Typology of Crop Residues and Energy Recovery in Heavily Agricultural Areas: Case of the Departments of Soubré, Daloa, Issia and Sassandra (Côte d’Ivoire)

The valorization of crop residues could constitute an energy source (biogas) allowing to reduce the energy needs of populations in agricultural regions, improve their living conditions and slow down deforestation as well as greenhouse gas emissions. This work aims to determine the typology of agricultural waste in the departments of Soubré, Sassandra, Daloa and Issia, to determine the number of residues generated in these departments, and to assess the biogas potential of these departments said residues. Field observations were made to identify the different types of waste, then, based on agricultural statistical data from the Ministry of Agriculture and biogas productivity indexes, the quantities of agricultural residues and biogas were estimated. Agricultural residues consist of pods (50%), stalks (19%), cobs (3%), Straws (8%), stalks (2%), shells (9%), fibers (7%), husks (1%), and bunches (1%). In addition, these localities have 465266.3 t of pods, 173583.2 t of stalks, 84280.0 t of shells, 75,857 t of straws, 12,000 t of husks, 10,987 t of bunches and 6793.0 t of fibers. The departments of Soubré, Sassandra, Daloa and Issia contain a total potential energy of 235.87 × 106 m3 of biogas. However, this is unevenly distributed among the localities. The volume of biogas recorded is higher in the department of Soubré (74.91 × 106 m3) which is followed respectively by the departments of Daloa (62.27 × 106 m3), Issia (52.77 × 106 m3 and Sassandra (45.93 × 106 m3). The departments of Soubré, Sassandra, Daloa and Issia have a very large potential for the production of agricultural residues that may be of interest to economic operators for recovery in biogas production units.

Incorporation of Crop Residues into Soil: A Practice to Improve Soil Chemical Properties

Crop residues have the potential to enhance soil fertility, but this is dependent on their biochemical properties. This study aimed to evaluate the chemical composition, and nutrients release patterns of selected crop residues (corn stalk, rice straw, millet straw and sorghum stalk). Thus, 20 g of each crop residue were put in litter bags and placed in a plastic pot containing 10 kg of soil with a moisture content of 40% - 60%. Five replications were considered per type of residue and some samples were taken every 4 weeks. Results showed that crop residues got a pH varying between 5.09 and 6.5. The lowest C content (33.11%) and nitrogen (0.27%) were measured in sorghum stalk when the highest C content (47.6%) and nitrogen content (0.55%) were registered in corn stalk. The highest phosphorus content (0.58%) was got in corn stalk. Potassium content was higher in millet straw than in others. The highest calcium content (0.37%) and magnesium (0.29%) were found in rice straw. There was an increase of soil chemical composition after crop residues burial. Significant increase in carbon, nitrogen, and phosphorus content was noted in soil at week 4 with the highest at week 16. At the end of the experiment, the highest C content (53.1%) and the highest nitrogen content (0.88%) in the soil were observed after burial of rice straw. The highest phosphorus content (0.82%) registered in the soil was got with millet straw. Nutrient release efficiency of crop residues occurred in the following order: rice straw > millet straw > sorghum stalk > corn stalk. This study has demonstrated that rice straw and millet straw released nutrients faster and this is beneficial for early planted crops, while sorghum stalk and corn stalk released nutrients slowly which is appropriate for long-term availability of plant nutrients.

Advanced Thermochemical Conversion Approaches for Green Hydrogen Production from Crop Residues

The huge volumes of crop residues generated during the production,processing,and consumption of farm products constitute an ecological nuisance when ineffectively managed.The conversion of crop residues to green hydrogen is one of the sustainable management strategies for ubiquitous crop residues.Production of green hydrogen from crop residue sources will contribute to deepening access to clean and affordable energy,mitigating climate change,and ensuring environmental sustainability.However,the deployment of conventional thermochemical technologies for the conversion of crop residues to green hydrogen is costly,requires long residence time,produces low-quality products,and therefore needs to be upgraded.The current review examines the conventional,advanced,and integrated thermochemical conversion technologies for crop residues for green hydrogen production.After a brief overview of the conventional thermochemical techniques,the review delves into the broad narration of advanced thermochemical technologies including catalytic pyrolysis,microwave pyrolysis,co-pyrolysis,hyropyrolysis,and autothermal pyrolysis.The study advocates the deployment of integrated pyrolysis,anaerobic digestion,pyrolysis,and gasification technologies will ensure scalability,decomposition of recalcitrant feedstocks,and generation of high grade green hydrogen.The outlook provides suggestions for future research into cost-saving and sustainable integrated technologies for green hydrogen production towards achieving carbon neutrality and a circular bio-economy.

Integration of Multiple Spectral Data via a Logistic Regression Algorithm for Detection of Crop Residue Burned Areas:A Case Study of Songnen Plain,Northeast China

The burning of crop residues in fields is a significant global biomass burning activity which is a key element of the terrestrial carbon cycle,and an important source of atmospheric trace gasses and aerosols.Accurate estimation of cropland burned area is both crucial and challenging,especially for the small and fragmented burned scars in China.Here we developed an automated burned area mapping algorithm that was implemented using Sentinel-2 Multi Spectral Instrument(MSI)data and its effectiveness was tested taking Songnen Plain,Northeast China as a case using satellite image of 2020.We employed a logistic regression method for integrating multiple spectral data into a synthetic indicator,and compared the results with manually interpreted burned area reference maps and the Moderate-Resolution Imaging Spectroradiometer(MODIS)MCD64A1 burned area product.The overall accuracy of the single variable logistic regression was 77.38%to 86.90%and 73.47%to 97.14%for the 52TCQ and 51TYM cases,respectively.In comparison,the accuracy of the burned area map was improved to 87.14%and 98.33%for the 52TCQ and 51TYM cases,respectively by multiple variable logistic regression of Sentind-2 images.The balance of omission error and commission error was also improved.The integration of multiple spectral data combined with a logistic regression method proves to be effective for burned area detection,offering a highly automated process with an automatic threshold determination mechanism.This method exhibits excellent extensibility and flexibility taking the image tile as the operating unit.It is suitable for burned area detection at a regional scale and can also be implemented with other satellite data.

Crop residues: applications of lignocellulosic biomass in the context of a biorefinery

Interest in lignocellulosic biomass conversion technologies has increased recently because of their potential to reduce the dependency on non-renewable feedstocks. Residues from a variety of crops are the major source of lignocellulose, which is being produced in increasingly large quantities worldwide. The commercial exploitation of crop residues as feedstocks for biorefineries which could be used to produce a variety of goods such as biofuels, biochemicals, bioplastics, and enzymes is an attractive approach not only for adding value to residues but also for providing renewable products required by the expanding bioeconomy market. Moreover, the implementation of biorefineries in different regions has the potential to add value to the specific crop residues produced in the region. In this review, several aspects of crop residue application in biorefineries are discussed, including the role of crop residues in the bioeconomy and circular economy concepts, the main technical aspects of crop residue conversion in biorefineries, the main crop residues generated in different regions of the world and their availability, the potential value-added bioproducts that can be extracted or produced from each crop residue, and the major advantages and challenges associated with crop residue utilization in biorefineries. Despite their potential, most biomass refining technologies are not sufficiently advanced or financially viable. Several technical obstacles, especially with regard to crop residue collection, handling, and pre-treatment, prevent the implementation of biorefineries on a commercial scale. Further research is needed to resolve these scale-up-related challenges. Increased governmental incentives and bioeconomic strategies are expected to boost the biorefinery market and the cost competitiveness of biorefinery products.

Investigation on emission factors of particulate matter and gaseous pollutants from crop residue burning

Emission factors of particulate matter （PM）, element carbon （EC）, organic carbon （OC）, SO2, NOx, CO, CO2, and ten ions （Na^＋, NH4^＋, K^＋, Mg^2＋, Ca^2＋, Fˉ, Clˉ, NO2ˉ, NO3ˉ, SO42ˉ） were estimated from the domestic burning of four types of commonly produced crop residues in rural China： rice straw, wheat straw, corn stover, and cotton stalk, which were collected from the representative regions across China. A combustion tower was designed to simulate the cooking conditions under which the peasants burned their crop residues in rural China, to measure the emission factors. Results showed that wheat straw had the highest emission factor for the total PM （8.75 g/kg） among the four crop residues, whereas, corn stover and wheat straw have the highest emission factor for EC （0.95 g/kg） and OC （3.46 g/kg）, respectively. Corn stover also presents as having the highest emission factors of NO, NOx, and CO2, whereas, wheat straw, rice straw, and cotton stalk had the highest emission factors of NO2, SO2, and CO, respectively. The water-soluble ions, K^＋ and Clˉ, had the highest emission factors from all the crops. Wheat straw had a relatively higher emission factor of cation species and Fˉ, Clˉ, NO2ˉ than other residues.

The Effects of Different Tillages on Crop Residue Sequestration, Soil Available Nutrients and Some Biochemical Properties in the Chinese Black Soil Region

Three-year field experiments were conducted to investigate the effects of different tillage operations after harvest on crop residues sequestration and their subsequent effects on soil available nitrogen （N）, phosphorus （P）, some soil biochemical properties, and three enzymatic activities during the following growing seasons in a soybean （Glycine max）-soybean- corn （Zea mays） rotation farming system in Northeast China. Two different managements were implemented after crop harvest every year, which were tillage （T） and no tillage （NT）. Results showed that crop residue masses on soil surface and in the 0-20 cm layer after soybean harvest were about 1 450 and 340 kg ha-1, respectively, in October 2006 and 2007. While, soybean residue mass in the 0-20 cm soil layer was about 340 kg ha-1 in NT and about 1 550 kg ha-1 in T before sowing in May 2007 and 2008. The adverse results were found after corn crop plantation, that corn residue mass was about 270 and 860 kg ha-1 on soil surface and in the 0-20 cm soil layer, respectively, after harvest in October 2008, while residue mass in the 0-20 cm soil layer was only 466 kg ha-1 in T but 863 kg ha-1 in NT before planting in May 2009. So T had effectively sequestered soybean residue into soil but not corn. Results also showed that T after harvest helped to improve soil available N, P, soil microbial biomass carbon （MBC）, and nitrogen （MBN） contents and soil enzymes activities （urease, acid phosphatase, and protease） during the 2007 and 2008 seasons, but the positive effects decreased during the 2009 season. T practice had significant positive effects on available N, P, MBC, and MBN contents, protease and urease activities, however, no obvious effects on acid phosphatase activity. In this study, T practice after soybean harvest was proved to be preferable to improve soil microbial and enzyme activities during the following seasons due to an efficient sequestration of soybean residues. However, NT could be considered preferential after corn crop harvest.

Linking changes in the soil microbial community to C and N dynamics during crop residue decomposition

Crop residues are among the main inputs that allow the organic carbon(C)and nutrients to be maintained in agricultural soil.It is an important management strategy that can improve soil fertility and enhance agricultural productivity.This work aims to evaluate the extent of the changes that may occur in the soil heterotrophic microbial communities involved in organic matter decomposition and C and nitrogen(N)mineralization after the addition of crop residues.Soil microcosm experiments were performed at 28℃ for 90 days with the addition of three crop residues with contrasting biochemical qualities:pea(Pisum sativum L.),rapeseed(Brassica napus L.),and wheat(Triticum aestivum L.).Enzyme activities,C and N mineralization,and bacterial and fungal biomasses were monitored,along with the bacterial and fungal community composition,by the highthroughput sequencing of 16 S rRNA and ITS genes.The addition of crop residues caused decreases in β-glucosidase and arylamidase activities and simultaneous enhancement of the C mineralization and net N immobilization,which were linked to changes in the soil microbial communities.The addition of crop residues decreased the bacterial and fungal biomasses 90 days after treatment and there were shifts in bacterial and fungal diversity at the phyla,order,and genera levels.Some specific orders and genera were dependent on crop residue type.For example,Chloroflexales,Inquilinus,Rubricoccus,Clitocybe,and Verticillium were identified in soils with pea residues;whereas Thermoanaerobacterales,Thermacetogenum,and Hypoxylon were enriched in soils with rapeseed residues,and Halanaerobiales,Rubrobacter,and Volutella were only present in soils with wheat residues.The findings of this study suggest that soil C and N dynamics in the presence of the crop residues were driven by the selection of specific bacterial and fungal decomposers linked to the biochemical qualities of the crop residues.If crop residue decomposition processes showed specific bacterial and fungal operational taxonomic unit(OTU)signatures,this study also suggests a strong functional redundancy that exists among soil microbial communities.

Tillage, crop residue, and nutrient management effects on.soil organic carbon in rice-based cropping systems： A review

Soil organic carbon （SOC） sequestration is one of the major agricultural strategies to mitigate greenhouse gas （GHG） emissions, enhance food security, and improve agricultural sustainability. This paper synthesizes the much-needed state- of-knowledge on the effects of tillage, crop residue, and nutrient management practices on SOC sequestration and identifies potential research gap, opportunities, and challenges in studying SOC dynamics in rice （Oryza sativa L.）-based cropping systems in South Asia, mainly in Bangladesh, Bhutan, India, Nepal, Pakistan, and Sri Lanka. Improved management prac- tices such as reduced- and no-tillage management, nitrogen （N） fertilizer and farmyard manure （FYM） application, and crop residue addition can improve SOC accumulation. Positive effects of no-tillage, crop residue addition, N addition through manure or compost application, and integration of organic and chemical fertilizers on SOC accumulation in rice-based cropping systems have been documented from South Asia. However, limited data and enormous discrepancies in SOC measurements across the region exist as the greatest challenge in increasing SOC sequestration and improving agricultural sustainability. More research on SOC as influenced by alternative tillage, crop residue, and nutrient management systems, and development of SOC monitoring system for existing long-term experiments will advance our understanding of the SOC dynamics in rice-based cropping systems and improve agricultural system sustainability in South Asia.

Contributions of Different N Sources to Crop N Nutrition in a Chinese Rice Field

N availability is one of the most important factors limiting crop yield enhancement.The recovery of applications of 15 N-labeled fertilizer and crop residues in a rice-wheat cropping system was determined for up to 6 consecutive growing seasons.The crop residues from the previous season were either incorporated or removed as two different treatments.Our results showed that 16.55%-17.79% (17.17% on average) of the fertilizer N was recovered in the crop during the first growing season,suggesting that more than 80% of crop N was not directly from the N fertilizer.When 15 N-labeled residues were applied,12.01% was recovered in the crop in the first growing season.The average recoveries of fertilizer N and crop residue N in the soil after the first growing season were 33.46% and 85.64%,respectively.N from soil organic matter contributed approximately 83% of the N in the crop when 15 N fertilizer was applied or 88% when crop residues were applied.There was a larger difference in the total 15 N recovery in plant and soil between N applications in the forms of fertilizer and crop residues.Incorporation of crop residues following the 15 N fertilizer application did not significantly promote 15 N recovery in the crop or soil.On average,only additional 1.94% of N for the fertilizer-applied field or 5.97% of N for the crop residue-applied field was recovered by the crops during the 2nd and 3rd growing seasons.The total recoveries of 15 N in crop and soil were approximately 64.38% for the fertilizer-applied field after 6 growing seasons and 79.11% for the crop residue-applied field after 5 growing seasons.Although fertilizer N appeared to be more readily available to crops than crop residue N,crop residue N replenished soil N pool,especially N from soil organic matter,much more than fertilizer N.Therefore,crop residue N was a better source for sustaining soil organic matter.Our results suggested that the long-term effect of fertilizer or crop residues on N recovery were different in the crop and soil.However,there was little difference between the practices of crop residue incorporation and residue removal following the N fertilizer application.

Fate of Nitrogen from Organic and Inorganic Sources in Rice-Wheat Rotation Cropping System

The lower availability of N is one of the most important limiting factors impeding crop yield enhancement among the various factors that affect crop yield under the multiple-cropping agroecosystem in China.In this study,the recovery of a single application of 15N-labeled fertilizer or residues in rice-wheat cropping system was determined,in order to provide theoretical foundation for the nitrogen management in sustainable agricultural production.A continuous trace experiment was conducted for 15N microplots by using randomized block design with four treatments and four replications（T1 = 15N-labeled fertilizer with crop residue incorporation,T2 = 15N-labeled residues,T3 = 14N fertilizer to generate unlabeled crop residue,and T4 = 15Nlabeled fertilizer without crop residue incorporation）.Our results showed that,on average,17.17 and 12.01% of crop N was derived from N fertilizer and 15N-labeled residues,respectively during the first growing season,suggesting that approximately 82.83 or 87.99% of crop N was derived directly from soil N pool.There was a larger difference in the 15N recovery pattern in crop when N was applied as fertilizer or residues,i.e.,most of crop N derived from N fertilizer was absorbed in the first growing season（92.04%）,and the relevant value was 38.03% when 15N-labeled residues were applied.This implied that most of N fertilizer was recovered in the present cropping season,while a longer residue effect will be found for 15N-labeled residues.Thus,the average recovery of N fertilizer and N residue in the soil after the first growing season was 33.46 and 85.64%,respectively.The recovery of applied N in soil when N was applied as residues was significantly higher than that when N was applied as fertilizer.There was a larger difference in the total 15N recovery in plant and soil when N was applied as fertilizer or residues.By the end of the fifth or sixth cropping season,the total 15N recovery in plant and soil when N was applied as fertilizer or residues were estimated at 64.38 and 79.11%,respectively.On the contrary,there was little difference between the practices of residue incorporation and residue removal following the N fertilizer application.N fertilizer appeared to be more readily available to crops than residue-N,and residue-N replenished soil N pool,especially N in soil organic matter,much more than N fertilizer after six growing seasons.Therefore,residue-N is a better source for sustaining N content of soil organic matter.Thus,one possible management practice is to use both organic and inorganic N sources simultaneously to improve the use efficiency of N while protecting the sustainability of soil.

Identification of Techno-Economically Viable Crop Residue Utilization in India

India generates more than 140 million tonnes of surplus crop residue every year In Haryana, the agricultural sector alone produces 24.64 million tonnes of residue annually;of which only 71% is consumed in various domestic and commercial activities within the state. The rest of the material is burned causing severe contamination of air with smoke. There is an urgent need to identify suitable and sustainable conversion technologies that are efficient, eco-friendly as well as cost-effective for managing the huge available biomass not only in the state but also in the country. This paper reviews briefly the available crop residue and quantities burned, proposes a scheme to incorporate part of the residue in the field for its fertilizer value. The remaining biomass is harvested for animal feed and the excess is converted to bioenergy and biofuels. Among the developed and developing biofuels, the paper identifies biogas production from biomass for on-farm use. Pelletization is identified as an enabling technology to provide high quality feedstock for conversion to heat/power and in near future to advanced biofuels.

Estimates on nitrogen uptake in the subsequent wheat by aboveground and root residue and rhizodeposition of using peanut labeled with^(15)N isotope on the North China Plain

Leguminous crops play a vital role in enhancing crop yield and improving soil fertility. Therefore, it can be used as an organic N source for improving soil fertility. The purpose of this study was to(i) quantify the amounts of N derived from rhizodeposition, root and above-ground biomass of peanut residue in comparison with wheat and(ii) estimate the effect of the residual N on the wheat-growing season in the subsequent year. The plants of peanut and wheat were stem fed with 15 N urea using the cotton-wick method at the Wuqiao Station of China Agricultural University in 2014. The experiment consisted of four residue-returning strategies in a randomized complete-block design:(i) no return of crop residue(CR0);(ii) return of above-ground biomass of peanut crop(CR1);(iii) return of peanut root biomass(CR2); and(iv) return of all residue of the whole peanut plant(CR3). The 31.5 and 21% of the labeled 15 N isotope were accumulated in the above-ground tissues(leaves and stems) of peanuts and wheat, respectively. N rhizodeposition of peanuts and wheat accounted for 14.91 and 3.61% of the BG15 N, respectively. The 15 N from the below-ground 15 N-labeled of peanuts were supplied 11.3, 5.9, 13.5, and 6.1% of in the CR0, CR1, CR2, and CR3 treatments, respectively. Peanut straw contributes a significant proportion of N to the soil through the decomposition of plant residues and N rhizodeposition. With the current production level on the NCP, it is estimated that peanut straw can potentially replace 104 500 tons of synthetic N fertilizer per year. The inclusion of peanut in rotation with cereal can significantly reduce the use of N fertilizer and enhance the system sustainability.

Inclusion of Yeast Cultures (<i>Saccharomyces cerevisiae</i>) to Dairy Cows’ Urea-Treated Rice Straw Diets Improves Mozzarella Cheese Processing and Yield

This research paper addresses the hypothesis that adding yeast cultures (Saccharomyces cerevisiae) to urea-treated cereal crop residues could improve milk composition to the level of milk produced on pastures for the manufacture of Mozzarella cheese. In three equal groups, Nine Friesian cows were randomly assigned to three treatment diets in a completely randomized design. The treatments were pasture (P), urea treated rice straw (UTRS), and urea treated rice straw with yeast inclusion (UTRS + Y). Urea inclusion was at 3.8% of the dry matter to treat rice straw, while yeast culture inclusion was 10 g/cow/day. The experimental period was 21 days, with 14 days of adaptation. Data analysis used general linear model procedure of SAS, fitting diet as a fixed effect and milk composition, syneresis, curd firmness and cheese yield as the response variables. Milk produced on UTRS diet yielded (p < 0.05) the highest fat content (4.79%) and the lowest density (1016.37 Kg·m-3) and casein-to-fat ratio (0.51). Yeast inclusion in the diet (UTRS + Y) significantly improved milk density (1022.68 Kg·m-3) with marginal reduction in milk fat content (4.53%). In cheese making, milk produced on URTS diets had significantly lower renneting time (1.4 minutes vs 3.47 minutes and 2.39 minutes), least viscous gel, lowest syneresis (755 mL vs 860 mL and 836 mL from 1000 mL), and lowest cheese yield (9.0% vs 11% and 10.5%) compared to P and UTRS + Y diets. Milk produced from P and UTRS + Y did not show any significant difference in cheese yield. The findings indicated that urea treated rice straw with yeast cultures improves syneresis, gel viscosity and Mozzarella cheese yield. Therefore, we recommend the inclusion of yeast to urea treated cereal crop residues to produce milk destined for Mozzarella cheese making.

Benefits of Conservation Agriculture on Soil and Water Conservation and Its Progress in China

Conservation agriculture has been practised for three decades and has been spread widely. There are many nomenclatures surrounding conservation agriculture and differ to each other lightly. Conservation agriculture （CA） is a system approach to soil and water conservation, high crop productivity and profitability, in one word, it is a system approach to sustainable agriculture. Yet, because conservation agriculture is a knowledge-intensive and a complex system to learn and implement, and also because of traditions of intensive cultivation, adoption rates have been low, since to date, only about seven percent of the world＇s arable and permanent cropland area is farmed under conservation agriculture. The practice and wider extention of conservation agriculture thus requires a deeper understanding of its ecological underpinnings in order to manage its various elements for sustainable intensification, where the aim is to conserve soil and water and improve sustainability over the long term. This paper described terms related to conservation agriculture, presented the effects of conservation agriculture on soil and water conservation, crop productivity, progress and adoption of CA worldwide, emphasized obstacles and possible ways to increase CA adoption to accelerate sustainable development of China agriculture.

Characteristics of maize residue decomposition and succession in the bacterial community during decomposition in Northeast China

Microbes are decomposers of crop residues,and climatic factors and residue composition are known to influence microbial growth and community composition,which in turn regulate residue decomposition.However,the succession of the bacterial community during residue decomposition in Northeast China is not well understood.To clarify the property of bacterial community succession and the corresponding factors regulating this succession,bags containing maize residue were buried in soil in Northeast China in October,and then at different intervals over the next 2 years,samples were analyzed for residue mass and bacterial community composition.After residue burial in the soil,the cumulative residue mass loss rates were 18,69,and 77%after 5,12,and 24 months,respectively.The release of residue nitrogen,phosphorus,and carbon followed a similar pattern as mass loss,but 79%of residue potassium was released after only 1 month.The abundance,richness,and community diversity of bacteria in the residue increased rapidly and peaked after 9 or 20 months.Residue decomposition was mainly influenced by temperature and chemical composition in the early stage,and was influenced by chemical composition in the later stage.Phyla Actinobacteria,Bacteroidetes,and Firmicutes dominated the bacterial community composition in residue in the early stage,and the abundances of phyla Chloroflexi,Acidobacteria,and Saccharibacteria gradually increased in the later stage of decomposition.In conclusion,maize residue decomposition in soil was greatly influenced by temperature and residue composition in Northeast China,and the bacterial community shifted from dominance of copiotrophic populations in the early stage to an increase in oligotrophic populations in the later stage.

Phosphorus and nitrogen in the soil interface between two plant residues differing in C/nutrient ratio:A short-term laboratory incubation study

In studies on the effects of mixing residues with different properties on decomposition rate and nutrient release,the extent of contact between the different residues is not known.In this study,we used an experimental design where crop residues were spatially separated by a layer of soil.Microcosms were set up using young faba bean residue(low carbon(C)/nutrient ratio,L)and mature barley straw(high C/nutrient ratio,H).The microcosms comprised of two caps of PVC tubes,each filled with moist soil.Between the two caps,there were three layers each separated from the others by fine nylon mesh with the middle layer being the moist interface soil.Microcosms had similar(H/H or L/L)or different(L/H)residue types,or only residue type(H/S or L/S)while the other cap had no residue.In treatments with only one residue,measured parameters,except microbial biomass P(MBP),were higher in L/S than H/S.In treatments with two residues,all parameters were lowest in H/H.In L/H compared to L/L after 14 days,available P and microbial biomass N(MBN)were lower,available N was similar and MBP was higher.After 28 days,available P and N were lower in L/H than L/L,but MBP and MBN did not differ.In L/H,measured resin P,MBP and MBN were higher than expected whereas available N was lower.The experimental design used in this study allows assessing the effect of residues on properties of the soil between them.

Size distributions of aerosol and water-soluble ions in Nanjing during a crop residual burning event

To investigate the impact on urban air pollution by crop residual burning outside Nanjing, aerosol concentration, pollution gas concentration, mass concentration, and water-soluble ion size distribution were observed during one event of November 4-9, 2010. Results show that the size distribution of aerosol concentration is bimodal on pollution days and normal days, with peak values at 60- 70 and 200-300 nm, respectively. Aerosol concentration is 104 cm-3.nm-1 on pollution days. The peak value of spectrum distribution of aerosol concentration on pollution days is 1.5-3.3 times higher than that on a normal day. Crop residual burning has a great impact on the concentration of fine particles. Diurnal variation of aerosol concentration is trimodal on pollution days and normal days, with peak values at 03：00, 09：00 and 19：00 local standard time. The first peak is impacted by meteorological elements, while the second and third peaks are due to human activities, such as rush hour traffic. Crop residual burning has the greatest impact on SO2 concentration, followed by NO2, 03 is hardly affected. The impact of crop residual burning on fine particles （〈 2.1 μm） is larger than on coarse particles （〉 2.1 μm）, thus ion concentration in fine particles is higher than that in coarse particles. Crop residual burning leads to similar increase in all ion components, thus it has a small impact on the water-soluble ions order. Crop residual burning has a strong impact on the size distribution of K^＋, Cl^-, Na^＋, and F- and has a weak impact on the size distributions of NH4^＋, Ca^2＋, NO3^- and SO4^2-.

Dynamics of major air pollutants from crop residue burning in China's Mainland,2000–2014

Based on satellite image data and China＇s Statistical Yearbooks（2000 to 2014）, we estimated the total mass of crop residue burned, and the proportion of residue burned in the field vs.indoors as domestic fuel. The total emissions of various pollutants from the burning of crop residue were estimated for 2000-2014 using the emission factor method. The results indicate that the total amount of crop residue and average burned mass were 8690.9 Tg and4914.6 Tg, respectively. The total amount of emitted pollutants including CO2, CO, NOx,VOCs, PM（2.5）, OC（organic carbon）, EC（element carbon） and TC（total carbon） were 4212.4–8440.9 Tg, 192.8–579.4 Tg, 4.8–19.4 Tg, 18.6–61.3 Tg, 18.8–49.7 Tg, 6.7–31.3 Tg, 2.3–4.7 Tg, and8.5–34.1 Tg, respectively. The emissions of pollutants released from crop residue burning were found to be spatially variable, with the burning of crop residue mainly occurring in Northeast, North and South China. In addition, pollutant emissions per unit area（10 km ×10 km） were mostly concentrated in the central and eastern regions of China. Emissions of CO2, NOx, VOCs, OC and TC were mainly from rice straw burning, while burning of corn and wheat residues contributed most to emissions of CO, PM（2.5） and EC. The increased ratio of PM（2.5） emissions from crop residue burning to the total emitted from industry during the study period is attributed to the implementation of strict emissions management policies in Chinese industry. This study also provides baseline data for assessment of the regional atmospheric environment.

Soil physical quality as influenced by long-term fertilizer management under an intensive cropping system

In China’s major rice(Oryza sativa L.)production regions,the traditional fertilization modes are challenged by the continued decrease in manure and increase in mineral fertilizer.However,limited information exists on the influences of long-term fertilizer management on soil organic carbon(SOC)and soil physical properties under the intensive rice production system in southern China.The objective of this study was to characterize the changes of soil physical properties as related to mineral fertilizer,crop residues,and manure application based on a long-term field experiment.The experiment,initiated in 1986,has five treatments:unfertilized,mineral fertilizer alone,rice residues plus mineral fertilizer,low manure rate plus mineral fertilizer,and high manure rate plus mineral fertilizer.The cropping system consists of barley(Hordaum vulgare L.),early rice,and late rice,three crops in a year.In May 2006,after barley harvest,soil samples were collected from the 0~10 cm and 10~20 cm layers to determine SOC concentration,aggregate size distribution,bulk density(rb),saturated hydraulic conductivity(Ks),and soil water characteristic curves(SWCC).The results indicated that manure significantly reducedrb,increased SOC concentration,soil aggregation,Ks,transmission and storage porosity,as well as water retention capacity.Combined application of crop residue and mineral fertilizer also improved soil physical properties,but the improvement by mineral fertilizer alone was limited.Correlation analysis demonstrated that S,the slope of the SWCC at its inflection point,was closely associated with the selected physical parameters,suggesting S was an effective parameter for soil physical quality evaluation.Nevertheless,in applying the S-theory,a unified approach to define the residual water content should be considered.