Dynamics of soil amino sugar pools during decomposition processes of corn residues as affected by inorganic N addition

Purpose  

Identifying the impact of inorganic-nitrogen (N) availability on soil amino sugar dynamics during corn (Zea mays L.) residue decomposition may advance our knowledge of microbial carbon (C) and N transformations and the factors controlling these processes in soils. Amino sugars are routinely used as microbial biomarkers to investigate C and N sequestration in microbial residues, and they are also involved in microbial-mediated soil organic matter (SOM) turnover. We conducted a 38-week incubation study using a Mollisol which was amended with corn residues and four levels of inorganic N (i.e., 0, 60.3, 167.2, and 701.9 mg N kg⁻¹ soil). The objective of this study was to examine the effects of inorganic-N availability on fungal and bacterial formation and stabilization of heterogeneous amino sugars during the corn residue decomposition in soil.     

Impact of in-season split application of nitrogen on intra-panicle grain dynamics,grain quality,and vegetative indices that govern nitrogen use efficiency in sorghum

Background

The correct rate and timing of nitrogen (N) has the potential to improve sorghum productivity through modified grain yield components and quality. The impacts of in-season split application of N have little documentation.

Aim

An experiment was conducted to determine the optimum rate and timing of N to relate vegetative indices that govern nitrogen use efficiency and to maximize grain yield and quality under different soil types.

Methods

Pioneer 86P20 was grown in three environments on two different soil types following a completely randomized block design with nine N application treatments. Treatments included differing N rates applied at critical developmental stages of sorghum (planting, panicle initiation, and booting), accompanied with high temporal aerial phenotyping.

Results

Opportunities to increase grain protein content while using split N applications were observed, with panicle initiation identified as a critical developmental stage. In-season split application of N enhances grain yield under low soil mineral N. Split application of 31 kg N ha⁻¹ each at the time of planting, panicle initiation, and booting emerged as optimum N treatment to increase protein content in sorghum. Vegetative indices, that is, normalized difference vegetation index and normalized difference red edge index are capable of predicting grain yield and protein content, respectively. Intra-panicle grain numbers and weights were altered significantly at different portions within panicles, with an opportunity to enhance yield potential at the bottom portion. The strong stay-green trait in this hybrid locked a large proportion of nitrogen in the leaves, which warrants the need for balancing stay-green and senescence in sorghum improvement programs.

Conclusions

Findings highlight that in grain sorghum remobilization of residual leaf N into grain is a target to increase yield and grain quality. An optimized stay-green trait balanced with senescence is recommended for enhancing sorghum yield potential.     

Compost type effects on nitrogen leaching from Inceptisol,Ultisol, and Andisol in a column experiment

Purpose  

To more efficiently utilize composts as N sources while minimizing the environmental impact, it is necessary to understand the effects of compost type on N mobility in compost-amended soil with different characteristics. The objectives of this study are to investigate the effects of livestock manure composts on N leaching from soils and to identify the principal physicochemical variables of the composts that affect N leaching.     

Soil soluble organic carbon and nitrogen pools under mono- and mixed species forest ecosystems in subtropical China

Purpose  

The objective of the present study was to assess the differences in soil total C and N, microbial biomass C and N, soil soluble organic C and N among eight mono- and mixed species forest ecosystems (18-year-old restoration) in subtropical China.     

Assessing long term effects of compost fertilization on soil fertility and nitrogen mineralization rate

Background

Fertilization with organic waste compost can close the nutrient cycles between urban and rural environments. However, its effect on yield and soil fertility must be investigated.

Aim

This study investigated the long-term effect of compost on soil nutrient and potentially toxic elements (PTEs) concentration, nutrient budgets, and nitrogen (N) mineralization and efficiency.

Methods

After 21 years of annual compost application (100/400 kg N ha^–1 year^–1 [100BC/400BC]) alone and combined with mineral fertilization, soil was analyzed for pH, organic carbon (SOC), nutrient (total N and P, N_min, extractable CAL-P, CAL-K, and Mg), and PTE (Cu, Ni, Zn) concentrations. Yields were recorded and nutrient/PTE budgets and apparent net mineralization (ANM, only 2019) were calculated.

Results

N efficiency was the highest in maize and for mineral fertilization. Compost application led to lower N efficiencies, but increased ANM, SOC, pH, and soil N, and surpluses of N, P, and all PTEs. Higher PTE concentrations were only found in 400BC for Cu. Nutrient budgets correlated with soil nutrient concentration. A surplus of 16.1 kg P ha^–1 year^–1 and 19.5 kg K ha^–1 year^–1 resulted in 1 mg kg^–1 increase in CAL-P and CAL-K over 21 years.

Conclusion

Compost application supplies nutrients to crops with a minor risk of soil-accumulation of PTEs. However, the nutrient stoichiometry provided by compost does not match crop offtakes causing imbalances. Synchronization of compost N mineralization and plant N demand does not match and limits the yield effect. In winter wheat only 65–70% of N mineralization occurred during the growth period.     

Long-term tree growth rate,water use efficiency,and tree ring nitrogen isotope composition of <Emphasis Type="Italic">Pinus massoniana</Emphasis> L. in response to global climate change and local nitrogen deposition in Southern China

Purpose  

We aimed to investigate long-term tree growth rates, water use efficiencies (WUE), and tree ring nitrogen (N) isotope compositions (δ¹⁵N) of Masson pine (Pinus massoniana L.) in response to global climate change and local N deposition in Southern China.     

Strategies for high nitrogen production and fertilizer value of plant-based fertilizers

Background

Organic vegetable production has a demand for alternative fertilizers to replace fertilizers from sources that are not organic, that is, typically animal-based ones from conventional farming.

Aims

The aim of this study was to develop production strategies of plant-based fertilizers to maximize cumulative nitrogen (N) production (equal to N yield by green manure crops), while maintaining a low carbon-to-nitrogen (C:N) ratio, and to test the fertilizer value in organic vegetable production.

Methods

The plant-based fertilizers consisted of the perennial green manure crops—alfalfa, white clover, red clover, and a mixture of red clover and ryegrass—and the annual green-manure crops—broad bean, lupine, and pea. The crops were cut several times at different developmental stages. The harvested crops were used fresh or pelleted as fertilizers for field-grown white cabbage and leek. The fertilizer value was tested with respect to biomass, N offtake, N recovery, and soil mineral N (N_min). Poultry manure and an unfertilized treatment were used as controls.

Results

The cumulative N production of the perennial green manure crops ranged from 300 to 640 kg N ha^–1 year^–1 when cut two to five times. The highest productions occurred at early and intermediate developmental stages, when cut three to four times. Annual green manure crops produced 110–320 kg N ha^–1 year^–1, since repeated cutting was restricted. The C:N ratio of the green manure crops was 8.5–20.5, and increased with developmental stage. The fertilizer value of green manure, as measured in white cabbage and leek, was comparable to animal-based manure on the condition that the C:N ratio was low (<18). N recovery was 20%–49% for green manure and 29%–42% for poultry manure. A positive correlation was detected between soil N_min and vegetable N offtake shortly after incorporating the green manure crops, indicating synchrony between N release and crop demand.

Conclusions

Plant-based fertilizers represent highly productive and efficient fertilizers that can substitute conventional animal-based fertilizers in organic vegetable production.     

Soil nitrogen mineralization and fate of (<Superscript>15</Superscript>NH<Subscript>4</Subscript>)<Subscript>2</Subscript>SO<Subscript>4</Subscript> in field-incubated soil in a hardwood plantation of subtropical Australia: the effect of mulching

Background, aim, and scope  

Mulching is frequently used to overcome the drought problem in hardwood plantations that are increasingly being established in lower rainfall areas of Queensland, Australia because of increasing land values. In addition to soil water content, soil nitrogen (N) availability is another critical determinant of plantation productivity in these areas. The purpose of this study was to understand how soil mineral N dynamics, in situ N mineralization, and the fate of fertilized N would be affected by mulching during the early establishment of hardwood plantations.     

Field-applying an inexpensive, 13C-depleted,labile carbon source to study in situ fate and short-term effects on soils

Background

Labile carbon (C_labile) limits soil microbial growth and is critical for soil functions like nitrogen (N) immobilization. Most experiments evaluating C_labile additions use laboratory incubations. We need to field-apply C_labile to fully understand its fate and effects on soils, especially at depth, but high cost and logistical difficulties hinder this approach.

Aims

Here, we evaluated the impact of adding an in situ pulse of an inexpensive and ¹³C-depleted source of C_labile—crude glycerol carbon (C_glyc), a by-product from biodiesel production—to agricultural soils under typical crop rotations in Iowa, USA.

Methods

We broadcast-applied C_glyc at three rates (0, 216, and 866 kg C ha⁻¹) in autumn after soybean harvest, tracked its fate, and measured its impact on soil C and N dynamics to four depths (0–5, 5–15, 15–30, and 30–45 cm). Nineteen days later, we measured C_glyc in microbial biomass carbon (MBC), salt-extractable organic C, and potentially mineralizable C pools. We paired these measurements with nitrate N (NO₃⁻–N) and potential net N mineralization to examine short-term effects on N cycling.

Results

C_glyc was found to at least 45-cm depth with the majority in MBC (18%–23% of total C_glyc added). The δ¹³C values of the other measured C pools were too variable to accurately track the C_labile fate. NO₃⁻–N was decreased by 13%–57% with the 216 and 866 kg C ha⁻¹ rates, respectively, and was strongly related to greater microbial uptake of C_glyc (i.e., immobilization via microbial biomass). Crude glycerol application had minor effects on soil pH—the greatest rate decreased pH 0.18 units compared to the control.

Conclusions

Overall, glycerol is an inexpensive and effective way to measure in situ, C_labile dynamics with soil depth—analogous to how mobile, dissolved organic C might behave in soils—and can be applied to rapidly immobilize NO₃⁻–N.     

Nitrogen loading levels affect abundance and composition of soil ammonia oxidizing prokaryotes in semiarid temperate grassland

Purpose  

Global nitrogen deposition has profound impact on the terrestrial ecosystem including the semiarid temperate grassland, causing vegetation community shifts and soil acidification. Little is known regarding the effect of nitrogen (N) deposition on the belowground microbial communities. This study aimed to examine the response of ammonia-oxidizing bacteria (AOB) and archaea (AOA) to added N in semiarid temperate grassland.     

A lysimeter study of nitrate leaching and optimum nitrogen application rates for intensively irrigated vegetable production systems in Central China

Background, aim, and scope  

Nitrate leaching from intensive vegetable production is an important contributor of nitrate contamination of water resources. The aim of this study was to quantify NO₃ ⁻ leaching losses under intensive vegetable production as affected by different rates of N fertilizer and to determine the optimum N application rates both for vegetable production and for meeting the drinking water standard.     

Carbon dynamics in subtropical forest soil: effects of atmospheric carbon dioxide enrichment and nitrogen addition

Purpose  

The levels of atmospheric carbon dioxide concentration ([CO₂]) are rapidly increasing. Understanding carbon (C) dynamics in soil is important for assessing the soil C sequestration potential under elevated [CO₂]. Nitrogen (N) is often regarded as a limiting factor in the soil C sequestration under future CO₂ enrichment environment. However, few studies have been carried out to examine what would happen in the subtropical or tropical areas where the ambient N deposition is high. In this study, we used open-top chambers to study the effect of elevated atmospheric [CO₂] alone and together with N addition on the soil C dynamics in the first 4 years of the treatments applied in southern China.     

Photosynthesis acclimation,leaf nitrogen concentration,and growth of four tree species over 3 years in response to elevated carbon dioxide and nitrogen treatment in subtropical China

Purpose  

Up to date, most studies about the plant photosynthetic acclimation responses to elevated carbon dioxide (CO₂) concentration have been performed in temperate areas, which are often N limited under natural conditions and with low ambient N deposition. It is unclear whether photosynthetic downregulation is alleviated with increased N availability, for example, from increased N deposition due to fossil fuel combustion in the tropics and subtropics. Awareness of plant photosynthetic responses to elevated CO₂ concentration will contribute to the better understanding and prediction of future forest productivity under global change.     

Symbiotic nitrogen fixation and soil N availability under legume crops in an arid environment

Purpose  

Legume crops often present an important option to maintain and improve soil nitrogen (N) quality and fertility in a dryland agroecosystem. However, the work on the integral assessment of the symbiotic N₂ fixation (N_fix) and their effects on soil N availability under field conditions is scare.     

A liquid chromatographic/mass spectrometric method to evaluate <Superscript>13</Superscript>C and <Superscript>15</Superscript>N incorporation into soil amino acids

Purpose  

Amino acids are highly associated with biogeochemical cycling and represent an important potential source and sink of carbon (C) and nitrogen (N) in terrestrial ecosystems. Tracing the isotope dynamics of amino acids can improve the understanding of the origin and transformation of amino acids in soil matrix at process-levels; hence, the liquid chromatographic/mass spectrometric (LC/MS) method to evaluate ¹³C or ¹⁵N enrichment in amino acids is necessary to be established.     

Effect of soil sealing on the microbial biomass,N transformation and related enzyme activities at various depths of soils in urban area of Beijing,China

Purpose  

Sealing of soils prevents the exchange of gas, water and nutrient between soil and other environmental compartments, and affects urban N flux, thereby resulting in certain negative impacts on soil functioning and urban environment. However, little information is available on the biogeochemical cycling and biological activities after sealing of soils in urban areas. The aim of this study was to assess the effects of soil sealing on N transformation and associated microbial properties.     

Suppression of NH<Subscript>3</Subscript> and N<Subscript>2</Subscript>O emissions by massive urea intercalation in montmorillonite

Purpose  

A large amount of nitrogen (N) fertilizers has been broadcasted over soil surface for reliable crop production. Unfortunately, the broadcasted N vulnerable to volatilization and leaching can lead to serious environmental problems. As a new approach to mitigate N loss of broadcasted fertilizers, massive intercalation of urea into montmorillonite (MMT) was recently proposed to innovatively enhance the urea use efficiency. This study focuses on demonstrating the behaviors of the urea intercalated into MMT in soils.     

Nitrogen deposition influences nitrogen isotope composition in soil and needles of <Emphasis Type="Italic">Pinus massoniana</Emphasis> forests along an urban-rural gradient in the Pearl River Delta of south China

Purpose  

Atmospheric nitrogen (N) deposition remains globally and regionally a significant N source in forest ecosystems, with intensive industrial activities. Stable N isotope ratio (δ¹⁵N) is a useful indicator widely adopted to assess environmental and ecological impacts of anthropogenic N inputs. On the basis of temporal changes in tree ring δ¹⁵N established recently, the present study investigated the influence of N deposition on δ¹⁵N in needles of Masson pine (Pinus massoniana L.) and forest soil along an urban–rural gradient in the Pearl River Delta of south China.     

Soil soluble organic nitrogen and active microbial characteristics under adjacent coniferous and broadleaf plantation forests

Purpose  

Soil soluble organic nitrogen (SON) is considered as a sensitive indicator of soil nitrogen (N) status and plays an important role in N cycling in forest ecosystems. Most work on forest soil SON to date has been conducted in temperate areas. The information about soil SON pools and dynamics in tropical and subtropical areas is limited. The aim of this study was to investigate the effects of different forest types on soil SON availability and associated microbial properties.     

Appraisal of 15N enrichment and 15N natural abundance methods for estimating N2 fixation by understorey Acacia leiocalyx and A. disparimma in a native forest of subtropical Australia

Purpose  

It is anticipated that global climate change will increase the frequency of wildfires in native forests of eastern Australia. Understorey legumes such as Acacia species play an important role in maintaining ecosystem nitrogen (N) balance through biological N fixation (BNF). This is particularly important in Australian native forests with soils of low nutrient status and frequent disturbance of the nutrient cycles by fires. This study aimed to examine ¹⁵N enrichment and ¹⁵N natural abundance techniques in terms of their utilisation for evaluation of N₂ fixation of understorey acacias and determine the relationship between species ecophysiological traits and N₂ fixation.