Nitrogen Release Research Articles

Litter functional dissimilarity accelerates carbon and nitrogen release from the decomposition of straw but not root in maize/legume intercropping

Litter functional dissimilarity accelerates carbon and nitrogen release from the decomposition of straw but not root in maize/legume intercropping

All-Natural Plant-Derived Polyurethane as a Substitute of a Petroleum-Based Polymer Coating Material.

The development of efficient, biobased polyurethane controlled-release fertilizers from sustainable and eco-friendly biomaterials has received increased research attention, owing to concerns regarding global food security and environmental sustainability. Most previous studies focused on replacing petroleum-based polyols with biopolyols; however, the other main raw material, isocyanate, remained a petrochemical product. Herein, all-natural, plant-derived polyurethane-coated urea was successfully developed using castor oil and biobased isocyanate, and the performance of the coating shell before and after modification was compared. The results showed that the incorporation of a low dose of lauric acid copper into the coating material simultaneously enhanced the hydrophobicity and elasticity of the all-biobased polyurethane membrane, which prolonged the nitrogen release longevity from 3 to 112 days. In addition, the modified membrane showed excellent biodegradability in a soil environment. The novel all-biobased polyurethane coating material and modification technique provide insight for developing sustainable and eco-friendly controlled-release fertilizers.

Short-term responses of soil enzyme activities and stoichiometry to litter input in Castanopsis carlesii and Cunninghamia lanceolata plantations.

Litter input triggers the secretion of soil extracellular enzymes and facilitates the release of carbon (C), nitrogen (N), and phosphorus (P) from decomposing litter. However, how soil extracellular enzyme activities were controlled by litter input with various substrates is not fully understood. We examined the activities and stoichiometry of five enzymes including β-1,4-glucosidase, β-D-cellobiosidase, β-1,4-N-acetyl-glucosaminidase, leucine aminopeptidase and acidic phosphatase (AP) with and without litter input in 10-year-old Castanopsis carlesii and Cunninghamia lanceolata plantations monthly during April to August, in October, and in December 2021 by using an in situ microcosm experiment. The results showed that: 1) There was no significant effect of short-term litter input on soil enzyme activity, stoichiometry, and vector properties in C. carlesii plantation. In contrast, short-term litter input significantly increased the AP activity by 1.7% in May and decreased the enzymatic C/N ratio by 3.8% in August, and decreased enzymatic C/P and N/P ratios by 11.7% and 10.3%, respectively, in October in C. lanceolata plantation. Meanwhile, litter input increased the soil enzymatic vector angle to 53.8° in October in C. lanceolata plantations, suggesting a significant P limitation for soil microorganisms. 2) Results from partial least squares regression analyses showed that soil dissolved organic matter and microbial biomass C and N were the primary factors in explaining the responses of soil enzymatic activity to short-term litter input in both plantations. Overall, input of low-quality (high C/N) litter stimulates the secretion of soil extracellular enzymes and accelerates litter decomposition. There is a P limitation for soil microorganisms in the study area.

A GSH-activated photosensitizer prodrug for fluorescence imaging-guided chemo-photodynamic therapy

To improve the treatment efficacy of chemotherapy and reduce its side effects, combination therapy has gained increasing recognition. Nonetheless, it also faces with challenges including off-target effects and damage to normal cells. Herein, we designed a GSH-activated photosensitizer prodrug (NBSCEA) for fluorescence imaging and selective tumor elimination. Firstly, NBSCEA is encapsulated in DSPE-PEG2000 micelles to form NBSCEA@D nanoparticles for prodrug delivery. Then, the overexpressed GSH in tumor microenvironment can destroy the disulfide bonds of NBSCEA, and release nitrogen mustard and NBS-NH. Furthermore, upon exposure to 660 nm light, NBS-NH will produce Reactive oxygen species (ROS) that combine with chemotherapy to eradicate tumor cells. In vivo studies show that NBSCEA@D can not only be used for tumor imaging, but also effectively inhibit tumor growth through synergistic treatment. Our work demonstrates a highly efficient fluorescence imaging-accurate treatment strategy of cancer.

Characterization and in vitro digestibility of soybean tofu: Influence of the different kinds of coagulant

This study explored the effect of diverse coagulants (glucono-δ-lactone (GDL), gypsum (GYP), microbial transglutaminase (MTGase), and white vinegar (WVG)) on microstructure, quality, and digestion properties of tofu. The four kinds of tofu were significantly different in their structure, composition, and digestibility. Tofu coagulated with MTGase had the highest springiness and cohesiveness while GDL tofu had the highest enthalpy (6.54 J/g). However, the WVG and GYP groups outperformed others in terms of thermodynamic, and digestion properties. The WVG group exhibited the highest nitrogen release (84.3%), water content, denaturation temperature, and the highest free-SH content but the lowest S-S content. Compared to WVG, the GYP group had the highest ash content, hardness, and chewiness. Results demonstrated that the tofu prepared by WVG and GYP show high digestibility. Meanwhile, the former has better thermal properties and the latter has better texture properties.

Enchytraeid-stimulation of nitrogen mineralization from green plant residues in an organic soil

Faunal-mediated nutrient cycling, especially N mineralization, has the potential to make a significant contribution to nutrient supply to crop plants in production systems involving e.g. green manure cover crops. We investigated the effects of enchytraeids on N mineralization from mung bean residues in microcosm experiments using an organically-farmed soil with an inherently large population of enchytraeids. Enchytraeids promoted N mineralization by 23% after a distinct lag of between four and 12 weeks, concomitant with a substantial increase in population size followed by an almost complete collapse. Nitrogen release from the necromass would have contributed a small but significant fraction of the N mineralized, and the result suggested the presence of other mechanisms. Enchytraeids suppressed nematode populations, while did not affect the mean weight diameter (MWD) of soil aggregates, although mung bean residues increased MWD. We conclude that enchytraeids have potential to play significant roles in mediating N supply to crops but matching supply-and-demand periods may be challenging.

Effect of hydrothermal carbonization on pyrolysis behavior, nutrients and metal species distribution in municipal sludge

In this study, the effect of hydrothermal carbonation (HTC) on the pyrolysis behavior and the distribution of nutrients and metal species of waste-activated sludge (WAS) was investigated. Results showed that the pyrolysis activation energy range of WAS decreased from 11 to 57 kJ/mol to 10–36 kJ/mol when the hydrothermal carbonization was at 160 °C. As indicated by thermodynamic parameters, the hydrothermal carbonization process reduces the pyrolysis reaction activity of the hydrochar. The results of the chemical analysis indicate that hydrothermal carbonization significantly enhances the release of phosphorus and nitrogen, with maximum recovery at a temperature of 200 °C. The standard measurement and testing protocol revealed that hydrothermal carbonization increased the content of non-apatite inorganic P fraction in hydrochar and enhanced the availability of P. Heavy metal analysis shows that hydrothermal carbonization can strengthen the stability of heavy metals in WAS.

Experimental and ReaxFF MD study on the release characteristics of gaseous nitrogen during pressurized bituminous coal gasification

Coal gasification is the leading technology of clean coal technology such as Integrated Gasification Combined Cycle (IGCC). The release pattern of gaseous nitrogen during coal gasification is crucial for clean coal technology. This paper investigated the gaseous nitrogen emission characteristics of pressurized gasification through experiments and molecular dynamics studies. The experimental results show that the elevated temperatures promoted the release of NO and accelerated the conversion of nitrogen-containing precursors (HCN, NH3). However, high pressure weakened the effect of temperature and resulted in the decreased emissions of HCN, NH3, and NO. Because high pressure facilitated the conversion of fuel nitrogen to nitrogen. The emissions of HCN and NH3 decreased as the CO2 blending ratio increased, while NO emissions increased. The observed difference was primarily attributed to the amounts of free radicals and was also related to gas-phase reactions involving H2O and CO2. Furthermore, as the primary nitrogen-containing structure in bituminous coal, the pyrrole was used in Reactive force field molecular dynamics (ReaxFF MD) to study the release of gas-phase nitrogen during gasification process. The simulation results show that both temperature and pressure promote the migration of pyrrole nitrogen and also provided the main nitrogen migration paths during gasification which can be used to (indirectly) confirm the experimental analysis. The O2/N2/CO2 gasification system supplied additional O and OH radicals to enhance NO emissions, while H2O directly participated in reaction paths such as CN, NCO → NHi or provided H radicals to increase NH3 emissions.

Nutrient enrichment alters phytoplankton biomass and composition via silicon limitation

Despite management efforts, anthropogenic nutrient enrichments continue to enhance phytoplankton blooms worldwide. Release of nitrogen and phosphorus compounds not only provides surplus of nutrients but also disbalances their stoichiometry. Declines in the relative availability of dissolved silicon might induce limitation in diatoms, major primary producers with silicified shells. We studied experimentally how nutrient enrichment and resulting decline in dissolved silicon to nitrogen ratios (Si:N) affect the structure and functioning of natural plankton communities. Nitrate was added to create a range of Si:N ratios and phosphate was supplied in Redfield ratio to nitrogen. We also manipulated copepod abundance to understand the top-down effects on communities experiencing nutrient enrichment. Nitrogen and phosphorus additions resulted in a steep phytoplankton biomass increase, followed by a post-bloom decline. Phytoplankton bloom biomass was higher in high nitrogen treatments but during the post-bloom period this trend switched. Biomass was sustained longer in high Si:N treatments, indicating that silicon limitation terminates the bloom. Many diatom species did not benefit from nitrogen and phosphorus enrichment and diatom dominance ceased below Si:N of 0.4:1. Under high grazing pressure, silicate was taken up faster suggesting that silicification is important in diatom defense. Copepods shaped plankton communities via feeding on dinoflagellates, chlorophytes and the diatom Skeletonema costatum but there was no significant effect of nitrogen and phosphorus enrichment on copepod abundance. Our results, combined with previous studies, show that while nutrient concentrations define the total phytoplankton bloom biomass, resource ratios are important in sustaining biomass and determining community structure and composition.

Exploring the Potential of 3D-Printable Agar–Urea Hydrogels as an Efficient Method of Delivering Nitrogen in Agricultural Applications

Amidst population growth and challenges with existing fertilizers, the development of smart and environmentally friendly agrochemicals is imperative. While 3D printing is widespread, its potential in slow-release agrochemicals remains unexplored. This proof-of-concept study employed solvent casting and 3D printing to develop agar–urea structures. These structures, comprising 2.5% (w/w) agar, incorporated either 7% (w/w) or 13% (w/w) urea as nitrogen nutrients. Rheological, mechanical, and morphological properties and sorption capabilities were explored. Rheological analysis revealed a substantial impact of urea, enhancing material resistance to deformation. In mechanical tests, inclusion of urea showed no significant impact on compressive strength. SEM analysis confirmed the successful entrapment of urea within the agar matrix. The inclusion of urea resulted in a diminished water sorption capacity, attributed to the urea–water interactions disrupting the hydrogen bonding ability of agar. Agar–urea inks were employed in 3D printing utilizing the direct-ink writing technique, and the nitrogen release behavior was investigated. Results revealed nearly complete urea release in the positive control within 48 h. In contrast, agar–urea formulations with 7% (w/w) and 13% (w/w) achieved nitrogen release rates of 88.8% and 94.4%, respectively, suggesting potential for 3D-printed agar formulations to modify the immediate release behavior seen in conventional urea fertilizers.

Mechanism of ball milling pretreatment to improve the anaerobic digestion performance and energy conversion efficiency of corn straw

In this study, the effects of ball-milling (BM) pretreatment on the anaerobic digestion (AD) performance and energy conversion efficiency of corn straw (CS) were explored. The AD testing was conducted by varying BM times (0–120 min) and TS (4–10 %). The results showed that BM pretreatment increased microbial and enzyme accessibility to the CS and facilitated the hydrolytic acidification process of AD. The peak concentration of volatile fatty acids (VFAs) (5325.69 mg/L) and chemical oxygen demand (COD) (14524 mg/L) were increased, resulting in more substrates available for methanogenic bacteria. The lag phase time was shortened (37.41–56.12 %) and the cumulative methane production was increased (45.63–104.11 %). Accelerated rate of total ammonia nitrogen (TAN) release resulted in increased buffering capacity of the digestion system. Reduced the initial density of the digestive slurry (6.91–9.58 %) and altered the water distribution (maximum increase in free water content to 70.4 %), which facilitated the agitation of the AD process. Excessive BM times (>60 min) and TS (>8%) are not recommended. The BM60-6 presented the highest volatile solids (VS) removal (78.79 %), cellulose degradation (92.07 %) and biochemical methane potential (BMP) (309.69 mL/g VS). The BM pretreatment also improved the rheological characteristics of digestive slurry and reduced the stirring power consumption of the AD process. The BM60-6 showed the largest net energy benefit (28.2101 KJ/g VS) and net residual value (0.5000), and the high energy input of the pretreatment was balanced. This discovery breaks the conventional wisdom that mechanical pretreatment is meaningless because of higher power consumption.

Evaluating novel biodegradable polymer matrix fertilizers for nitrogen-efficient agriculture.

Enhanced efficiency fertilizers (EEFs) can reduce nitrogen (N) losses in temperate agriculture but are less effective in the tropics. We aimed to design a new EEF and evaluate their performance in simple-to-complex tests with tropical soils and crops. We melt-extruded urea at different loadings into biodegradable polymer matrix composites using biodegradable polyhydroxyalkanoate (PHA) or polybutylene adipate-co-terephthalate (PBAT) polymers with urea distributed throughout the pellet. These contrast with commercially coated EEF that have a polymer-coated urea core. We hypothesized that matrix fertilizers would have an intermediate N release rate compared to fast release from urea or slow release from coated EEF. Nitrogen release rates in water and sand-soil columns confirmed that the matrix fertilizer formulations had a more progressive N release than a coated EEF. A more complex picture emerged from testing sorghum [Sorghum bicolor (L.) Moench] grown to maturity in large soil pots, as the different formulations resulted in minor differences in plant N accumulation and grain production. This confirms the need to consider soil interactions, microbial processes, crop physiology, and phenology for evaluating fertilizer performance. Promisingly, crop δ15N signatures emerged as an integrated measure of efficacy, tracking likely N conversions and losses. The three complementary evaluations combine the advantages of standardized high-throughput screening and more resource-intensive and realistic testing in a plant-soil system. We conclude that melt-blended biodegradable polymer matrix fertilizers show promise as EEF because they can be designed toward more abiotically or more microbially driven N release by selecting biopolymer type and N loading rate.

A Tale of Two Catchments: Causality Analysis and Isotope Systematics Reveal Mountainous Watershed Traits That Regulate the Retention and Release of Nitrogen

AbstractMountainous watersheds are characterized by variability in functional traits, including vegetation, topography, geology, and geomorphology, which determine nitrogen (N) retention, and release. Coal Creek and East River are two contrasting catchments within the Upper Colorado River Basin that differ markedly in total nitrate (NO3−) export. The East River has a diverse vegetation cover, and sinuous floodplains, and is underlain by N‐rich marine shale. At 0.21 ± 0.14 kg ha−1 yr−1, the East River exports ∼3.5 times more NO3− relative to the conifer‐dominated Coal Creek (0.06 ± 0.02 kg ha−1 yr−1). While this can partly be explained by the larger size of the East River, the distinct watershed traits of these two catchments imply different mechanisms controlling the aggregate N‐export signal. A causality analysis shows physical and biogenic processes were critical in determining NO3− export from the East River catchment. Stable isotope ratios of NO3− (δ15NNO3 and δ18ONO3) show the East River catchment is a strong hotspot for biogeochemical processing of NO3− at the hillslope soil‐saprolite. By contrast, the conifer‐dominated Coal Creek retained nearly all atmospherically deposited NO3−, and its export was controlled by catchment hydrological traits (i.e., snowmelt periods and water table depth). The conservative N‐cycle within Coal Creek is likely due to the abundance of conifer trees, and smaller riparian regions, retaining more NO3− overall and reduced processing prior to export. This study highlights the value of integrating isotope systematics to link watershed functional traits to mechanisms of watershed element retention and release.

Preparation and antibacterial properties of β-SiAlON/AlN composite ceramics

In this study, β-SiAlON/aluminum nitride (AlN) composite ceramics were synthesized using a wet-mixing method at 1500 °C under a N2 atmosphere. X-ray diffraction and scanning electron microscopy were used to characterize the ceramics before and after immersing them in water for 7 d. The change in pH and release of ammonia nitrogen were studied to investigate the reaction and antibacterial mechanisms of AlN hydrolysis. The effects of the AlN content on the phase composition, microstructure, chemical properties, and antibacterial efficacy of the composite ceramics were investigated. As the AlN content increased, the antibacterial efficiency gradually increased. The antibacterial efficiency of the composite ceramic with an AlN content of 60 wt% was 100%, indicating that an increase in pH and amount of ammonia nitrogen could synergistically enhance the antibacterial effect. However, in a lysogeny broth medium, the buffering effect of the culture medium and promotion of bacterial proliferation may reduce the antibacterial efficiency. Therefore, β-SiAlON/AlN composite ceramics show considerable potential for antibacterial applications.

Nutrient and growth elucidation of a novel coated urea on oilseed rape in three main cultivation areas

A novel coated urea (MVCU) was prepared, and its application effect was verified by field trials of oilseed rape in three main cultivation areas. Meanwhile, the nutrient release and coating layer changes of MVCU in static water at 25 °C and different soils were systematically evaluated. MVCU showed a long nutrient release time under static water (77 days) and soil incubation (140 days) conditions due to the slow degradation of the coating layer in MVCU, and its nitrogen release coincided well with oilseed rape nitrogen demand. The above results were further confirmed by FT-IR spectra and SEM analysis. Compared with conventional urea (U), the field trials of MVCU in the three main cultivation areas showed high nitrogen utilization efficiency and yield advantages in oilseed rape. The field trials results indicated that the MVCU significantly enhanced the aboveground dry matter (28.7%), the seed nitrogen concentration (9.5%) and aboveground nitrogen accumulation (42.5%) of oilseed rape at the mature stage as compared to that of the U. The oilseed rape yield enhanced by 932.8 kg/hm2, the average growth rate was 65.1%, and nitrogen utilization efficiency increased by 21.2%. In short, MVCU has the advantages of excellent slow-release performance and strong applicability, and its yield-increasing effect on oilseed rape could reach or even be better than that of traditional fertilization.

Early‐season biomass and weather enable robust cereal rye cover crop biomass predictions

AbstractFarmers need accurate estimates of winter cover crop biomass to make informed decisions on termination timing or to estimate potential release of nitrogen from cover crop residues to subsequent cash crops. Utilizing data from an extensive experiment across 11 states from 2016 to 2020, this study explores the most reliable predictors for determining cereal rye cover crop biomass at the time of termination. Our findings demonstrate a strong relationship between early‐season and late‐season cover crop biomass. Employing a random forest model, we predicted late‐season cereal rye biomass with a margin of error of approximately 1,000 kg ha−1 based on early‐season biomass, growing degree days, cereal rye planting and termination dates, photosynthetically active radiation, precipitation, and site coordinates as predictors. Our results suggest that similar modeling approaches could be combined with remotely sensed early‐season biomass estimations to improve the accuracy of predicting winter cover crop biomass at termination for decision support tools.Core Ideas Cereal rye winter cover crop biomass modeled on data from 35 site‐years. We found a strong relationship between early and late‐season biomass. Random forest model with early‐season biomass and weather data performed well. Similar approach could improve decision support tools for cover crop management.

Nitrogen Cycling Dynamics: Investigating Volatilization and its Interplay with N2 Fixation

The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems, the conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is atmospheric nitrogen, making it the largest source of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle. Human modification of the global nitrogen cycle can negatively affect the natural environment system and also human health. Volatilization and its Relationship to N2 fascination in Nitrogen Cycle in agriculture field is discuss in this paper.

Potential impacts of coal mining activities on nitrate sources and transport in a karst river basin in southwest China.

Typical sources of nitrate pollution in the fragile ecological environment of karst areas, such as agricultural production activities and domestic sewage, have long attracted serious concern. However, coal development can play an equally significant role in releasing the nitrogen fixed in coal into surface watersheds in the form of nitrate, nitrite, or ammonia, consequently threatening the water quality of surface water systems in mining areas. In this study, a typical karst surface watershed system affected by coal mining activities was selected for an in-depth investigation with the aim of realistically assessing the potential contribution of coal mining to nitrogen pollution. The results reveal increasingly concerning nitrate pollution from August 2020 to November 2021 in the Huatan River watershed under the influence of anthropogenic activities, especially mining development and agricultural production. Given that the nitrogen and oxygen isotope compositions of nitrate do not support the presence of denitrification, the variation in the NO3-/Cl- ratio and the relatively stable Cl- concentration may be a reflection of nitrification. Although the leaching of atmospheric precipitation on the strata in the basin promoted the release of nitrogen associated with coal mining, the higher rate of nitrogen cycling in the oligotrophic mine water environment limited the contribution of coal mining to nitrogen pollution in the surface watershed. Specifically, the contribution of coal mining activities to nitrogen pollution in surface karst river is mainly NH4+-N, which contributes 10% or less to the nitrate input to the waters of the Huatan River. The findings thus highlight the necessity of further uncovering the geochemical cycling process of nitrogen during the transport of mine water in the coal mining environment.

Combining dredging with modified zeolite thin-layer capping to control nitrogen release from eutrophic lake sediment

Dredging is widely used to control internal sediment nitrogen (N) pollution during eutrophic lake restoration. However, the effectiveness of dredging cannot be maintained for long periods during seasonal temperature variations. This study used modified zeolite (MZ) as a thin-layer capping material to enhance dredging efficiency during a year-long field sediment core incubation period. Our results showed that dredging alone more effectively reduced pore water N, N flux, and sediment N content than MZ capping but showed more dramatic changes during the warm seasons. The N flux in dredged sediment in summer was 1.8 and 2.5 times that in spring and autumn, respectively, indicating a drastic N regeneration process in the short term. In contrast, the combination method reduced the extra 10% pore water N, 22% N flux, and 8% sediment organic N content compared with dredging alone and maintained high stability during seasonal changes. The results indicated that the addition of MZ to the surface of dredged sediment not only enhanced the control effect of dredging by its adsorption capacity but may also smooth the N regeneration process via successive accumulation (in the channel of the material) and activation of bacteria for months, which was evidenced by the variation in microbial diversity in the MZ treatment. As a result, the combination of dredging with modified zeolite simultaneously enhanced the efficiency and stability of the single dredging method in controlling sediment N content and its release, exhibiting great prospects for long-term application in eutrophic lakes with severe pollution from internal N loading.

Use of irradiated chitosan as a matrix for slow-release urea and in vitro fermentation characteristics of slow-release urea supplementation in ruminant rations

Background and Aim: Irradiated chitosan can be used as a matrix for slow-release urea (SRU) production. This study aimed to (1) determine the optimal formulation of irradiated chitosan matrix for controlling nitrogen release and (2) evaluate the characteristics of SRU in vitro fermentation based on irradiated chitosan as a feed supplement. Materials and Methods: In the first phase of the investigation, four chitosan-based SRU formulations with varying amounts of acrylamide (3 and 5 g) and gamma irradiation (5 and 10 kGy) were evaluated. Scanning electron microscopy, Fourier transform mid-infrared spectroscopy, and ammonia release characteristics were used to observe morphological, functional group, and ammonia release characteristics. In the second phase of research, the most effective SRU formulation was utilized as a supplement to ruminant rations based on rice straw, sorghum straw, and alfalfa. Gas production, rumen fermentation characteristics, and methane gas production were observed in vitro. Results: On the basis of surface image analysis, the four SRU formulas generate a similar appearance. Compared with untreated urea, the SRU3 formula reduced the percentage of ammonia emission by 12.85%–27.64% after 24 h of incubation (p = 0.05), as determined by the first phase study. SRU3 became the basis for the second testing phase. The addition of SRU3 did not affect the optimal gas production in vitro. SRU3 treatment produced less gas than Optigen® treatment (p = 0.05). With regard to rumen fermentation and digestibility, Optigen® yielded better results than SRU3 (p = 0.05). However, the treatment with SRU3 resulted in reduced methane production compared to that in the control (p = 0.05). Conclusion: Irradiated chitosan as an SRU matrix may control the release of ammonia in the rumen medium. The SRU3 formulation is the most effective. The addition of SRU to rice straw-based rations reduces methane production without affecting in vitro digestibility. Keywords: fermentation characteristics, irradiated chitosan, ruminant, slow-release urea.