Amino Sugar Nitrogen Research Articles

Plateau pika bioturbation leads to lower soil organic nitrogen fractions of bare patches in alpine meadows

The small semi–fossorial herbivore bioturbation has been verified to affect available soil nitrogen in grasslands, but the effects of small semi–fossorial herbivore bioturbation on soil organic nitrogen (SON) fractions that are main compositions of soil total nitrogen and sources of soil available nitrogen remain poorly known. The plateau pika (Ochotona curzoniae) bioturbation creates numerous bare patches, which intersperse within vegetated surfaces in grasslands. In this study, plateau pika was considered as an example animal to examine the differences of SON fractions between bare patches and vegetated surfaces under the small semi–fossorial herbivore bioturbation across six sites. This study demonstrated that acid–hydrolysable nitrogen (AHN) was 27.58% lower in bare patches than in vegetated surfaces. Amino acid nitrogen (AAN), ammonium nitrogen (AN), amino sugar nitrogen (ASN) and unknown nitrogen (UN) in bare patches were 35.23%, 17.07%, 17.70% and 19.87% lower than those in vegetated surfaces, respectively. The contribution of AAN to AHN was 5.3% lower in bare patches than in vegetated surfaces, but the contributions of AN, ASN and UN to AHN were 2.42%, 1.11%, and 1.77% higher, respectively. The response of AAN to plateau pika bioturbation was more sensitive than AN, ASN and UN. These findings verify the plateau pika bioturbation leads to a lower potential capacity of soil nitrogen supply in bare patches than in vegetated surfaces, and present a possible pattern of SON fractions in relation to small semi–fossorial herbivore bioturbation in grasslands.

Effects of Different Ecological Restoration Pattern on Soil Organic Nitrogen Components in Alpine Sandy Land

Ecological restoration can improve soil fertility and have a significant impact on the soil nitrogen cycle. Nitrogen (N) is an essential nutrient element for plant growth and development, and also an important factor limiting soil productivity. As an important part of soil nitrogen, the composition and proportion of soil organic nitrogen components can directly or indirectly affect the difficulty of soil organic nitrogen mineralization and nitrogen availability, and then affect soil fertility. However, the current studies on soil nitrogen under ecological restoration mainly focus on nitrogen accumulation and nitrogen mineralization, while there are relatively few studies on changes in soil organic nitrogen components, especially in alpine regions. Therefore, in this study, three restoration pattern of mixed forage (MG), single shrub (SA) and shrub combination (SG) that have been restored continuously for 15 years in northwest Sichuan, China, were taken as the research object, and natural sandy land (CK) without manual intervention was taken as the control. Through field sampling and laboratory analysis, the characteristics of the soil nitrogen content and its proportion to soil total nitrogen (TN) under ecological restoration in alpine sandy land in northwest Sichuan, China, were investigated, and the correlation between the nitrogen content and soil physicochemical properties was analyzed. The results showed that the three ecological restoration patterns significantly increased the contents of acylated ammonium nitrogen (AMMN), acid-lyzed amino sugar nitrogen (ASN), acid-lyzed amino acid nitrogen (AAN), acid-lyzed unknown nitrogen (HUN), acid-lyzed total nitrogen (AHN) and non-acid-lyzed nitrogen (NHN) in soil, and the change trend was consistent with that of soil TN. Ecological restoration improved soil nitrogen mineralization and storage capacity by increasing the proportion of AAN, HUN and NHN to soil TN, and the effect was most obvious in the MG pattern 20–40 cm and SG pattern 40–60 cm soil layers. In general, except ASN, the soil nitrogen content was positively correlated with the soil TN, soil water content (SWC) and soil organic carbon (SOC), and negatively correlated with the soil bulk density (BD) and pH. The results of this study will help us to understand the supply capacity of soil nitrogen under ecological restoration and provide a scientific basis for the selection of an ecological restoration mode and the improvement of the restoration effect and efficiency in alpine sandy land.

Response of Soil Nitrogen Components and nirK- and nirS-Type Denitrifying Bacterial Community Structures to Drip Irrigation Systems in the Semi-Arid Area of Northeast China

Denitrification is a key process in soil available nitrogen (N) loss. However, the effects of different water-saving irrigation systems on soil N components and denitrifying bacterial communities are still unclear. In this study, quantitative fluorescence PCR and Illumina MiSeq sequencing were used to investigate the effects of three main irrigation systems, conventional flooding irrigation (FP), shallow buried drip irrigation (DI), and mulched drip irrigation (MF), on the abundance, community composition, and diversity of soil nirK- and nirS-type denitrifying bacteria in the semi-arid area of Northeast China, and to clarify the driving factors of nirK- and nirS-type denitrifying bacterial community variations. The results showed that, compared with FP, MF significantly increased soil moisture, alkaline hydrolyzed nitrogen (AHN), nitrate nitrogen (NO3−-N), non-acid hydrolyzed nitrogen (AIN), and amino sugar nitrogen (ASN), but significantly decreased the contents of ammonium nitrogen (NH4+-N) and acid hydrolyzed ammonium nitrogen (AN). The irrigation system changed the relative abundance of the dominant genera of denitrifying bacteria, DI and MF significantly increased nitrate reductase (NR) and nitrite reductase (NiR) activities, and MF significantly increased the diversity of nirK- and nirS-type denitrifying bacteria but significantly decreased the richness. The community structure of nirK- and nirS-type denitrifying bacteria was significantly different among the three irrigation systems. NO3−-N was the main driving factor affecting the community structure of nirS-type denitrifying bacteria, and moisture significantly affected the community structure of nirK-type denitrifying bacteria. DI and MF significantly increased the abundance of nirK- and nirS-type denitrifying bacteria and also increased the abundance ratio of nirS/nirK genes. Therefore, although DI and MF significantly increased the abundance of denitrifying microorganisms, they did not lead to an increase in the N2O emission potential.

Long-term straw returning improved soil nitrogen sequestration by accelerating the accumulation of amino acid nitrogen

Straw incorporation has been widely recommended as an effective management practice to increase soil nitrogen stocks in agroecosystems worldwide. However, the overall trend and magnitude of changes in various soil organic nitrogen fractions in response to crop residue return and their contribution to soil nitrogen sequestration remain uncertain. Here, we show through a long-term experiment (12 years) that straw return increased soil total nitrogen and soil nitrogen sequestration rate by 20.01% and 120.95%, respectively. Ammonia nitrogen, amino acid nitrogen, and amino sugar nitrogen were affected by straw and its interaction with year, and increased by 43.08%, 27.70%, and 46.56%, respectively, with the highest growth rate in amino acid nitrogen (10.51 mg kg−1 yr−1). Furthermore, redundancy analyses showed that soil total organic carbon and C:N ratio were the major factors explaining the variations in soil organic nitrogen fractions, which increased by 46.22% and 21.75%, respectively. The structural equation model further revealed that amino acid nitrogen was a pivotal driver of soil nitrogen sequestration, because the soil C:N ratio indirectly influenced soil nitrogen sequestration via affecting the accumulation of amino acid nitrogen. Our results suggest that long-term straw return can improve nitrogen sequestration by accelerating the accumulation of amino acid nitrogen and that soil nitrogen storage and supply capacity may be improved by adopting straw incorporation and other appropriate management practices to regulate soil stoichiometry.

Impact of fertilization and grazing on soil N and enzyme activities in a karst pasture ecosystem

The biggest obstacle to economic development in karst areas comes from the ecological crisis, so healthy soil and adequate food are important. Soil nitrogen (N) is an important factor in maintaining soil quality. Understanding the changes in soil N fractions and enzyme activities under different management practices is important to maintain sustainable pastureland in karst areas. In this study, we investigated how grazing and fertilization affect different soil nitrogen fractions and enzyme activities of karst pastureland. The four treatments were unused land (UL, undisturbed utilization), abandoned-grazing pastureland (APL, grazing for three years followed by abandonment for six years), grazing pastureland (GPL, controlled grazing without fertilizer) and fertilized-grazing pastureland (FGPL, controlled grazing + fertilizer), with the aim of determining the management practices that is most beneficial to soil N in the area. Our results indicated that FGPL is the most beneficial in enhancing soil N fractions. This is reflected in greater total nitrogen (TN), alkaline driven nitrogen (NOH), inorganic nitrogen (TON), anaerobic mineralized nitrogen (The average increase in each soil layer over UL was 1.43 times; TMN), microbial biomass nitrogen (The average increase in each soil layer over UL was 3.51 times; MBN), amino acid nitrogen (AAN), amino sugar nitrogen (ASN), acidolyzed unknown nitrogen (TUN) and unacidified nitrogen (AIN) in FGPL soils. Likewise, greater enzyme activities were also found in nitrogen conversion-related enzymes (soil urease (S-UE), soil N-acetyl-β-D-aminoglucosidase (S-NAG), nitrate reductase (S-NR), and soil acid protease (S-ACPT)). In addition, the combination of grazing and balanced nutrient inputs slowed soil acidification and maintained high levels of total phosphorus (TP) and total potassium (TK). In contrast, the soil N fractions responded significantly to APL (low TN and plant effective nitrogen), while insufficient conversion capacity (enzyme activity, MBN) was the main reason for the compromised soil N availability at GPL. Government policy makers and livestock producers should encourage controlled grazing with proper fertilizer supplementation, and avoid prolonged abandonment of grazing lands.

Impacts of Different Long-Term Fertilizer Management Regimes on Soil Nitrogen Mineralization and Its Enzyme Activities under a Double-Cropping Rice System in Southern China

Soil extracellular enzyme activities play an important role in regulating the soil nitrogen (N) mineralization process in paddy fields. However, there is still a need to further study how N mineralization responds to different fertilizer management techniques and the soil extracellular enzyme activities for N mineralization in paddy fields. Therefore, the influence of different long-term (35 years) fertilizer regimes on soil N mineralization, hydrolysable N fractions—such as hydrolyzed unknown nitrogen (HUN), amino acid nitrogen (AAN), amino sugar nitrogen (ASN), ammonia nitrogen (AN), and total acid-hydrolyzed nitrogen (TAN)—and their extracellular enzyme activities (soil urease, L-glutaminase, β-glucosidase, arylamidase, and β-glucosaminidase) in a double-cropping rice field in southern China were investigated in this study. The field experiment included the following fertilizer regimes: rice straw and inorganic fertilizer (RF), 30% organic manure and 70% inorganic fertilizer (OM), inorganic fertilizer alone (MF), and no application of inorganic fertilizer as a control (CK). The results show that the soil ammonium N, amino sugar N, hydrolysable unidentified N, and amino acid N contents in the paddy field with RF treatment increased by 30.56%, 5.51%, and 62.74% compared with the CK treatment. The results show that the soil aerobic and anaerobic N mineralization rates in the paddy fields with OM and RF treatments increased by 22.92% and 18.27% compared with those with MF treatment. Moreover, soil extracellular enzyme activities under RF and OM treatments significantly increased, which indicated that the main substrate of microbial activity was effective. Correlation analysis indicated that the soil L-glutaminase activity, amino sugar N, amino acid N, and total acid-hydrolysable N contents were positively correlated with soil aerobic and anaerobic N mineralization rates in paddy fields. However, there was a negative correlation between the soil N mineralization rate and soil β-glucosaminidase activity in paddy fields. This finding shows that the yields of early rice and late rice under the RF and OM treatments were significantly higher than those under the MF and CK treatments. Compared with the MF treatment, the yields of double-cropping rice with RF and OM treatments increased by 9.84% and 11.37%, respectively. As a result, the application of straw or organic manure and inorganic fertilizer was effective for improving soil N mineralization, the soil acid-hydrolyzed N content, and extracellular enzyme activities in double-cropping rice fields.

Mixed Plantations Induce More Soil Macroaggregate Formation and Facilitate Soil Nitrogen Accumulation

Nitrogen plays a crucial role in limiting plant growth and determining net primary productivity in forest ecosystems. However, variations and influencing factors of soil nitrogen distribution on the aggregate scale in pure and mixed Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations remain unclear. This study aimed to explore how soil aggregate composition, geometric mean diameter (GMD), mean weight diameter (MWD), total nitrogen (TN), total acidolyzable nitrogen (TAN), available nitrogen (AN), nonacidolyzable nitrogen (AIN), amino acid nitrogen (AAN), nitrate nitrogen (NO3−-N), cidolyzable ammonia nitrogen (AMN), unknown-acidolyzable nitrogen (HUN), amino sugar nitrogen (ASN), and ammonium nitrogen (NH4+-N) contents and stocks varied with aggregate size (>2, 1–2, 0.25–1, and <0.25 mm) and stand type [Chinese fir mixed with Michelia macclurei Dandy (CF + MM), Chinese fir mixed with Mytilaria laosensis Lecomte (CF + ML) and pure stands of Chinese fir (CF)] in 0–20 and 20–40 cm soil depth. Soil N content in different stand types of Chinese fir plantations decreased as the aggregate size increased, whereas the soil N stock exhibited the opposite trend. In contrast to CF soil, CF + MM and CF + ML soil displayed a significant increase in MWD, GMD, and aggregate-associated TN, AN, NO3−-N, NH4+-N, AIN, AAN, ASN, and AMN contents and stocks, especially CF + MM soil. Organic N was more sensitive to the response of aggregate size and stand type than mineral N. Redundancy analysis and Pearson’s correlation analysis indicated that the 0.25–1 mm aggregate proportion was the main controlling factor for the variations in soil N content and storage. Overall, this study contributed significantly to the promotion of the sustainable use of soil resources and reference information for the scientific management and sustainable development of Chinese fir forests.

The six-year biochar retention interacted with fertilizer addition alters the soil organic nitrogen supply capacity in bulk and rhizosphere soil

Nitrogen fractions in soil, like organic nitrogen, mineral nitrogen, and free amino acids, are sensitive pointers to the soil nitrogen pools involved in nutrient cycling. As a potential improvement measure, biochar might improve soil fertility and nutrient availability. However, few studies have focused on the long-term effects of biochar retention on the soil nitrogen supply capacity of bulk and rhizosphere soil in brown earth. Therefore, a six-year field experiment was conducted in 2013, concentrating on the impact of biochar retention on soil nitrogen fractions. Four biochar rates were tested: no biochar amendment (CK); 15.75 t ha−1 of biochar (BC1); 31.5 t ha−1 of biochar (BC2); 47.25 t ha−1 of biochar (BC3). Our results showed that the elevated application rates significantly enhanced soil organic matter (SOM), and total nitrogen (TN), and improved pH in both bulk and rhizosphere soils. Acid-hydrolyzable nitrogen (AHN) content in biochar treatments was higher than that of CK in bulk and rhizosphere soil. The content of non-hydrolyzable nitrogen (NHN) was increased in 47.25 t ha−1 of biochar retention. Ammonium nitrogen (AN) and amino sugar nitrogen (ASN) contents were higher in bulk soil than in rhizosphere soil. Neutral amino acid contents were the highest both in bulk and rhizosphere soil. Principal component analysis (PCA) showed that soil organic nitrogen was significantly influenced by BC3 treatment in bulk soil, and largely influenced by other treatments in rhizosphere soil. Partial least square path modeling (PLSPM) revealed that NH4+-N was mainly derived from amino acid nitrogen (AAN) and AN in bulk soil and AAN and ASN in rhizosphere soil. These results indicate that different biochar retention rates contributed to improve soil nutrients. Amino acid nitrogen was the prominent nitrogen source of NH4+-N in bulk and rhizosphere soils.

Impacts of long-term different fertilization managements on soil acid hydrolysable organic nitrogen fractions in double-cropping rice field

To clarify the impacts of long-term different fertilization modes on the soil acid hydrolysable organic nitrogen and its components in the double-cropping rice field of southern China, a long-term (36-year) location field experiment was used as a platform to systematically analyze the variations of soil acid hydrolysable organic nitrogen and its components (amino acid nitrogen, amino sugar nitrogen, ammonium nitrogen, unidentified hydrolysable nitrogen) at 0-10 cm and 10-20 cm soil layers under four fertilization treatments, including chemical fertilizer alone (CF), rice straw and chemical fertilizer (RF), 30% organic manure and 70% chemical fertilizer (OM), and control (CK). The relationships of soil acid hydrolysable organic nitrogen content and soil total nitrogen, soil organic carbon content were also analyzed. The results showed that compared with CK, OM and RF treatments significantly increased the contents of total nitrogen, available nitrogen, and organic carbon at both soil layers. The contents of soil acid hydrolysable organic nitrogen at 0-10 cm and 10-20 cm layers of OM, RF and CF treatments were 10.7%-42.6% and 12.2% -51.5% higher than that of CK, respectively. Compared with CF and CK treatments, OM and RF treatments significantly increased the contents of amino acid nitrogen, ammonium nitrogen, unidentified hydrolysable nitrogen and amino sugar nitrogen contents atboth soil layers. The soil acid hydrolysable organic nitrogen and non-hydrolysable nitrogen contents at 0-10 cm and 10-20 cm paddy soils under different fertilization treatments decreased in an order of OM>RF>CF>CK. The contents of soil amino acid nitrogen, ammonium nitrogen, amino sugar nitrogen and non-hydrolysable nitrogen at 0-10 cm soil layer of each fertilization treatment were higher than those at 10-20 cm soil layer. In addition, the contents of soil acid hydrolyzed organic nitrogen were positively correated with the contents of soil total nitrogen and soil organic carbon. In conclusion, RF and OM treatments were beneficial to increase organic nitrogen content at 0-10 and 10-20 cm soil layers of double cropping paddy fields, with postive consequences on nitrogen supply capacity and soil fertility.

Slowed down nitrogen mineralization under bacterial community-driven conditions by adding inhibitors during rice straw composting

The aim of this paper was to confirm the role of inhibitors addition, namely adenosine triphosphate (ATP) and malonic acid (MA), on nitrogen availability during rice straw (RS) composting. The results showed that inhibitors addition slowed down the mineralization of ammonium nitrogen and nitrate nitrogen compared to CK. Meanwhile, amino sugar nitrogen and hydrolysable unknown nitrogen contents in ATP and MA treatments were higher, indicating that their addition improved the retention of organic nitrogen components. Furthermore, inhibitors additions attenuated the responsive relationship between bacterial communities and nitrogen components. The main reason was that the addition changed the bacterial community structure of RS compost. The final structural equation verified that inhibitors addition enhanced conversion between nitrogen components, that was, to complex nitrogen components to improve the quality of compost, and the remodeling of bacterial community played an important role. Therefore, adding inhibitors had a driving effect on promoting nitrogen sequestration.

Variations of soil organic nitrogen fractions during degradation succession in the Gahai Wetland, Northwest China.

This study amined to explore the variation of soil organic nitrogen components across the degradation succession of Gahai Wetland. By combining field sampling and laboratory analysis, the content and distribution characteristics of soil organic nitrogen components, i.e., hydrolytic total nitrogen (HTN), unidentified acidolytic nitrogen (HUN), ammonium nitrogen (AMN), amino acid nitrogen (AAN) and acid amino sugar nitrogen (ASN) were investigated in undegraded (UD), lightly degraded (LD), moderately degraded (MD), and heavy degraded (HD) Gahai Wetland. The results showed that, in the 0-10 cm layer, the contents of total nitrogen (TN), HUN, AMN, and AAN in LD decreased by 17.3%, 19.4%, 8.6%, and -5.6%, 28.0%, 19.4%, 17.1% and 0 in MD, and 35.8%, 28.8%, 28.6% and 55.6% in HD, respectively. In the 10-20 cm layer, the four components decreased by 4.0%, 10.3%, 2.9% and 9.1% in LD, 21.0%, 18.3%, -2.9% and -9.1% in MD, and 9.9%, 38.9%, 21.2% and 51.4% in HD, respectively. The corresponding contents in the 20-40 cm soil layer did not change. The proportion of soil acid-hydrolyzed nitrogen components to TN under four degradation stages was HUN (25.9%-32.5%) > AMN (6.7%-11.1%) > AAN (4.8%-11.1%) > ASN (1.2%-4.4%). Soil water content was the main driving factor for variations of soil organic nitrogen components as indicated by the results of redundancy analysis. Degradation of the Gahai Wetland significantly reduced the content of soil TN and the components of acid-hydrolyzed nitrogen in 0-10 cm soil layer, and weakened the nitrogen "sink" function of soils. The AAN and ASN were sensitive to wetland degradation.

Impact of amendments on soil organic nitrogen fractions irrigated with sodic water

Present study was carried out to evaluate the effects of FYM and gypsum on organic nitrogen fractions in soil of long-term field experiment irrigated with sodic water since 1994 at research farm of Department of Vegetable Science, CCS Haryana Agricultural University Hisar, India (2014-2015). Field was irrigated with high RSC (11.5 me/l) sodic water having three levels of gypsum G0 (control), G1 (50 % neutralization of RSC), G2 (100% neutralization of RSC), along with three levels of FYM; F0 (control), F1 (10 tonnes/ha), F2 (20 tonnes/ha). The Results obtained in April 2014 showed that all N fractions (Non hydrolysable-N, NH3-N, amino acid-N, amino sugar-N, hydrolysable unknown-N and total hydrolysable-N) were more dynamic in various treatments consisting FYM and gypsum levels. All nitrogen fractions increased with increasing levels of FYM and gypsum. Averages of amino acid nitrogen, amino sugar nitrogen, ammonia nitrogen and hydrolysable unknown nitrogen constituted about 28-30, 9-12, 27-29 and 29- 36% of total hydrolysable nitrogen, respectively. Adverse effect of residual alkalinity of irrigation water was quite prominent on chemical properties (pH, EC, organic carbon) of soil. The pH of soil was found to be very high under F0G0 and decreased with the use of FYM and gypsum as amendments. This result indicates that the combined use of FYM and gypsum improved soil health and maintained the sustainability of the different vegetable cropping system.

Fractions and mineralization potential of the sediment organic nitrogen in Daya Bay, South China Sea: Anthropogenic influence and ecological implications

Nitrogen mineralization is a critical biogeochemical process that transfers organic nitrogen into inorganic forms using heterotrophic microorganisms. However, few studies have focused on this potential nutrient supplier. In this study, the composition of sediment organic nitrogen (SON) was studied, and nitrogen mineralization flux entering the water column was quantified. The results indicate that acid-hydrolyzable nitrogen (AHN) accounts for more than 40% of the SON, especially in the riverine input and marine aquaculture areas, which had significantly higher concentrations than the bay mouth area. Similar results were found for the ammonium nitrogen (AN), amino-sugar nitrogen (ASN), the total hydrolyzable amino acid (THAA), and unidentified hydrolyzable nitrogen (HUN). The mineralization rate in the marine aquaculture area was as high as 9.03 ± 1.33 mg·kg−1·d−1, while those of the riverine input (4.77 ± 1.55 mg·kg−1·d−1) and bay mouth (5.12 ± 1.42 mg·kg−1·d−1) areas were lower. The SON fractions, including the AHN, AN, ASN, and AAN, could obviously affect the mineralization of the SON. However, the extracellular enzymes, including proteinase and urease, are the predominant factors controlling the SON mineralization process. Anthropogenic activities, including riverine input and marine aquaculture, exert significant influences on the fractions and mineralization of the SON, and thus, they may increase the amount of dissolved inorganic nitrogen in the bottom of the water column in Daya Bay.

The conversion of organic nitrogen by functional bacteria determines the end-result of ammonia in compost

The conversion of organic nitrogen determines the quality of composting and its environmental impact, but its underlying microbial mechanism is unclear. Hence, in static composting reactors with forced ventilation, vegetable waste, straw and pig manure were used as raw materials to simulate the composting for 33 days with or without adding 9% biochar. In composting, amino acid and amino sugar nitrogen were most easily converted to ammonium and hydrolysable unknown nitrogen was synthesized from ammonium. The aprA and chiA-related bacteria converted amino acid nitrogen to ammonium, and ammonium to hydrolysable unknown nitrogen, while amoA and HAO-related bacteria converted amine and amino sugar nitrogen to ammonium. Additionally, soluble microbial byproduct-like materials (62.4%) significantly affect organic nitrogen transformation, and could reduce ammonia emission by increasing ammoxidation rates. Thus, whether or not adsorbent substances are added, microorganisms affect the production of ammonia by controlling the conversion of organic nitrogen.

Enzymatic mechanism of organic nitrogen conversion and ammonia formation during vegetable waste composting using two amendments

Elucidating the mechanism of nitrogen conversion during composting is crucial for controlling nutrient loss and improving the quality of compost. To explore the enzymatic mechanism of organic conversion during composting, composting experiments using vegetable waste and chicken manure mixed with wheat straw and corn stalk as two separate treatments: WS and CS, respectively, were conducted in 63 L aerated static pile reactors for 33 d. The changes in the nitrogen fractions and related-enzymes activities were analyzed during different periods. The total nitrogen content increased by 34.3% during WS and decreased by 6.22% during CS after 33d of composting. The ammounium nitrogen content decreased by 79.6% and 51.4% during WS and CS. The nitrate, nitrite, organic, acid-insoluble organic nitrogen contents increased by approximately 52.6–123.9%, 590.9–5875%, 59.1–213.8%, and 764.4–7834.1%, respectively. The amount of total hydrolysable organic nitrogen increased by 18.8% during WS and decreased by 26.7% in CS. Structural equation modeling revealed that the contributions of different types of nitrogen to the formation of NH4+ during WS composting decreased as follows: amine nitrogen (AN) > amino acid nitrogen (AAN) > amino sugar nitrogen (ASN) > hydrolysable unknown nitrogen (HUN), while the corresponding nitrogen contributions during CS decreased as follows: AAN > AN > HUN > ASN. The AN and AAN were most easily converted into NH4+ during WS and CS, respectively, while ASN was synthesized from NH4+ during vegetable waste composting. Using redundancy analysis it was revealed that nitrate reductase (50.1%), nitrite reductase (23.2%) and urease (7.1%) played leading roles in nitrogen transformation. Furthermore, total organic carbon (59.6%) was the main factor that affected enzymes activities.

The changes in carbon, nitrogen components and humic substances during organic-inorganic aerobic co-composting

In this article, the changes in carbon, nitrogen components, and humic substances during organic-inorganic aerobic co-composting, with adding biochar as an additive or not, were studied. Results showed that adding a certain amount of inorganic fertilizers had no adverse effects on the compost fermentation process. Biochar enhanced the temperature, pH, oxygen content in the compost piles and ultimately hastened the fermentation process. Biochar contributed to the decomposition of hemicellulose, cellulose, lignin and promoted compost humification. Adding biochar increased the contents of acid hydrolysis nitrogen, amino acid nitrogen, amino sugar nitrogen, unidentified organic nitrogen and decreased the content of ammonia organic nitrogen thus improved nitrogen transformation and reduced nitrogen loss. The addition of biochar increased the nutrients contents in mature composts. The amendment of 10–15% biochar by weight as an additive would be optimum for the co-composting of organic-inorganic materials. These results contributed to produce value-added composting fertilizers.

Soil pH Buffering Capacity and Nitrogen Availability Following Compost Application in a Tropical Acid Soil

ABSTRACTTropical acid soils are highly weathered as they exist under tropical environment with high rainfall and temperature throughout the year, which affects nitrogen availability. Soil organic nitrogen is important in estimating soil nitrogen availability. The combined use of urea and compost in this study was carried out to decrease sole dependence on urea, buffer soil acidification, and reduce nitrogen losses through leaching. Thus, soil buffering capacity, incubation, and organic nitrogen fractionation studies were conducted to determine soil buffering capacity, availability of total nitrogen, organic fractions nitrogen, and inorganic nitrogen in soil after 90 days of incubation following compost. Soil pH, buffering capacity, total nitrogen, organic nitrogen fractions, exchangeable ammonium, and available nitrate were higher in all treatments with compost and combined use of urea and compost. Total hydrolyzable nitrogen, ammonium-nitrogen, (ammonium + amino sugar)-nitrogen, amino sugar-nitrogen, and amino acid-nitrogen were higher in soils with urea and compost suggesting that decomposition of soil organic fractions nitrogen into inorganic nitrogen (ammonium and available nitrate was affected by the addition of urea and compost. Urea can be amended with compost to regulate availability nitrogen in soil for crop use.

Nitrogen Fertility Island Stability around Prosopis glandulosa Sprouts after Mechanical Shrub Control in a Degraded Grassland

ABSTRACTWe examined the effects of mechanical chopping to reduce shrub cover for grassland restoration in a semi-desert environment near Douglas, Arizona, USA. Specifically, soils were sampled to determine spatial and treatment differences, after 10 years, in soil-N fertility islands associated with undisturbed honey mesquite shrubs (Prosopis glandulosa Torr. var. glandulosa) compared with resprouted mesquite shrubs. Honey mesquite is the dominant shrub of this degraded grassland community.One decade after mechanical crushing of shrubs for grassland restoration, soil amino sugar nitrogen (N) values and patterns for resprouted honey mesquite and undisturbed shrubs did not differ from one another according to a repeated measures analysis of variance. However, the concentrations in samples of the surficial 30-cm of soil around undisturbed and resprouted shrubs combined differed statistically at 161 parts per million (ppm) at trunk, 100 ppm midway between trunk and dripline, 78 ppm at the dripline, and 46 ppm beyond the dripline.The results indicate that soil N fertility remained stable, but with decreasing levels at regular, radial sample points extending from the trunk to beyond the dripline, around mesquite shrubs that resprouted 10 years after mechanical crushing of tops for grassland restoration.

It Was Found That Amino Sugar Nitrogen Was a New Source of Energy for Plant

Amino sugar nitrogen (ASN) is one of the most important nitrogen sources for plants. Whether ASN such as glucosamine can be absorbed directly by plants has remained unclear, because the technology for investigating its mechanism of absorption has been lacking. Using Positron Emission Tomography (PET) with 18F-fluorodeoxyglucose (18F-FDG), we observed that ASN was absorbed directly by tomatoes and rice and this absorption was significantly influenced by the carbon to nitrogen ratio (C/N) and the pH value of the growth substrate solution of tomatoes and rice. Absorption and transportation of ASN was measured at C/N ratios of 10 or 25 at pH 7.0 or 8.0 in tomato and at pH 5.5 or 6.5 in rice. A C/N ratio of 10 resulted in higher ASN absorption and transportation than a C/N ratio of 25 in both tomatoes and rice. At C/N ratio of 10, tomatoes absorbed more ASN at pH 8.0 than at pH 7.0. In rice, absorption was more at pH 5.5 than 6.5. In a word, a lower C/N ratio yielded a higher ASN absorption and transportation for both tomatoes and rice. Tomatoes showed a slight preference for alkaline conditions, whereas rice preferred acidic conditions.

Changes in Soil Organic Carbon and Nitrogen Fractions with Duration of No‐Tillage Management

The influence of no-tillage (NT) management on labile soil N is poorly defined. To quantify changes in soil C and N fractions with duration of NT, we sampled Kempsville sandy loam (fine-loamy, siliceous, subactive, thermic Typic Hapludults) soils in the Coastal Plain of Virginia from farm fields that had similar cropping histories and nutrient management but varied in amount of time in continuous NT from 0 to 11 yr. At the 0- to 2.5-cm soil depth, there was a linear increase with time in NT for total organic C, total organic N, particulate organic matter (POM)-C, POM-N, POM-C/total organic C, POM-N/total organic N, hydrolyzable unidentified-nitrogen (hUN-N) and NH4–N (hNH4–N), and various biochemical classes of pyrolysate compounds determined by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). At the 2.5- to 7.5-cm soil depth, there was a linear increase with time in NT for total organic C and N, hUN-N, hNH4–N, hydrolyzable α amino acid-nitrogen (AA-N) and amino sugar-nitrogen (AS-N) only; these rates of increase were lower than at the 0- to 2.5-cm depth. No measured C and N fractions increased at the 7.5- to 15-cm soil depth but POM-C/total organic C and POM-N/total organic N declined (p ≤ 0.10) at this depth, suggesting that the recalcitrance of C and N fractions increased at 7.5- to 15-cm in 11 yr. These patterns indicate that a new equilibrium level for these C and N fractions had not been reached but that their stratification of C and N pools with soil depth increased during 11 yr in NT. At the 0- to 2.5-cm depth, the labile N fractions, AA-N and AS-N approached or reached new equilibrium levels within 11 yr. Since these fractions are derived from soil microbial and plant biomass, the initial rapid increase in these fractions likely reflects an increase in N immobilization in the short term (3–6 yr) following adoption of NT. After this initial transition period, levels of AA-N and AS-N approach new elevated equilibrium levels, which would be reflected in a higher net N mineralization rate than under the previous tilled system. These results indicate that absolute values for labile soil N fractions such as AA-N and AS-N may not be readily interpretable with respect to soil fertility recommendations without considering whether these values are changing over time or are at an equilibrium level. Different patterns of change in POM-N vs. AA-N and AS-N indicate that these labile N fractions are distinct and may provide different types of information with respect to quantifying changes in soil fertility with time under NT.