Crop Straw Research Articles

Effect of liquid volume and microflora source on degradation rate and microbial community in corn stover degradation

Degradation is the bottleneck in the utilization of crop straw. In this paper, we screened the microbial consortia degrading corn stover from straw degrading consortia MC1 (M), sheep feces (Y), and mixtures (Q) of M, Y, and cattle feces. The effects of microflora source and liquid volume (representing dissolved oxygen) on the microbial community and degradation rate of corn stover were investigated. The results showed that the degradation rate and cellulase activity of a 200 mL liquid volume (L2) were significantly higher than that of 100 mL (L1). Microflora source had a significant effect on bacterial and fungal diversity, composition and taxa. Q and Y had higher bacterial and fungal α-diversity than that of M. The degradation rate was significantly correlated with cellulase activity but not with microbial diversity. This indicated that liquid volume had a significant effect on degradation rate while microflora source had a significant effect on microbial community in corn stover degradation.

AGRICULTURE IN THE INTERFLUVE OF DNIESTER AND IKVA AT OLD RUSSIAN PERIOD ACCORDING TO ARCHAEOLOGICAL FINDINGS

The article sums up the results of archaeological investigations of the settlements of South Volyn (the territory around annalistic Danyliv town) and Western Podillia (the territory of sites complex of Zbruch cultural center, annalistic Terebovlia). Authors conducted generalization of findings of agriculture implements, white straw crops remains and supplemented source base. During archaeological investigations of the settlements and fortified settlements of Western Podillia and South Volyn at the end of 20th — beginning of 21th centuries scientists discovered 64 metal objects connected with agriculture found at 14 sites and palaeoethnobotanical materials at 11 sites (table 1; fig. 1). Functionally metal objects divide into tools connected with land cultivating: tips on plowing tools (4), coulter (2) (fig. 2), hoes (3) and shovels ironing (4) (fig. 3); and the tools for harvesting: sickles (33; fig. 6) and scythes (18; fig. 7). Only one palaeoethnobotanical complex from 11 sites is of interest to statistics (table 2; fig. 5).
 Agriculture analysis is conducted according to the process: from land cultivating to preservation and harvest processing. Plowing tools are represented by developed tips types maximally similar to tusks. Findings of coulters prove existence of the most efficient tools of plough type for plowing. Set of ironings for shovels and hoes represents kitchen gardening and horticulture.
 One full paleoethnobotanical spectrum connected with the region is derived which helps to characterize grain farming and spectrum indicators resemble early Slavic. At the same time indicators of efficient capricious white straw crops are rather substantial and that proves high level of tillage.
 Presence of sickles and scythes is an undoubted proof of local agriculture. For harvest preserving some special grain pits were used.
 The survey of materials concerned with agriculture proves its high level. Further thorough and combined investigations will give an opportunity to refine these conclusions and place and role of agriculture in life of ancient communities in the interfluve of Dniester and Ikva at Old Russian period.

Influence of the structure and properties of lignocellulose on the physicochemical characteristics of lignocellulose-based residues used as an environmentally friendly substrate

The extensive use of nonrenewable peat does not meet the strategic goals of sustainable development. This study explores the advantages and disadvantages of using lignocellulose-based agricultural and forestry wastes as peat substitute in substrates for soilless cultivation; further, it also investigates the key factors influencing the physical and chemical properties of the substrates. Accordingly, the physical and chemical properties of four gramineous crop straws and two woody forestry wastes were determined and compared with those of peat and coconut bran. In addition, cellulose, hemicellulose, and lignin were extracted from wheat straw and pine sawdust, and their basic characteristics and structures were compared and analyzed. The results showed that the influence of particle size on the physical properties of substrates was significantly higher (P < 0.01) than the influence of the substrate type, especially with respect to the water-holding and aeration porosities, which had effect sizes (Eta2) of 73.8% and 68.2%, respectively. The electrical conductivity values of the four straws (1.87–3.42 mS/cm) were higher than those of peat and coconut bran (0.50–0.96 mS/cm), which was mainly due to the high hemicellulose contents (28.52%–30.10%) and total nutrient contents (28.46–47.81 g/kg) of the straws. In contrast, the electrical conductivity values of the woody waste substrates were lower (0.28–0.33 mS/cm) than those of peat and coconut bran. Peat and coconut bran contained the lowest cellulose (17.84%–20.95%) and hemicellulose contents (5.14%–7.19%) of all substrates, resulting in a low degradability and good stability. The crystallinity of coconut bran (23.06%) was significantly lower than that of all other substrates (30.36%–43.03%), which mainly contributed to the superior compressibility of coconut bran. The best pretreatment method for biomass waste used as a substrate should be selected according to the target properties of the corresponding components.

Effect of crop straw biochars on the remediation of Cd-contaminated farmland soil by hyperaccumulator Bidens pilosa L.

Cadmium (Cd) due to its strong toxicity and high mobility, which poses a considerable threat to soil environment and human health, has aroused widespread concern. Biochar has been used for remediating Cd-contaminated soil recently, however this method has the risk of fixed-Cd re-release. Phytoremediation can make up for its shortcoming. In this study, a pot experiment was carried out, where Bidens pilosa L. (B.pilosa) was as the tested plant and biochars (maize straw biochar and wheat straw biochar with two particle sizes) were as amendments. The mechanism of how biochars promoted B.pilosa Cd accumulation in Cd-contaminated farmland soil was explored. Results showed that the application of 5% wheat straw fine biochar (WF), wheat straw coarse biochar (WC), maize straw fine biochar (MF) and maize straw coarse biochar (MC) increased the total Cd accumulation of B.pilosa to 251.57%, 217.41%, 321.64% and 349.66%, respectively. Biochars amendment significantly promoted B.pilosa growth and increased Cd accumulation by improving soil physical properties, nutrient levels (available nitrogen, available phosphorus (AP), available potassium (AK) and organic matter (OM)) and microbial activity, and changing the nutrients distribution in B.pilosa organs although tissues although DTPA-Cd reduced to some extent. The effect of MF on AP increase was better than MC, while the effect of WF on AK increase was better than WC. Fine-particle was superior to coarse-particle in increasing B.pilosa biomass of aboveground, OM and microbial activity in soil. The changes of N, P and K concentrations in B.pilsosa roots, stems and leaves were closely related to the changes of AN, AP and AK in soil after biochars application. The results indicated that the combination of straw biochars and hyperaccumulators had the synergistic effect. This study can provide data support and meaningful reference values for remediating actual Cd-contaminated soil.

Effects of accumulated straw residues on sorption of pesticides and antibiotics in soils with maize straw return

Outspread straw return practice leads to accumulation of structurally diverse organic materials in soils, including raw straw and straw residues. This practice provides a supplementary source of organic sorbents for compounds released into soils. However, effects of accumulated straw materials on sorption of compounds in soils remain poorly understood. Here we report that straw materials accumulated in soils display changing chemical structure and properties during decomposition, the majority of which distribute in exponential growth or decay manners with decomposition extents of materials. Sorption of straw materials toward 40 commonly used pesticides and antibiotics takes a compromise of decreasing crystalline index and increasing water absorption capacity of the sorbent materials during decomposition. This tradeoff in sorption leads to case-specific sorption trends of organic compounds in soils with straw return practice, following a composite linear sorption model of mixed soils and straw materials. The predictive model shows that relatively hydrophobic, hydrogen bond acceptor-rich chemicals (about 22.5% of the 40 compounds) display decreasing sorption capacity in organic matter-rich and/or relatively acidic soils with straw return. This finding may contradict the notion that crop straw return usually increases sorption and decreases leaching of compounds in soils.

Assessment of the effects of straw burning bans in China: Emissions, air quality, and health impacts

Open biomass burning (OBB) plays an important role in air pollution and climate change by releasing short-term but intensive amounts of particulate matter and gaseous air pollutants. During past years, policies with respect to prohibition on open straw burning have been issued in China in order to mitigate the air pollution problems and the effectiveness of these straw burning bans in different regions remains to be evaluated. In this study, open crop straw burning (OCSB) emissions during 2010–2018 were analyzed based on a commonly used emission inventory with high spatial and temporal resolution. High emissions concentrated over Northeast China (31.8% of national total PM2.5 emissions in 2018), East China (24.0%), and North China (16.6%). Simulations based on an integrated meteorology-air quality modeling system and an exposure-response function show that OCSB emissions could increase monthly PM2.5 concentration by as much as 10 μg/m3 during burning seasons in Northeast China and were associated with 4741 premature deaths in 2018. Spatial heterogeneities were observed with respect to the trends of OCSB emissions during 2010–2018. In East China, North China, and Central China, OCSB emissions showed a general declining trend since 2013 while an opposing increasing trend was observed in Northeast China with peak emissions in 2017. Comparing 2013 (before intensive implementation of straw burning bans) and 2018 (after), national total PM2.5 emissions from OCSB activities decreased by 46.9%, ranging from −14.1% to +70% depending on the specific regions. Northeast China is the only region that showed higher OCSB emissions in 2018 compared to 2013, probably associated with the relatively delayed implementation of the straw burning bans. Avoided number of premature deaths due to reduced OCSB emissions was estimated to be 4256 on a national scale, with most health benefits gained in East and Central China. Results from this study demonstrate the importance of OCSB contribution to PM2.5 concentrations and spatial heterogeneities exist in terms of the effectiveness of the straw burning bans in reducing OCSB emissions and gained health benefits.

Enhanced Biogas Production by Ligninolytic Strain Enterobacter hormaechei KA3 for Anaerobic Digestion of Corn Straw

Lignin-feeding insect gut is a natural ligninolytic microbial bank for the sustainable conversion of crop straw to biogas. However, limited studies have been done on highly efficient microbes. Here, an efficient ligninolytic strain Enterobacter hormaechei KA3 was isolated from the gut microbiomes of lignin-feeding Hypomeces squamosus Fabricius, and its effects on lignin degradation and anaerobic digestion were investigated. No research has been reported. Results showed that strain KA3 had better lignin-degrading ability for corn straw with a higher lignin-degrading rate (32.05%) and lignin peroxidase activity (585.2 U/L). Furthermore, the highest cumulative biogas yield (59.19 L/kg-VS) and methane yield (14.76 L/kg-VS) were obtained for KA3 inoculation, which increased by 20% and 31%, respectively, compared to CK. Higher removal rates of COD, TS, and vs. of 41.6%, 43.11%, and 66.59% were also found. Moreover, microbial community diversity increased as digestion time prolonged in TG, and bacteria were more diverse than archaea. The dominant genus taxon, for methanogens, was Methanosate in TG, while in CK was Methanosarcina. For bacteria, dominant taxa were similar for all groups, which were Solibacillus and Clostridium. Therefore, strain KA3 improved the methane conversion of the substrate. This study could provide a new microbial resource and practical application base for lignin degradation.

Crop straw recycling prevents anthropogenic desilication of agricultural soil–plant systems in the temperate zone – Results from a long-term field experiment in NE Germany

Due to the fact that silicon (Si) increases the resistance of plants against diverse abiotic and biotic stresses, Si nowadays is categorized as beneficial substance for plants. However, humans directly influence Si cycling on a global scale. Intensified agriculture and corresponding harvest-related Si exports lead to Si losses in agricultural soils. This anthropogenic desilication might be a big challenge for modern agriculture. However, there is still only little knowledge about Si cycling in agricultural systems of the temperate zone, because most studies focus on rice and sugarcane production in (sub)tropical areas. Furthermore, many studies are performed for a short term only, and thus do not provide the opportunity to analyze slow changes in soil–plant systems (e.g., desilication) over long periods. We analyzed soil and plant samples from an ongoing long-term field experiment (established 1963) in the temperate zone (NE Germany) to evaluate the effects of different nitrogen-phosphorus-potassium (NPK) fertilization rates and crop straw recycling (i.e., straw incorporation) on anthropogenic desilication in the long term. Our results clearly show that crop straw recycling not only prevents anthropogenic desilication (about 43–60% of Si exports can be saved by crop straw recycling in the long term), but also replenishes plant available Si stocks of agricultural soil–plant systems. Furthermore, we found that a reduction of N fertilization rates of about 69% is possible without considerable biomass losses. This economy of the need for N fertilizers potentially can be combined with the benefits of crop straw recycling, i.e., enhancement of carbon sequestration via straw inputs and prevention of anthropogenic desilication of agricultural soil–plant systems. Thus crop straw recycling might have the potential to act as key management practice in sustainable, low fertilization agriculture in the temperate zone in the future.

Straw Incorporation with Nitrogen Amendment Shapes Bacterial Community Structure in an Iron-Rich Paddy Soil by Altering Nitrogen Reserves.

Incorporation of crop straw into the soil along with inorganic fertilization is a widespread agricultural practice and is essential in nutrient-scarce soils, such as iron-rich (ferruginous) paddy soils. The responses of soil bacterial communities to straw incorporation under different nitrogen inputs in iron-rich soils remain unclear. Therefore, 6000 kg ha−1 dry wheat (Triticum aestivum L. cv. Zhengmai 12) straw was applied to a rice paddy with and without nitrogen amendment (0, 80, 300, and 450 kg ha−1 N as urea), to investigate its effects on soil fertility and bacterial community structure. Organic matter, total nitrogen, and water contents tended to decrease in straw-incorporated soils with different nitrogen inputs. Proteobacteria was the dominant bacterial phylum across all treatments (26.3–32.5% of total sequences), followed by Chloroflexi, Acidobacteria, and Nitrospirae. Up to 18.0% of all the taxa in the bacterial communities were associated with iron cycling. Straw incorporation with nitrogen amendment increased the relative abundance of iron oxidizers, Gallionellaceae, while decreasing the relative abundance of iron reducers, Geobacteraceae. Bacterial community composition shifted in different treatments, with total nitrogen, water, and Fe(III) contents being the key drivers. Straw incorporation supplemented by 300 kg ha−1 N increased bacterial richness and enhanced all the predicted bacterial functions, so that it is recommended as the optimal nitrogen dosage in practice.

Contrasting effects of maize residue, coal gas residue and their biochars on nutrient mineralization, enzyme activities and CO2 emissions in sandy loess soil

Mismanagement of crop straw and coal gas residue threatens the atmosphere and the economy. Nevertheless, thermal-pyrolysis is an option for management that turns bio-waste into biochar; its viability and adoption by the public as soil amendments is dependent on the agronomic and environmental values compared between biochar and the raw materials. We undertook a 60-day short-term analysis to assess the impact of various wastes and biochars, as well as inorganic nutrients (N), on carbon dioxide (CO2) fluxes, soil enzyme activities, soil fertility status, and microbial activities. There were eight treatments of soil amendments: without an amendment (CK), Nutrients (N), straw + nutrients (S+N), straw biochar + nutrients (SB+N), coal gas residue + nutrients (C+N), coal gas residue biochar + nutrients (CB+N), straw + straw biochar + nutrients (S+SB+N) and coal gas residue waste + coal gas residue biochar + nutrients (C+ CB +N). The results indicated that soil EC, pH, nitrate N (NO3–- N), SOC, TN and available K were significantly (p < 0.05) increased coal gas residue biochar and combined with coal fly ash as compared to maize straw biochar and combined with maize straw and N treatments. The higher concentrations of soil MBC and MBN activities were increased in the maize straw application, while higher soil enzyme activity such as, invertase, urease and catalase were enhanced in the coal fly ash derived biochar treatments. The higher cumulative CO2 emissions were recorded in the combined applications of maize straw and its biochar as well as coal gas residue and its biochar treatment. Our study concludes, that maize straw and coal fly ash wastes were converted into biochar product could be a feasible substitute way of discarding, since land amendment and decreased CO2 fluxes and positive changes in soil microbial, and chemical properties, and can be confirmed under long-term conditions for reduction of economical and environment issues.

Characterisation of Bt maize IE09S034 in decomposition and response of soil bacterial communities

Returning straw to the soil is an effective way to improve the soil quality. As genetically modified (GM) crops experience expanded growing scales, returning straw to the soil could also be necessary. However, the impact of GM crop straws on soil safety remains unclear. The environment (including soil types, humidity and temperature) can result in a significant difference in the diversity of soil bacterial communities. Here, we compared the impacts of the straw from Bt maize IE09S034 (IE) and near-isogenic non-Bt maize Zong31 (CK) on soil bacterial community and microbial metabolic activity in three different environments. Sampling was carried out following 6–10 months of decomposition (May, June, July, and August) in three localities in Chinese cities (Changchun, Jinan, and Beijing). Our results showed that Bt maize residues posed no direct impact on soil bacterial communities in contrast to the environment and decomposed time. The microbial functional diversity and metabolic activity showed no significant difference between IE and CK. The results could be a reference for further assessing the effect of Bt maize residues on the soil that promotes the commercialisation of Bt maize IE09S034.

Pathways of dissolved unreactive phosphorus loss under long-term crop straw and manure application

Dissolved unreactive phosphorus (DUP) loss can increase the risk of water organic and inorganic compound pollution. Because DUP loss under different fertilizers has not been evaluated, selecting a fertilizer that decreases losses but maintains yields remains challenging. Therefore, we compared DUP losses via overland flow, leaching, and sediment in lysimeter plots (8 m × 4 m × 0.6 m) with mineral and organic fertilizers for two years. The six treatments, with three replicates, included no fertilizer (CK), mineral fertilizer (NPK), pig manure only (OM), pig manure combined with NPK (OMNPK), crop straw only (RSD), and crop straw combined with NPK (RSDNPK). The results showed that leaching accounted for 54–89% and was the major route for DUP loss. Compared with NPK (0.074 kg ha−1 year−1), in the OM and OMNPK, the annual DUP losses via leaching were substantially increased by 11.1% and 8.6%, respectively, whereas they were decreased by 13.2% and 6.2% in the RSD and RSDNPK treatments, respectively. There was a significant positive linear relationship between the soil P surplus and the annual total DUP loss loading (r = 0.80, p = 0.05). Compared with the NPK (43.44 kg ha−1 year−1), the values of the soil P surplus under the RSD and RSDNPK treatments were greatly reduced by 122.6% and 14.5%, thereby decreasing the annual total DUP loss by 34.5% and 26.4%, respectively. In conclusion, pig manure application can increase DUP leaching risk, whereas the combination of mineral fertilizers and crop straw residues can decrease the DUP loss without compromising the crop yield.

Energy, nitrogen partitioning, and methane emissions in dairy goats differ when an isoenergetic and isoproteic diet contained orange leaves and rice straw crop residues

The aim of this study was to evaluate the effects of incorporating rice straw and orange leaves into the diets for goats. Ten Murciano-Granadina goats at mid lactation weighing 45 ± 0.3 kg were used in a crossover design. Two isoproteic and isoenergetic diets (180 g/kg DM and 17 MJ/kg DM, respectively) with alfalfa hay as forage source (33% of DM) were fed. A control diet (CON) incorporated barley as energy source and soy hulls as fiber component. The experimental diet (ORG) replaced barley and soy hulls with orange leaves (19% on DM basis), rice straw (12%, on DM basis) and soya oil (2%). Peas and horsebeans were the protein source in both diets. Each goat received the 2 treatments in 2 periods. Goats were fed the experimental diets and after 14 d on their respective treatments moved to individual metabolism cages for another 7 d. Subsequently, feed intake, total fecal and urine output and milk yield were recorded daily over the first 5 d. During the next 2 d ruminal fluid and blood samples were collected, and then individual gas-exchange measurements were recorded by a mobile open-circuit indirect calorimetry system using a head box. No differences in dry matter intake were detected, and apparent total-tract digestibility was greater in CON than ORG. Efficiency of metabolizable energy intake for milk and maintenance also was lower in response to ORG (0.65 vs. 0.63), with energy balance being negative (-12 kJ/kg of BW0.75) due to mobilization of fat (-16 g/animal vs. 68 g/animal for ORG and CON, respectively). Although actual milk yield was lower in goats fed ORG (2.32 vs. 2.06 kg/d, respectively), energy-corrected milk did not differ (2.81 kg/d on average). In terms of milk quality, milk fat content, and concentrations of monounsaturated (18.54 vs. 11.55 g/100 g milk fat) and polyunsaturated fatty acids (5.75 vs. 3.99 g/100 g milk fat) were greater in goats fed ORG. Based on various indices, the milk produced by ORG would be less atherogenic and thrombogenic than CON milk. Compared with CON, enteric CH4 emission was lower due to feeding ORG (reduction of 38 g CH4/kg milk fat). Data suggest that greater fat mobilization in goats fed ORG might have been due to the apparent lack of synchrony between degradable protein and carbohydrate and the lipogenic nutrients associated with the lower cereal content of the ORG diet. Thus, goats fed ORG seemed to rely more on fat depots to help meet energy requirements and reach optimal performance. As such, the lower content of glucogenic nutrients in ORG did not favor body fat deposition and partitioning of ME into body tissue. Overall, responses in terms of CH4 emissions and milk quality suggest that inclusion of rice straw and orange leaves in diets for small ruminants could be a valuable alternative to reuse, recycle and revalue agricultural by-products.

Dynamics of microbial diversity during the composting of agricultural straw

The dynamic changes in microbial diversity during the aerobic composting of agricultural crop straw with additives were evaluated using high-throughput sequencing at four phases of composting (mesophilic, thermophilic, cooling and maturation phases). In addition, the physicochemical parameters of the composting system were determined in this study. The fermentation time of the thermophilic period was prolonged with the addition of urea or urea combined with a microbial agent. The ratio of C/N and germination index variation indicated that the additives were favorable for composting, because the additives directly changed the physicochemical properties of the compost and had effects on the diversity and abundance of bacteria and fungi. The abundance of operational taxonomic units (OTUs), diversity index (Shannon) and richness index (Chao1) of fungi and bacteria were found to significantly increase when urea+microbial agents were added to straw in the thermophilic phase. The relative abundance of the predominant bacteria and fungi at the phylum and genus levels differed during different composting phases. The abundance of the phyla Firmicutes and Proteobacteria declined in the order of treatments SNW>SN>S (S is straw only compost; SN is straw+5 kg t−1 urea compost; and SNW is straw+5 kg t−1 urea+ 1 kg t−1 microbial agent compost) in the thermophilic phase. The abundance of the genera Staphylococcus, Bacillus and Thermobifida followed the same order in the mesophilic phase. Ascomycota accounted for more than 92% of the total fungal sequences. With the progression of the composting process, the abundance of Ascomycota decreased gradually. The abundance of Ascomycota followed the order of S>SN>SNW during the thermophilic phase. The abundance of Aspergillus accounted for 4–59% of the total abundance of fungi and increased during the first two sampling periods. Aspergillus abundance followed the order of SNW>SN>S. Additionally, principal component analysis (PCA) revealed that the community compositions in the straw and straw+urea treatments were similar, and that the bacterial communities in treatments S, SN and SNW in the mesophilic phase (at day 1) were different from those observed in three other phases (at days 5, 11, and 19, respectively), while the fungal communities showed only slight variations in their structure in response to changes in the composting process. Canonical correlation analysis (CCA) and redundancy analysis (RDA) showed that total carbon (TC), NO3−-N (NN), electrical conductivity (EC) and pH were highly correlated with community composition. Therefore, this study highlights that the additives are beneficial to straw composting and result in good quality compost.

Crop straw retention influenced crop yield and greenhouse gas emissions under various external conditions.

Crop straw retention is a strongly recommended practice for sustainable agricultural production in China. However, a comprehensive analysis of straw retention effects on crop yield, N2O and CH4 emissions, net greenhouse gas (NGHG), and net greenhouse gas intensity (NGHGI) and their response to various external influence factors, including location/climatic conditions, soil properties, and field management practices, in a national scale were easily ignored. Based on the collected published literatures, we found that straw retention improved crop yield and N2O and CH4 emissions by 4.7% (-4.6 to 25.8%), 18.3% (-26.6 to 57.6%), and 21.0% (-49.0 to 214.5%) in contrast with no-straw retention. For different external conditions, crop yield was increased by 15.9% in temperate zone and 10.7% in upland soils with straw retention. N2O emissions which correspond to the above conditions were enhanced by 42.2% and 18.8%, while CH4 emissions were restrained by 49.0% in temperate zone. Negligible changes in crop yield and N2O emissions were observed for subtropical zone or paddy soils, but with increase in CH4 emissions. Additionally, straw retention enhanced NGHG and NGHGI by 20.7% and 15.4% on average regardless of various external conditions, respectively. However, NGHG was reduced under conditions of straw retention in temperature or mulching to field. Straw retention under appropriate site-specially conditions simultaneously safeguard food security and slightly increase environmental effects.

Intermediate Volatile Organic Compound Emissions from Residential Solid Fuel Combustion Based on Field Measurements in Rural China.

Residential solid fuel combustion (RSFC) is a key cause of air pollution in China. In these serial studies, field measurements of RSFC from 166 rural households in eastern China were conducted to update the database of emission factors (EFs) and chemical profiles of gaseous and particulate organic pollutants, and the present study focuses on the intermediate volatile organic compounds (IVOCs), which are precursors of secondary organic aerosol (SOA). The results show that the averaged EFs of IVOCs (EFIVOC) for crop straw, fuelwood, and coal are 550.7 ± 397.9, 416.1 ± 249.5, and 361.9 ± 308.0 mg/kg, respectively, which are among the EFIVOC of gasoline vehicle, diesel vehicle, non-road machinery, and heavy fuel oil vessel, and are significantly affected by fuel, stove, and combustion efficiency. The percentages of normal alkanes (n-alkanes), branched alkanes (b-alkanes), polycyclic aromatic hydrocarbons (PAHs), and unresolved complex mixture from RSFC are 3.5 ± 1.6, 8.0 ± 3.7, 17.6 ± 6.7, and 70.9 ± 8.1%, respectively, and the compositions are featured by lower b-alkanes and higher PAHs than those of vehicle sources. The proportions of some individual n-alkanes and PAHs (such as n-C12-n-C15, naphthalene, and its alkyl substituents) can be used as indicators to differentiate RSFC from vehicle sources, while methoxyphenols can be used to distinguish biomass burning from coal combustion. Based on China's energy statistics, the total IVOC emissions from RSFC in 2014 were 175.9 Gg. These data will help to update the IVOC emission inventory and improve the estimates of SOA production in China.

The Crop Residue Removal Threshold Ensures Sustainable Agriculture in the Purple Soil Region of Sichuan, China

Sichuan, a hilly area in southwestern China, is recommended as a bioethanol production base because of its abundant crop residue resources. However, removing the crop straw for bioethanol may negatively affect soil fertility and productivity due to the local purple soil vulnerability. To explore the impact of crop residue removal on soil fertility and productivity and meet the needs of sustainable agriculture, we conducted a crop residue removal experiment by measuring the soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents, and crop yield in the purple soil region in southwest China. Soil erosion was also simulated by Revised Universal Soil Loss Equation version 2 (RUSLE 2). The results showed that soil erosion increased with the increase of the straw removal rate. Compared with 0% removal treatment, the SOC content reduced at other removal rate treatments, especially for long-term residue removal. The effect of residue removal on soil TN and TP was not consistent within one year. After two years, residue removal greater than 25% caused a decrease in TN by 1.6–3.7%, and straw removal greater than 50% caused a TP decrease by 8.5–9.3%. More than 25% of the residue removed reduced maize and canola yields, and TN and TP content. However, all crop residue removal treatments resulted in SOC content reduction and soil erosion deterioration. In conclusion, crop residue removal was not recommended due to agricultural sustainability in Sichuan, China.

Analysis and optimization of process parameters of the degradable fiber mulch paper made from pineapple leaf and rice straw by response surface method

To improve the utilization rate of pineapple leaf and crop straw, and provide technical support for making biodegradable fiber mulch paper through organic cultivation, the process and properties of the degradable fiber mulch paper made from pineapple leaf and rice straw were studied. The degradable fiber mulch paper was prepared as a hybrid composite in which pineapple leaf fiber and rice straw fiber were used as raw materials, and environmentally friendly agents were added. A four-factor five-level quadratic orthogonal rotation central composite design of the response surface method was employed. The beating degree of pineapple leaf fiber, basis weight, addition ratio of pineapple leaf fiber, and wet strength agent content were process parameters; dry tension strength, wet tension strength, and bursting strength were objective functions. The optimal technology parameters of pineapple leaf and rice straw fiber mulch paper were 70 to 90 g/m2 basis weight of pineapple leaf fiber, 17% to 25% addition ratio of pineapple leaf fiber, 55 °SR beating degree, and 1.5% wet strength agent content. According to the tensile strength and bursting strength standards, the degradable fiber mulch paper made from pineapple leaf and rice straw was feasible. The results provide theoretical basis and technical support to use pineapple leaves and rice straw to make degradable mulch paper.

Size distribution and chemical characteristics of particles from crop residue open burning in North China

Crop residue open burning is an important emission source of ambient particles in China. This study analyzed the particle emission characteristics of crop residue open burning through combustion experiments with a novel open combustion simulation device using three typical crop straws in north China (corn, wheat, and rice). Particle samples size ranging from 0.006–9.890 µm were collected by an Electrical Low Pressure Impactor plus, a high size-resolution instrument capable of dividing particles into 14 size stages. The size distributions of organic carbon (OC), elemental carbon (EC), water-soluble ions, and elements were analyzed, and source chemical profiles were constructed for PM0.1, PM1, PM2.5, and PM10. The number concentration of particles was concentrated in the Aiken nuclei mode (0.006–0.054 µm), accounting for 75% of the total number, whereas the mass concentration was concentrated in the accumulation mode (0.054–0.949 µm), accounting for 85.43% of the mass loading. OC, EC, Cl−, and K(include total K and water-soluble K) were the major chemical components of the particles, whose mass percentage distributions differed from those of other components. These five main components exhibited a bell-shaped size distribution in the 0.006–9.890 µm range, whereas the other components exhibited a U-shaped distribution. Among the chemical profiles for PM0.1–PM10, OC was the most important component at 10–30%, followed by EC at 2%–8%. The proportions of K+, Cl−, and K varied substantially in different experimental groups, ranging from 0–15%, and K+ and Cl− were significantly correlated (r = 0.878, α = 0.000).

Comprehensive review on agricultural waste utilization and high-temperature fermentation and composting

Due to the high demand for food and meat for the world's growing population, the agricultural sector is expanding every year. Timely and effective treatment is of utmost importance to utilize organic matter in agricultural waste and avoid environmental pollution. Composting or aerobic fermentation is an effective way to treat agricultural waste and produce organic fertilizer. Improving the application rate of organic fertilizer in soil needs time to reduce dependence on chemical fertilizers. This review article presented the current status and traditional agricultural waste (livestock manure and crop straws) utilization methods, the art of aerobic fermentation process including ultrahigh temperature fermentation and composting. The selection of livestock manure and crop straws as agricultural waste for this review article is due to high nutrients contents and massive generation of them worldwide. This article also included the development of aerobic fermentation technology and listed the high-temperature fermentation tanks. Based on high-temperature aerobic fermentation process performance and quality compost production, recently, some researchers have started working on hyperthermophile pretreatment-assisted high temperature composting, also discussed. Finally, this article gave brief knowledge about compost maturity, which is very important to measure before its application as an organic fertilizer. This art of literature could provide comprehensive knowledge about agricultural waste utilization and high-temperature composting to researchers.