Straw Resources Research Articles

GHG emissions of straw treatments in rural China and scenario simulation based on life cycle perspective

The comprehensive utilization of straw plays an important role in GHG emissions reduction. The main breakthrough point of promoting straw resource utilization in China is on staple crops. In this study, the current straw utilization and treatment status of staple crops in rural China were studied based on data from the 2019 China Rural Development Survey, which included five provinces, 100 villages, and 1015 households. A life cycle assessment was conducted to identify the GHG emissions of the various crop straw utilization and treatment methods. The GHG emissions per unit area from the crop and household perspectives were also observed. Furthermore, the trend in GHG emissions from crop straw utilization and treatment was predicted through scenario simulation. The results showed that the comprehensive utilization rates of rice straw and wheat straw in rural China were 85.30% and 98.41%, respectively, in 2018, whereas the comprehensive utilization rate of maize straw was only 40.25%. Rice straw has the highest GHG emission level of 11771.90 kgCO2-eq/ha from a long-term perspective. On a national scale, the average GHG emissions per unit area of household is 1229.56 kgCO2-eq/ha, with significant differences between provinces, from a maximum of 12033.77 kgCO2-eq/ha in Jiangsu to a minimum of −3599.77 kgCO2-eq/ha in Jilin. According to the results of the scenario simulation, if the ambitious measures in reducing the straw incorporated into paddy soil are not taken, future GHG emissions of staple crop straw may persist and even rise rapidly in rural China.

Effects of Agronomic Measures on Decomposition Characteristics of Wheat and Maize Straw in China

The utilization of crop straw resources has been highly emphasized by governments and academia in recent decades. The growing importance of straw decomposition in the wheat-maize rotation system and the remarkable diversity of accumulated information on this topic inspired us to quantitatively explore variations in the outcomes of individual studies. We conducted a data analysis of 46 experimental studies reporting the effects of agronomic measures on the straw decomposition rates of wheat (14 studies) and maize (38 studies). Statistical results showed that maize straw crushed and buried in soil with turn-over or rotary tillage can significantly increase straw decomposition rates. Further, with the increase in nitrogen input and straw burial depth in the soil, the maize straw decomposition rate increased significantly, while the amount of straw return showed the opposite trend. Among all agronomic measures in this research, burial depth has demonstrated a significant positive effect on the wheat straw decomposition rate. The random forest analysis identified decomposition time as the most important predictor of straw decomposition rates for wheat and maize. In addition, some agronomic measures and straw decomposition time jointly affect the decomposition rate of straw. In general, agronomic measures are effective factors in controlling straw decomposition in a wheat-maize rotation system.

Effects of straw mulching combined with nitrogen application on soil organic matter content and atrazine digestion

To explore the response of atrazine (AT) degradation rate, soil organic matter (SOM) distribution and the relationship between them to straw mulching and nitrogen application, field experiments were conducted to study the distribution of SOM content and AT degradation rate under different straw returning modes combined with nitrogen fertilization in 2 years in Hetao Irrigation District. No (N0), low (NL), medium (NM), and high (NH) levels of N fertilization were incorporated into the soil combined with the surface coverage straw (Treatment BN0, BNL, BNM, BNH, respectively) and the deeply buried straw (Treatment SN0, SNL, SNM, SNH, respectively). The traditional cultivation was used as a control treatment (Treatment CK). The results showed that SOM content of Treatment B was accumulated in 0~20 cm soil layer. The largest SOM content of Treatments B in 0~20 cm soil layer was found in BNH treatment, with an average increase of 14.2% and 24.1% significantly when compared with those in CK and SNH (P < 0.05), respectively. The SOM content of Treatments B increased with the increase of nitrogen application and decreased with the deepening of soil depth. The SOM content of Treatment S was accumulated in the soil layer (20~40 cm and 40~60 cm) near the inter-layer. With the increase of nitrogen application and depth of soil layer, the SOM content increased firstly and then decreased. SNM had the largest SOM content in the soil layer of 20~40 cm and 40~60 cm, with an average increase of 82.6% and 67.7% when compared with Treatment CK (P < 0.05). In the soil layer over 60 cm, there was no significant difference in SOM content of different straw returning methods under the same nitrogen level (P > 0.05). Straw returning methods and nitrogen application level significantly affected AT digestion rate and digestion half-life, with significant differences among treatments (P < 0.05). It found that treatment SNM had the highest digestion rate and the shortest half-life of AT. Compared with Treatment CK, the digestion rate of Treatment SNM was increased by 5.3% on average, and the half-life was shortened by 3.9 days on average. Single regression and stepwise regression analysis of the half-life of AT degradation and SOM content in different soil layers (0~20 cm and 20~40 cm) showed that the degradation of AT was greatly affected by SOM content of 20~40 cm soil layer. Based on the comprehensive analysis, the effect of straw deep burial combined with medium nitrogen application rate (Treatment SNM) was best, which could achieve the goal of increasing SOM content and shortening the half-life of AT digestion. The research provided a technical support for straw resource utilization, alleviated AT pollution and improved farmland ecological environment in Hetao Irrigated District.

Study on influence mechanism of biochar on soil nitrogen conversion

ABSTRACT Straw had huge annual production, burning it in the air will cause serious air pollution. Burning straw into biochar and returning biochar to the field will not only make effective use of straw resources, but also improve soil quality. Different preparation conditions and addition levels of biochar were used to investigate the ammonia nitrogen, nitrate nitrogen, and total nitrogen contents in the soil leaching solution. The results showed that biochar had a favorable adsorption effect on ammonia nitrogen, the cumulative leaching of ammonia nitrogen reduced by 80.16% in the 2% and 400°C biochar addition treatment compared to that without adding biochar. The final leaching solution electrical conductivity value of the experimental group of biochar prepared at 500°C with 1% addition was the highest at 445 μS/cm. Sequencing of microorganisms revealed that biochar altered the structure and abundance of the soil microbial community, particularly increased the relative abundance of nitrifying bacteria.

Practice, pathways, and performance for resource utilization of crop straw: A case study of Xinyang City in China.

The open-air burning of the massive generated crop straw in rural areas has been a troubling problem in China in recent decades, and the utilization and valorization of crop straw have provided promising solutions to it. However, due to the limitations in straw resources, economic, social, and technological conditions, different regions vary greatly with each other in the technological pathways and performance of straw utilization. By taking ten counties and districts of Xinyang City in Henan Province of China as examples, it analyzed the spatial distribution of straw yields and the adoption of five pathways of crop straw utilization in Xinyang City, and summarized three typical combination modes. In addition, it also provided the integrated model of FBWM-TOPSIS-PROMETHEE to evaluate the performance of crop straw utilization in the ten counties and districts, to provide local decision-makers with the pathways for promoting the utilization and valorization of crop straw. The results indicated that: (1) The endowment of straw resources and the straw utilization pathways in the ten counties and districts of Xinyang City vary greatly with each other; (2) Returning crop straw to the fields as fertilizer after being crushed is the mainstream mode of resource utilization of crop straw, although five technological modes have been adopted in Xinyang City; (3) Among the 10 counties, Huaibin and Xixian have the best performance of resource utilization of crop straw, and Shangcheng is the worst performer.

Sorption Mechanism and Site Energy Distribution of Acetaminophen on Straw-derived Biochar

As one of the large dosages of pharmaceutical and personal care products (PPCPs), acetaminophen is widely present in the water environment and presents potential environmental risks. Therefore, it is necessary to study the removal mechanism of acetaminophen from the environment. Based on the high-value conversion demand of agricultural straw resources in China, straw-derived biochar prepared by pyrolysis has a good application prospect for the sorption and purification of acetaminophen in water. However, the sorption process and mechanism of straw-derived biochar for acetaminophen remain unclear. Four types of straw (rice, wheat, maize, and bean straw) were chosen as raw materials, and straw-derived biochars were prepared through the pyrolysis method at 400℃ and 500℃. The batch sorption experiments were used to study the sorption of acetaminophen to different sources and different pyrolysis temperature biochars. The effect of humic acid and pH on the sorption process was also studied. The results showed that:based on the Freundlich and site energy distribution models, the sorption of acetaminophen on biochar at 500℃ biochar was significantly higher than that at 400℃ biochar (the sorption coefficient KF was 1.16-2.53 times higher), and 500℃ biochar had more high-energy sorption sites. For high-temperature pyrolysis biochar, the primary sorption mechanism was pore sorption and π-π effect; for low-temperature pyrolysis biochar, the primary sorption mechanism for removing acetaminophen was H-bonding. The presence of humic acid enhanced the sorption of acetaminophen, which was attributed to the strong interaction between the humic acid selected in the experiment and acetaminophen, thus promoting adsorption. The decrease in sorption capacity of biochar caused by the increasing pH was mainly attributed to the pore blockage resulting from the aggregation of acetaminophen molecules. The pore sorption and π-π interaction of acetaminophen on straw-derived biochar could be promoted by increasing pyrolysis temperature. These experiments on humic acid and pH show that straw-derived biochar is not affected by humic acid and has good sorption performance in a low pH environment.

Straw Strip Mulching Increased Soil Organic Carbon Components of a Wheat Field in Dry Farming Regions of the Loess Plateau

To explore the response of soil organic carbon (SOC) and carbon components to surface coverage in wheat fields in semi-arid rainfed regions, a two-year field experiment was conducted under three treatments: straw strip mulching (SM), transparent plastic film mulching (PM) and no mulching (CK). We researched the dynamic feature of soil organic carbon (SOC) and its components at different growth stages of winter wheat under different mulching methods, including microbial biomass carbon (MBC), dissolved organic carbon (DOC), mineralizable carbon (PCM) and easily oxidized carbon (EOC). The results showed that SOC and its components in different soil layers decreased with an increase of soil layer depth. Compared with CK, the SM treatment increased SOC in the 0–40 cm soil layer by 2.83–8.92%, MBC by 12.09–18.40%, DOC by 3.73–9.79%, PCM by 4.82–12.48% and EOC by 6.01–11.68% during the different periods, and an overall increase was greater in the 0–20 cm soil layer than in the 20–40 cm soil layer. The impact of PM on SOC was less significant compared with CK; MBC and PCM had an overall positive effect, and DOC and EOC behaved differently from year to year. In conclusion, SM can improve SOC and its components content in dryland of northwest China, which is conducive to the sustainable management and efficient utilization of maize straw resources and has significant ecological benefits.

Structural Optimization of Sorghum Straw Powder/ZnO/PVA Nanocomposite Films

This study sought to improve the utilization of sorghum straw resources and promote the industrial production of new biomass materials. Herein, we fabricated SSP/ZnO/PVA nanocomposite films from sorghum straw powder (SSP), corn starch, polyvinyl alcohol (PVA), and nanostructured ZnO via the casting method. Then, we used response surface methodology to examine the effects of the mass concentrations of SSP, glycerol (Gly), and nanostructured ZnO, as well as the starch–PVA mass ratio on the tensile strength (TS) and water vapor permeability (WVP) of the SSP/ZnO/PVA nanocomposite films. The optimum preparation conditions were as follows: SSP mass concentration of 2.0 g/150 mL, Gly mass concentration of 2.5 g/150 mL, starch–PVA mass ratio of 6:4.5, and nanostructured ZnO mass concentration of 0.7 g/150 mL. The TS and WVP of the prepared films were 47.57% higher and 27.07% lower, respectively, than those of ZnO/PVA composite films without SSP. Scanning electron microscopy and atomic force microscopy showed that the SSP/ZnO/PVA nanocomposite films had smooth surfaces and dense cross-sections, without obvious delamination or phase separation. Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analyses revealed that SSP was highly compatible with the ZnO/PVA matrix. Thus, SSP addition could improve the crystallinity, thermal stability, and matrix interactions of SSP/ZnO/PVA nanocomposite films.

Straw strip mulching: A sustainable technology for saving water and improving efficiency in dryland winter wheat production

An improved straw mulching model may be a sustainable agricultural production technology due to its improvements in soil water and the fertilizer environment by the recycling of waste straw resources. A four-year field experiment was conducted in a randomized block design on the Loess Plateau of northwestern China in 2015–2019, which aimed to study the effects of straw strip mulching (SSM) and conventional flat planting without mulching (CK) on soil water storage, water consumption characteristics, water use efficiency, precipitation use efficiency, winter wheat growth, economic benefits, and nutrient benefits. The results obtained for the four years showed that the SSM treatment improved soil water storage in the 0–180 cm soil layer over the whole growth period, which was especially obvious in the 0–60 cm soil layer at the jointing and blooming stages. Compared with CK, SSM increased the contribution rate of precipitation to total evapotranspiration and increased it quite significantly by 20.4 percentage points in the earlier growth period. SSM significantly reduced soil water storage consumption in the 0–180 cm soil layer and ultimately reduced evapotranspiration by 11.2 mm during the whole period. In the 0–180 cm soil layer, SSM decreased evapotranspiration by 33.1 mm from the sowing to the jointing stages, but increased it by 19.5 mm from the jointing to the blooming stages. In addition, SSM improved the water use efficiency of grain yield by 21.6% and improved the precipitation use efficiency of grain yield by 18.6%, and it ultimately increased grain yield by 16.5% through improving spike number by 9.5% and kernel number per spike by 8.9%. SSM improved the water use efficiency of biomass yield by 13.5% and the precipitation use efficiency of biomass yield by 9.9%, and it ultimately increased biomass yield by 8.7% and plant height by 6.5%. Furthermore, SSM increased net income by 413 CNY ha–1 and the total amount of straw returned to the field after harvest by 8 876–9 619 kg ha–1. After returning straw to the field, SSM significantly increased the soil nutrient contents, which could significantly reduce the burden of fertilization by farmers after a few years. Therefore, straw strip mulching technology could probably be a sustainable and potentially useful practice, which could save water and increase efficiency in rainfed winter wheat production.

The effect of different prediction methods of population in villages and towns on assessing the suitability of biomass energy development

We investigate herein the development of biomass energy within a study area, to study how changes in population scale affects the suitability of biomass energy development in villages and towns. The analysis is performed by predicting the development trend of the total population and electricity consumption in the study area, and by establishing a biomass potential profit and loss model. With rural areas in western Guangdong as the research object, this study uses three different population prediction models, including the growth rate method, trend extrapolation method, and gray prediction method, to predict the population change trend of the study area in the next decade. The results of the growth rate method indicate a negative population growth rate of 5.28% for the study area over the next 10 years. We used Origin software to conduct polynomial fitting analysis on historical population data, and to make trend extrapolation predictions, the results demonstrate that in the short run, the population maintain a stable decline of approximately 1.7% by 2030. The results of the gray prediction model indicate that the population shows a slight decrease of 0.3‰.We determined the quantity of straw resources and the theoretical power generation potential of regional biomass based on the crop yields of Maoming, Zhanjiang, and Yangjiang, as well as the collectable coefficient and corresponding calorific value of straw in Guangdong Province. The total amount of crop straw resources in western Guangdong is approximately 120 522.6 tons, and the total biomass theoretical power generation potential is 305 × 103 MWh, the goal of 100% biomass energy supply will not be fully realized before 2030. Among these, the biomass energy supply in Maonan District of Maoming City is expected to reach 40–60%, and surplus energy demand may possibly combine with other renewable and traditional energy sources. The southern part of Zhanjiang has slightly less potential for biomass energy development than Maoming, with a maximum potential of 25%. All three prediction models suggest that Yangjiang is not suitable for biomass development in the short term, and its biomass potential will only meet 1% of its energy needs by 2030.

Biological delignification of rice straw using laccase from Bacillus ligniniphilus L1 for bioethanol production: A clean approach for agro-biomass utilization

The recalcitrance of lignocellulosic biomass due to severe lignification and complex cross-linking between lignin and cellulose fibers is a major hindrance in its clean and economical conversion to bioethanol . In the present study, the ligninolytic activity of purified bacterial laccase (BLac) from Bacillus ligniniphilus L1 was evaluated for delignification of rice straw for environment-friendly bioethanol production . BLac showed significant delignification activity at varying pH (3, 4, 7, and 9), and decreased the lignin (8.93%) and phenolic (44.8%) contents of rice straw. The chemical and structural changes in rice straw caused by BLac pretreatment determined via scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and Fourier transform infrared (FTIR) spectroscopy confirmed the successful delignification of rice straw. BLac improved the cellulase (CL) hydrolysis of rice straw by releasing 15.8 mg/mL glucose and 21.8 mg/mL reducing sugar, and produced 22.3 mg/mL bioethanol. These findings indicate that BLac has the potential to efficiently utilize the rice straw resources for economical and environmentally feasible bioethanol production. • BLac reduced lignin (8.93%) and phenolic contents (44.8%) of rice straw. • BLac enhanced the release of glucose (15.8 mg/mL) and reducing sugar (21.8 mg/mL). • BLac caused significant physicochemical changes in rice straw biomass. • High ethanol production (22.3 mg/mL) from rice straw via BLac pretreatment.

Utilization of Straw Resources May Affect the Speciation of Cd and Its Solubility in Cd-Contaminated Paddy Soil

Rice-wheat rotation has long been the most typical cropping system along the mid-lower reaches of the Yangtse River in China, and the full amount returning of wheat straw before rice season is widely practiced in the rotation system. However, massive incorporation of fresh wheat straw may activate Cd in the soil solid phase and cause more labile Cd entering soil solution in Cd-contaminated soil during the flooded rice season. An incubation experiment was conducted under flooded conditions to investigate the solubility and speciation of Cd and its variation and driving factors with an ongoing decomposition phase in simulated Cd-contaminated paddy soil treated with wheat straw addition. The results indicated that wheat straw addition enhanced Cd solubility, and soluble Cd concentration increased with the ongoing decomposition phase. The observed significant positive correlation (r = 0.648, p &amp;lt; 0.01, n = 77) between soluble Cd concentration and DOC content in soil leachate was gradually strengthened with ongoing decomposition. Wheat straw addition decreased the exchangeable fraction of Cd and increased the residual fraction during the first 5 days of decomposition, while the exchangeable Cd increased and the residual Cd decreased after 10 days of decomposition. The exchangeable Cd increased and the residual Cd decreased gradually with ongoing decomposition. Correlation analysis showed that the exchangeable and residual fractions were sensitive to DOC content. Nitrogen fertilizer input further activated Cd by promoting wheat straw decomposition. In summary, wheat straw addition would activate Cd by increasing Cd solubility and promoting the translation from immobile fraction to labile fraction in Cd-contaminated paddy soil under flooded conditions.

Fluid Movement Law and Influencing Factors of Shredding on Rice Straw Briquetting Machines

The briquetting technology of rice straw could increase the bulk density of the straw, reduce transportation and storage costs, and improve resource utilization. This paper analyzed the working principle of the air-conveying integrated device in briquetting machines. High-speed photography technology was used to track and record the movement process of crushed straw material in the air-conveying cylinder area. It was compared with the simulation results of the average velocity of crushed straw material to verify the reliability of the simulation. The results showed that the flow of straw scraps in the straw-shredding and air-conveying integrated device was relatively stable when the impeller speed was 630 r/min, the number of blades was three, the blades were tilted back 15°, and the radius of curvature of the air-conveying tube elbow was 700 mm. At the same time, the speed distribution was uniform, and the highest throwing speed reached 4.5 m/s to 4.8 m/s. After optimization, the average increase rate of briquette density was 2.61% and the average increase rate of briquette productivity was 2.52%. The fluid movement law of the straw-shredding and air-conveying integrated device studied in this paper could be used to optimize the air-conveying device, improve the efficiency of straw briquetting and the utilization rate of straw resources.

StrawFeed model: An integrated model of straw feedstock supply chain for bioenergy in China

With the growing concerns of fossil fuel scarcity and its negative impacts on global environment, bioenergy as an alternative energy source has attracted more attention as climate change mitigation. As one of the largest carbon emission and agricultural production countries in the world, China has abundant straw resources and great potential for energy utilization, and the number of straw-to-energy business projects is increasing dramatically. Correspondingly, there is a strong demand to design a stable and sustainable straw feedstock supply chain. However, due to the uncertainty of system boundary and neglect of potential risks, the procurement cost for bioenergy conversion plants (BCP) is varied significantly. Model is a critical approach in strengthening the understanding that leads to promoting supply efficiency. Therefore, an open-source & GIS-enabled linear programming model, named StrawFeed, is proposed to simulate the operation of straw feedstock supply. The costs of raking, baling, loading and transporting have been investigated as components in the StrawFeed model. The model is applied to case analysis of corn straw supply in Nongan county, a major corn production region in Northeast China. The results illustrate that the straw supply cost could be 172 CNY/ton, and the reasonable profit allocation mechanism could achieve the triple-win solution among farmers, brokers, and BCP. Furthermore, the challenges and opportunities for optimization are investigated with scenario analysis, based on unique circumstances and supporting policies in China. Unfavorable weather could delay the available working day, and thereby cost would increase up to 13%. The optimized scheme of straw utilization could achieve better environmental and ecological benefits, but the transportation distance for straw supply has to be expanded and the increased cost would be up to 53%. Cross-regional operation of agricultural machinery and machine procurement subsidies could reduce the cost by 18% and 5% respectively. This model is helpful to estimate accurate supply cost and deploy sustainable straw feedstock supply, which could contribute to assisting investors and policymakers for bioenergy industry in China.

Study on the Influence of Straw Resources and Comprehensive Utilization on Green Agricultural Development in Yantai

To explore the impact of comprehensive utilization of straw resources on green agricultural development in Yantai, this thesis comprehensively analyzes the crop straw resources and utilization in Yantai in recent five years according to the Yantai Statistical Yearbook (2017-2021), which estimates the number of straw resources and comprehensively assesses the potential of straw fertilizing and biogas utilization during that period in Yantai. Moreover, reasonable suggestions are put forward for the comprehensive utilization of straw in Yantai in the future based on its current situation and existing problems of straw resource utilization. Through the research and integrated analysis of this paper, it can provide relevant advice for the development of comprehensive straw utilization in Yantai, so as to develop green agriculture sustainably and promote the building of a resource-saving and environment-friendly society.

Structural Model of Straw Briquetting Machine with Vertical Ring Die and Optimization of Briquetting Performance

The solidification and molding of straw has been an effective method for comprehensive utilization of straw resources. However, the existing die-roll extrusion-type straw briquetting machine has challenges, such as the easy blockage of ring die holes and the unstable quality of the briquette. In this paper, the influence of four factors, including moisture content of straw, molding temperature, clearance between die and roller, and spindle speed on the quality of the briquette were studied. The regression model of the relaxed density and impact resistance of the briquette were established to obtain the optimal values of these factors to provide the best parameters for producing straw briquette. The results indicate that under the experimental conditions of moisture content 22.335%, temperature 85.127 °C, clearance between die and roller 3.099 mm, and spindle speed 172.712 r/min, the maximum relaxed density and impact resistance of the briquette were 1.144 g/cm3 and 74.76%, respectively. The performance of the briquette already meets the requirements for combustion, transportation, and storage.

Research Progress and the Development Trend of the Utilization of Crop Straw Biomass Resources in China.

The utilization of crop straw biomass resources is highly emphasized by governments and academia in recent decades. Based on the core databases of the literature in China National Knowledge Infrastructure (CNKI) academic journals, CiteSpace software is used to analyze and process the hotspots, and this study proposed the primary coverage and evolutionary trends of research on the utilization of crop straw resources. The thesis proposes the research development trend for improving the institutional mechanism of the utilization of crop straw resources, strengthening technology research and development, exploring the economic model of green cycle agriculture, accelerating the construction of the industrial system, and designing new paths of resource utilization in multiple ways, which helps estimate the development trend of the utilization of crop straw resources and provide inspiration and direction for future research and practices.

Contribution of straw disposal to carbon source and sink under the framework of carbon neutrality

Exploring the spatio-temporal variation characteristics of carbon source and carbon sink under different disposal methods of crop straw is of great significance for optimizing the utilization policy of crop straw resources in China and realizing the goal of maximizing carbon emission reduction and carbon neutralization. Based on data from National Statistical Yearbook, we examined the changing trends of both the amount and value of carbon emission, carbon emission reduction, carbon sink enhancement under different crop straw disposal methods in 31 provinces of Chinese mainland. The results showed that the mean annual carbon emissions of straw burning in China from 2008 to 2019 were 8.74 million tons of CO2e. Since 2014, the mean annual reduction rate of carbon emissions was 17.3%. The mean annual carbon emission reduction of energy utilization was 39.82 million tons of CO2e, with solid briquette fuel produced by straw contributing the most with a contribution of about 98%. The amount of carbon sequestration of straw returning to field was increasing annually, with an average annual value of 271 million tons of CO2e. There was a carbon ecological surplus in straw disposal in China. The annual growth rate of net carbon emission reduction was 9.8%. The net carbon emission reduction intensity and its value were increasing, reaching 2.62 t·hm-2 and 76.19 yuan·hm-2 in 2019, respectively. A spatial pattern of 'high in the east and low in the west' was observed for the mean annual carbon emissions of straw, energy carbon emission reduction, carbon sink of straw returning to the field, and net carbon emission reduction in China, with main external characteristics of the regional differences and spatial aggregation.

Study on the calculating methodology of the collectible straw resources for biomass power plants based on the indirect measurement

Replacing coal with biomass for power generation can effectively mitigate greenhouse gas emissions and reduce acid rain. In order to estimate the collectible straw resources using the straw-to-grain ratio method more accurately and provide reliable data support for the site selection of biomass power plants, this study constructed a calculation model of collectible straw using four food crops (corn, rice, wheat, and soybean) in 31 provinces in China as examples. Based on the definition of straw-to-grain ratio analysis, six parameters (straw-to-grain ratio, process residues index, stubble residues index, crop’s economic yield, straw moisture content, and transport losses) may affecting the collectible amount of straw were proposed. The regional and provincial distributions of straw resources were studied as well. The accuracy of the collected straw resource estimation was also verified. The results showed the average collectible straw resources of corn, rice, wheat, and soybean in 2020 in China were 0.44 kg/m2 to 0.491 kg/m2, 0.427 kg/m2 to 0.484 kg/m2, 0.341 kg/m2 to 0.42 kg/m2 for, and 0.296 kg/m2 to 0.321 kg/m2, respectively. The calculated collectible volume data were in good agreement with the data from field research, which verified the accuracy of the constructed computational model.

Nitrogen accumulation and nitrogen substitution effect of maize under straw returning with continuous cropping

<p id="C3">Crop straw resources in Northeast China are rich, but burning and discarding are serious, and nutrient utilization rate is very low. We explored the feasibility of the substitution of straw returning to nitrogen fertilizer and its effects on nitrogen accumulation under continuous cropping in cold region. A frame culture and continuous positioning experiment was carried out in the experimental site of Northeast Agricultural University from 2017 to 2019, with ¹⁵N labeled urea. A three-factor split-plot design was adopted in this experiment, the main plot was straw returning method with no straw returning (S0) and straw returning (S1), and the sub-plot was nitrogen application levels with 0 (N0), 175 (N1), and 350 (N2) kg hm^-2. Two application methods were set for each fertilizer application amount, one ratio of base fertilizer and top dressing applied was 1:1, and the other ratio of base fertilizer and top dressing applied was 1:0. The results were as follows: When the straw returning amount was 12 t hm^-2, the returning straw could replace 36.8 kg hm^-2 pure nitrogen. The average amount of maize straw was 46.50 million tons in Heilongjiang Province from 2017 to 2019, and straw returning could replace 142,700 tons pure nitrogen. The replace amount of pure nitrogen in the ratio of base fertilizer and top dressing (1:1) was 26.88% higher than that in 1:0. Straw returning was negatively correlated with nitrogen use efficiency in maize. The average nitrogen use efficiency of maize in S0 treatment was 6.09% higher than S1 treatment, and the yield of S1 treatment was 4.66% higher than S0 treatment when the urea application amount was 350 kg hm^-2 (161 kg hm^-2 pure nitrogen). The highest yield of maize was 268.22 g frame^-1 in the treatment of straw returning and topdressing with commonly fertilizer applied in local agriculture. In conclusion, the nitrogen substitution effect was remarkable under maize straw returning in Northeast China. Long-term combined application of crop straw and nitrogen fertilizer significantly improved the biomass, yield, and nitrogen accumulation of maize, which was a cultivation mode for increasing yield and efficiency of maize in Northeast China.