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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.
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Nitrogênio , Oryza , Agricultura/métodos , China , Fertilizantes , Nitrogênio/análise , Fósforo/análise , Água/análiseRESUMO
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.
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Fertilizantes , Solo , Agricultura , China , Poluição Ambiental , Nitrogênio/análise , Óxido Nitroso/análiseRESUMO
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.
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Agricultura , Plásticos , China , Produtos Agrícolas , Ecossistema , Abastecimento de Alimentos , SoloRESUMO
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 0.06â¯mgâ¯L-1 at the rice maturation stage. The concentration was lower than that of incoming irrigation water (0.13â¯mgâ¯L-1) and rainwater (0.17â¯mgâ¯L-1). Although both paddy soil and ditch sediment had low degree of P saturation, the ditch sediment had greater P binding energy (1.58â¯Lâ¯mg-1) and larger maximum P sorption (526â¯mgâ¯kg-1) than the soil (0.88â¯Lâ¯mg-1 and 455â¯mgâ¯kg-1, respectively). The P mass balance for the rice season over the four consecutive years showed a net depletion of 3.36-8.11â¯kgâ¯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.
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Oryza , Fósforo , Agricultura , China , Solo , Movimentos da ÁguaRESUMO
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.
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Rios , Poluentes Químicos da Água , China , Monitoramento Ambiental , Nitrogênio , Nutrientes , FósforoRESUMO
Substituting synthetic fertilizers with manures in agriculture enhances soil properties and crop yield. However, the impact on nitrous oxide (N2O) emissions, especially from the soil profile, remains poorly understood. This study examined emissions from 2017 to 2019 on a well-established (>10-year) maize field site in the North China Plain. Three treatments were compared: 100â¯% synthetic nitrogen (NPK), 50â¯% synthetic fertilizer Nâ¯+â¯50â¯% manure N substitution (50%MNS), and 100â¯% manure N substitution (100%MNS). N2O emissions were monitored for three years, and in 2019, N2O concentrations at 20â¯cm and 40â¯cm soil depths were analyzed in relation to surface N2O fluxes and environmental factors. The results showed manure substitution resulted in about 13.8â¯%-25.2â¯% (50%MNS) and 40.3â¯%-72.2â¯% (100%MNS) reduction in N2O emissions over the 3-year period compared with the NPK treatment. Throughout the maize growing season, the top-dressing accompanied by rainfall was responsible for the N2O emissions. The difference in N2O concentrations between all the treatments at 20â¯cm depth was insignificant, but at 40â¯cm depth the N2O concentrations were significantly higher for the 50%MNS treatment than the other treatments. The N2O fluxes and N2O concentration were not synchronized especially in NPK. The decoupled relationship between the N2O fluxes and the N2O concentration in the soil profile depth suggested the contribution of N2O produced in the soil profile to the surface N2O fluxes is limited. This study highlights that manure substitution is an efficient measure to reduce N2O emissions.
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Microbial nitrogen (N) removal is crucial for purifying surface water quality in paddy irrigation and drainage units (IDUs). However, the spatiotemporal microbial N removal potential characteristics within these IDUs and the effects of changing anaerobic conditions on this potential remain insufficiently studied. In this study, we investigated the microbial N removal potential of conventional rice-wheat rotation and anaerobically enhanced rice-crayfish rotation IDUs using field measurements, isotope tracing techniques, and quantitative PCR. Our findings reveal that paddy fields were identified as hotspots for anammox activity, contributing to 76.0 %-97.4 % of the total anammox N removal potential in the IDU, while denitrification processes in ditches accounted for 43.5 %-77.4 % of the IDU's denitrification potential. During the rice transplanting period, the anammox N removal potential peaked, representing 35.8 % and 71.8 % of the total anammox N removal potential of the paddy fields in rice-wheat and rice-crayfish IDUs, respectively. An increase in anaerobic conditions diminished the anammox N removal potential while amplifying denitrification capabilities. The N removal potential in paddy fields decreased with increasing depth, contrasting with the relative stability in ditches. Spatiotemporal fluctuations in N removal potentials within these units are influenced by Fe2+ concentration, carbon and N content, WFPS, and pH levels. This study provides a scientific basis for improving nitrogen removal and water quality treatment in IDUs.
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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.
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Poluentes Químicos da Água , Qualidade da Água , Monitoramento Ambiental , Chuva , Rios , Lagos , Nitrogênio/análise , China , Poluentes Químicos da Água/análiseRESUMO
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.
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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.
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Oryza , Solo , Nitrogênio/análise , Ecossistema , Óxido Nitroso/análise , Agricultura/métodos , China , Triticum , Metano/análise , Fertilizantes/análiseRESUMO
In recent years, the excessive application of nitrogen and phosphorus fertilizers has caused serious pollution and eutrophication, especially in paddy fields. Accordingly, a two-year (2018-2019) study was conducted at a rice paddy field under different fertilizer application rates and straw mulching in Chengdu Plain. N and P losses through the rainfall and surface runoff in the paddy field were measured under natural rainfall conditions. The results showed that nitrogen mainly existed in the form of ammonium nitrogen, and phosphorus mainly existed in the form of soluble phosphorus in the wet deposition. The wet deposition of nitrogen and phosphorus mainly occurred in June, July, and August. Surface runoff was positively correlated with rainfall, whereas surface runoff nitrogen concentration was inversely correlated with rainfall. The highest runoff losses of TN (4.75 kg·hm-2 in 2018 and 2.68 kg·hm-2 in 2019) were produced by TR3 practice and were 26.73% and 43.32% higher than that of the conventional practice. TN runoff loss was significantly decreased by reducing the rate of N fertilizer (P<0.05). Compared with that in the conventional practice TR1, TR4 reduced the N loss by 36.33% in 2018 and 26.74% in 2019, respectively. Optimized fertilizer TR2 and nitrogen reduction practice TR4 decreased P loss from surface runoff, and high intensity rainfall could reduce the content of granular phosphorus in surface runoff. The surface runoff occurring in July, August, and September contributed mostly to the total N loss, whereas the loss of total P mainly occurred before July. Consequently, the use of balanced fertilizer and decreased nitrogen fertilization amount might be effective strategies to attenuate non-point source pollution in the Chengdu Plain in the paddy fields.
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Oryza , Fósforo , Fósforo/análise , Agricultura/métodos , Nitrogênio/análise , Fertilizantes , Fertilização , Movimentos da Água , Solo , ChinaRESUMO
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.
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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.
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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.
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Antibacterianos , Solo , Antibacterianos/farmacologia , Biossólidos , Resistência Microbiana a Medicamentos/genética , Genes Bacterianos , Esterco , Microbiologia do SoloRESUMO
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.
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Oryza , Animais , Astacoidea , Fertilizantes , Nitrogênio/análise , Fósforo , Solo , Triticum , Água/análiseRESUMO
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.
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Fósforo , Solo , Agricultura , China , Fertilizantes/análise , Nitrogênio/análise , Fósforo/análise , Verduras , Qualidade da ÁguaRESUMO
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.
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Fertilizantes , Gases de Efeito Estufa , Agricultura , Arachis , Biomassa , Carvão Vegetal , Fertilizantes/análise , Óxido Nitroso/análise , Solo , Microbiologia do SoloRESUMO
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.
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Metano , Oryza , Anaerobiose , Biocombustíveis , Reatores Biológicos , Ácidos Graxos VoláteisRESUMO
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.
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Agricultura , Monitoramento Ambiental/métodos , Praguicidas/efeitos adversos , Medição de Risco/métodos , Poluentes Químicos da Água , China , Política Ambiental , HumanosRESUMO
The emission of nitrogen and phosphorus via non-point source pollution from a small watershed has become the main pollution source of river waters, while climatic conditions and human activities directly affect the changes in rainfall-runoff and types of land use that are closely related to nitrogen and phosphorus pollution. In this study, we explore the runoff loss, nitrogen and phosphors concentration, and nitrogen and phosphorus emission in Huajiaogou small watershed on the upper reaches of Yangtze River. The rainfall, runoff, and temporal changes of nitrogen and phosphorus were analyzed using the continuous position monitoring data. The results showed that:â the runoff volumes were 10.05×105 m3 and 3.34×105 m3 from July 1st to September 30th, accounting for 76.58% and 56.51% in 2012 and 2013, respectively, and they were positively correlated to rainfall. The peak concentrations of ammonia nitrogen (NH4+-N) from April 1st to June 30th were 11.51 mg ·L-1 and 4.44 mg ·L-1in 2012 and 2013, respectively. â¡ The NH4+-N emission risk period was from July 1st to September 30th, accounting for 78.45% and 62.24% in 2012 and 2013, respectively. The peak concentration and emission risk period of total nitrogen (TN) and nitrate nitrogen (NO3--N) were from July 1st to September 30th, and NO3--N was the main form of the total nitrogen emission. The peak concentration of NO3--N was 6.06 mg ·L-1 and 11.43 mg ·L-1in 2012 and 2013, respectively, and the loss in NO3--N from July 1st to September 30th accounted for 88.74% and 65.55% in 2012 and 2013, respectively. â¢The emission risk period of total phosphorus (TP), dissolved total phosphorus (DTP), and particulate phosphorus (PP) was also from July 1st to September 30th, and the particulate phosphorus was the main form of the total phosphorus emission. The particulate phosphorus emission from July 1st to September 30th accounted for 36% and 68% in 2012 and 2013, respectively, and the ration of particle phosphorus to total phosphorus was easily affected by rainfall.