainable and resilient to climate change by improving irrigation drainage systems. Small water bodies, used to store drainage water and supply irrigation in traditional rice farming systems have gradually been abandoned in recent decades. This has resulted in a higher water footprint (WF) associated with rice farming due to increased freshwater usage and wastewater release, also leaving rice production more vulnerable to extreme weather events. Here, we propose how protecting and reactivating small water bodies for rice irrigation and drainage can decrease rice production WF in China by 30%, save 9% of China's freshwater consumption, increase irrigation self-sufficiency from 3% to 31%, and alleviate yield loss in dry years by 2-3%. These findings show that redesigning rice irrigation drainage systems can help meet water scarcity challenges posed by climate change.

Fate of 15N-labelled urea as affected by long-term manure substitution

Quantifying the fate of fertilizer nitrogen (N) is essential to develop more sustainable agricultural fertilization practices. However, the fate of chemical fertilizer N, particularly in long-term manure substitution treatment regimes, is not fully understood. The present study aimed to investigate the fate of ¹⁵N-labelled urea in a chemical fertilizer treatment (CF, 240 kg ¹⁵N ha^-1) and N manure 50 % substitution treatment (1/2N + M, 120 kg ¹⁵N ha^-1 + 120 kg manure N ha^-1) in two continuous crop seasons, based on a 10-year long-term experiment in the North China Plain (NCP). The results showed that manure substitution greatly enhanced ¹⁵N use efficiency (¹⁵NUE) (39.9 % vs. 31.3 %) and suppressed ¹⁵N loss (6.9 % vs. 7.5 %) compared with the CF treatment in the first crop. However, the N₂O emissions factor in the 1/2N + M treatment was increased by 0.1 % (0.5 kg ¹⁵N ha^-1 for CF vs. 0.4 kg ¹⁵N ha^-1 for 1/2N + M) compared with the CF treatment, although N leaching and NH₃ volatilization rates decreased by 0.2 % (10.8 kg ¹⁵N ha^-1 for CF vs. 5.1 kg ¹⁵N ha^-1 for 1/2N + M) and 0.5 % (6.6 kg ¹⁵N ha^-1 for CF vs. 2.8 kg ¹⁵N ha^-1 for 1/2N + M), respectively. In which, only NH₃ volatilization presented significantly difference between treatments. It is important to note that in the second crop, the residual ¹⁵N in soil (0-20 cm) remained mostly in the soil for the CF (79.1 %) and the 1/2N + M treatment (85.3 %), and contributed less to crop N uptake (3.3 % vs. 0.8 %) and leached losses (2.2 % vs. 0.6 %). This proved that manure substitution could enhance the stabilization of chemical N. These results suggested that long-term manure substitution effectively increases NUE, suppresses N loss, and improves N stabilization in soil, but negative impacts such as N₂O emissions due to climate change should be investigated further.

Potential to mitigate nitrogen emissions from paddy runoff: A microbiological perspective

Ditches and ponds are the basic units of agroecosystems that serve irrigation and drainage and also perform the natural ecological function of reducing nitrogen (N) emissions. To better enhance the design and advance management strategies in the paddy field ecosystem to minimize N emission, the N cycling microorganism in the paddy field ecosystem including interconnected fields with rice-wheat rotation, ditches, and ponds in central China was investigated by metagenomic techniques. Our results showed that ditches and ponds may be N removal hotspots by microorganisms in the rice and wheat seasons respectively. Given seasonal variation, the abundance of N-related microorganisms was high during the rice season. However, the Shannon and Simpson indices were lower and the microbial co-occurrence network was destabilized, which could make microbes in the rice season fragile and sensitive. Phytoplankton as key environmental factors affecting the N cycling microbial could promote more stable microbial communities through maintaining a good mutualistic symbiosis. While high algae concentration significantly promotes the abundance of norB than nosZ (P < 0.05), which may result in more N₂O production. To trade off N removal and N₂O emission, the algae concentration needs to be controlled. Our findings provide a systematic profile of N-related microorganisms in the paddy field ecosystem, and it would benefit in developing effective strategies for limiting N pollution in agriculture.

Managing landscape patterns at the riparian zone and sub-basin scale is equally important for water quality protection

Widespread attention has been given to understanding the effect of the landscape pattern on river water quality. However, which spatial scale (riparian zone versus sub-basin) has the greater impact on water quality has long been controversial, since the key metrics that affect water quality varied with spatial scale. Thus, quantifying the spatial scale effects of key landscape metrics on water quality is critical to clarifying which scale of landscape pattern is more conducive to water quality conservation. Here, we adopted variation partitioning analysis (VPA) and random forest models to quantify the landscape pattern impact on water quality at northern Erhai Lake during the 2019 rainy season (early, mid, and late), and comprehensively analyze the key landscape metrics on different scales. The results revealed that the riparian zone and sub-basin scale landscape patterns explained similar water quality variations (difference only 0.9%) in the mid (August) and late rainy season (October), but exhibited a large difference (24.1%) during the early rainy season (June). Furthermore, rivers were primarily stressed by nitrogen pollution. Maintaining the Grassland_ED > 27.99 m/ha, Grassland_LPI > 4.19%, Farmland_LSI < 3.2 in the riparian zone, and Construction_ED < 1.69 m/ha, Construction_LSI < 2.46, Farmland_PLADJ < 89.0% at the sub-basin scale could significantly reduce the TN concentration in the stream. Meanwhile, managing of these metrics can effectively prevent rapid increases of TN in rivers. Moreover, due to the low phosphorus concentration in the rivers, none of the landscape metrics significantly explained the variation in TP. This study explored the spatial scale effect of landscape patterns on water quality and revealed the driving factors of nutrient variation. This study will provide a scientific basis for aquatic environmental management in plateau watersheds.

Rice-crayfish pattern in irrigation-drainage unit increased N runoff losses and facilitated N enrichment in ditches

The rice-crayfish (RC) integrated pattern has been developed vigorously in China, but how it affects the nitrogen (N) runoff loss and distribution status during rice production is still poorly studied. Based on this, we selected two types of irrigation and drainage units (IDUs), which adopted the traditional rice-wheat (RW) rotation pattern and burgeoning RC rotation pattern separately, to investigate the effect of the RC pattern on N runoff loss, inorganic N distribution and N balance of the IDU. The results showed that there was a 241 kg ha^-1 yr^-1 and 135 kg ha^-1 yr^-1 N surplus achieved under RW and RC, respectively. Among these, the N surplus of RC was 53 % lower than that of RW during the rice growing season and was 37 % lower at other times. The NH₄⁺-N contents of paddy field soils, rice yields and productive traits were not affected by rotation patterns. Nevertheless, the total nitrogen (TN), dissolved organic nitrogen (DON) and NH₄⁺-N concentrations of RC field water were significantly higher (P < 0.01), and the N runoff losses of the RC pattern increased by 103 % to 855 % compared with the RW pattern. In addition, the NH₄⁺-N reserved in RC ditch sediments substantially increased regardless of the dynamic changes during the rice growing season or from the vertical distribution at depths of 0-40 cm. Our results indicated that the RC pattern was beneficial for decreasing the N surplus without impacting the rice yield. However, larger N runoff losses and more available N flowing into crayfish farming ditches still pose great environmental risks. Therefore, more efficient and cleaner measures should be applied for the N management of IDU under the RC pattern.

Improved estimation of nitrogen dynamics in paddy surface water in China

Paddy surface water is the direct source of artificial drainage and surface runoff leading to N loss from rice paddy fields. Quantifying the N dynamics in paddy surface water on a large scale is challenging because of model deficiencies and the limitations of field measurements. This study analyzed the N dynamics and the influencing factors in paddy surface water in the three main Chinese rice-growing regions: Northeast Plain, Yangtze River Basin, and Southeast Coast. An improved first-order kinetic model was proposed to evaluate the total nitrogen (TN) dynamics at a countrywide scale by improving the calculation method of the initial TN concentration (C₀) and providing the optimum value of attenuation coefficient (k). The results show that: (1) the average reduction rate of TN concentration on the 7th day after fertilization increased with the growth period (85%, 90%, and 95% during the basal, tillering, and panicle fertilization periods, respectively); (2) the attenuation coefficient k for the growth periods was ranked as follows: panicle fertilization period > tillering fertilization period > basal fertilization period. The Yangtze River Basin had the highest average k value (0.31-0.34), followed by the Southeast Coast (0.24-0.41) and Northeast Plain (0.22-0.30); and (3) the improved first-order kinetic model performed well in the N dynamics estimation (R² > 0.6). High TN concentration with high fertilizer application amounts and precipitation caused the Yangtze River Basin to have a high N runoff loss risk. The proposed universal model realizes the simulation of N dynamics from a single site to multi-sites while greatly saving multi-site monitoring costs. This study provides a basis for effectively optimizing N management and preventing N loss in rice paddies.

Restriction of biosolids returning to land: Fate of antibiotic resistance genes in soils after long-term biosolids application

Although the utilization of biosolids in agricultural lands is widely considered as an effective way to improve resource reuse, the presence of antibiotic resistance genes (ARGs) severely restricts biosolids returning to fields. A 12-year long-term experiment with different biosolids application rates (from 0 to 36 t ha^-1 yr^-1) was conducted to study the effect of biosolids application on shaping ARGs in soil. Biosolids application significantly increased ARGs abundance in the soil, except for MBS treatment (9 t ha^-1 yr^-1 biosolids application). The abundance of ARGs in soil did not increase linearly with the dose of biosolids applied, but they were significantly (P < 0.05) positively correlated. A total of 173 subtypes were detected, among them mobile genetic elements (MGEs), aminoglycoside, and multidrug resistance genes were the most dominant types. Except for MBS treatment, most of the ARGs detected were enriched in amended soils after long-term continuous biosolids application. Specifically, tetPA, sul1, mefA, and IS6100 were highly enriched in all amended soils. In addition, biosolids application increased soil nutrients and heavy metals, and changed the soil microbial community, all of which affected ARGs formation. But MGEs may be a greater factor for shaping ARGs profiles than soil properties. Overall, controlling the rate of biosolid application is the key to reducing the accumulation and horizontal transfer of ARGs in soils.

Leached phosphorus apportionment and future management strategies across the main soil areas and cropping system types in northern China

Excess phosphorus (P) leached from high fertiliser input cropping systems in northern China is having detrimental effects on water quality. Before improved management can be directed at specific soils and cropping system types estimates of P leached loss apportionment and mitigation potentials across the main soil (fluvo-aquic soil, FAS; cinnamon soil, CS; black soil, BS) areas and cropping systems (protected vegetable fields, PVFs; open vegetable fields, OVFs; cereal fields, CFs) are needed. The present study designed and implemented conventional fertilisation and low input system trials at 75 sites inclusive of these main soils and cropping system types in northern China. At all sites, a uniform lysimeter design (to 0.9 m depth) enabled the collection and analysis of leachate samples from 7578 individual events between 2008 and 2018. In addition, site-specific static and dynamic activity data were recorded. Results showed that annual total phosphorus (TP) leached losses across the main soil areas and cropping systems were 4.99 × 10⁶ kg in northern China. A major finding was PVFs contributed to 48.5% of the TP leached losses but only accounted for 5.7% of the total cropping areas. The CFs and OVFs accounted for 40.3% and 11.2% of the TP leached losses, respectively. Across northern China, the TP leached losses in PVFs and OVFs were greatest in FAS areas followed by CS and BS areas. The higher TP leached losses in FAS areas were closely correlated with greater P fertiliser inputs and irrigation practices. From a management perspective in PVFs and OVFs systems, a decrease of P inputs by 10-30% would not negatively affect yields while protecting water quality. The present study highlights the importance of decreasing P inputs in PVFs and OVFs and supporting soil P nutrient advocacy for farmers in China.

Impact of Thyroid Tissue Status on the Cut-Off Value of Lymph Node Fine-Needle Aspiration Thyroglobulin Measurements in Papillary Thyroid Cancer

Objective: To study the optimal cut-off value of thyroglobulin measurement in a fine-needle aspiration (FNA-Tg) in diagnosing malignant lymph nodes and benign lymph nodes (LNs) according to the thyroid tissue status.

Methods: A total of 517 LNs were aspirated: 401 preoperative LNs, 42 LNs after subtotal thyroidectomy and 74 suspected LNs after total thyroidectomy. The cut-off value of FNA-Tg was obtained from receiver operating characteristic (ROC) analysis. The cut-off value with the best diagnostic performance was then obtained by comparing different cut-off values from other studies.

Results: LN FNA-Tg levels differed between preoperative and total thyroid disease (p < 0.001) and subtotal thyroidectomy and total thyroidectomy (p = 0.03), but not between preoperative and subtotal thyroidectomy (p = 1.00). Accordingly, those 443 LNs with preoperative and subtotal thyroidectomy were compared to those 74 without thyroid tissue. The optimal cut-off value in thyroid tissue group was 19.4 ng/ml and the area under the ROC curve (AUC) was 0.95 (95% CI 0.92–0.97). The optimal cut-off value in thyroid tissue absence group was 1.2 ng/ml and the AUC was 0.93 (0.85–0.98). After the analysis and comparison of multiple cut-off values, the optimal diagnostic performance was still found to be 19.4 ng/ml and 1.2 ng/ml.

Conclusion: The influential factors of FNA-Tg are still controversial, and the optimal cut-off value of FNA-Tg can be determined based on the presence or absence of thyroid tissue. FNA-Tg can be used as an important auxiliary method for diagnosing cervical metastatic LNs of thyroid cancer.

The impact of immersed liquid circulation on anaerobic digestion of rice straw bale and methane generation improvement

Immersed liquid circulation is assumed to improve solid-state anaerobic digestion (SS-AD) with digestate flow convection on the surface of solid-state bed (SSB), which depends on SSB concentration and circulation rate (CR). In this study, the impact of CR on rice straw SS-AD was investigated within a 30 L pilot digester. Results showed that SSB threshold concentration for efficient biogas conversion was 10%-12% TS, achieving the methane yield of 185.3 mL/g VS. Within the threshold, methane production progress and VFAs release could be enhanced simultaneously by rational CR increasing, but no significant methane yield improvement was observed; above, the rapid and stable biogas generation could be acquired with a competitive methane yield of 174.7 mL/g VS (150% CR). No matter within or above the threshold, efficient lingo-cellulosic degradation was always accompanied by the moderate CR for effective methane generation. SSB was proposed to be above threshold for industrial application.

[The relationship between elevated antiphospholipid antibodies and thrombosis in hospitalized patients]

Objective: Assess the relationship between elevated antiphospholipid antibodies and thrombosis in hospitalized patients. Methods: Case control study. A total of 385 patients (149 males and 236 females, aged from 1 to 105 years, with a median age of 37 years) who were hospitalized in Peking University First Hospital from January 2015 to December 2019 and tested positive for any one of the anti-phospholipid antibodies were included in the study. All subjects were divided into thrombotic group and non-thrombotic group according to whether thrombus was detected by imaging examination during hospitalization. In thrombosis group, there were 66 males and 36 females, aged from 3 to 105 years, with a median age of 58 years. In non-thrombosis group, there were 83 males and 200 females, aged from 1 to 94 years, with a median age of 31 years. Clinical data and laboratory data of patients were recorded. ACL-IgM/IgG and anti-β2GPI-IgM/IgG were detected by ELISA and LA was detected by dRVVT and SCT on automatic coagulation analyzer. The rates of age, gender, smoking, obesity, hypertension, hyperlipidemia, diabetes and the median level of antiphospholipid antibodies were compared between two groups. Logistic multivariate regression analysis was used to determine the risk factors for thrombotic events. The mid-to-high titer value of aCL was established by the χ²-trend test and verified by logistic regression. Results: The median age (58 years) and the rates of male (64.7%), smoking (16.7%), hypertension (63.7%) and diabetes (28.4%) in thrombus group were significantly higher than those in non-thrombus group (Z=7.685, χ²=38.077, 16.312, 37.769, 24.749 respectively; P<0.01). The positive rate of anti-β2GPI-IgG and dRVVT in thrombosis group (11.8% and 78.4%) was significantly higher than that in non-thrombosis group (5.3% and 60.1%), as well as the median level of dRVVT (1.29 RU/ml vs 1.23 RU/ml) (χ²=3.864 and 10.309, Z=3.539; P<0.05). The median level of aCL-IgM was higher in non-thrombosis group (2.3 MPL vs 2.0 MPL). The positive rate of aCL-IgG was slightly higher in thrombosis group (18.6% vs 10.6%). Logistic regression analysis showed that men, hypertension, diabetes, advanced age, elevated dRVVT, and elevated anti-β2GPI-IgG are risk factors for thrombosis. Taking 36 GPL as the medium-to-high titer value of aCL-IgG, the risk of thrombosis increased by 2.45 times. Conclusions: In the anti-phospholipid antibody profile, LA detected by dRVVT method, anti-β2GPI-IgG and aCL-IgG may be valuable laboratory indicators for inpatient thrombotic events. The mid-to-high titer value of aCL-IgG is set at 36 GPL to distinguish the risk of thrombosis.

Joint analytical hierarchy and metaheuristic optimization as a framework to mitigate fertilizer-based pollution

The emission of nitrogenous pollution from agricultural lands in form of ammonia volatilization, leaching, runoff, N₂O emissions, etc. is still a serious challenge to which agricultural sector faces. In this context, a vast number of decision support systems have been developed and tested to find the best nitrogen application rate. These models are highly dependent on crop simulation models, mathematical and regression models, evolutionary algorithms and artificial intelligent, GIS-based models, etc., while in most cases have ignored to be interfered with regional and national regulations established by experts in the field. In this study, a new framework combining analytical hierarchy (AHP)/modified AHP methods (MAHP) plus metaheuristic optimization techniques has been suggested to find the best nitrogen application rate considering regional capacities and requirements. To reach the objectives of the present study a three yield field experiment was conducted upon which crop yield, nitrogen use efficiency, nitrogen uptake, soil nitrate, ammonia volatilization, N₂O emissions, and N leaching were monitored or measured. Using the results from the field experiments and a survey from local experts, the models were developed. AHP-assisted optimization model could cause some biases in the final results due to its intrinsic nature which avoids direct pairwise comparison among indicators (so called sub-criteria) under two different main-criteria. On the contrary, MAHP-assisted model could well reflect the concerns of experts and notably decrease hotspot pollution. Such decision support system can satisfy both farmers and environmentalists' need because of the created high profit and low environmental pollution, while saving resources and ensuring a sustainable production system.

Effects of biochar application with fertilizer on soil microbial biomass and greenhouse gas emissions in a peanut cropping system

This study investigated the effects of biochar application with organic or mineral fertilizers on soil microbial biomass, and associated emissions of CO₂ and CH₄ under field settings planted with peanut. The results indicated that physicochemical properties of soil were improved under biochar application. Soil microbial biomass carbon (MBC) was significantly increased with the application of biochar plus organic fertilizer compared to that of organic fertilizer only, but no significant difference of MBC was found between the treatment under biochar application plus mineral fertilizer and that under mineral fertilizer only. Biochar application did not affect the amount of microbial biomass nitrogen (MBN) with either mineral or organic fertilizer. The cumulative CO₂ emission did not change under biochar application, while the cumulative CH₄ emission was significantly decreased (p < 0.05) by 68.67% on average with the application of organic fertilizer plus biochar compared to that of organic fertilizer only. When biochar was applied in combination with either mineral or organic fertilizer, both the net global warming potential (GWP) and the greenhouse gas intensity (GHGI) were significantly decreased compared to that without biochar amendment. In all, biochar can improve soil quality, and enhance soil carbon sequestration as well as peanut yields.

How long-term excessive manure application affects soil phosphorous species and risk of phosphorous loss in fluvo-aquic soil

The excessive application of manure has caused a high load of phosphorus (P) in the North China Plain. Having an understanding of how manure application affects soil P changes and its transport between different soil layers is crucial to reasonably apply manure P and reduce the associated loss. Based on our 28-year field experiments, the compositions and changes of P species and the risk of P loss under excessive manure treatments were investigated, i.e., no fertilizer (CK), mineral fertilizer NPK (NPK), NPK plus 22.5 t ha^-1 yr^-1 swine manure (LMNPK), and NPK plus 33.75 t ha^-1 yr^-1 swine manure (HMNPK). Manure application increased the content of orthophosphate and myo-inositol hexaphosphate (myo-IHP), especially the orthophosphate content exceeded 95%. The amount of orthophosphate in manure and the conversion of organic P to inorganic P in soil were the main reasons for the increased soil orthophosphate. Compared with NPK treatment, soil microbial biomass phosphorus and alkaline phosphatase activity in LMNPK and HMNPK treatments significantly increased. Compared with NPK treatment, a high manure application rate under HMNPK treatment could increase the abundance of organic P-mineralization gene phoD by 60.0% and decrease the abundance of inorganic P-solubilization gene pqqC by 45.9%. Due to the continuous additional manure application, soil P stocks significantly increased under LMNPK and HMNPK treatments. Furthermore, part of the P has been leached to the 60-80 cm soil layer. Segmented regression analysis indicated that CaCl₂-P increased sharply when Olsen-P was higher than 25.1 mg kg^-1, however the content of Olsen-P did not exceed this value until 10 years after consecutive excessive manure application. In order to improve soil P availability and decrease the risk of P loss, the manure application rate should vary over time based on soil physicochemical conditions, plants requirements, and P stocks from previous years.

The reactive nitrogen loss and GHG emissions from a maize system after a long-term livestock manure incorporation in the North China Plain

The use of livestock manure as a substitution for synthetic nitrogen (N) fertilizers is recommended to improve the sustainable use of manure nutrients and alleviate the adverse impacts of synthetic N fertilizers on the environment. A thorough understanding of how such substitutions affect reactive N losses and greenhouse gas (GHG) emissions in cereal production systems in the North China Plain (a main livestock production region in China), is needed to achieve an environmental friendly and sustainable production. Based on a long-term field experiment, different manure/chemical fertilizer treatments were designed, i.e., non-fertilization control (CK), chemical fertilizers alone (NPK), and manure substitution for chemical N fertilizers (with equivalent N rate; NPKP, 50% N from pig manure; NPKC, 50% N from chicken manure). Crop yield, nitrogen use efficiency (NUE), soil fertility, N losses, and GHG emissions were chosen as prominent indicators to evaluate the consequences of manure substitutions for N-based fertilizers. The replacement of synthetic fertilizers by livestock manure decreased NO₃-N leaching and NH₃ volatilization by 46.2% and 5.61-22.2%, respectively, while sustained the crop yields and improved NUE. However, both NPKP and NPKC treatments did not have any impact on N₂O and CO₂ mitigation. Compared with NPK, NPKC and NPKP meaningfully increased SOC by 9.56% and 19.6%, respectively. More specifically, NPKC increased TN content by 14.7% (P < 0.05) compared to NPK treatment. The results showed that 50% substitution of manure for synthetic N fertilizers is a potential option in maize production systems to decrease N losses (including NH₃, N₂O emissions and N leaching) by approximately 45% (42.8-48.1%). However, only 1.81% of the total farmers surveyed (i.e., 16,595) have being applied livestock manure for maize cultivation in the North China Plain. Therefore, famers in this plain should be encouraged to use manure to improve ecological aspects of cereal cultivation and decrease the associated environmental pollutions.

Plastic pollution in croplands threatens long-term food security

Plastic pollution is a global concern given its prevalence in aquatic and terrestrial ecosystems. Studies have been conducted on the distribution and impact of plastic pollution in marine ecosystems, but little is known on terrestrial ecosystems. Plastic mulch has been widely used to increase crop yields worldwide, yet the impact of plastic residues in cropland soils to soil health and crop production in the long term remained unclear. In this paper, using a global meta-analysis, we found that the use of plastic mulch can indeed increase crop yields on average by 25%-42% in the immediate season due to the increase of soil temperature (+8%) and moisture (+17%). However, the unabated accumulation of film residues in the field negatively impacts its physicochemical properties linked to healthy soil and threatens food production in the long term. It has multiple negative impacts on plant growth including crop yield (at the mean rate of -3% for every additional 100 kg/ha of film residue), plant height (-2%) and root weight (-5%), and soil properties including soil water evaporation capacity (-2%), soil water infiltration rate (-8%), soil organic matter (-0.8%) and soil available phosphorus (-5%) based on meta-regression. Using a nationwide field survey of China, the largest user of plastic mulch worldwide, we found that plastic residue accumulation in cropland soils has reached 550,800 tonnes, with an estimated 6%-10% reduction in cotton yield in some polluted sites based on current level of plastic residue content. Immediate actions should be taken to ensure the recovery of plastic film mulch and limit further increase in film residue loading to maintain the sustainability of these croplands.

Potential nutrient removal function of naturally existed ditches and ponds in paddy regions: Prospect of enhancing water quality by irrigation and drainage management

Conventionally, paddy fields are regarded as important non-point sources of nutrient pollution, while ecological ditches and ponds are developed to reduce or retain nutrient export from agricultural fields. To quantify the potential nutrient removal function of ditches and ponds that naturally existed in rice growing regions, a representative paddy irrigation and drainage unit (IDU) composed of fields, ditches and a pond in the one-season rice region of the middle Changjiang River basin, China was monitored for two years. With data and knowledge gained, a Water Quantity and Quality Model for Paddy IDUs (WQQM-PIDU) is developed and applied for 30 years simulation to produce a general view. The monitored and modelled results showed that nutrient concentration peaks after fertilization was delayed and lowered in ditches and ponds, compared to those in paddy fields. Concentrations of runoff from the IDU outlet were generally lower than from the field during the whole rice growing season except the transplanting period. If fully utilized as temporary reservoirs, ditches and ponds naturally existed in a typical paddy IDU would reduce 39% nitrogen loads from field edges with a range of 17%-93% and 28% phosphorus loads with a range of 12%-92%. Although typical paddy IDUs discharge fewer nutrient loads than the content input into them, the discharge concentrations may be risky to surface waters. For their nutrient removal function, natural ditches and ponds are recommended to be included into irrigation and drainage management with accurate water level management during drainage, which is a promising and cost-effective approach to enhance surface water quality in rice growing regions.

Impact of human activities on phosphorus flows on an early eutrophic plateau: A case study in Southwest China

The net anthropogenic phosphorus inputs (NAPI) model has been used extensively to assess changes in phosphorus (P) inputs and cycling in the environment. However, temporary populations have generally been unconsidered in these assessments. In this study, the NAPI model was used to estimate P loads from the 16 towns and villages in the Erhai Lake Basin (ELB), Southwest China and to evaluate the potential impact from temporary residents (tourism). The results showed that the average value P inputs in the basin (estimated at 2384 kg P km^-2 year^-1) were 5 times the national average level, and that temporary residents contributed 1%. Agriculture accounted for most of the net P, with chemical fertilizers (55% of the inputs) as the main source, followed by food and animal feed. Only 9.54% of the P inputs to the basin were exported. River water quality and NAPI were significantly correlated (P < 0.01). Tourism industry contributes significantly to regional economic growth and prosperity, but its beneficial effects on the economy does not equate with the adverse impact on environment. This study illustrates what is happening in Southwest China and provides scientific evidence that shows we need to find novel ways to reduce nutrients.

Evaluating national ecological risk of agricultural pesticides from 2004 to 2017 in China

In recent years, excessive application and loss of pesticides have caused great risks to the aquatic systems, but the spatio-temporal variability in the ecological risk that agricultural pesticides pose to aquatic systems has not been explored at the national scale. In this study, an integrated assessment framework was proposed for the potential ecological risk of surface water caused by agricultural pesticide loss. The spatio-temporal variability in the potential ecological risk caused by agricultural pesticide runoff was evaluated. Based on the results, the total pesticide emissions increased from 165.47 tons in 2004 to 179.77 tons in 2017. Among the three pesticide types, insecticide had the largest application, but its runoff was estimated as the lowest. High-risk areas of insecticide runoff were concentrated in the east, south and central part of China, while the central region of China was identified as a hotspot due to the high and the ever-increasing ecological risk. This study provides an integrated method for potential ecological risk assessment of agricultural pesticide runoff to adjacent water bodies in large-scale regions and the results of the study have direct implications for environmental policies on pesticide management in China and around the world.

Investigation of watershed nutrient export affected by extreme events and the corresponding sampling frequency

Although the real-time monitoring technique has been widely applied due to the improvement of sensors, development of traditional sampling methods is still worth of being discussed due to the economically feasibility. Currently, extreme events (e.g. extreme rainfall caused by climate change) play a relatively important role in nutrient export. However, impacts of extreme events on the optimization of sampling strategy is still not well addressed despite the uncertainty of different frequency sampling programs has been sufficiently discussed in previous studies. Therefore, the corresponding impact of extreme events impact on the optimization of sampling strategy was investigated by examining temporal (i.e., inter-annual and seasonal) variations of available data. Uncertainty of nutrient flux estimates under different sampling frequencies was explored by subsampling daily monitoring data. Results showed that uncertainty in flux estimates differed between nitrogen and phosphorus. The relative error (RE) in annual TN flux estimates ranged from -4.2% to 2.4% (once per three-day) to -21.4-31.1% (monthly sampling), while the RE in annual TP flux estimates varied from -14.1% to 8.2% (once per three-day) to -65.9%-163.4% (monthly sampling). Biweekly and weekly sampling routines are considered the optimal sampling program for total nitrogen (TN) and for total phosphorus (TP) when the extreme events impact were not been considered. The uncertainty of flux estimates with different sampling frequencies increased with the increasing extreme events. High level of uncertainty occurred in years with the most extreme events in 2012 (RE: 21.4-69.0% for TN, 33.3-96.6% for TP), while the lowest can be found in 2011 (RE: 0-20.7% for TN, 0-48.3% for TP) (with the fewest extreme events). In addition, uncertainty in TN and TP flux estimates was generally greater during summer season than during other seasons. These results highlighted the important role of extreme events in nutrient export. Approximately half of the annual TN and TP flux occurred in some extreme days that only accounted for less than 20% in the same year. The onset of these extremes of nutrient export was likely due to the stormflow with addition of external fertilizer and the direct discharge of surface ponding water from paddy fields during special periods of time. These results would be helpful for the optimization of sampling strategy.

Achievements of biochar application for enhanced anaerobic digestion: A review

Anaerobic digestion (AD) and pyrolysis are two promising technologies used worldwide for waste biomass treatment. Interests on intensification techniques of AD has been increasing to obtain sufficient and sustainable methane production with stable digester performance. For instance, considerable attention has been devoted to the coupling of AD with biochar, which is produced by biomass thermochemical conversion. This manuscript presents a comprehensive review about recent achievements in enhancing AD efficiency with the utilization of biochar. The key roles of biochar include enhancing and equilibrating hydrolysis, acidogenesis-acetogenesis, and methanogenesis, as well as alleviating inhibitor stress were summarized. Biochar can promote biomethane process mainly by serving as a provision for bioelectrical connections between fermentative bacteria and methanogens, a support for microbial colonies, and a reinforcer for buffer capacity. Through an overview of the early applications, this paper aims to pinpoint the potential mechanism and future explorative directions of biochar enhancing AD performance.

National assessment of spatiotemporal loss in agricultural pesticides and related potential exposure risks to water quality in China

Pesticide loss during agricultural development has a serious effect on related water quality, and the critical concern is quantifying the potential exposure risks that pesticide loss pose to water quality at the national scale. In this study, an integrated assessment framework is proposed to scale emission factors from 232 monitoring plots to the national scale, while also considering the physicochemical properties of pesticides in dissolved or adsorbed forms. Based on the results of this study, the total pesticide emissions increased by 29.39% from 146.55 tons in 2004 to 189.62 tons in 2013 and the average loss intensities of insecticides, herbicides and fungicides were 35.25 g/km², 44.24 g/km² and 48.57 g/km², respectively. Central and Southeastern China are identified as hotspots for pesticide loss, while the proportions of high or extremely high-risk areas mainly comprise >50% of farmland. In addition, single-field crops and single-crop rice are the major cropping patterns for pesticide loss in Northern and Southern China. Our results identify key areas for the management of pesticides at the national scale and have direct implications for environmental policies on reducing the potential exposure risk of agricultural pesticides to water quality.

Dimethylolurea as a Novel Slow-Release Nitrogen Source for Nitrogen Leaching Mitigation and Crop Production

Rapid hydrolysis of urea results in further fertilization frequency and excessive nitrogen (N) input. A modified urea, dimethylolurea (DMU), was synthesized in this study. The structure of the sample was characterized by Fourier transform infrared and nuclear magnetic resonance analysis, manifesting the formation of DMU. N release investigation confirmed that DMU enabling provided a gradual N supply. The N leaching experiment indicated that increasing the applied DMU significantly reduced the NH₄⁺-N, NO₃^--N, and total N leaching, compared with urea application alone. The application effect on maize and wheat was evaluated. The results revealed that singly applied DMU with 100% or 80% N input, irrespective of the amount, promoted crop yield and agronomic characteristic and N use efficiency (NUE) of maize and wheat, beyond urea with two split applications at the recommended rate. Thus, the potential availability of DMU was proven; this could be widely used in agricultural fields as a slow-release fertilizer.

Effect of irrigation-drainage unit on phosphorus interception in paddy field system

In lowland agriculture, paddy fields are present in the form of irrigation-drainage unit (IDU), which consists of paddy fields and natural ditches around the fields. Phosphorus (P) export from IDUs significantly impacts water quality in adjacent water bodies. In this study, we explored the characteristics and behavior of P in a typical IDU in Jianghan Plain, China. From 2012 to 2015, we measured P concentrations in different water components of the IDU, i.e., rainwater, irrigation water, field ponding water, runoff water and ditch water, and accounted for spatial and temporal variabilities of the P concentrations. Across the rice growing season, the highest total P (TP) concentration was observed in the field ponding water. Total P concentration in ditch water gradually declined and it reached 0.06 mg L^-1 at the rice maturation stage. The concentration was lower than that of incoming irrigation water (0.13 mg L^-1) and rainwater (0.17 mg L^-1). Although both paddy soil and ditch sediment had low degree of P saturation, the ditch sediment had greater P binding energy (1.58 L mg^-1) and larger maximum P sorption (526 mg kg^-1) than the soil (0.88 L mg^-1 and 455 mg kg^-1, respectively). The P mass balance for the rice season over the four consecutive years showed a net depletion of 3.36-8.11 kg P ha^-1 yr^-1. Overall, IDUs substantially reduced the P concentrations in outputs from the IDUs as compared to inputs through irrigation and rainfall. The IDUs functioned for P retention by extending P settling time and natural degradation of P in the system. Optimizing the IDU management by controlling water discharge during fertilization and disturbance periods can be popularized for its cost saving and environmental benefits.

Effects of different types of biochar on the anaerobic digestion of chicken manure

This study investigated the impact of different types of biochar on the anaerobic digestion (AD) of chicken manure. Wheat straw, discarded fruitwood, and air-dried chicken manure were pyrolysed at 350, 450, and 550 °C to generate biochar. A lab-scale batch anaerobic digestion experiment was conducted at 35 ± 1 °C. Substantial improvements in methane production were observed for all nine types of biochar. With the production of 294 mL CH₄/g VS_added, fruitwood char pyrolysed at 550 °C increased the methane yield by 69% from the control. Characteristic analysis indicated that fruitwood char pyrolysed at 550 °C exhibited the largest specific surface area and highest total ammonia nitrogen reduction capacity. The buffering capacity of the AD system was improved by the biochar through accelerating the transformation of macromolecular substances to dissolved substrates and reducing the contents of soluble salts, total ammonia nitrogen, and free ammonia.

Contrasting impacts of long-term application of manure and crop straw on residual nitrate-N along the soil profile in the North China Plain

The effects of long-term animal manure application and crop straw incorporation on the migration of carbon (C) and nitrogen (N) deep into the soil profile and the associated N leaching risk in particular have not been thoroughly elucidated to date. Soil profile samples were collected from depths of up to 200 cm from the following four treatments in a 27-year field experiment on the North China Plain: N + phosphorus (P) + potassium (K) fertilizers (NPK), NPK + 22.5 t ha^-1 swine manure (NPKM), NPK + 33.7 t ha^-1 swine manure (NPKM+) and NPK + straw incorporation (NPKS). The results revealed that long-term manure application and straw incorporation significantly enhanced the soil organic C (SOC) and total N (TN) contents in the upper 20 cm and that this effect was weaker in the deeper soil layers (P < 0.05). Residual nitrate-N (NO₃^--N) contents at 0 to 40 cm and 120 to 200 cm in the NPKM and NPKM+ were 4-16 and 2-9 times higher than those in the NPK and NPKS, respectively. These results indicated a greater potential for N leaching from manure addition and a higher propensity for NO₃^--N leaching out of the 40-100 cm soil layer. Pearson relationship analysis demonstrated that NO₃^--N content was clearly affected by SOC and dissolved organic N (DON) contents along the soil profile (20-200 cm), implying that the higher residual NO₃^--N contents in the deeper soil from manure addition were partially attributable to the mineralization and nitrification of the downward SOC and DON. Interestingly, a low level of residual NO₃^--N combined with negative mineralization in the 120-200 cm soil layers of the NPKS treatment was observed, suggesting that straw incorporation promotes soil NO₃^--N retention. Thus, we concluded that long-term manure application is beneficial for soil NO₃^--N content retention, whereas long-term straw incorporation benefits NO₃^--N retention.

[Protective effect of picroside Ⅱ on the brain tissue through antioxidation in stroke rats]

Objective: To investigate the effect and mechanisms of picroside Ⅱ on the brain tissue after cerebral ischemia reperfusion(I/R) in rats. Methods: The middle cerebral artery occlusion(MCAO) rat model was established by inserting a monofilament into middle cerebral artery. The experimental rats were treated by injecting picroside Ⅱ intraperitoneally. The modified neurological severity score (mNSS) and body weight were determined before modeling and after reperfusion of 22 h. The cerebral infarct volume was measured by TTC staining and the cerebral water content was measured in rats. At the same time, ROS content and NADPH oxidase activity were detected. The structure of neurons was observed by electron microscope and the mRNA and protein levels of Rac-1 and Nox2 were detected by RT-PCR and Western blotting. Results: After modeling, the mNSS score was significantly increased (12.6±1.3 vs 0, P<0.001), while the body weight was lost (13.3%±2.5% vs 4.9%±0.8%, P<0.01). The cerebral infarct volume increased obviously (33.5%±3.4% vs 0, P<0.001), brain water content increased significantly (81.5%±0.9% vs 77.7%±0.9%, P<0.05) and the structure of neuron was damaged obviously. The protein and mRNA levels of Rac-1 and Nox2 were significantly increased (P<0.05). After treatment with picroside Ⅱ, mNSS score decreased significantly (7.9±0.8 vs 12.6±1.3, P<0.05) and the body weight increased obviously (9.3%±1.1% vs 13.3%±2.5%, P<0.05). The infarct volume of brain was significantly reduced (18.2%±1.9% vs 33.5%±3.4%, P<0.05), brain water content decreased obviously (79.1%±0.7% vs 81.5±0.9%, P<0.05), the morphological structures of neurons was restored, and the expressions of Rac-1 and Nox2 were significantly decreased (P<0.05). Conclusion: It is suggested that picroside Ⅱ could exert antioxidation to protect the brain tissue through inhibiting the expression of Rac-1 and Nox2.

Comparative evaluation of the use of acidic additives on sewage sludge composting quality improvement, nitrogen conservation, and greenhouse gas reduction

The aim of this study was investigated the effects of acidic additives apple pomace (AP), citric acid (CA), elemental sulphur (ES), phosphoric acid (PA), magnesium hydrogen phosphate (PM), and calcium superphosphate (CP)) on N conservation and greenhouse gas (GHG) emissions during sewage sludge composting. Results showed that adding the additives have no negative effects on compost hygienisation, but could improve the N conservation. Treatments with additives showed 2.56-5.48% N loss of initial N, which is lower than the control (9.73%). Compared to other compost products, ES- and PA-treatments had the lower NH₃ volatilizations (0.80% and 0.98% of initial N, respectively) and germination index values (0.52 and 0.74, respectively), while the higher N₂O emissions (2.48% and 2.29% of initial N, respectively) and salinities. Comprehensive evolution of N loss, GHG emissions and compost maturity in this study, the feasibility of using AP, CA, and PM in high-quality compost production is promising.

Influences of agricultural land use composition and distribution on nitrogen export from a subtropical watershed in China

Despite the significant impacts of agricultural land on nonpoint source (NPS) nitrogen (N) pollution, little is known about the influence of the distribution and composition of different agricultural land uses on N export at the watershed scale. We used the Soil and Water Assessment Tool (SWAT) to quantify how agricultural distribution (i.e., the spatial distributions of agricultural land uses) and composition (i.e., the relative percentages of different types of agricultural land uses) influenced N export from a Chinese subtropical watershed, accounting for aquatic N retention by river networks. Nitrogen sources displayed high spatial variability, with 40.7% of the total N (TN) export from the watershed as a whole derived from several subwatersheds that accounted for only 18% of the watershed area. These subwatersheds were all located close to the watershed mouth. Agricultural composition strongly affected inputs to the river network. The percentages of dry agricultural land and rice paddy fields, and the number of cattle together explained 70.5% of the variability of the TN input to the river network among different subwatersheds. Total N loading to the river network was positively correlated with the percentage of dry land in total land areas and the number of cattle within subwatersheds, but negatively with the proportion of paddy fields. Distribution of agricultural land uses also affected N export at the mouth of the watershed. Moreover, N retention in the river network increased with increasing N transport distance from source subwatershed to the watershed mouth. Results provide important information to support improved planning of agricultural land uses at the watershed scale that reduces NPS nutrient pollution.

Long-term manure application increased greenhouse gas emissions but had no effect on ammonia volatilization in a Northern China upland field

The impacts of manure application on soil ammonia (NH₃) volatilization and greenhouse gas (GHG) emissions are of interest for both agronomic and environmental reasons. However, how the swine manure addition affects greenhouse gas and N emissions in North China Plain wheat fields is still unknown. A long-term fertilization experiment was carried out on a maize-wheat rotation system in Northern China (Zea mays L-Triticum aestivum L.) from 1990 to 2017. The experiment included four treatments: (1) No fertilizer (CK), (2) single application of chemical fertilizers (NPK), (3) NPK plus 22.5t/ha swine manure (NPKM), (4) NPK plus 33.7t/ha swine manure (NPKM+). A short-term fertilization experiment was conducted from 2016 to 2017 using the same treatments in a field that had been abandoned for decades. The emissions of NH₃ and GHGs were measured during the wheat season from 2016 to 2017. Results showed that after long-term fertilization the wheat yields for NPKM treatment were 7105kg/ha, which were higher than NPK (3880kg/ha) and NPKM+ treatments (5518kg/ha). The wheat yields were similar after short-term fertilization (6098-6887kg/ha). The NH₃-N emission factors (EF_amm) for NPKM and NPKM+ treatments (1.1 and 1.1-1.4%, respectively) were lower than NPK treatment (2.2%) in both the long and short-term fertilization treatments. In the long- and short-term experiments the nitrous oxide (N₂O) emission factors (EF_nit) for NPKM+ treatment were 4.2% and 3.7%, respectively, which were higher than for the NPK treatment (3.5% and 2.5%, respectively) and the NPKM treatment (3.6% and 2.2%, respectively). In addition, under long and short-term fertilization, the greenhouse gas intensities for the NPKM+ treatment were 33.7 and 27.0kg CO₂-eq/kg yield, respectively, which were higher than for the NPKM treatment (22.8 and 21.1kg CO₂-eq/kg yield, respectively). These results imply that excessive swine manure application does not increase yield but increases GHG emissions.

Ammonia emissions from paddy fields are underestimated in China

Excessive nitrogen (N) fertilizers are often used in China, and a large proportion of the N can be lost as ammonia (NH₃). However, quantifying the NH₃ emission from paddy fields is always affected by large uncertainties due to different measuring methods and other factors such as climate. In this study, using a standardized method, we measured the NH₃ emissions in three typical annual rice cropping systems: single rice, double rice and rotation with other crops. The measurements were conducted for 2 years with a total of 3131 observations across China. Results showed that NH₃ emissions accounted for 17.7% (14.4-21.0%) of the N applied under current farm practice, which was 33.1% (10.6-52.6%) higher than previous estimates. Nitrogen application rate was the dominant factor influencing NH₃ emission rate, which exponentially increased with the N fertilizer rate (p < .001). Total NH₃ emissions from paddy fields were estimated at 1.7 Tg N yr^-1 in 2013 in China, several times the amount of N lost through leaching or runoff. This suggests that mitigation measures for non-point source pollution from cropland should take into account not only the N lost to water, but also to air, thereby improving air quality.

Optimizing the nitrogen application rate for maize and wheat based on yield and environment on the Northern China Plain

Optimizing the nitrogen (N) application rate can increase crop yield while reducing the environmental risks. However, the optimal N rates vary substantially when different targets such as maximum yield or maximum economic benefit are considered. Taking the wheat-maize rotation cropping system on the North China Plain as a case study, we quantified the variation of N application rates when targeting constraints on yield, economic performance, N uptake and N utilization, by conducting field experiments between 2011 and 2013. Results showed that the optimal N application rate was highest when targeting N uptake (240kgha^-1 for maize, and 326kgha^-1 for wheat), followed by crop yield (208kgha^-1 for maize, and 277kgha^-1 for wheat) and economic income (191kgha^-1 for maize, and 253kgha^-1 for wheat). If environmental costs were considered, the optimal N application rates were further reduced by 20-30% compared to those when targeting maximum economic income. However, the optimal N rate, with environmental cost included, may result in soil nutrient mining under maize, and an extra input of 43kgNha^-1 was needed to make the soil N balanced and maintain soil fertility in the long term. To obtain a win-win situation for both yield and environment, the optimal N rate should be controlled at 179kgha^-1 for maize, which could achieve above 99.5% of maximum yield and have a favorable N balance, and at 202kgha^-1 for wheat to achieve 97.4% of maximum yield, which was about 20kgNha^-1 higher than that when N surplus was nil. Although these optimal N rates vary on spatial and temporal scales, they are still effective for the North China Plain where 32% of China's total maize and 45% of China's total wheat are produced. More experiments are still needed to determine the optimal N application rates in other regions. Use of these different optimal N rates would contribute to improving the sustainability of agricultural development in China.

Biochar amendment with fertilizers increases peanut N uptake, alleviates soil N2O emissions without affecting NH3 volatilization in field experiments

Biochar application to soil is currently widely advocated for a variety of reasons related to sustainability. However, the synergistic effects of biochar combined with mineral or organic fertilizer on soil N₂O emissions, NH₃ volatilization, and plant N uptake are poorly documented. Field plot experiments planted with peanut were conducted under the application of biochar (derived from rice husk and cottonseed husk, 50 t ha^-1) with organic or mineral fertilizer. It was found that biochar increased soil nutrient availability and decreased surface soil bulk density, demonstrating that biochar could improve the soil quality especially in the 0-20-cm profile. The total N content of the plant changed little with treatments, but the kernel N concentration increased significantly when biochar was applied with organic fertilizer. Peanut yield increased with biochar amendment while no significant difference was observed in plant biomass, suggesting biochar had a positive effect on belowground biomass. Peanut N uptake was also increased following biochar amendment with either organic or mineral fertilizers. While biochar amendment had no significant effect on soil NH₃ volatilization, it did decrease the cumulative N₂O emission by 36.3% on average with organic fertilizer, and by 32.6% with mineral fertilizer, respectively (p < 0.05). The copy numbers of 16S rDNA, nifH, nirK, and nirS were not influenced by the application of biochar; however, the copy number of nosZ was significantly increased under biochar plus mineral fertilizer treatment. The results imply that biochar application can suppress N₂O emissions, as a result of abiotic factors and enhanced peanut N uptake rather than changes of denitrification genes.

Methane production and characteristics of the microbial community in the co-digestion of spent mushroom substrate with dairy manure

Spent mushroom substrate (SMS) is a potential biomass material generated during mushroom cultivation. In this study, the methane yield and microbial community resulting from co-digestion of SMS and dairy manure (DM) at different mixing ratios (0:4, 1:1, 3:1, and 1:3), were evaluated. Co-digestion analysis showed that the methane yield from the mixtures was 6%-61% higher than the yield from SMS or DM alone, indicating a synergistic effect of co-digestion of SMS with DM. For the SMS of F.velutipes (SFv) and P.erygii var. tuoliensis (SPt), co-digestion of DM/SMS at a ratio of 1:1 was optimal, but for the SMS of P. eryngi (SPe), co-digestion of DM/SMS at a ratio of 3:1 was ideal. The pH at all co-digestion ratios was in the range of 6.8-8.0, indicating that adding DM could increase the systemic buffering capacity. Methanosaetaceae was shown to be the predominant methanogens present during the co-digestion of DM/SMS.

Temporal-spatial variations and influencing factors of nitrogen in the shallow groundwater of the nearshore vegetable field of Erhai Lake, China

Nitrogen export from the nearshore vegetable field of Erhai Lake seriously threatens the water quality of Erhai Lake, which is the second largest highland freshwater lake in Yunnan Province, China. Among the nitrogen flows into Erhai Lake, shallow groundwater migration is a major pathway. The nitrogen variation and influencing factors in the shallow groundwater of the nearshore vegetable field of Erhai Lake are not well documented. A 2-year field experiment was conducted to determine the concentrations of nitrogen species in the shallow groundwater and their influencing factors in the nearshore vegetable field of Erhai Lake. The results showed that concentrations of TN, NO₃^--N, and NO₂^--N gradually increased with increasing elevation and distance from Erhai Lake, but the opposite was observed for NH₄⁺-N in the shallow groundwater. The concentrations of nitrogen species in the rainy season were greater than those in the dry season. NO₃^--N accounted for more than 79% of total nitrogen in shallow groundwater. Redundancy analysis showed that more than 70% of the temporal and spatial variations of nitrogen concentrations in the shallow groundwater were explained by shallow groundwater depth, and only approximately 10% of variation was explained by the factors of soil porosity, silt clay content of soil, and NH₄⁺-N and NO₃^--N concentrations of soil (p < 0.05). The shallow groundwater depth had more notable effects on nitrogen concentrations in the shallow groundwater than other factors. This result will strongly support the need for further research regarding the management practices for reducing nitrogen concentrations in shallow groundwater.

[Effect of picroside Ⅱ on the expression of mitochondrial VDAC1 after cerebral ischemia/reperfusion in rats]

Objective: To explore the effect of picroside Ⅱ on the expression of mitochondrial voltage-dependent anion channel 1 (VDAC1) in rats after cerebral ischemiareperfusion. Methods: A total of 70 Wistar rats models with middle cerebral artery occlusionreperfusion (MCAO/R) were randomly divided into the sham group, model group, picroside (Picr) group, ruthenium red (RuR) group, RuR+ Picr group, Spermine (Sper) group, Sper+ Picr group (n=10 per group). Modified neurological severity scale (mNSS) was used to evaluated the neurobehavioral function, the expression of reactive oxygen species (ROS) in brain tissues were measured by enzyme-linked immunosorbent assay (ELISA), the morphology of brain tissues was observed by hematoxylin-eosin (HE) staining, the apoptotic cells were counted by terminal deoxynucleotidyl transferase dUTP nick end labeling assay (TUNEL), and the expressions of VDAC1 and endonuclease G (EndoG) were determined by immunohistochemical assay and Western blot. Results: Compared with the shame group, the mNSS scores (9.6±1.9), the expression of ROS[(47.6±2.7)U/ml], the apoptosis of neuron(23.8±2.8), and the expressions of VDAC1(0.94±0.06) and EndoG in cytoplasm (0.76±0.06) and nuclei(0.75±0.06)were enhanced in the model group (all P<0.05). The Picr group had obviously decreased mNSS scores (5.7±0.9), ROS expression[(35.6±2.2)U/ml], number of apoptotic cells (14.5±2.1), VDAC1 (0.63±0.06) and EndoG in cytoplasm (0.34±0.05) and nuclei (0.31±0.06)expressions compared to the model group (P<0.05). Conclusion: Picroside Ⅱ could attenuate cerebral I/R injury by down-regulating the expression of VDAC1 and inhibiting the EndoG release from mitochondria into cytoplasm.

Iron deficiency stress can induce MxNAS1 protein expression to facilitate iron redistribution in Malus xiaojinensis

Iron (Fe) is a vital trace element in plants, and deficiency of this element in apple trees can reduce fruit quality. Nicotianamine (NA) is known to play an important role in Fe transport and endogenous hormone balance. In the present study, we investigated the role of a nicotianamine synthase 1 gene (MxNas1) in an apple species, Malus xiaojinensis, that has a more Fe-efficient genotype than other apple species and ecotypes. To characterise the response of M. xiaojinensis to Fe deficiency, we used quantitative Q-PCR to determine the level of expression of MxNas1 and Western blot to measure protein levels. Immunohistochemical staining and GFP fluorescence localisation of the MxNAS1 protein were also carried out. HPLC and polarised absorption spectrophotometry were performed to investigate the effects of overexpression of MxNas1 in order to elucidate the role of MxNAS1 in the cellular uptake of active Fe in tobacco suspension cells. We found that MxNas1 expression and protein levels were higher under Fe deficiency stress than under Fe sufficiency. Immunohistochemical staining showed that MxNAS1 was localised mainly in the epidermal and vascular tissues of the roots, vascular tissues of the stem and palisade cells of mature leaves, and in parenchyma cells of young leaves. MxNAS1 was mainly localised in the plasma membranes and vesicles of protoplasts. In addition, overexpression of MxNas1 in stable transgenic tobacco cells increased NA and active Fe content under Fe sufficiency. The results suggest that MxNas1 expression in M. xiaojinensis is induced in response to Fe deficiency stress, resulting in higher levels of the protein. MxNAS1 may be involved in the redistribution of Fe in M. xiaojinensis under Fe deficiency.

Evaluating the risk of phosphorus loss with a distributed watershed model featuring zero-order mobilization and first-order delivery

Many semi-distributed models that simulate pollutants' losses from watersheds do not handle well detailed spatially distributed and temporal data with which to identify accurate and cost-effective strategies for controlling pollutants issuing from non-point sources. Such models commonly overlook the flow pathways of pollutants across the landscape. This work aims at closing such knowledge gap by developing a Spatially and Temporally Distributed Empirical model for Phosphorus Management (STEM-P) that simulates the daily phosphorus loss from source areas to receiving waters on a spatially-distributed grid-cell basis. STEM-P bypasses the use of complex mechanistic algorithms by representing the phosphorus mobilization and delivery processes with zero-order mobilization and first-order delivery, respectively. STEM-P was applied to a 217km² watershed with mixed forest and agricultural land uses situated in southwestern China. The STEM-P simulation of phosphorus concentration at the watershed outlet approximated the observed data closely: the percent bias (P_bias) was -7.1%, with a Nash-Sutcliffe coefficient (E_NS) of 0.80 on a monthly scale for the calibration period. The P_bias was 18.1%, with a monthly E_NS equal to 0.72 for validation. The simulation results showed that 76% of the phosphorus load was transported with surface runoff, 25.2% of which came from 3.4% of the watershed area (classified as standard A critical source areas), and 55.3% of which originated from 17.1% of the watershed area (classified as standard B critical source areas). The standard A critical source areas were composed of 51% residences, 27% orchards, 18% dry fields, and 4% paddy fields. The standard B critical source areas were mainly paddy fields (81%). The calculated spatial and temporal patterns of phosphorus loss and recorded flow pathways identified with the STEM-P simulations revealed the field-scale critical source areas and guides the design and placement of effective practices for non-point source pollution control and water quality conservation.

Cropping systems affect paddy soil organic carbon and total nitrogen stocks (in rice-garlic and rice-fava systems) in temperate region of southern China

The accumulation of soil organic carbon (SOC) in agricultural soils is critical to food security and climate change. However, there is still limited information on the dynamic trend of SOC sequestration following changes in cropping systems. Paddy soils, typical of temperate region of southern China, have a large potential for carbon (C) sequestration and nitrogen (N) fixation. It is of great importance to study the impacts of changes in cropping systems on stocks of SOC and total nitrogen (TN) in paddy soils. A six-year field experiment was conducted to clarify the dynamics of SOC and TN stocks in the paddy topsoil (0-20cm) when crop rotation of rice (Oryza sativa L.) -garlic (Allium sativum) (RG) was changed to rice-fava (Vicia faba L.) (RF), and to examine how the dynamics were affected by two N management strategies. The results showed that SOC stocks increased by 24.9% in the no N (control) treatment and by 18.9% in the treatment applied with conventional rate of N (CON), when RG was changed to RF. Correspondingly, TN stocks increased by 8.5% in the control but decreased by 2.6% in the CON. Compared with RG, RF was more conducive to increase the contents of soil microbial biomass C and N. Moreover, changing the cropping system from RG to RF increased the year-round N use efficiency from 21.6% to 34.4% and reduced soil N surplus in the CON treatment from 547kg/ha to 93kg/ha. In conclusion, changes in the cropping system from RG to RF could markedly increase SOC stocks, improve N utilization, reduce soil N surplus, and thus reduce the risk of N loss in the paddy soil. Overall, this study showed the potential of paddy agro-ecological systems to store C and maintain N stocks in the temperate regions.

Row Ratios of Intercropping Maize and Soybean Can Affect Agronomic Efficiency of the System and Subsequent Wheat

Intercropping is regarded as an important agricultural practice to improve crop production and environmental quality in the regions with intensive agricultural production, e.g., northern China. To optimize agronomic advantage of maize (Zea mays L.) and soybean (Glycine max L.) intercropping system compared to monoculture of maize, two sequential experiments were conducted. Experiment 1 was to screening the optimal cropping system in summer that had the highest yields and economic benefits, and Experiment 2 was to identify the optimum row ratio of the intercrops selected from Experiment 1. Results of Experiment 1 showed that maize intercropping with soybean (maize || soybean) was the optimal cropping system in summer. Compared to conventional monoculture of maize, maize || soybean had significant advantage in yield, economy, land utilization ratio and reducing soil nitrate nitrogen (N) accumulation, as well as better residual effect on the subsequent wheat (Triticum aestivum L.) crop. Experiment 2 showed that intercropping systems reduced use of N fertilizer per unit land area and increased relative biomass of intercropped maize, due to promoted photosynthetic efficiency of border rows and N utilization during symbiotic period. Intercropping advantage began to emerge at tasseling stage after N topdressing for maize. Among all treatments with different row ratios, alternating four maize rows with six soybean rows (4M:6S) had the largest land equivalent ratio (1.30), total N accumulation in crops (258 kg ha(-1)), and economic benefit (3,408 USD ha(-1)). Compared to maize monoculture, 4M:6S had significantly lower nitrate-N accumulation in soil both after harvest of maize and after harvest of the subsequent wheat, but it did not decrease yield of wheat. The most important advantage of 4M:6S was to increase biomass of intercropped maize and soybean, which further led to the increase of total N accumulation by crops as well as economic benefit. In conclusion, alternating four maize rows with six soybean rows was the optimum row ratio in maize || soybean system, though this needs to be further confirmed by pluri-annual trials.

Identifying critical nitrogen application rate for maize yield and nitrate leaching in a Haplic Luvisol soil using the DNDC model

Identification of critical nitrogen (N) application rate can provide management supports for ensuring grain yield and reducing amount of nitrate leaching to ground water. A five-year (2008-2012) field lysimeter (1 m × 2 m × 1.2 m) experiment with three N treatments (0, 180 and 240 kg Nha(-1)) was conducted to quantify maize yields and amount of nitrate leaching from a Haplic Luvisol soil in the North China Plain. The experimental data were used to calibrate and validate the process-based model of Denitrification-Decomposition (DNDC). After this, the model was used to simulate maize yield production and amount of nitrate leaching under a series of N application rates and to identify critical N application rate based on acceptable yield and amount of nitrate leaching for this cropping system. The results of model calibration and validation indicated that the model could correctly simulate maize yield and amount of nitrate leaching, with satisfactory values of RMSE-observation standard deviation ratio, model efficiency and determination coefficient. The model simulations confirmed the measurements that N application increased maize yield compared with the control, but the high N rate (240 kg Nha(-1)) did not produce more yield than the low one (120 kg Nha(-1)), and that the amount of nitrate leaching increased with increasing N application rate. The simulation results suggested that the optimal N application rate was in a range between 150 and 240 kg ha(-1), which would keep the amount of nitrate leaching below 18.4 kg NO₃(-)-Nha(-1) and meanwhile maintain acceptable maize yield above 9410 kg ha(-1). Furthermore, 180 kg Nha(-1) produced the highest yields (9837 kg ha(-1)) and comparatively lower amount of nitrate leaching (10.0 kg NO₃(-)-Nha(-1)). This study will provide a valuable reference for determining optimal N application rate (or range) in other crop systems and regions in China.