Biomass from agriculture, forestry, and urban wastes is a potential renewable organic resource for energy generation. Many investigations have demonstrated that anaerobic fungi and methanogens could be co-cultured to degrade lignocellulose for methane generation. Thus, this study aimed to evaluate the effect of natural anaerobic fungi-methanogens co-culture on the methane production and lignocellulosic degradation of wastes from rice, corn and sugarcane. Hu sheep rumen digesta was used to develop a natural anaerobic fungi-methanogen co-culture. The substrates were rice straw (RS), rich husk (RH), corn stover (CS), corn cobs (CC), and sugarcane baggage (SB). Production of total gas and methane, metabolization rate of reducing sugar, glucose, and xylose, digestibility of hemicellulose and cellulose, activity of carboxymethylcellulase and xylanase, and concentrations of total acid and acetate were highest (P < 0.05) in CC, moderate (P < 0.05) in RS and CS, and lowest (P < 0.05) in SB and RH. The pH, lactate and ethanol were lowest (P < 0.05) in CC, moderate (P < 0.05) in RS and CS, and lowest (P < 0.05) SB and RH. Formate was lowest (P < 0.05) in CC, RS and CS, moderate (P < 0.05) in SB, and lowest (P < 0.05) in RH. Therefore, this study indicated that the potential of methane production and lignocellulosic degradation by natural anaerobic fungi-methanogens co-culture were highest in CC, moderate in RS and CS, and lowest in SB and RH.

BACKGROUND:Providing high-quality roughage is crucial for improvement of ruminant production because it is an essential component of their feed. Our previous study showed that feeding bio-fermented rice straw (BF) improved the feed intake and weight gain of sheep. However, it remains unclear why feeding BF to sheep increased their feed intake and weight gain. Therefore, the purposes of this research were to investigate how the rumen microbiota and serum metabolome are dynamically changing after feeding BF, as well as how their changes influence the feed intake, digestibility, nutrient transport, meat quality and growth performances of sheep. Twelve growing Hu sheep were allocated into 3 groups: alfalfa hay fed group (AH: positive control), rice straw fed group (RS: negative control) and BF fed group (BF: treatment). Samples of rumen content, blood, rumen epithelium, muscle, feed offered and refusals were collected for the subsequent analysis.RESULTS:Feeding BF changed the microbial community and rumen fermentation, particularly increasing (P < 0.05) relative abundance of Prevotella and propionate production, and decreasing (P < 0.05) enteric methane yield. The histomorphology (height, width, area and thickness) of rumen papillae and gene expression for carbohydrate transport (MCT1), tight junction (claudin-1, claudin-4), and cell proliferation (CDK4, Cyclin A2, Cyclin E1) were improved (P < 0.05) in sheep fed BF. Additionally, serum metabolome was also dynamically changed, which led to up-regulating (P < 0.05) the primary bile acid biosynthesis and biosynthesis of unsaturated fatty acid in sheep fed BF. As a result, the higher (P < 0.05) feed intake, digestibility, growth rate, feed efficiency, meat quality and mono-unsaturated fatty acid concentration in muscle, and the lower (P < 0.05) feed cost per kg of live weight were achieved by feeding BF.CONCLUSIONS:Feeding BF improved the growth performances and meat quality of sheep and reduced their feed cost. Therefore, bio-fermentation of rice straw could be an innovative way for improving ruminant production with minimizing production costs.

To ensile rice straw (ENRS), a combination of lactic acid bacteria (LAB), consisting of Lactobacillus plantarum, L. buchneri and Pediococcus acidilactici at a ratio of 2:1:1 was added to rice straw (RS), and stored for 42 days at room temperature. We examined: 1) the nutritive quality of ENRS; 2) in vitro rumen fermentation parameters and microbiota composition with ENRS as substrate; and, 3) serum metabolites and average daily gain (ADG) of growing Hu lambs consuming ENRS. Ensiling of rice straw increased in vitro neutral detergent fiber (NDF) and acid detergent fiber (ADF) degradabilities (both P < 0.05), and total gas production (P < 0.05) but decreased (P < 0.05) methane (CH4) production. In addition, ensiling increased bacterial diversity and reduced the relative abundance of the methanogen Methanobrevibacter. Twelve male Hu lambs (initial live body weight = 25.2 & PLUSMN; 0.47 kg), aged 70 ( & PLUSMN; 6) days, were assigned randomly to one of two groups (n = 6) and offered a total mixed ration (TMR) that included 400 g/kg DM of either RS or ENRS for 4 weeks. Ensiling ruptured the physical structure of the RS, decreased (P < 0.05) dry matter and hemicellulose contents, and increased (P < 0.05) the concentrations of lactate, acetate and organic acids. Feeding ENRS up-regulated purine metabolism and improved ADG and gain to feed ratio of Hu lambs when compared to RS. In summary, ensiling was effective in improving both the nutritive quality of the feed and ADG of the lambs.

Bio-fermentation technology has been successfully developed for ensiling rice straw; however, its effects on the particle-attached microbial community remains unknown. Therefore, rice straw (RS) and bio-fermented rice straw (BFRS) were used as substrates for in vitro rumen fermentation to investigate the effect of bio-fermentation on particle-attached microbial community, as well as their effects on gas and methane production, fermentation products, and fiber degradation. Our results have shown that total gas production, fiber degradation, and in vitro fermentation products were significantly higher (p < 0.05) for the BFRS than the RS, while methane concentration in total gas volume was significantly lower (p < 0.05) for the BFRS than RS. Linear discriminant effect size (LefSe) analysis revealed that the relative abundance of the phyla Bacteroidetes, Fibrobacteres, Proteobacteria, and Lantisphaerae, as well as the genera Fibrobacter, Saccharofermentans, and [Eubacterium] ruminantium groups in the tightly attached bacterial community, was significantly higher (p < 0.05) for the BFRS than the RS, whereas other microbial communities did not change. Thus, bio-fermentation altered the tightly attached bacterial community, thereby improving gas production, fiber degradation, and fermentation products. Furthermore, bio-fermentation reduced methane concentration in total gas volume without affecting the archaeal community.

A novel, integrated process for the production of ethanol from lignocellulosic biomass is reported which involves simultaneous pretreatment, saccharification and fermentation using environmentally friendly technologies. The lignocellulosic biomass (8.33 g/L rice straw) was pretreated and saccharified with the anaerobic fungus Pecoramyces sp. F1, while the facultative anaerobic bacterium Zymomonas mobdis ATCC 31821 was employed to simultaneously ferment to produce ethanol. Without the need for additional pretreatment, the conversion from lignocellulosic biomass to ethanol was completed in four days with a production yield of 0.32 g ethanol/g glucose and a volumetric productivity of 0.010 g/L/h (0.98 g/L). Meanwhile, other metabolites were produced, including 0.024 g/L/h (2.28 g/L) acetate, 0.002 g/L/h (0.22 g/L) lactate and 0.002 g/L/h (0.15 g/L) formate. Results showed that the integrated process has the potential for ethanol production from lignocellulosic biomass.

Anaerobic fungi in the digestive tract of herbivores are one of the critical types of fiber-degrading microorganisms present in the rumen. They degrade lignocellulosic materials using unique rhizoid structures and a diverse range of fiber-degrading enzymes, producing metabolic products such as H2/CO2, formate, lactate, acetate, and ethanol. Methanogens in the rumen utilize some of these products (e.g., H2 and formate) to produce methane. An investigation of the interactions between anaerobic fungi and methanogens is helpful as it provides valuable insight into the microbial interactions within the rumen. During the last few decades, research has demonstrated that anaerobic fungi stimulate the growth of methanogens and maintain methanogenic diversity. Meanwhile, methanogens increase the fiber-degrading capability of anaerobic fungi and stimulate metabolic pathways in the fungal hydrogenosome. The ability of co-cultures of anaerobic fungi and methanogens to degrade fiber and produce methane could potentially be a valuable method for the degradation of lignocellulosic materials and methane production.

The use of fertilizers as addition inputs in agricultural systems can increase the yield of wheat and maize, while also stimulating the emission of carbon dioxide from soil that the main man-made greenhouse gas. Our objectives focused on the impact of different types of synthetic fertilizers and water quality. The purposes were to determine the feasibility of using wasted water for irrigation and to relate CO2 fluxes to the yield of maize and wheat, as well as to select the best fertilizer type with low CO2 emission and high yield. The experiment consisted of a double factors test focusing on four forms of fertilizer (urea, amine and slow release fertilizer) and the quality of water (reclaimed water and underground water). The results showed that the reclaimed water was not significant on the CO2 discharge rate, the maize-wheat yield or the soil properties in 2014 or 2015; however, the CO2 emission increased slightly in 2015. Focusing on fertilizer treatments, the reclaimed water & amine fertilizer treatment (CAF) that had higher cumulative CO2 emissions was 32.75 t·ha-1 in 2014 and 33.86 t·ha-1 in 2015. According to the ratio CO2/Y, the slow released fertilizer that reduces CO2 emissions and keeps the yield high is the preferred choice.

Brackish water has been widely used to irrigate crops to compensate for insufficient freshwater water supply for agricultural use. The goal of this research was to determine an efficient brackish water use method to increase irrigation efficiency and reduce N2O emission. To this end, we conducted a field experiment with four salinity levels of irrigation water (1.1, 2.0, 3.5, and 5.0 g·L−1 with drip irrigation) at Hetao Irrigation District (Inner Mongolia, China) in 2017 and 2018. The results show that irrigation with 3.5–5.0 g·L−1 water salinity increased the soil salinity compared with irrigation using 1.1–2.0 g·L−1 water salinity. The soil water content with 5.0 g·L−1 brackish water irrigation was significantly higher than with 1.1–3.5 g·L−1 water salinity due to the effect of salinity on crop water uptake. The overall soil pH increased with the increase in irrigation water salinity. Saturated soil hydraulic conductivity decreased with the increase in irrigation water salinity. These results indicate that brackish water irrigation aggravates the degree of soil salinization and alkalization. The soil N2O cumulative flux resulting from irrigation with 5.0 g·L−1 water salinity was 51.18–82.86% higher than that resulting from 1.1–3.5 g L−1 water salinity in 2017, and was 32.38–44.79% higher than that resulting from 1.1–2.0 g·L−1 in 2018. Irrigation with brackish water reduced maize yield, and the reduction in yield in 2018 was greater than that in 2017, but irrigation with 2.0 g·L−1 brackish water did not significantly reduce maize yield in 2017. These results suggest that reducing the salinity of irrigation water may effectively reduce soil N2O emission, alleviate the degree of soil salinization, and increase crop yield.

Raindrop splashing is one of the driving forces of soil erosion, and it also leads to the loss of soil nutrients. However, the effects of raindrop splashing on nitrogen loss and the mechanisms of detachment are still not well understood, especially under different types of rainfall and soil amendment applications, such as polyacrylamide, which has been widely used to reduce soil erosion. In this paper, indoor artificial rainfall experiments were performed to investigate the impact of the raindrop diameter and polyacrylamide (PAM) applications on runoff and soil and nitrogen losses. Three raindrop diameter treatments (1.52, 2.45 and 3.59 mm) and three PAM application treatments (0, 1.0 and 2.0 g/m(2)) were applied to Kastanozem soil. The results indicated that the infiltration rate, sediment rate and nitrogen concentration in the runoff decreased sharply with the rainfall duration for the first 10 min, but the runoff rate increased under simulated rainfall splashing. In general, the sediment rate for runoff and nitrogen loss increased with the raindrop diameter. The amounts of runoff, sediment, and ammonia and nitrate nitrogen loss were highly reduced with the addition of PAM. The soil and nitrate nitrogen loss decreased with the increasing PAM application rates, and a PAM application rate of 2 g/m(2) was optimized for the soil of the test area. Moreover, the ammonia and nitrate nitrogen concentrations were linearly proportional to the sediment rate in the runoff, and the slopes of the linear regression equations increased with the increasing raindrop diameter but were reduced by PAM application. This study provides effective information on the runoff, soil erosion and nitrogen loss that occur during rainfall splash, and it can improve our understanding of splash erosion and nutrient transport.

The removal of nutrients by overland flow remains a major source of non-point pollution in agricultural land. In this study, a mathematical model of ammonium nitrogen transport from soil solution to overland flow was established. The model treated the mass transfer coefficient (k(m)) as a time-dependent parameter, which was not a constant value as in previous studies, and it was evaluated with a four-slope gradient and three rainfall intensities. The kinematic-wave equation for overland flow was solved by an approximately semi-analytical solution based on Philip's infiltration model, while the diffusion-based mass conversation equation for overland nutrient transport was solved numerically. The results showed that the simulated runoff processes and ammonium nitrogen concentration transport to the overland flow agreed well with the experimental data. Further correlation analyses were made to determine the relationships between the slope gradient, rainfall intensity and the hydraulic and nutrient transport parameters. It turned out that these parameters could be described as a product of exponential functions of slope gradient and rainfall intensity. Finally, a diffusion-based model with a time-dependent mass transfer coefficient was established to predict the ammonium nitrogen transport processes at the experimental site under different slope gradients and rainfall intensities.

Alternative irrigation between saline water and groundwater can alleviate shortages of available agricultural water while effectively slowing the adverse effects of saline water on the soil-crop system when compared with continuous irrigation with saline water and blending irrigation between saline water and groundwater. In 2018, we tested the effect on soil CO2 and N2O emissions by two types of irrigation regimes (alternating groundwater and saline water (GW-SW), and alternating groundwater, followed by two cycles of saline water (GW-SW-SW)) between groundwater and three levels of salinity of irrigation water (mineralization of 2 g/L, 3.5 g/L, and 5 g/L), analyzed the correlation between gas emissions and soil properties, calculated comprehensive global warming potential (GWP), and investigated the maize yield. The results show that, with the same alternate irrigation regime, cumulative CO2 emissions decreased with increasing irrigation water salinity, and cumulative N2O emissions increased. Cumulative CO2 emissions were higher in the GW-SW regime for the same irrigation water salinity, and cumulative N2O emissions were higher in the GW-SW-SW regime. The GW-SW-SW regime had less comprehensive GWP and maize yield as compared to the GW-SW regime. The 2 g/L salinity in both regimes showed larger comprehensive GWP and maize yield. The 3.5 g/L salinity under the GW-SW regime will be the best choice while considering that the smaller comprehensive GWP and the larger maize yield are appropriate for agricultural implication. Fertilizer type and irrigation amount can be taken into consideration in future research direction.