Fire Reduces Soil Nitrate Retention While Increasing Soil Nitrogen Production and Loss Globally.

Elucidating the response of soil gross nitrogen (N) transformations to fires could improve our understanding of how fire affects N availability and loss. Yet, how internal soil gross N transformation rates respond to fires remains unexplored globally. Here, we investigate the general response of gross soil N transformations to fire and its consequences for N availability and loss.

[Meta-analysis of Organic Carbon in Sandy Soil in Response to Amendment Application].

Proper application of soil amendments can effectively increase the accumulation of soil organic carbon （SOC） in poor soils, thereby enhancing soil fertility level. The impacts of different types of amendments on the SOC content of sandy soils varies widely. Investigating the effects of various amendments on the SOC content of sandy soils and associated key controlling factors provides a scientific basis for formulating strategies to enhance the fertility of sandy soils.

Biochar addition under straw return reduces carbon dioxide and nitrous oxide emissions in acidic tea field soil.

Straw return and biochar application are prevalent agricultural practices that bolster soil health, enhancing crop yields. However, their synergistic effects on carbon dioxide (CO) and nitrous oxide (NO) emissions in the acidic tea field soil at different age stages have not been fully elucidated. Herein, tea field soil with 5 and 15 years planting (5a and 15a, respectively) were individually incubated in five distinct indoor experiments: control, soil with urea (N), soil with urea and biochar (N + C), soil with urea and straw (N + S), and soil with urea, biochar, and straw (N + C + S).

[Effects of Biochar Application Two Years Later on NO and CH Emissions from RiceVegetable Rotation in a Tropical Region of China].

The effects of biochar application on soil nitrous oxide （NO） and methane （CH） emissions in a typical rice-vegetable rotation system in Hainan after two years were investigated. The aim was to clarify the long-term effects of biochar on greenhouse gas emissions under this model， and it provided a theoretical basis for NO and CH emission reduction in rice-vegetable rotation systems in tropical regions of China. Four treatments were set up in the field experiment， including no nitrogen fertilizer control （CK）； nitrogen， phosphorus， and potassium fertilizer （CON）； nitrogen， phosphorus， and potassium fertilizer combined with 20 t·hm biochar （B1）； and nitrogen， phosphorus， and potassium fertilizer combined with 40 t·hm biochar （B2）.

Twelve-year conversion of rice paddy to wetland does not alter SOC content but decreases C decomposition and N mineralization in Japan.

Land-use change worldwide has been driven by anthropogenic activities, which profoundly regulates terrestrial C and N cycles. However, it remains unclear how the dynamics and decomposition of soil organic C (SOC) and N respond to long-term conversion of rice paddy to wetland. Here, soil samples from five soil depths (0-25 cm, 5 cm/depth) were collected from a continuous rice paddy and an adjacent wetland (a rice paddy abandoned for 12 years) on Shonai Plain in northeastern Japan.

Climate controls on nitrate dynamics and gross nitrogen cycling response to nitrogen deposition in global forest soils.

Understanding the patterns and controls regulating nitrogen (N) transformation and its response to N enrichment is critical to re-evaluating soil N limitation or availability and its environmental consequences. Nevertheless, how climatic conditions affect nitrate dynamics and the response of gross N cycling rates to N enrichment in forest soils is still only rudimentarily known. Through collecting and analyzing 4426-single and 769-paired observations from 231 N labeling studies, we found that nitrification capacity [the ratio of gross autotrophic nitrification (GAN) to gross N mineralization (GNM)] was significantly lower in tropical/subtropical (19%) than in temperate (68%) forest soils, mainly due to the higher GNM and lower GAN in tropical/subtropical regions resulting from low C/N ratio and high precipitation, respectively.

Initial evidence on the effect of copper on global cropland nitrogen cycling: A meta-analysis.

Copper (Cu) is a key cofactor in ammonia monooxygenase functioning responsible for the first step of nitrification, but its excess availability impairs soil microbial functions and plant growth. Yet, the impact of Cu on nitrogen (N) cycling and process-related variables in cropland soils remains unexplored globally. Through a meta-analysis of 1209-paired and 319-single observations from 94 publications, we found that Cu (Cu addition or Cu-polluted soil) reduced soil potential nitrification by 33.

Land Use Change from Natural Tropical Forests to Managed Ecosystems Reduces Gross Nitrogen Production Rates and Increases the Soil Microbial Nitrogen Limitation.

Understanding the underlying mechanisms of soil microbial nitrogen (N) utilization under land use change is critical to evaluating soil N availability or limitation and its environmental consequences. A combination of soil gross N production and ecoenzymatic stoichiometry provides a promising avenue for nutrient limitation assessment in soil microbial metabolism. Gross N production via N tracing and ecoenzymatic stoichiometry through the vector and threshold element ratio (Vector-TER) model were quantified to evaluate the soil microbial N limitation in response to land use changes.

New vegetable field converted from rice paddy increases net economic benefits at the expense of enhanced carbon and nitrogen footprints.

China accounts for around 50 % of the global vegetable harvested area which is expected to increase continuously. Large cropland areas, including rice paddy, have been converted into vegetable cultivation to feed an increasingly affluent population and increase farmers' incomes. However, little information is available on the balance between economic benefits and environmental impacts upon rice paddy conversion into vegetable fields, especially during the initial conversion period.

Five-year vegetation conversion from pasture to C and C plants affects dynamics of SOC and TN and their natural stable C and N isotopes via mediating C input and N leaching.

Understanding the effects of land-use change on stock and composition of soil organic carbon (SOC) and nitrogen (N) is pivotal for sustainable agriculture and climate change adaption. However, previous studies have often overlooked the specific vegetation type in land-use changes. Therefore, a five-year lysimeter block experiment was conducted, involving non-vegetation, eulalia (C plant), and clover (C plant) to investigate the impacts of vegetation conversion from pasture on SOC and N dynamics and their natural stable isotopes.

Aridity creates global thresholds in soil nitrogen retention and availability.

Identifying tipping points in the relationship between aridity and gross nitrogen (N) cycling rates could show critical vulnerabilities of terrestrial ecosystems to climate change. Yet, the global pattern of gross N cycling response to aridity across terrestrial ecosystems remains unknown. Here, we collected 14,144 observations from 451 N-labeled studies and used segmented regression to identify the global threshold responses of soil gross N cycling rates and soil process-related variables to aridity index (AI), which decreases as aridity increases.

[Runoff Simulation and Its Response to Extreme Precipitation in the Yangtze River Basin].

Studies on runoff are crucial for the scientific allocation, utilization, and development of water resources and can provide an important basis for the prevention and control of flood and drought disaster, as well as water environmental pollution management. Affected by global warming, the frequency and intensity of extreme climate events, particularly extreme precipitation, have significantly changed in recent years, which can directly or indirectly impact runoff changes. In this study, we used the SWAT model to simulate the spatiotemporal variations in runoff in the Yangtze River Basin from 1965 to 2019 and analyzed the response of runoff to precipitation under extreme conditions.

Carbon and nitrogen fractions control soil NO emissions and related functional genes under land-use change in the tropics.

Converting natural forests to managed ecosystems generally increases soil nitrous oxide (NO) emission. However, the pattern and underlying mechanisms of NO emissions after converting tropical forests to managed plantations remain elusive. Hence, a laboratory incubation study was investigated to determine soil NO emissions of four land uses including forest, eucalyptus, rubber, and paddy field plantations in a tropical region of China.

[Effects of Biochar Amendment on NO Emission and Its Functional Genes in Pepper Growing Soil in Tropical Areas].

Biochar application may mitigate NO emissions and increase crop yield, yet little is known about microbial dynamics variation. To investigate the potential of increasing yield and reducing emissions of biochar in tropical areas and the dynamic mechanism of related microorganisms, a pot experiment was conducted to investigate the biochar application on pepper yield, NO emissions, and dynamic variation of related microorganisms. Three treatments were applied:2% biochar amendment (B), conventional fertilization (CON), and no nitrogen (CK).

[Effect of Different Fertilization Treatments on Methane and Nitrous Oxide Emissions from Rice-Vegetable Rotation in a Tropical Region, China].

The study of the effects of different fertilization treatments on soil methane (CH) and nitrous oxide (NO) emissions in rice-vegetable rotation systems is of great significance to supplement the research gap on greenhouse gas emissions in tropical regions of China. In this study, four fertilization treatments were set up during the pepper season:phosphorus and potassium fertilizer application (PK); nitrogen, phosphorus, and potassium (NPK) application; half application of nitrogen, phosphorus, and potassium plus half application of organic fertilizer (NPK+M); and application of organic fertilizer (M). There was no fertilizer application during the following early rice season.

[Effects of manure substituting chemical nitrogen fertilizer on rubber seedling growth and soil environment.].

The substitution of manure for chemical nitrogen fertilizers has great impacts on the growth of rubber seedlings and soil environment, with implications for rubber cultivation and transplantation and soil environment improvement. In this study, rubber seedlings of thermal research '7-33-97' strain were cultivated under four treatments: No fertilizer application (CK), only application of chemical fertilizer (N), manure replacing 50% chemical fertilizer (M+N), and manure replacing 100% chemical fertilizer (M). Plants parameters (including plant height, basal diameter, biomass, and chlorophyll), soil physicochemical properties (including pH, soil organic carbon and nitrogen, soil enzyme activities), and their relationships were investigated.

Biochar-induced reduction of NO emission from East Asian soils under aerobic conditions: Review and data analysis.

Global meta-analyses showed that biochar application can reduce NO emission. However, no relevant review study is available for East Asian countries which are responsible for 70% of gaseous N losses from croplands globally. This review analyzed data of the biochar-induced NO mitigation affected by experimental conditions, including experimental types, biochar types and application rates, soil properties, and chemical forms and application rates of N fertilizer for East Asian countries.

Winter nocturnal warming affects the freeze-thaw frequency, soil aggregate distribution, and the contents and decomposability of C and N in paddy fields.

Climate warming is expected to cause greater increases in nocturnal temperatures than daytime temperatures, thereby altering freeze-thaw cycles. Although the importance of freeze-thaw cycles in regulating soil aggregate stability and nutrient availability has attracted increasing attention, little is known about how winter nocturnal warming modulates freeze-thaw frequency, soil aggregate distribution, or the contents and mineralization of soil organic carbon (SOC) and total nitrogen (TN) in paddy fields. The nocturnal soil temperature in the upper 0-2 cm layer in a paddy field was elevated by approximately 2 °C using a passive nocturnal warming method during winter.

[Effects of Biochar Addition Under Different Water Management Conditions on NO Emission From Paddy Soils in Northern Hainan].

Alternating dry and wet conditions affect the main processes of NO production, such as nitrification and denitrification. Such conditions are very common in tropical rice-growing areas, such as Hainan. As a type of soil amendment, biochar is widely used to improve physical and chemical properties of soil and to reduce soil greenhouse gas emissions.

[Effects of Coconut Chaff Biochar Amendment on Methane and Nitrous Oxide Emissions from Paddy Fields in Hot Areas].

Based on the rice-vegetable crop rotation model, in-situ measurements of nitrous oxide (NO) and methane (CH) emissions were conducted in double-cropping rice fields in Hainan to determine the impact of coconut chaff biochar on greenhouse gas emissions. The experiment involved four treatments:conventional farming fertilization (CON), nitrogen fertilizer combined with 20 t ·hm biochar (B1), nitrogen fertilizer combined with 40 t ·hm biochar (B2), and no nitrogen fertilizer, as the control (CK). The NO and CH emissions were measured using static chamber-gas chromatography during the two paddy seasons, and the global warming potential (GWP) and greenhouse gas intensity (GHGI) were also estimated.

[Effects of Water and Fertilization Management on CH and NO Emissions in Double-rice Paddy Fields in Tropical Regions].

Paddy soils are widely considered a main source of methane (CH) and nitrous oxide (NO). Comprehensively evaluating CH and NO emissions from double-rice systems in tropical regions with different water irrigation and fertilizer applications is of great significance for addressing greenhouse gas emissions from such systems in China. In this study, eight treatments were evaluated:conventional irrigation-PK fertilizer (D-PK), conventional irrigation-NPK fertilizer (D-NPK), conventional irrigation-NPK+organic fertilizer (D-NPK+M), conventional irrigation-organic fertilizer (D-M), continuous flooding-PK fertilizer (F-PK), continuous flooding-NPK fertilizer (F-NPK), continuous flooding-NPK+organic fertilizer (F-NPK+M), and continuous flooding-organic fertilizer (F-M).