Management of Cereal Crop Residues for Sustainable Rice-wheat Production System in the Indo-gangetic Plains of India

Recovery of filter paperase from mouldy rice husk in solid state fermentation by Aspergillus protuberus

Recovery of enzymes such as FPase (filter paperase) or exoglucanase from fermented substrate is a sustainable approach in enzyme production; however, there is a scarcity of optimization studies in this field. The present study was aimed to standardize number of parameters (selection of solvent, solvent volume, soaking time, leaching conditions and number of washes) to extract maximum amount of FPase from fermented rice husk by Aspergillus protuberus. Novel Aspergillus protuberus was first report from our lab on cellulases production in solid state fermentation (SSF). Among the tested solvents, citrate phosphate buffer (0.02 M, pH 5.0) proved best solvent for maximum recovery of FPase. Consequent experimental parameters were further optimized with citrate phosphate buffer. Two washes with citrate phosphate buffer each by shaking (60 min) in a ratio of 1 g of rice husk: 5 ml of citrate phosphate buffer together attained higher recovery efficiency (88 %) of FPase from the fermented rice husk.

Interactive effects of long-term management of crop residue and phosphorus fertilization on wheat productivity and soil health in the rice-wheat

In the context of degradation of soil health, environmental pollution, and yield stagnation in the rice-wheat system in the Indo-Gangetic Plains of South Asia, an experiment was established in split plot design to assess the long-term effect of crop residue management on productivity and phosphorus requirement of wheat in rice-wheat system. The experiment comprised of six crop residue management practices as the main treatment factor with three levels (0, 30 and 60 kg P2O5 ha-1) of phosphorus fertilizer as sub-treatments. Significant improvement in soil aggregation, bulk density, and infiltration rate was observed under residue management (retention/incorporation) treatments compared to residue removal or residue burning. Soil organic carbon (SOC), available nutrient content (N, P, and K), microbial count, and enzyme activities were also significantly higher in conservation tillage and residue-treated plots than without residue/burning treatments. The residue derived from both crops when was either retained/incorporated improved the soil organic carbon (0.80%) and resulted in a significant increase in SOC (73.9%) in the topsoil layer as compared to the conventional practice. The mean effect studies revealed that crop residue management practices and phosphorus levels significantly influenced wheat yield attributes and productivity. The higher grain yield of wheat was recorded in two treatments, i.e. the basal application of 60 kg P2O5 ha-1 without residue incorporation and the other with half the P-fertilizer (30 kg P2O5 ha-1) with rice residue only. The grain yield of wheat where the rice and wheat residue were either retained/incorporated without phosphorus application was at par with 30 and 60 kg P2O5ha-1. Phosphorus levels also significantly affected wheat productivity and available P content in the soil. Therefore, results suggested that crop residue retention following the conservation tillage approach improved the yield of wheat cultivated in the rice-wheat cropping system.

Harnessing synergy: Integrating agricultural waste and nanomaterials for enhanced sustainability

This paper aims to explore the cooperative use of agricultural waste and nanomaterials to improve environmental sustainability. The introduction highlights global environmental challenges and the objectives of integrating the two are highlighted. Valorization of agricultural waste is considered to reduce waste generation, while nanomaterials act as conversion catalysts that help to increase the efficiency of waste conversion and environmental remediation. In addition, synergistic approaches are discussed, including the combination of agricultural waste and nanomaterials, as well as the concept of enhanced resource management. The paper also presents case studies that demonstrate the success of such synergistic applications in pollution control and environmental remediation. Despite the challenges and risks, this approach can provide new ways to create more sustainable and resilient environments through the integration of resources, interdisciplinary cooperation and policy support.

Long-term application of agronomic management strategies effects on soil organic carbon, energy budgeting, and carbon footprint under rice-wheat cropping system

In the plains of western North India, traditional rice and wheat cropping systems (RWCS) consume a significant amount of energy and carbon. In order to assess the long-term energy budgets, ecological footprint, and greenhouse gas (GHG) pollutants from RWCS with residual management techniques, field research was conducted which consisted of fourteen treatments that combined various tillage techniques, fertilization methods, and whether or not straw return was present in randomized block design. By altering the formation of aggregates and the distribution of carbon within them, tillage techniques can affect the dynamics of organic carbon in soil and soil microbial activity. The stability of large macro-aggregates (> 2 mm), small macro-aggregates (2.0-2.25 mm), and micro-aggregates in the topsoil were improved by 35.18%, 33.52%, and 25.10%, respectively, over conventional tillage (0-20 cm) using tillage strategies for conservation methods (no-till in conjunction with straw return and organic fertilizers). The subsoil (20-40 cm) displayed the same pattern. In contrast to conventional tilling with no straw returns, macro-aggregates of all sizes and micro-aggregates increased by 24.52%, 28.48%, and 18.12%, respectively, when conservation tillage with organic and chemical fertilizers was used. The straw return (aggregate-associated C) also resulted in a significant increase in aggregate-associated carbon. When zero tillage was paired with straw return, chemical, and organic fertilizers, the topsoil's overall aggregate-associated C across all aggregate proportions increased. Conversely, conventional tillage, in contrast to conservation tillage, included straw return as well as chemical and organic fertilizers and had high aggregate-associated C in the subsurface. This study finds that tillage techniques could change the dynamics of microbial biomass in soils and organic soil carbon by altering the aggregate and distribution of C therein.

Strategies for economic utilization of rice straw residues into value-added by-products and prevention of environmental pollution

Rice straw management, along with the prevalent practice of residue burning, poses multifaceted challenges with substantial environmental and human health implications. After harvest, a considerable amount of straw is left behind, often disposed of through burning, releasing several pollutants into the environment. Carbon dioxide (CO2) dominates at 70%, accompanied by methane (CH4) at 0.66%, carbon monoxide (CO) at 7%, and nitrous oxide (N2O) at 2.09%. This process further compounds issues by depleting soil nutrients like nitrogen and organic matter. This review focuses on strategies for residue management and using straw as value-added by-products. We address research gaps and offer potential recommendations for rice straw management using economically feasible and practical routes. We elaborate that to improve rice straw digestibility, utilization in mushroom cultivation, and other value-added products, low silica (Si) rice varieties must be developed using modern technologies including marker-assisted selection breeding or genome editing. Developing low Si rice could also reduce arsenic uptake by rice, as rice plants use the same transporters for the uptake of both elements. Conversely, silica is also indispensable for quality rice production; hence, optimizing silicon content in rice is worth investigating. More research is required to understand the extent of silicon's effect on the utilization of straw for various purposes. This review also discusses the importance of educating farmers about the straw burning issue and its environmental consequences. We highlight the significance of tailoring rice straw management methods to local suitability, moving away from a universal approach. More extension work is needed to encourage farmers to opt for environmentally and economically sound options for rice straw management. Policy intervention to incentivize farmers and develop technologies for the widespread use of rice straw for various industries and product development could help in the management of rice straw and will also create a circular economy.

Tillage, green manuring and crop residue management impacts on crop productivity, potassium use efficiency and potassium fractions under rice-wheat system

The conventional crop production practices including intensive tillage and open field crop residue burning in world' largest rice-wheat system (RWS) are adversely affecting crop productivity besides deteriorating natural resources and ecosystems' sustainability. In order to improve system productivity, potassium (K) use efficiency and apparent K balance, adoption of conservation tillage in a RWS with residue management is considered highly effective. We therefore, studied the effect of wheat straw retention and green manure (GM) in rice (main plot treatment), and tillage and rice residue management in subsequent wheat (sub-plot treatments) on crop productivity, K use efficiency and its transformation amongst different fractions of variable solubility. These results revealed that rice straw retention along with GM significantly (p < 0.05) increased the rice yields by ∼5.3-6.7% and wheat yields by ∼10.2-16.9%, compared to the conventional tillage (CT) without GM. Green manuring during the intervening period (CTR_W0+GM) significantly increased the rice grain K uptake by ∼36.2% than in plots with no-GM (CTR_W0). However, it increased by ∼29.8% under CTR_W25+GM, compared with CTR_W25-GM treatment. As compared with CTR_W0, CTR_W0+GM significantly increased the reciprocal internal use efficiency of K of rice by 3.8 kg Mg^-1 grain yield (∼29.5%). However, CTR_W25+GM increased the RIUE_K of rice by 3.3 kg Mg^-1 grain yield (∼22.4%), compared with no-GM (CTR_W25). Although, apparent K balance was net negative for CTR_W25, ZTW_R100 treatments, yet there was decreased K mining of 56-262 kg K ha^-1 (∼11.9-61.2%) for CTR_W25 and ZTW_R100 over CTR_W0 and ZTW_R0. The increased crop yield, K uptake and K use efficiency were significantly related to K enrichment in water soluble K, exchangeable K, non-exchangeable-K, hydrochloric acid extractable-K, lattice-K and total K fractions by ∼1.3, 3.4, 18.6, 11.0 and 34.1%, respectively due to residue retention, compared with no residue. Therefore, conventional tillage with puddled transplanted rice (CTR) with wheat residue and green manure during intervening period (CTR_W25+GM), and zero tillage wheat with rice residue retention (ZTW_R100) were emerged as highly valuable technological options for mitigating soil degradation effects under intensive RWS for food grains in north-western India.

The food-energy-water-carbon nexus of the rice-wheat production system in the western Indo-Gangetic Plain of India: An impact of irrigation system, conservational tillage and residue management

The conventional rice-wheat system in the western Indo-Gangetic plain of India is energy and water intensive with high carbon footprint. The transition towards resource-efficient eco-friendly production technologies with lower footprint is required for inclusive ecological sustenance. A five-year (2016-17 to 2020-21) field experiment was conducted in RWS with hypothesis that pressurized irrigation systems [drip (DRIP) and mini-sprinkler (MSIS)] in conservation tillage [reduced (RT)/zero (ZT)] and crop residue management [incorporation (RI)/mulch (RM)] might result in higher resource use efficiency with lesser carbon footprint compared to conventional system. Experiment consisted five treatments namely (1) puddled transplanted rice followed by conventionally tilled wheat (PTR/CTW), (2) DRIP irrigated reduced till direct seeded rice (RTDSR) followed by zero-till wheat with 100 % rice residue mulching (ZTW + RM) (DRIP-RTDSR/ZTW + RM), (3) surface irrigated RTDSR followed by ZTW + RM (SIS-RTDSR/ZTW + RM), (4) MSIS irrigated RTDSR followed by ZTW + RM (MSIS-RTDSR/ZTW + RM), and (5) MSIS irrigated RTDSR with 1/3rd wheat residue incorporation followed by ZTW + RM (MSIS-RTDSR + RI/ZTW + RM). The pressurized irrigation system in RWS established under conservational tillage and residue management (DRIP-RTDSR/ZTW + RM and MSIS-DSR + RI/ZTW + RM) produced at par system productivity compared to PTR/CTW. Substantial nitrogen (79-114 ka ha^-1) and irrigation water (536-680 mm) savings under pressurized irrigation systems resulted in 41-64 % higher partial factor productivity of nitrogen with 48-61 % lower water footprint. These systems had lower energy consumption attaining 15-21 % higher net energy, 44-61 % higher energy use efficiency, and 31-38 % lower specific energy. Efficient utilization of farm inputs caused lower greenhouse gas emission (39-44 %) and enhanced carbon sequestration (35-62 %) resulting 63-76 % lower carbon footprint over PTR/CTW. The information generated here might useful in developing policies for resource and climate-smart food production system aiming livelihood security and ecological sustainability in the region. Further, trials are needed for wider adaptability under different climate, soil and agronomic practices to develop site-specific climate smart practices.

Conservation Tillage and Waste Crop Residue Based Zinc Fortification in Rice and Wheat under Reclaimed Sodic Soils: Progress toward Nutrient Circularity and Sustainability

Nearly 50% of the population across the globe is at risk of malnutrition with respect to zinc (Zn) in areas where a cereal based dietary system dominates. The present study estimated daily Zn intake in humans through field experiments in reclaimed sodic soil, utilizing waste crop residue (CR) in conservation tillage where CR played a vital role in enhancing Zn uptake in rice and wheat grains. Zn dynamics, its bioavailability, interaction with soil properties, and plausible contribution in dietary intake were studied extensively to supplement the research. A higher mobility factor (2.70%) and plant available Zn resulted in its higher uptake in rice (58.2 mg kg^-1) and wheat (67.2 mg kg^-1) under zero tillage in rice followed by zero tillage in wheat where CR was retained on the surface (ZT_R-ZT_W+CR). Daily Zn intake was found to be maximum (0.651 mg kg^-1 day^-1) under ZT_R-ZT_W+CR, demonstrating zinc sufficiency. Thus, this study may help in formulating actionable policies for combating both nutritional security and environmental hazards due to CR burning.

Influence of Residue Type and Method of Placement on Dynamics of Decomposition and Nitrogen Release in Maize-Wheat-Mungbean Cropping on Permanent Raised Beds: A Litterbag Study

Decomposition influences carbon and nutrient cycling from crop residues. The nylon-mesh-bag technique was implied to study the decomposition and N-release dynamics from different crop residues under field conditions. The four types of residues were: maize (lower than 50% below the cob), wheat (lower than 25% of wheat stubbles), a whole mung bean residue, and a mixture of wheat + mung bean residue (1:1 ratio) put on the soil surface and in below the sub-surface. Decomposition and N release from both at-surface- and below-surface-placed residues were accurately described by a single-pool first-order exponential decay function as a function of thermal time (based on the accumulative daily mean temperature). The simple first-order exponential model met the criteria of goodness of fit. Throughout the decomposition cycle (one thermal year), the rate of decomposition as measured by a decrease in residue mass and the release of total N were statistically higher from the sub-surface compared to the surface-placed residue, irrespective of the residue type. At the end of the 150-day decomposition cycle, the release of total N was highest in mung bean (32.0 kg N ha−1), followed by maize (31.5 kg N ha−1) > wheat + mung bean (16.1 kg N ha−1), and the minimum (6.54 kg N ha−1) in wheat residue. Crop residues with a wider C/N ratio such as maize and wheat, when applied on the soil surface in conservation agriculture, caused the decomposition to occur at slower rates, thereby providing long-term beneficial effects on the soil thermal regime, soil moisture conservation, and C sequestration in North-West India.

Emerging Issues and Potential Opportunities in the Rice-Wheat Cropping System of North-Western India

The rice-wheat cropping system (RWCS) is the backbone of Indian farming, especially in the north-western region. But continuous adoption of the RWCS in northwest India has resulted in major challenges and stagnation in the productivity of this system. Additionally, the Indo-Gangetic Plains of Pakistan, Nepal, and Bangladesh are also facing similar challenges for sustainable production of the RWCS. Several emerging problems, such as the exhausting nutrient pool in soil, deteriorating soil health, groundwater depletion, escalating production cost, labor scarcity, environmental pollution due to crop residue burning and enhanced greenhouse gas emissions, climatic vulnerabilities, and herbicide resistance in weed species, are a few major threats to its sustainability. To address these challenges, a wide range of sustainable intensification technologies have been developed to reduce the irrigation and labor requirements, tillage intensity, and straw burning. Awareness and capacity building of the stakeholders and policy matching/advocacy need to be prioritized to adopt time- and need-based strategies at the ground level to combat these challenges. This review summarizes the current status and challenges of the RWCS in the northwest region of the country and also focuses on the precision management options for achieving high productivity, profitability, and sustainability.

Rice straw biochar application to soil irrigated with saline water in a cotton-wheat system improves crop performance and soil functionality in north-west India

Applications of biochar to degraded soils have attracted considerable interest because of its capacity to enhance nutrients availability to the plants, sequester C and immobilize organic and inorganic pollutants. A five-year field experiment was conducted in a cotton-wheat system to investigate the effect of different levels of irrigation water salinity (0.3, 5, 10, and 15 dS m^-1) and rice straw biochar (0, 2, 4, and 8 t ha^-1) on the crop yield and soil functions. Rice straw-derived biochar was applied every year to cotton and its residual effect was observed on wheat. Results of the study indicated that regular irrigation with saline water (5-15 dS m^-1) reduced both seed cotton (12-44%) and wheat grain (7-27%) yield. However, application of biochar (2-8 t ha^-1) to plots irrigated with saline water showed 6-23% and 13-27% greater seed cotton and wheat grain yield compared with unamended plots, respectively. Likewise, biochar application to soil irrigated with canal or saline water showed significant beneficial effects on soil pH, EC, nutrient metabolism and availability, bulk density, infiltration rate and microbial biomass carbon. Our results indicated that biochar amendment especially at the optimum rate of 4 t ha^-1 effectively promoted crop performance by ameliorating soil physical, chemical, and biological properties. In the absence of any chemical amendment for alleviating salinity stress, the results of the present study established that the biochar holds promising potential as a soil amendment in ameliorating soil functions and promoting plant productivity under saline water irrigated conditions.

Air Quality Before and After COVID-19 Lockdown Phases Around New Delhi, India

BACKGROUND

The COVID-19 pandemic has had a deep global impact, not only from a social and economic perspective, but also with regard to human health and the environment. To restrict transmission of the virus, the Indian government enforced a complete nationwide lockdown except for essential services and supplies in phases from 25 March to 31 May 2020. Ambient air quality in and around New Delhi, one of the most polluted cities of world, was also impacted during this period.

OBJECTIVE

The aim of the present study was to assess and understand the impact of four different lockdown phases (LD1, LD2, LD3 and LD4) on five air pollutants (particulate matter (PM) PM2.5, PM10, nitrogen oxide (NOx), sulfur dioxide (SO2) and ozone (O3)) compared to before lockdown (BLD) at 13 air monitoring stations in and around New Delhi.

METHODS

Secondary data on five criteria pollutants for 13 monitoring stations in and around New Delhi for the period 1 March to 31 May 2020 was accessed from the Central Pollution Control Bard, New Delhi. Data were statistically analyzed across lockdown phases, meteorological variables, and prevailing air sources around the monitoring stations.

RESULTS

Pollutant concentrations decreased during LD1 compared to BLD except for O3 at all stations. PM2.5 and PM10 remained either close to or higher than the National Ambient Air Quality Standards (NAAQS) due to prevailing high-speed winds. During lockdown phases, NO2 decreased, whereas O3 consistently increased at all stations. This was a paradoxical situation as O3 is formed via photochemical reactions among NOx and volatile organic compounds. Principal component analysis (PCA) extracted two principal components (PC1 and PC2) which explained up to 80% of cumulative variance in data. PM2.5, PM10 and NO2 were associated with PC1, whereas PC2 had loadings of either O3 only or O3 and SO2 depending upon monitoring station.

CONCLUSIONS

The present study found that air pollutants decreased during lockdown phases, but these decreases were specific to the site(s) and pollutant(s). The decrease in pollutant concentrations during lockdown could not be attributed completely to lockdown conditions as the planetary boundary layer increased two-fold during lockdown compared to the BLD phase. Such restrictions could be applied in the future to control air pollution but should be approached with caution.

COMPETING INTERESTS

The authors declare no competing financial interests.

Soil Properties and Weed Dynamics in Wheat as Affected by Rice Residue Management in the Rice-Wheat Cropping System in South Asia: A Review

The rice–wheat cropping system (RWCS) has substantially contributed in making India self-sufficient in food grain production; however, rice residue management is of great concern, threatening the sustainability of this system. Rice residue is invariably disposed of by farmers through open burning. In addition to environmental pollution, residue burning of rice also leads to loss of soil nutrients. One of the alternatives to overcome these problems and sustain the RWCS is managing the rice residues in the field itself. Rice residue retention has variable effects on agricultural pests (namely, weeds, insect pests, diseases, and rodents) in the RWCS. High weed infestation in the RWCS results in high consumption of herbicides, which leads to several ecological problems and evolution of herbicide resistance. The shift from intensive tillage to conservation tillage causes major changes in weed dynamics and herbicide efficacy. Incorporation of rice residue reduces weed density and helps in improving soil physical, chemical, and biological properties. Rice residue retention on the surface or mulching reduces weed density and the biomass of both grass and broadleaf weeds in wheat crop as compared to its removal. Long-term field studies involving the use of rice residue as a component of integrated weed management strategies are needed to be done in the RWCS.

In situ decomposition of crop residues using lignocellulolytic microbial consortia: a viable alternative to residue burning

Open field burning of crop residue causes severe air pollution and greenhouse gas emission contributing to global warming. In order to seek an alternative, the current study was initiated to explore the prospective of lignocellulolytic microbes to expedite in situ decomposition of crop residues. Field trials on farmers' field were conducted in the state of Haryana and Maharashtra, to target the burning of rice and wheat residue and sugarcane trash, respectively. A comparative study among crop residue removal (CRR), crop residue burning (CRB) and in situ decomposition of crop residues (IND) revealed that IND of rice and wheat residues took 30 days whereas IND of sugarcane trash took 45 days. The decomposition status was assessed by determining the initial and final lignin to cellulose ratio which increased significantly from 0.23 to 0.25, 0.21 to 0.23 and 0.24 to 0.27 for rice, wheat residues and sugarcane trash, respectively. No yield loss was noticed in IND for both rice-wheat system and sugarcane-based system; rather IND showed relatively better crop yield as well as soil health parameters than CRB and CRR. Furthermore, the environmental impact assessment of residue burning indicated a substantial loss of nutrients (28-31, 23-25 and 51-77 kg ha-1 of N+P2O5+K2O for rice, wheat and sugarcane residue) as well as the emission of pollutants to the atmosphere. However, more field trials, as well as refinement of the technology, are warranted to validate and establish the positive potential of in situ decomposition of crop residue to make it a successful solution against the crop residue burning.

Rice–wheat system in the northwest Indo-Gangetic plains of South Asia: issues and technological interventions for increasing productivity and sustainability

Puddled transplanted rice (Oryza sativa L.) followed by intensively tilled wheat (Triticum aestivum L.) (R–W) is the most predominant cropping system and the lifeline for billions of people in South Asia. The cultivation of R–W system requires high amounts of water, nutrients and energy, resulting in increased production costs and increased emissions of greenhouse gases. There are also increasing concerns of yield stagnation or decline in the R–W system, with increasing environmental footprints. Hence, the sustainability of the R–W system in South Asia, particularly in the northwest Indo-Gangetic Plains (IGPs), has been questioned and heavily debated. Based on the findings from peer-reviewed literature, this review aims to identify unsustainability issues and research gaps in the R–W system and propose possible solutions to mitigate those issues and technological interventions to close the research gaps. Among the unsustainability issues that the review has identified are declining crop, water and land productivity, deterioration of soil health, emissions of greenhouse gases due to intensive tillage and residue burning, deepening of groundwater levels and shift in weed flora and development of herbicidal resistance in crops. Potential solutions or technological interventions to mitigate the unsustainability issues include resource conservation technologies (RCTs) such as rice residue management, reduced tillage, laser land leveling, soil matric potential based irrigation scheduling, delayed rice transplanting, cultivation on permanent raised beds, direct-seeded rice (DSR), mechanical transplanting of rice and crop diversification with legumes. These interventions have the potential to reduce energy, water and carbon (C) footprints from the R–W system. Rice residue retention with Happy Seeder and adoption of zero tillage (ZT) for wheat establishment have significantly lowered the environmental footprints, with increased soil C sequestration due to additions of large amounts of plant-mediated C input. Residue mulching has helped increase root length of wheat by ~25% and root length density by ~40% below 15 cm depth, compared to no mulching. The Happy Seeder saved ~30% of irrigation water due to reduction of soil evaporation by ~42–48 mm through residue mulching. Crop cultivation on permanent raised beds is less energy-intensive and results in ~7.8–22.7% higher water use efficiency yet crop productivity in long run could be affected due to reduced root growth on beds. The puddled transplanted rice (PTR) established under wet tillage, however, can decrease the water percolation losses by 14–16% and crop water demand by ~10–25%, and it forms hard pan in soil plough (7–10 cm) layer due to increased soil bulk density. Water stagnation under continuously flooded PTR is the major source of methane emissions with serious environmental implications. Methane emissions from flooded rice can increase global warming potential by 18.1–27.6% compared to intermittently flooded rice with multiple aerations. The conventional tillage can favor the germination of grassy weeds in wheat, while the broad-leaved weeds increase under zero tillage. Zero tillage with mulch load conserved ~4.0% higher moisture due to ~2.3% lesser soil temperature and evaporated ~27.6% lesser than the conventional tillage. Delayed rice transplanting with short-duration variety has potential of saving of up to ~140 mm of irrigation water in the semiarid areas of NW IGPs. Although the DSR had lower yield potential than the PTR, it saved ~50% irrigation water. The laser land leveling technology saved ~30% irrigation water and ~25% electricity and had a yield advantage of ~4%, compared with PTR on un-leveled fields. The mechanical transplanted rice had higher grain yield and more water saving than the manual transplanting or DSR. The review demonstrates that a single technology may not be applicable everywhere and integrated approaches with the multiple criteria—productivity, economics, energy and environmental sustainability—would be required to address the unsustainability issues of the R–W system of the NW IGPs. There is a need to elucidate and disseminate various site- and context-specific RCTs appropriate for the region to address the unsustainability issues and challenges of the system. Sustainable R–W production technologies with reduced water, energy and C footprints are required for increased water and energy productivity and C sequestration for the NW IGPs of South Asia.

Management of Crop Residues for Improving Input Use Efficiency and Agricultural Sustainability

Crop residues, the byproduct of crop production, are valuable natural resources that can be managed to maximize different input use efficiencies. Crop residue management is a well-known and widely accepted practice, and is a key component of conservation agriculture. The rapid shift from conventional agriculture to input-intensive modern agricultural practices often leads to an increase in the production of crop residues. Growing more food for an ever-increasing population brings the chance of fast residue generation. Ecosystem services from crop residues improve soil health status and supplement necessary elements in plants. However, this is just one side of the shield. Indecorous crop residue management, including in-situ residue burning, often causes serious environmental hazards. This happens to be one of the most serious environmental hazard issues witnessed by the agricultural sector. Moreover, improper management of these residues often restrains them from imparting their beneficial effects. In this paper, we have reviewed all recent findings to understand and summarize the different aspects of crop residue management, like the impact of the residues on crop and soil health, natural resource recycling, and strategies related to residue retention in farming systems, which are linked to the environment and ecology. This comprehensive review paper may be helpful for different stakeholders to formulate suitable residue management techniques that will fit well under existing farming system practices without compromising the systems’ productivity and environmental sustainability.

Characterization on Physical, Mechanical, and Morphological Properties of Indian Wheat Crop

The absence of scalable and economically viable alternatives for managing residues coupled with shorter planting window and growing labour shortages and energy prices requires a sustainable solution for the crop residue management in northern India. As per “Need of the Hour”, the present research work focused on physical, mechanical, and morphological characterizations of wheat, which will help in further design of the low-cost straw combine. For this purpose, two varieties of wheat (HD-2967 and WH-1105) were used for the present study, as these are the prevalent varieties of Haryana state. The straw specimens were collected at harvesting period from a farmer’s field, which is located at a longitude of 75.64 and latitude of 29.15. The physical characterization of the crops was conducted on the basis of diameter, length, and thickness of nodes of straws. In contrast, the mechanical characterizations was performed by calculating the tensile and shear strength of the straws. The morphological analysis was performed by using field emission scanning electron microscopy (FESEM). The energy dispersive spectroscopy was performed to analyse the presence of constituting elements of straw. The statistical analysis showed that moisture content in the straw had a significant effect on tensile strength and shear strength.

Ambient air quality changes after stubble burning in rice-wheat system in an agricultural state of India

Ground-based ambient air monitoring was conducted to assess the contribution of crop residue burning of wheat (Triticum aestivum) and rice (Oriza sativa) at different locations in three districts (Kaithal, Kurukshetra, and Karnal) of the agricultural state of Haryana in India for two successive years (2016 and 2017). The Air Quality Index (AQI) and concentration of primary pollutants (SO_x, NO_x, and PM_2.5) were determined in rice and wheat crop season, for burning and non-burning periods. During crop residue burning periods, concentrations of SO_x, NO_x, and PM_2.5 were exceeded the NAAQS values by 78%, 71%, and 53%, respectively. A significant increase in SO_x (4.5 times), NO_x (3.8 times), and PM_2.5 concentration (3.5 times) was observed in stubble burning periods as compared to pre-burning (p < 0.05). A positive and significant correlation among the three pollutant concentrations was observed (p < 0.01). The AQI of KA site in Karnal district fell in severely polluted category during 2016 for rice as well as wheat residue burning period, and of KK site in Kaithal during wheat residue burning in year 2017. Results of present study indicate a remarkable increase in pollutant concentration (SO_x, NO_x, and PM_2.5) during the crop residue burning periods. To the best of our knowledge, the outcomes of present study in this region have not been reported in earlier reports. Hence, there is an urgent need to curb air pollution by adopting sustainable harvesting technologies and management of residues.

Crop Residue Burning in India: Policy Challenges and Potential Solutions

India, the second largest agro-based economy with year-round crop cultivation, generates a large amount of agricultural waste, including crop residues. In the absence of adequate sustainable management practices, approximately 92 seems a very small number of metric tons of crop waste is burned every year in India, causing excessive particulate matter emissions and air pollution. Crop residue burning has become a major environmental problem causing health issues as well as contributing to global warming. Composting, biochar production and mechanization are a few effective sustainable techniques that can help to curtail the issue while retaining the nutrients present in the crop residue in the soil. The government of India has attempted to curtail this problem, through numerous measures and campaigns designed to promote sustainable management methods such as converting crop residue into energy. However, the alarming rise of air pollution levels caused by crop residue burning in the city of Delhi and other northern areas in India observed in recent years, especially in and after the year of 2015, suggest that the issues is not yet under control. The solution to crop residue burning lies in the effective implementation of sustainable management practices with Government interventions and policies. This manuscript addresses the underlying technical as well as policy issues that has prevented India from achieving a long-lasting solution and also potential solutions that have been overlooked. However, effective implementation of these techniques also requires us to look at other socioeconomic aspects that had not been considered. This manuscript also discusses some of the policy considerations and functionality based on the analyses and current practices. The agricultural waste sector can benefit immensely from some of the examples from other waste sectors such as the municipal solid waste (MSW) and wastewater management where collection, segregation, recycling and disposal are institutionalized to secure an operational system. Active stakeholder involvement including education and empowerment of farmers along with technical solutions and product manufacturing can also assist tremendously. Even though the issue of crop residue burning touches many sectors, such as environment, agriculture, economy, social aspects, education, and energy, the past governmental efforts mainly revolved around agriculture and energy. This sectorial thinking is another barrier that needs to be broken. The government of India as well as governments of other developing countries can benefit from the emerging concept of nexus thinking in managing environmental resources. Nexus thinking promotes a higher-level integration and higher level of stakeholder involvement that goes beyond the disciplinary boundaries, providing a supporting platform to solve issues such as crop residue burning.

Azolla pinnata, Aspergillus terreus and Eisenia fetida for enhancing agronomic value of paddy straw

In the present study rice straw (R, control) was mixed with Cowdung (C), Azolla (A) and cellulolytic fungus Aspergillus terreus (F) in different combinations viz. RC, RA, RF, RCF, RCA, RFA and RCFA and subjected to aerobic composting (Acom) and vermicomposting (Vcom - with Eisenia fetida). It was found that addition of azolla and cattledung to two parts straw(RCA-666: 314:20 g) caused fastest degradation (105 days), gave maximum population buildup of E. fetida (cocoons, hatchlings and worm biomass), highest decline in pH, EC, TOC and C/N ratio and maximum increase over control in N(17.72%), P(44.64%), K(43.17%), H (7.93%), S (14.85%), Ca(10.16%), Na(145.97%), Fe(68.56%), Zn(12.10%) and Cu(32.24%). Rice straw (R) took longest time for degradation i.e. 120 and 140 days and had lowest content of nutrients in Vcom as well as Acom group. RCFA was also converted into Vcom at the same time but other parameters were less than RCA except for highest content of B (19.87%), Mg(21.27%) and Mn (5.58%). Bioconversion of three parts straw (RCA-735:245:20 g) was also faster (110 days) with vermicomposting than all the mixtures of Acom group (130–140 days) but nutrient content was slightly less than RCA with 2 parts straw. The results show that azolla reduces dependence on cattledung for recycling the carbon rich rice straw and enhances its agronomic value.

Intercomparison of MODIS AQUA and VIIRS I-Band Fires and Emissions in an Agricultural Landscape-Implications for Air Pollution Research

Quantifying emissions from crop residue burning is crucial as it is a significant source of air pollution. In this study, we first compared the fire products from two different sensors, the Visible Infrared Imaging Radiometer Suite (VIIRS) 375 m active fire product (VNP14IMG) and Moderate Resolution Imaging Spectroradiometer (MODIS) 1 km fire product (MCD14ML) in an agricultural landscape, Punjab, India. We then performed an intercomparison of three different approaches for estimating total particulate matter (TPM) emissions which includes the fire radiative power (FRP) based approach using VIIRS and MODIS data, the Global Fire Emissions Database (GFED) burnt area emissions and a bottom-up emissions approach involving agricultural census data. Results revealed that VIIRS detected fires were higher by a factor of 4.8 compared to MODIS Aqua and Terra sensors. Further, VIIRS detected fires were higher by a factor of 6.5 than Aqua. The mean monthly MODIS Aqua FRP was found to be higher than the VIIRS FRP; however, the sum of FRP from VIIRS was higher than MODIS data due to the large number of fires detected by the VIIRS. Besides, the VIIRS sum of FRP was 2.5 times more than the MODIS sum of FRP. MODIS and VIIRS monthly FRP data were found to be strongly correlated (r2 = 0.98). The bottom-up approach suggested TPM emissions in the range of 88.19-91.19 Gg compared to 42.0-61.71 Gg, 42.59-58.75 Gg and 93.98-111.72 Gg using the GFED, MODIS FRP, and VIIRS FRP based approaches, respectively. Of the different approaches, VIIRS FRP TPM emissions were highest. Since VIIRS data are only available since 2012 compared to MODIS Aqua data which have been available since May 2002, a prediction model combining MODIS and VIIRS FRP was derived to obtain potential TPM emissions from 2003-2016. The results suggested a range of 2.56-63.66 (Gg) TPM emissions per month, with the highest crop residue emissions during November of each year. Our results on TPM emissions for seasonality matched the ground-based data from the literature. As a mitigation option, stringent policy measures are recommended to curtail agricultural residue burning in the study area.

Soil bacterial diversity under conservation agriculture-based cereal systems in Indo-Gangetic Plains

In Indo-Gangetic plains (IGP) of India, natural resources (soil, water, and environment) are degrading under the conventional-till (CT)-based management practices in rice-wheat cropping system. A long-term field experiment was conducted to understand the soil bacterial diversity and abundance under different sets of management scenarios (Sc). The study comprised of four scenarios, namely, -Sc.I CT-based rice-wheat system (farmers' practice); Sc.II, partial conservation agriculture (CA) based in which rice is under CT-wheat and mungbean under zero-tillage (ZT); Sc.III, full CA-based in which rice-wheat-mungbean are under ZT and Sc.IV, where maize-wheat-mungbean are under ZT. These scenarios varied in cropping system, tillage, and crop residue management practices. Using Illumina MiSeq sequencing technology, the variable regions V3-V4 of 16S rRNA were sequenced and the obtained reads were analyzed to study the diversity patterns in the scenarios. Results showed the presence of 53 bacterial phyla across scenarios. The predominant phyla in all scenarios were Proteobacteria, Acidobacteria, Actinobacteria, and Bacteroidetes which accounted for more than 70% of the identified phyla. However, the rice-based systems (Sc.I, Sc.II, and Sc.III) were dominated by phylum Proteobacteria; however, maize-based system (Sc.IV) was dominated by Acidobacteria. The class DA052 and Acidobacteriia of Acidobacteria and Bacteroidetes of Bacteroidia were exceptionally higher in Sc.IV. Shannon diversity index was 8.8% higher in Sc.I, 7.5% in Sc.II, and 2.7% in Sc.III compared to Sc.IV. The findings revealed that soil bacterial diversity and abundance are influenced by agricultural management practices as bacterial diversity under full CA-based management systems (Sc.III and Sc.IV) was lower when compared to farmer's practice (Sc.I) and partial CA (Sc.II) scenarios.

Synergistic effect of fly ash in in-vessel composting of biomass and kitchen waste

The present study aims to utilize coal fly ash for its property to adsorb heavy metals and thus reducing the bioavailability of the metals for plant uptake. Fly ash was incorporated into the in-vessel composting system along with organic waste. The in-vessel composting experiments were conducted in ten plastic vessels of 15 L capacity comprising varying proportions of biomass waste, kitchen waste and fly ash. In this study, maximum degradation of organic matter was observed in Vessel 3 having k value of 0.550 d^-1. In vessel 10, 20% fly ash with a combination of 50% biomass waste and 30% kitchen waste along with the addition of 5% jaggery as an additive produced the best outcome with least organic matter (%C) loss and lowest value of rate constant (k).

Assessing soil properties and nutrient availability under conservation agriculture practices in a reclaimed sodic soil in cereal-based systems of North-West India

Soil quality degradation associated with resources scarcity is the major concern for the sustainability of conventional rice-wheat system in South Asia. Replacement of conventional management practices with conservation agriculture (CA) is required to improve soil quality. A field experiment was conducted to assess the effect of CA on soil physical (bulk density, penetration resistance, infiltration) and chemical (N, P, K, S, micronutrients) properties after 4 years in North-West India. There were four scenarios (Sc) namely conventional rice-wheat cropping system (Sc1); partial CA-based rice-wheat-mungbean system (RWMS) (Sc2); CA-based RWMS (Sc3); and CA-based maize-wheat-mungbean (Sc4) system. Sc2 (1.52 Mg m^-3) showed significantly lower soil bulk density (BD). In Sc3 and Sc4, soil penetration resistance (SPR) was reduced and infiltration was improved compared to Sc1. Soil organic C was significantly higher in Sc4 than Sc1. Available N was 33% and 68% higher at 0-15 cm depth in Sc3 and Sc4, respectively, than Sc1. DTPA extractable Zn and Mn were significantly higher under Sc3 and Sc4 compared to Sc1. Omission study showed 30% saving in N and 50% in K in wheat after four years. Therefore, CA improved soil properties and nutrient availability and have potential to reduce external fertilizer inputs in long run.