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Abstract: Total reflection coefficients and break-up patterns for incident atomic carbon, C2, CH, CH2, CH3, CH4, C2H, C2H2, C2H3, C2H4, C2H5 and C2H6 from an amorphous hydrocarbon surface with a H:C ratio of 0.66 are calculated using the HCParcas molecular dynamics code with an empirical Brenner potential. Incident molecules are separately equilibrated at incident energies ranging from thermal up to the maximum energies at which the molecules can be structurally stabilized to mimic the conditions in an equilibrium plasma. [Copyright &y& Elsevier]

Highlights: [•] Impact of permanent bed planting on total SOC contents under IGP was evaluated. [•] Plots with permanent bed planting had higher total SOC than CT in the 0–5cm layer. [•] About 9.3% of the gross C input retained in 30cm soil under residue treated plots. [•] Nearly 8.6 and 10.2% of the gross C input retained under CT and ZT, respectively. [•] CT with bed planting had least total SOC and may not be adopted. [ABSTRACT FROM AUTHOR]

Abstract Available results on the evaluation of nitrogen (N) use efficiency in conservation agriculture (CA) are inconsistent and studies that cover all three components of CA are sparse, especially in tropical agro-ecosystems. Hence, CA effects on variations in total soil N (TSN) and aggregate-associated 15N on a sandy loam soil were evaluated after 15N urea (~5% atom excess) application at 120 kg ha−1 to wheat in the fourth year of an experiment in the Indo-Gangetic Plains (IGP). The cropping system during 2008–2011 was cotton (Gossypium hirsutum)-wheat (Triticum aestivum), that was changed to maize (Zea mays)-wheat in 2011–2012. Results revealed that plots under zero tillage with residue retention of both crops (ZT + R) had better topsoil (0–5 cm layer) aggregation and higher residual 15N in soils than conventionally tilled (CT) plots. The ZT + R plots also had higher macro-aggregates (0.25–8 mm) with less silt + clay sized particles than the CT plots in the 5–15 cm soil layer. Furthermore, both tillage and residue management had significant effects on TSN and aggregate-associated N stocks. The plots under ZT + R had ~9% higher TSN in topsoil than the CT plots and the ZT and ZT + R plots had about 48 and 34% higher large macro-aggregate associated N stocks than CT and CT + R plots, respectively. However, the potential N-mineralization data of the macro-aggregates of ZT + R (CA) and CT plots were similar. In addition, the fertilizer 15N use efficiency, the residual fertilizer 15N in soil (0–45 cm layer) and the calculated unaccounted fertilizer 15N data of both CA and CT plots were also similar after the fourth year of cultivation. In summary, although CA (ZT + R) adoption had better soil aggregation and with more TSN accumulation within macro-aggregates, it could not affect the fertilizer 15N use efficiency within a short period (4 years). Thus, with a short-term adoption of CA, fertilizer-N dose may not be reduced in a sandy loam soil of the IGP and similar agro-ecosystems. Highlights • Conservation agriculture (CA) had better topsoil aggregation and higher residual 15N in soils than conventional till (CT) plots. • Fertilizer 15N use efficiency values under CA plots were similar to CT plots. • The potential N-mineralization of the macroaggregates of both plots were similar. • Hence, other component technologies may be adopted with CA for saving fertilizer N. [ABSTRACT FROM AUTHOR]

Highlights • Crop residues positively influenced soil microbial activities in a rainfed system. • Soil glomalin and aggregate stability were highest under residue treated plots. • Legume based cropping had ∼12% higher soil glomalin than cereal-cereal system. • There was positive relationship between aggregate stability and glomalin content. • Both residue and crop rotation had positive effects on microbial biomass C and labile C. Abstract This 3-year study investigated the effects of crop rotation and residue management (surface retention of residues under zero tillage) on soil carbon pools, selected soil physical properties (soil aggregation, mean weight diameter) and biological properties (glomalin and ergosterol contents, soil respiration and enzyme activities) and their inter-relationships in a semi-arid soil of India under rainfed condition. The field study consisted of three different cropping systems (pearl millet-wheat, pearl millet-chickpea and pearl millet-mustard) in the main plots and three residue management practices (no residue, crop residue and Leucaena mulch cover) in the sub-plots, with three replications. All crops were cultivated adopting zero tillage (ZT). Surface (0–15 cm) samples were taken from fields after 3-years. Results revealed that crop rotation had no impacts on total soil organic C (SOC), Walkley-Black C (WBC) and soil aggregation, but significantly affected labile C. However, residue retention or addition significantly affected total SOC, labile C and soil aggregation. Plots under crop residue and Leucaena mulching had ∼30 and 26% higher large macroaggregates (>2 mm diameter) than no residue treated plots. A similar trend was observed for the proportion of macroaggregates, resulting in about 20 and 17% increase in mean weight diameter (MWD), respectively, in the crop residue and Leucaena added plots compared to the residue removal plots (∼0.91 mm). The residue retained plots had ∼40 and 13% higher soil glomalin content compared with residue removal (∼290 μg g−1 soil) and Leucaena added plots, respectively. Both soil glomalin and ergosterol contents were significantly (P < 0.05) related with large macroaggregates and there were significant relationships between glomalin and WBC concentration and glomalin and MWD in the surface soil. Glomalin, microbial biomass C, dehydrogenase, fluorescein diacetate (FDA), glucosidase and alkaline phosphatase activities were significantly increased by both crop rotation and residue management. Thus, the legume based cropping system (pearl millet-chickpea system) with ZT and residue retention under rainfed conditions had significant impact on soil aggregation and biological health, even after a short-term adoption. [ABSTRACT FROM AUTHOR]

The Indo-Gangetic Plains (IGP) of India is dominated with rice − wheat cropping system that occupies almost 10.5 million ha area. The sustainability of rice-wheat system is under threat due to numerous water-, nutrients-, weeds- and environment-related problems, mainly, due to the cultivation of rice. Suitable crop and soil management practices with a bias to conservation agriculture (CA) that can sustain soil and environmental health as well as improve crop and water productivity, are required for the Indian IGP. Maize can be a viable alternative to rice and a potential driver for diversification of rice-wheat system. The acreage of maize is on the increase in conventional and conservation agriculture-based cereal systems of India in recent years. Therefore, a field experiment, involving a maize ( Zea mays L.)-wheat cropping system was undertaken on a sandy clay loam soil for three years (2010–11 to 2012-13) in New Delhi to evaluate the impacts of CA on crop and water productivity, profitability and soil organic carbon (SOC) accumulation. There were five CA-based treatments in first year, and two treatments were introduced in second year (2011-12) onwards. The experiment was laid out in a randomized complete block design with three replications. In all the residue retention plots, wheat residue was retained in maize crop and maize residue was retained in wheat crop under zero till conditions. Results showed that the plots under permanent broad bed with residue (PBB + R) and without residue (PBB) resulted in ∼29 and ∼26% higher maize grain yield, respectively than conventional tillage (CT) (2.6 t ha −1 ), but wheat grain yields were comparable in all the treatments in first year. Maize grain yield in second year under PBB + R and zero tillage with residue (ZT + R) were 55 and 43% higher than CT plots (2.8 t ha −1 ). Three-year mean maize yields due to PBB + R and permanent narrow bed with residue (PNB + R) were 28 and 15% higher than that in CT plots (3.3 t ha −1 ). The PBB + R resulted in 11% higher two-year mean water productivity in maize than PBB (∼without residue), but both these treatments were comparable in this regard in wheat. The ZT + R plots resulted in 14% and 22% higher two-year mean water productivity, respectively in maize and wheat than ZT plots. Overall, the plots under PBB + R had 57% and 19% higher mean water productivities in maize and wheat, respectively compared with CT plots. Again, the PBB + R plots gave 12% higher two-year mean net returns compared with CT plots. With regard to net returns, the plots under permanent narrow bed with and without residue (PNB + R; PNB) were inferior to PBB, PBB + R, ZT and ZT + R plots. Retention of both-season crop residues could significantly improve SOC concentration in surface (0–5 cm) soil. The PBB + R resulted in highest SOC pool at 0–30 cm soil layer, which was significantly higher than that in CT. This system showed maximum carbon sequestration potential. Thus, this CA practice, which involves PBB + R is superior to other practice. This would save water through higher water-use efficiency, and lead to accumulation of more carbon in soil with higher sequestration potential, besides giving sustainable production through maize-wheat system over the years. This can be adopted across the IGP regions of India, where irrigated rice-wheat system is in practice, and in similar agro-ecologies of the tropics and sub-tropics under irrigated conditions. [ABSTRACT FROM AUTHOR]

This study evaluated energy requirements and input-output energy relationship in a maize-wheat-greengram cropping system under conventional and conservation agriculture. Conventional tillage with flat bed (CTF) and raised bed (CTB) and zero tillage with flat bed (ZTF) and raised bed (ZTB) were supplemented with crop residue management viz., no residue (CON), wheat residue in maize crop (WR), maize residue in wheat crop (MR) and wheat + maize residue in both maize & wheat crops (WMR). Results showed that ZTB (89170 MJ/ha) consumed 8% lower input energy than CTF. ZTB saved 91% and 38% energy in land preparation and irrigation, respectively. The output and net energy return were significantly higher with ZTF (387235 MJ/ha; 295397 MJ/ha), which were 2.0% higher than ZTB. Energy ratio and productivity were significantly higher with ZTB. WMR contributed the highest input and output energy and lowered energy ratio and productivity. Reduced energy ratio and energy productivity can be ignored as it returned to soil to improve its quality. Surface retained residues had better effect on crop productivity. With this view, ZTB with WMR was better and would be a substitute of the conventional agricultural system for adoption in maize-wheat-greengram cropping system in the irrigated north western Indo-Gangetic Plains. [ABSTRACT FROM AUTHOR]

Retention of carbon (C) in arable soils has been considered as a potential mechanism to mitigate soil degradation and to sustain crop productivity. Hence, we appraised the 3-year effect of different conservation agriculture (CA) practices on grain yield, biomass productivity and soil organic C (SOC) accumulation rates under a tropical rice ( Oryza sativa L.)-wheat ( Triticum aestivum L.) and rice–wheat–green gram (mungbean in Hindi; Vigna radiata ) cropping systems. Results indicate mean (of three years) rice grain yield under mungbean residue + direct seeded rice (DSR) followed by zero tilled wheat (ZTW) with rice residue (RR) retention and zero tilled relay summer mungbean (MBR + DSR-ZTW + RR-ZTMB) plots was similar to farmers’ practice [transplanted rice (TPR)- conventionally tilled wheat (CTW)], despite TPR-CTW plots had ∼18% higher rice yield than MBR + DSR-ZTW + RR-ZTMB plots in the first year. The MBR + DSR-ZTW + RR-ZTMB treated plots had about 15 and 10% higher mean wheat grain yield and mean system productivity (sum of grain yields of all crops) than TPR-CTW plots, respectively. The plots under DSR + brown manuring (BM)-ZTW + RR plots had comparable mean rice and wheat yields to MBR + DSR- ZTW + RR-ZTMB plots. Harvestable aboveground biomass productivity of MBR + DSR-ZTW + RR-ZTMB treated plots was ∼2.89 Mg ha −1 yr −1 higher than TPR-CTW. Total estimated C input (∼12.1 Mg C ha −1 in three years) under MBR + DSR-ZTW + RR-ZTMB treated plots was ∼117 and 127% higher than DSR-ZTW and TPR-CTW treatments, respectively. All CA plots had significantly higher gain (over initial value) in total SOC than that in TPR-CTW and TPR-ZTW treatments in the 0–15 cm layer and the gain in total SOC in the plots under MBR + DSR- ZTW + RR-ZTMB was significantly higher than all CA plots, despite having similar total SOC stocks. Again, plots under MBR + DSR-ZTW + RR-ZTMB had ∼24% larger labile C pools than that of TPR-CTW (3.1 g kg −1 ) treated plots in the topsoil. Soil bulk density under MBR + DSR- ZTW + RR-ZTMB and DSR + BM-ZTW + RR treated plots significantly decreased in the 5–15 cm layer compared to TPR-CTW plots. Thus, the MBR + DSR-ZTW + RR-ZTMB treatment (a novel CA practice), has considerable potential to retain C in surface soil, decrease soil compaction and increase system (rice–wheat–green gram) productivity and hence its adoption is recommended. [ABSTRACT FROM AUTHOR]

The COVID-19 disease caused by severe acute respiratory syndrome coronavirus -2 (SARS-CoV-2) has posed as a major health concern for people all across the globe. Along with the increasing confirmed patients being readmitted with complaints for fever, cough, cold, the effective monitoring of 'relapse' of the SARS-CoV-2 virus in the previously discharged patients have become the next area of focus. However, availability of limited data on reactivation of SARS-CoV-2 makes the disease prognosis as well as the effective control of re-infection an immense challenge. Prompted by these challenges, we assessed the possibility of re-infection in discharged patients and the risk of the transmission, proficiency of RT-PCR results and approximate period required for the quarantine, and the real challenges for the development of vaccine. In the present review, the published literature on all the possible cases of re-infection from February to July were reported, thereby selected 142 studies from a hub of overall 669 studies after full text screening. The incomplete virus clearance, poor sensitivity of the present diagnostic testing, emergence of mutant strains, insufficient mucus collection from the throat swab etc., are some of the possible causes of re-infection. The new protocols for management of COVID-19 discharged patients should be revised in the guidelines. [ABSTRACT FROM AUTHOR]

Highlights: [•] Permanent broad-bed (PBB) planting effects on cotton–wheat system was evaluated. [•] Plots with PBB with residue had 3.1Mg higher wheat equivalent yield/ha/year than CT. [•] The PBB+residue (R) plots had 48% more mean system water productivity than CT. [•] The PBB+R plots had 36 and 13% more income than CT and permanent narrow-bed (PNB). [•] The PBB+R plots had higher mean water productivity than PNB+R, ZT and ZT+R plots. [ABSTRACT FROM AUTHOR]

Abstract: In a study on sandy loam soil of Indian Agricultural Research Institute (IARI) farm of New Delhi, soil hydrothermal environment under bed planted wheat was compared with conventionally flat planted wheat for evaluating the suitability of bed-planting system for the semiarid climate of this region. The soil temperature and water contents of the 0–20 cm soil profile under bed and conventional planting were monitored during drying cycle after 2nd and subsequent irrigations. Results revealed that mostly soil water content under bed planting was lower by 0.5–1% (w/w) than under conventional system mainly due to lower application of irrigation water and because of more porous soil environment. But it was also noticed that by applying irrigation at 22 days interval, soil water under bed remained within the available soil water range. It was observed that under both methods of planting magnitude of the maximum temperature decreased with an increase in soil water content, but for both high and low soil water contents (SWC), the temperatures were higher by 0.5–3 °C at the surface and subsurface (up to 20 cm) under bed than under conventional flat planting. Soil temperature data collected at 2 h interval during the day to monitor the maximum soil temperature showed that magnitudes of the peak at all depths were higher in bed planting and their arrival times were also earlier than in conventional planting. Again, at low SWC, peak soil temperature at the surface was near or higher than aerial temperature and at higher SWC, it was lower than aerial temperature. For similar aerial temperatures (30 °C), with an increase in SWC, both volumetric heat capacity and thermal diffusivity increased and their magnitude on bed was lower than that on conventional planting. [Copyright &y& Elsevier]

• Unified SQI was developed after 8 years of CA through PCA using 15 soil parameters. • The ZTDSR – ZTM – ZTSMB (+R) system had highest, whereas TPR-CTM had lowest SQI. • The ZTDSR – ZTM – ZTSMB (+R) resulted in ∼14 % higher total SOC than the TPR – CTM. • The key indicators were hydraulic conductivity, pH, total N, available P and K. • CA practice maintained higher soil quality and crop yield in rice-mustard system. The systematic research on the effect of medium-term conservation agriculture (CA) on soil quality, especially under the rice (Oryza sativa L.)-based cropping systems is limited. Hence, the specific objective of the study was to develop soil quality indices with key soil physical, chemical and biological indicators under the conservation and conventional tillage practices in a rice–mustard [ Brassica juncea (L.) Czern.] cropping system. Eight treatment combinations including tillage and crop establishment, crop residue and cropping system intensification with inclusion of short duration summer mungbean [ Vigna radiata (L.) Wilczek] were adopted in rice - mustard cropping system in hot semi-arid, sub-tropical north-western Indo-Gangetic Plains agro-ecoregion of India. Soil samples collected from topsoil (0−5 cm) and 5−15 cm soil layer were analyzed for 15 physical, chemical and biological properties to develop unified soil quality index (SQI) through principal component analysis (PCA). The highest SQI was obtained in the zero till direct seeded rice (ZTDSR) – zero till mustard (ZTM) –ZT summer mungbean (ZTSMB (+R) (mungbean residue in ZTDSR - rice residue in ZTM- mustard residue in ZTSMB) treatment followed by the ZTDSR + BM (brown manuring) – ZTM (+R) (mustard residue in ZTDSR with BM – rice residue in ZTM). The lowest SQI was obtained in transplanted puddled rice (TPR) - conventional till mustard (CTM) for both soil layers. The identified key indicators for SQI in this Inceptisol were saturated hydraulic conductivity (K s), pH, total N, available P, and available K. Besides, the plots under ZTDSR – ZTM – ZTSMB (+R) resulted in 14 % higher total organic C in topsoil and 28 % higher aggregate stability than the TPR - CTM plots. This ZTDSR – ZTM -ZTSMB (+R) treatment had 65 % higher surface soil microbial biomass C than the TPR – CTM treatment. The ZTDSR – ZTM -ZTSMB (+R) treatment also led to higher K s , which was in the order of triple ZT > double ZT > ZT > conventional tillage. Thus, the medium-term CA with triple or double zero tillage with crop residue retention could lead to maintain agricultural sustainability under rice-mustard system. Hence, it may be recommended to the farmers for adoption. [ABSTRACT FROM AUTHOR]

• A CA-based DSR–mustard(M)–mungbean system gave 11 % lower rice yield than TPR-CTM. • It resulted in 30 % higher mustard yield and higher net returns than TPR-CTM system. • It gave 44 % higher system yield and 36 % higher water productivity than TPR-CTM. • It had higher very labile (50.6 %) and labile (47.7 %) carbon at 0−5 cm soil layer. • CA based practices reduced weed density in mustard than the TPR-CTM system. Developing suitable crop rotations and crop establishment practices is an important mechanism that can enhance factor productivity and sustainability of an agro-ecosystem. However, the impact of Conservation Agriculture (CA) on alternate crop rotation of the most-dominant but tillage- and input-intensive rice (Oryza sativa L.)-wheat (Triticum aestivum (L.) emend Fiori & Paol) rotation of the Indo-Gangetic Plains (IGP) of India is not elaborately studied. Hence, we evaluated the effect of CA on crop and water productivity, profitability, and soil carbon status in rice-mustard (Brassica juncea L.) rotation in the North-western IGP of India for five consecutive years. Eight treatments comprising of tillage, crop residue, brown manuring (BM) using Sesbania bispinosa , and summer mungbean [ Vigna radiata (L.) Wilczek] (SMB) were adopted in rice - mustard cropping system. The conventional transplanted puddled rice (TPR) - conventional till mustard (CTM) (∼TPR-CTM) rotation resulted in significantly higher rice grain yield than zero till direct-seeded rice (ZTDSR) – ZT mustard (ZTM) system with or without crop residue in all five years. However, in this regard, the CA-based ZT rice – mustard - SMB with residue [ZTDSR-ZTM-ZTSMB (+R)] was comparable with it during first three years, but was inferior to it in 4th and 5th years. The ZTDSR-ZTM-ZTSMB (+R) had overall 10.9 % lower five-year mean rice yield than that in the TPR-CTM system. This CA-based system gave significantly higher mustard grain yield in all the years (except first year), and the five-year mean mustard yield was 30.3 % higher than in the TPR-CTM. Another CA-based double cropping system having ZTDSR + BM – ZTM (+R) was comparable with TPR-CTM in all the years and resulted in 27.6 % higher five-year mean mustard yield than the TPR–CTM practice. The ZTDSR-ZTM-ZTSMB (+R) practice gave 44 % (including SMB) and 8.1 % (excluding SMB) higher system productivity and significantly higher sustainable yield index of the rice-mustard system compared with the TPR-CTM practice. The ZTDSR-ZTM-ZTSMB (+R) practice encountered significantly lower weed density in mustard in all five years than TPR-CTM system. The cost-benefit analysis revealed that this CA practice fetched higher net returns by INR 53,000 and 21,400 ha−1 from the rice-mustard system with and without SMB, respectively over the TPR-CTM system. Again, this ZTDSR -ZTM- ZTSMB (+R) system led to an increase in irrigation water productivity by 27.8 % in rice and 35.1 % in mustard, and the total water (irrigation + rainfall) productivity by 35.7 % in mustard crop compared with the TPR-CTM system (P ≤ 0.05). This CA-based rice-mustard system resulted in significantly higher very labile (∼50.6 %) and labile (∼47.7 %) carbon concentration at 0–5 cm depth of soil compared to the conventional TPR-CTM system. The CA system being productive, profitable, and resource-efficient can be recommended for North-western IGP of India and in similar agro-ecologies of the tropics and sub-tropics. It can be adopted with suitable site-specific refinement in South-Asian countries, where decline in crop productivity and soil health is a consistent pervasive problem due to continuous cereal-cereal rotation. [ABSTRACT FROM AUTHOR]