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Globally, topsoil in most agroecosystems is being increasingly eroded by intensive land use practices. In semi-arid regions, restoring topsoil is particularly an important cue to optimize soil multifunctionality, as the loss of soil organic carbon (SOC) is often accompanied by the loss of soil fertility. Here, we test the additive effects of different crop residue incorporation regimes on topsoil multifunctionality in a decade long field experiment on a maize-maize-potato cropping system. In each year, crop residues of a double maize rotation (Spring-Summer) were exposed to three contrasting managements, i.e., no residue incorporation (NRI), burnt residue incorporation (BRI) and raw residue incorporation (RRI), before planting a potato crop in the Fall. Our results showed a proportional increase in SOC stocks of up to 49–69% for RRI compared to BRI and NRI, respectively. Similarly, RRI also contributed to greater qualitative C stocks, such as particulate (PAOC) by 74–86% and mineral (MAOC) associated organic carbon by 63–107% than BRI and RRI. In contrast, BRI showed no discernible change in organic C stocks, but a significant destabilizing effect on soil pH, electrical conductivity (EC), and bulk density (BD). The water extractable organic carbon (WEOC) and the C-lability index were significantly reduced in BRI plots and consequently curtailed soil microbial activity and microbial biomass synthesis. Interestingly, BRI showed a decrease in P-acquiring enzymes compared to C- and N-cycling enzymes, possibly reflecting the different demand of soil microbes for different nutrients. In contrast, an ensured availability of C substrate by RRI significantly increased the population of cultivable microflora (e.g., bacteria, fungi, actinomycetes). Above all, RRI was very effective in improving soil ecosystem multifunctionality, as evidenced by improved soil structural stability due to greater C accumulation and stabilization, resulting in enhanced NPK availability, although the low soil structural stability index (SSI ≤ 3%) still highlights the pervasive risk of land degradation. [Display omitted] • Burnt residue incorporation significantly destabilized soil pH, EC, and BD. • Microbial biomass synthesis was affected by burning-induced substrate limitation. • Raw residue elicited 1.25–1.87-fold higher SOC stocks than other treatments. • Improved NPK availability was positively associated with WEOC's C lability. • Repeated raw residue incorporation led to an improved soil multifunctionality. [ABSTRACT FROM AUTHOR]

Being a primary toxic heavy metal, lead (Pb) contamination presents an imposing environmental and public health concern worldwide. A Bacillus subtilis PbRB3, displaying higher Pb tolerance, was isolated from the textile effluent. The bacterial culture was able to remove >80% of Pb from culture solution. Upon screening in the presence of Pb, PbRB3 strain exhibited significant plant growth promoting potential. A 3 weeks long pot experiment was established to examine the capability of PbRB3 strain for physiological and biochemical traits, and Pb accumulation tendency of mung bean at 250 and 500 mg kg−1 of Pb toxicity, respectively. With respect to control treatments, photosynthetic pigments, protein synthesis, net assimilation rate, transpiration rate and stomatal conductance were significantly constrained by Pb toxicity levels. Intrinsic and instantaneous water use efficiencies were considerably improved in inoculated plants under Pb toxicity. Compared to inoculated control, significantly higher superoxide dismutase activity in both Pb toxicity treatments, while higher malondialdehyde contents only at Pb500 treatment was recorded with PbRB3 inoculation. Catalase activity between Pb250 and Pb500 treatments was comparable at both inoculation level. Moreover, PbRB3 inoculation led to significantly higher peroxidase activity under Pb toxicity treatments compared to inoculated control. The PbRB3 inoculation led to comparable differences in root Pb content between Pb250 and Pb500 treatments. These results suggest that inoculation of Pb tolerant, Bacillus subtilis PbRB3, could be employed to improve mung bean growth potential and adaptation against Pb toxicity, and thereby accelerated Pb rhizoaccumulation from metal contaminated environment. • A Bacillus subtilis PbRB3 was isolated from textile effluent. • PbRB3 removed >80% of Pb from spiked culture solution. • Photosynthetic pigments impaired by Pb toxicity even upon inoculation. • PbRB3 improved plant water use efficiency at Pb250 and Pb500. • PbRB3 mediated Pb translocation from root to aerial part. [ABSTRACT FROM AUTHOR]

A field study was conducted to test the potential of 5-year consecutive application of fresh industrial sludge (FIS) and composted industrial sludge (CIS) to restore soil functions at surface (0–15 cm) and subsurface (15–30 cm) of the degraded agricultural land. Sludge amendments increased soil fertility parameters including total organic carbon (TOC), soil available nitrogen (SAN), soil available phosphorus (SAP) and soil available potassium (SAK) at 0–15 cm depth. Soil enzyme activities i.e. dehydrogenase (DHA), β-glucosidase (BGA) and alkaline phosphatase (ALp) were significantly enhanced by FIS and CIS amendments in surface soil. However, urease activity (UA) and acid phosphatase (ACp) were significantly reduced compared to control soil. The results showed that sludge amendments significantly increased microbial biomass nitrogen (MBN) and microbial biomass phosphorus (MBP) at both soil depth, and soil microbial biomass carbon (MBC) only at 0–15 cm depth. Significant changes were also observed in the population of soil culturable microflora (bacteria, fungi and actinomycetes) with CIS amendment in surface soil suggesting persistence of microbial activity owing to the addition of organic matter source. Sludge amendments significantly reduced soil heavy metal concentrations at 0–15 cm depth, and the effect was more pronounced with CIS compared to unamended control soil. Sludge amendments generally had no significant impact on soil heavy metal concentrations in subsoil. Agronomic viability test involving maize was performed to evaluate phytotoxicity of soil solution extract at surface and sub-surface soil. Maize seeds grown in solution extract (0–15 cm) from sludge treated soil showed a significant increase of relative seed germination (RSG), relative root growth (RRG) and germination index (GI). These results suggested that both sludge amendments significantly improved soil properties, however, the CIS amendment was relatively more effective in restoring soil functions and effectively immobilizing wastewater derived heavy metals compared to FIS treatment. [ABSTRACT FROM AUTHOR]

Dry land soils from the Indo-Gangetic plains are inherently poor in organic matter content and phosphorus (P). Amendment of these soils with P-enriched compost, together with P solubilizing rhizobacterial (PSR) inoculation has been suggested to improve plant growth and P uptake. We performed 3 × 2 factorial experiment using compost i.e. control, raw saw dust P compost (RPC) and acidified saw dust P compost (APC), and PSR inoculation as factors. The pot study investigated the effects of compost and PSR on maize growth, yield, P nutrition and soil biochemical properties. PSR inoculation with APC enhanced shoot length, cob diameter, grain yield and plant P uptake compared to control. APC amendment, either alone or in combination with PSR, also improved root growth and caused extension of rhizosphere by increasing the root length density of the maize plants. Significant improvement in soil biochemical properties i.e. dehydrogenase (DHA), β-glucosidase (BGA), urease (UA) activity, dissolved organic carbon (DOC), soil organic carbon (SOC) and microbial biomass carbon (MBC) are due to the additive effect of compost amendments. A substantial increase in P availability and associated biochemical attributes reflect the significance of substrate quality, structural stability and optimized pH conditions of added compost that may have enhanced PSR performance, specifically with APC. Moreover, increased carboxylate secretions and PSR abundance in the root zone, lowering of pH and increase in rhizosphere fungal parameters, suggest PSR and APC to be synergetic driving of increased P availability for maize. We conclude that efficiency of P enriched compost could be increased with suitable compost additive in the presence of PSR in dry land soil. [ABSTRACT FROM AUTHOR]

Ecological benefits associated with plant growth-promoting rhizobacteria (PGPR) inoculants offer a promising integrated nutrient management option to counteract plant nitrogen (N) deficiency. We performed field experiments to evaluate the effect of integrated N fertilizer regime involving chemical N fertilizer (CNF) and N-enriched compost (NEC), either alone or combined with selected PGPR ( Pseudomonas aeruginosa) on sunflower seed quality, N use efficiency (NUE) and soil fertility during 2014-2015. We found that integrated N biofertilizer application resulted in significantly higher seed oil concentration, fatty acid composition, and harvest index in both cropping years. Greater effects on N yield efficiency (NYE), N use efficiency (NUE), N physiological efficiency (NPE), and photosynthetic N use efficiency (PNUE) were recorded in nitrogen-enriched compost+PGPR inoculant (NECPI) treatment followed by chemical N fertilizer+PGPR inoculant (CNFPI) treatment. Statistically significant differences were observed in linoleic and linolenic acid, NYE, and NUE for treatment × year interaction, thus, suggesting that the integrated N biofertilizer approach facilitates the efficient N use by sunflower for improving yield and seed quality. Moreover, we also found considerable enhancement of soil N fertility after two consecutive cropping years of sunflower. The enhancement of seed quality, N use efficiencies, and soil N fertility through integrated N biofertilizer application emphasizes the importance of balanced crop N nutrition, ensuring sufficient N supply to sunflower with adequate N balance in soil for the next crop. Overall, combination of PGPR with NEC amendment may optimize N uptake efficiency and reduce N fertilizer losses, which is necessarily required for the sustainable sunflower production. [ABSTRACT FROM AUTHOR]

The environmental and economic impacts of chemical fertilizer have encouraged farmers to integrate them with organic materials, an important nutrient management strategy for sustainable agriculture production. In the present study, we conducted field experiments to study the effects of nitrogen enriched compost (NEC) and mineral nitrogen (MN) fertilizer with a selected plant growth promoting rhizobacterial (PGPR) strain, Pseudomonas aeruginosa QS40, on productivity of sunflower and soil fertility. The results demonstrated that integrated application of PGPR with organic-inorganic N significantly increased shoot and root length, leaf area, total chlorophyll, head diameter, fresh biomass, straw-achene yield and N uptake in sunflower compared to unamended control and PGPR alone. The results also showed that integrated N biofertilizer regime enhanced soil microbial biomass, enzymatic activities and soil nitrogen contents. We also observed significant changes in rhizosphere soil pH, abundance of cultivable bacteria and arbuscular mycorrhizae fungi (AMF) root colonization. Treatment and year interaction was significant for dissolved organic carbon (DOC) and microbial biomass carbon (MBC) only. These results suggest that the efficiency of PGPR could be improved with increased availability of labile C substrate resource in NEC amended aridisol. We conclude that the application of NEC fertilizer with efficient PGPR biofertilizer may improve sunflower productivity and soil chemical and biological fertility in nutrient-poor agroecosystems of arid and semi-arid regions. [ABSTRACT FROM AUTHOR]

Abstract: Eighteen rhizobacterial isolates, with ACC deaminase activity, were screened for their growth promoting activity in maize under axenic conditions. Out of these, two strains Pseudomonas thivervalensis (STF3) and Serratia marcesens (STJ5), demonstrating maximum growth promotion effect, were characterized and used in the field experiments. The classical triple response assay supported the involvement of ACC deaminase in growth promotion. Selected rhizobacterial strains were investigated for their growth and yield promoting potential under field conditions with 50, 75 and 100% recommended chemical fertilizers (CF). Results of the study revealed that the rhizobacterial isolates, with 75 and 100% CF, significantly improved the growth and yield of maize compared to the uninoculated control treatment. The growth and yield promoting effect of rhizobacterial strain P. thivervalensis (STF3) with 75% CF were similar to that of CF alone. However, with 100% CF, same rhizobacterial strain significantly increased plant height, total biomass, grain yield, 1000-grain weight and chlorophyll content compared to the uninoculated control. Varied ACC deaminase activity might be responsible for differential behavior of P. thivervalensis (STF3) and S. marcesens (STJ5) under axenic and filed conditions. However, the selected rhizobacterial isolates differed markedly for presence of multifarious growth promoting characteristics which may also partly explain the variations in their efficiency to promote growth and yield of maize. [Copyright &y& Elsevier]

Greenhouse gaseous (GHGs) emissions from cropland soils are one of the major contributors to global warming. However, the extent and pattern of these climatic breakdowns are usally determined by the management practices in-place. The use of biochar on cropland soils holds a great promise for increasing the overall crop productivity. Nevertheless, biochar application to agricultural soils has grown in popularity as a strategy to off-set the negative feedback associated with agriculture GHGs emissions, i.e., CO 2 (carbon dioxide), CH 4 (methane), and N 2 O (nitrous oxide). Despite increasing efforts to uncover the potential of biochar to mitigate the farmland GHGs effects, there has been little synthesis of how different types of biochar affect GHGs fluxes from cropland soils under varied experimental conditions. Here, we presented a meta-analysis of the interactions between biochar and GHGs emissions across global cropland soils, with field experiments showing the strongest GHG mitigation potential, i.e. CO 2 (RR = −0.108) and CH 4 (RR = −0.399). The biochar pyrolysis temperature, feedstock, C: N ratio, and pH were also found to be important factors influencing GHGs emissions. A prominent reduction in N 2 O (RR = −0.13) and CH 4 (RR = −1.035) emissions was observed in neutral soils (pH = 6.6–7.3), whereas acidic soils (pH ≤ 6.5) accounted for the strongest mitigation effect on CO 2 compared to N 2 O and CH 4 emissions. We also found that a biochar application rate of 30 t ha−1 was best for mitigating GHGs emissions while achieving optimal crop yield. According to our meta-analysis, maize crop receiving biochar amendment showed a significant mitigation potential for CO 2 , N 2 O, and CH 4 emissions. On the other hand, the use of biochar had shown significant impact on the global warming potential (GWP) of total GHGs emissions. The current data synthesis takes the lead in analyzing emissions status and mitigation potential for three of the most common GHGs from cropland soils and demonstrates that biochar application can significantly reduce the emissions budget from agriculture. [Display omitted] • Biochar effects on croplands GHGs emissions were evaluated using a meta-analysis of 45 research articles. • Effectiveness of biochar to mitigate GHGs emissions from croplands relied on soil types and biochar properties. • Maize was the most responsive crop to biochar related GHGs mitigation. • Maximum mitigation effects were observed when biochar was applied at the rate of 30 t ha−1. [ABSTRACT FROM AUTHOR]

Pollution from potentially toxic metals (PTMs) is one of the most pressing global environmental challenge with soaring human health concerns. It is now critical to seek out effective remediation technologies to control PTMs in the terrestrial environment. Biochar has piqued the interest of researchers due to its ability to immobilize PTMs, particularly in soil, with the assumption that biochar having unique physico-chemical properties may influence PTM mobility. A meta-analysis was performed using 1503 observations extracted from 80 peer-reviewed articles to determine: (a) the effects of various physico-chemical properties of biochar on the bioavailability of PTMs (As, Cd, Cu, Ni, Pb, Zn) in soil and plants, and (b) the best specification of physico-chemical properties of biochar for effective remediation of these PTMs. The findings revealed that the reduction rate of PTM bioavailability is heavily influenced by the physico-chemical properties of both biochar and soil. The physico-chemical parameters of biochar that have effective response to PTMs immobilization were as; 101–500 m2 g−1 surface area, neutral to alkaline pH, pyrolysis temperature > 500 °C, with best application rate of 1.1–3%. However, overall results indicate that the biochar, with given specification of physico-chemical attributes, can decrease the bioavailability of PTMs by 40% in soil and 22% in plants. Moreover, edaphic factors such as soil pH, texture, and crop type can also influence the biochar mediated PTMs adsorption and transformation under field or pot conditions. Furthermore, research gaps remain to be filled in order to investigate the efficiency, high specificity, and secondary pollution aspects of biochar, particularly on large-scale applications as an amendment for PTM remediation. [Display omitted] • Eighty peer reviewed publications were used to conduct this meta-analysis. • Biochar addition can reduce PTMs concentration in soil by 40% and in plants by 22%. • Biochar pyrolyzed at >500 °C with 101–500 m2 g−1 surface area showed effective results. • Immobilization of PTMs can be a function of physicochemical properties of biochar. • Criteria should be established for uniform classification of biochar. [ABSTRACT FROM AUTHOR]

Given the significance of nitrogen (N) as the most constraining nutrient in agro-ecosystems, it is crucial to develop an updated model for N fertilizers management to achieve higher crop yields while minimizing the negative impacts on the environment. Coated urea is touted as one of the most important controlled-release N fertilizers used in agriculture to reduce cropland emissions and improve nitrogen use efficiency (NUE) for optimal crop yields. The sustainability of coated urea depends on the trade-offs between crop productivity, NUE and greenhouse gas emissions (CO 2 , CH 4 and N 2 O); however, role of various agro-edaphic factors in influencing these trade-offs remains unclear. To determine the effects of soil properties, climatic conditions, experimental conditions, and type of coated urea on greenhouse gas emissions, NH 3 losses, crop productivity, and NUE, we conducted a meta-analysis using data from 76 peer-reviewed studies. Our results showed that the application of coated urea under field conditions contributed to a greater reduction in N 2 O emissions (−48.67%) and higher NUE (58.72%), but crop yields were not significant. Across different climate regions, subtropical monsoon climate showed a perceptible mitigation for CO 2 , CH 4 and NH 3 (−78.38%; −83.33%; −27.46%), while temperate climate reduced N 2 O emissions by −70.36%. For different crops, only rice demonstrated reduction in CO 2 , CH 4 , N 2 O and NH 3 losses. On the other hand, our findings revealed a mitigating trade-off between CO 2 and CH 4 emissions on medium-textured soils and N 2 O emissions on fine-textured soils. A significant reduction in N 2 O and NH 3 losses was evident when coated urea was applied to soils with a pH > 5.5. Interestingly, application of coated urea to soils with higher C/N ratios increased NH 3 losses but showed a noticeable N 2 O reduction. We found that polymer-coated urea reduced CH 4 and N 2 O emissions and NH 3 losses at the expense of higher CO 2 emissions. Moreover, application of a lower dose of coated urea (0–100 kg N ha−1) enhanced CO 2 and CH 4 mitigation, while N 2 O mitigation increased linearly with increasing dose of coated urea. Most importantly, our results showed that the application of coated urea leads to a large mismatch between NUE, crop yields and greenhouse gas mitigation. By and large, the application of coated urea did not correspond with higher crop yields despite significant reduction in the emissions and improved NUE. Overall, these results suggest that site-specific agro-edaphic conditions should be considered when applying coated urea to reduce these emissions and N volatilization losses for increasing NUE and crop yields. • Coated urea led to greater NUE by reducing N 2 O emissions under field conditions. • Rice unequivocally exhibited significant GHGs mitigation and reduced NH 3 losses. • Coated urea reduced CO 2 -CH 4 emissions on medium and N 2 O on fine-textured soils. • Crop yields did not match the improved NUE and GHGs mitigation effects of coated urea. • Efficacy of coated urea fertilizers could depend on the given agro-edaphic conditions. [ABSTRACT FROM AUTHOR]

In semi-arid regions, soil phosphorus (P) dynamics in cereal-legume intercropping are not yet fully elucidated, particularly in relation to integrated application of fertilizers. To this aim, we investigate the effects of different fertilizers on various P fractions in relation to the rhizosphere-microbial processes in a cowpea/maize intercropping system. Field experiments were conducted during two consecutive years (2016–2017) in a split-plot design by establishing cowpea/maize alone or intercropped onto the main plot, while the sub-plot was treated with four types of fertilization, i.e. no fertilizer addition (control), organic amendment (compost), mineral fertilizers (NPK) and multi-nutrient enriched compost (NPKEC). Our results showed that NPKEC fertilizer increased NaHCO 3 -P i by 69% in maize, 62% in cowpea and 93% in intercropped plots compared to control plots. Similarly, a significant increase in the NaHCO 3 -P o fraction was also recorded with NPKEC treatment in all cropping systems. In case of moderately labile P, NPKEC fertilizer caused the highest increase of NaOH-P o (12.87 ± 0.50 mg P kg−1 soil) and NaOH-P i (22.29 ± 0.83 mg P kg−1 soil) fractions in intercropped plots. Except for intercropping, NPK application caused an increase in the non-available P fraction (HCl-P i), while the use of NPKEC decreased the HCl-P i concentration in all cropping systems, suggesting stronger merits both for intercropping and NPKEC. Surprisingly, maize exhibited substantially higher phosphatases activity compared to cowpea in monoculture amended with compost, implying distinct crop strategies for adaptation under low P conditions. Based on the multi-factor analysis, the close association of NaHCO 3 –P with P solubilizing bacteria, root carboxylates and pH indicated that rhizosphere processes are the strongest predictors of immediately available P. Since alkaline phosphatase (ALP) is a P-degrading enzyme of microbial origin, rhizosphere related ALP association may have originated from root-associated microflora promoting P mobilization. Furthermore, the strong association of microbial biomass P (MBP) and acid phosphates (ACP) with NaOH–P fraction indicated moderately available P cycle in soil was mainly driven by microbial-related processes. Factor analysis map and two-way ANOVA confirmed that fertilization regime had a stronger effect on all tested variables compared to cropping system. Altogether, our results suggest that a combination of microbial-rhizosphere processes controls the dynamics of P fertility in semi-arid soils. In the broader context of improving soil P fertility, it is highly recommended the use of environmentally sustainable sources of fertilizer, such as NPKEC, which can enhance the competitive performance of legume-cereal intercropping under semi-arid agroecosystems. Image 1 • Multi-nutrient compost (NPKEC) was tested for P fertility under cowpea-maize cropping. • In all cropping systems, NPKEC increased labile inorganic P ~62–93% than control. • Intercropping with NPKEC reduced non-available inorganic P by 29% over NPK fertilizers. • Type of fertilization steers intercropping related rhizosphere-microbial P processes. • Multi-nutrient compost enhanced competitiveness of intercrops in semi-arid agroecosystem. [ABSTRACT FROM AUTHOR]

Salinity stress is one of the major environmental stresses that impose global socio-economic impacts, as well as hindering crop productivity. Halotolerant plant growth-promoting rhizobacteria (PGPR) having potential to cope with salinity stress can be employed to counter this issue in eco-friendly way. In the present investigation, halotolerant PGPR strains, AP6 and PB5, were isolated from saline soil and characterized for their biochemical, molecular and physiological traits. Sequencing of 16 S rRNA gene and comparative analysis confirmed the taxonomic affiliation of AP6 with Bacillus licheniformis and PB5 with Pseudomonas plecoglossicida. The study was carried out in pots with different levels of induced soil salinity viz. 0, 5, 10 and 15 dSm−1 to evaluate the potential of bacterial inoculants in counteracting salinity stress in sunflower at different plant growth stages (30, 45 and 60 days after sowing). Both the bacterial inoculants were capable of producing indole acetic acid and biofilm, solubilizing inorganic rock phosphate, and also expressed ACC deaminase activity. The PGPR inoculated plants showed significantly higher fresh and dry biomass, plant height, root length and yield plant−1. Ameliorative significance of applied bacterial inoculants was also evidenced by mitigating oxidative stress through upregulation of catalase (CAT), superoxide dismutase (SOD) and guaiacol peroxidase (GPX) antioxidant enzymes. Increase in photosynthetic pigments, gas exchange activities and nutrient uptake are crucial salt stress adaptations, which were enhanced with the inoculation of salt tolerant biofilm producing PGPR in sunflower plants. Although increase in salinity stress levels has gradually decreased the plant's output compared to non-salinized plants, the plants inoculated with PGPR confronted salinity stress in much better way than uninoculated plants. Owing to the wide action spectrum of these bacterial inoculants, it was concluded that these biofilm PGPR could serve as effective bioinoculants and salinity stress alleviator for sunflower (oil seed crop) by increasing crop productivity in marginalized agricultural systems. Image 1 • Biofilm forming PGPR inoculant approach was developed to improve sunflower salt tolerance. • Biofilm PGPR solubilized P, secreted IAA, and expressed ACC-deaminase activity. • PGPR mediated salt tolerance in sunflower was evident by oxidative stress reduction. • Plant physiological and biochemical functions at highest salinity level were improved by biofilm bacteria. • Biofilm PGPR could be an appealing option to improve productivity of salt affected soil. [ABSTRACT FROM AUTHOR]

The understanding of the carbon (C) and nitrogen (N) mineralization is essential to mitigate the climate change and improve the soil quality for agricultural sustainability. An incubation study was carried out to investigate the effects of corncob-derived biochar with and without the corncob residues, as added organic matter (AOM), on C and N mineralization in an organic C deficient alkaline soil. The study used biochar produced from corncobs by pyrolysing the biomass at 400 °C and consisted of four treatments: unamended control soil, soil + 2% biochar (45 tons ha − 1 ), soil + 2% corncob residue (45 tons ha − 1 ) and soil + 1% corncob residue + 1% biochar (22.5 tons ha − 1 each of biochar and residue). Soil C mineralization was quantified by measuring soil respiration periodically throughout the experiment over the 54 d incubation period. Soils were analyzed for microbial biomass C (MBC), water extractable organic C (WEOC) and N mineralization. We also calculated microbial metabolic quotient ( q CO 2 ), net C mineralization (NCM), net CO 2 efflux and priming effect values. The results revealed that only a very little fraction of biochar was respired whereas a high proportion of corncob was decomposed. Biochar addition suppressed decomposition of native and AOM by 16.31% and 30.13% respectively through negative priming effect (− 40.01%). Compared to the corncob residue alone, addition of biochar with corncob residue significantly increased MBC but decreased WEOC, q CO 2 , NCM and net CO 2 efflux. Moreover, residue significantly increased the net CO 2 efflux, NCM and q CO 2 and, at the same time, decreased net N mineralization. Extractable NH 4 + -N, NO 3 − -N and mineral-N contents were the highest in the biochar and biochar + residue treatments. In addition, biochar alone and in combination with residue resulted in higher negative net N mineralization/immobilization. Enhanced MBC contents and reduced q CO 2 indicated efficient C utilization by microorganisms. The results of this study conclude that biochar could decrease C mineralization but enhanced microbial C use efficiency and, therefore, offer an important management strategy to improve C sequestration in nutrient and organic C deficient alkaline soil. The results also imply that the amendment of corncob residue with biochar had a potential to reduce the rate of the soil N leaching and N 2 O emission by N immobilization and sorption to biochar. [ABSTRACT FROM AUTHOR]

Wastewater is an alternative, valuable and cost effective resource for irrigation in water-scarce arid and sami-arid regions of the world including Pakistan. Soils near urban centers are cultivated for vegetable and cash crops using untreated wastewater. Current study was performed with objectives of assessing impacts of untreated textile wastewater on some soil chemical, biological and enzymatic activities. The microcosm incubation study used a clay loam soil that received 0 (distilled-water), 25, 50 and 100% wastewater concentrations and incubated for 30 and 60 days under optimum temperature and moisture conditions. Soil respiration was measured periodically throughout the experiment over 60 days. After the incubation periods of 30- and 60-d, soils were destructively analyzed for pH, electrical conductivity (EC), water extractable organic matter (WEOM), microbial biomass carbon (MBC), microbial metabolic quotient ( q CO 2 ) and dehydrogenase enzymatic activity. Results revealed that wastewater and incubation time significantly altered chemical, biological and enzymatic properties of soils. The observed large surge in soil respiration, at initial stage, was stimulated by dissolved organic matter in wastewater. Dehydrogenase activity increased significantly with increasing wastewater concentrations. Increase in q CO 2 with wastewater concentration and incubation time suggested more stress to microorganisms but also enhanced microbial activity under stress to synthesize biomass. We found significant positive (R 2 = 0.64, p < 0.001) relationship between soil respiration and MBC, however, correlation between WEOM and MBC was significant negative (R 2 = 0.18, p < 0.01) indicating a dynamic mismatch between carbon substrate, soil respiration and buildup of MBC pool. Wastewater concentration and incubation time interaction had significant (p < 0.01) effect on WEOM suggesting that WEOM accumulated over time and comparatively less utilized by microorganisms. Short- and long-term effects of untreated wastewater on soil physico-chemical and biological health should be assessed before its use for crop production. [ABSTRACT FROM AUTHOR]

Heavy metal contamination of agricultural soil has become a serious global problem. This study was aimed to evaluate the effects of two chromium (Cr) tolerant plant growth promoting bacteria (PGPB) in combination with salicylic acid (SA) on plant growth, physiological, biochemical responses and heavy metal uptake under Cr contamination. A pot experiment (autoclaved sand as growing medium) was performed using maize ( Zea mays L.) as a test crop under controlled conditions. Cr toxicity significantly reduced plant growth, photosynthetic pigment, carbohydrates metabolism and increased H 2 O 2 , MDA, relative membrane permeability, proline and Cr contents in maize leaves. However, inoculation with selected PGPB ( T2Cr and CrP450 ) and SA application either alone or in combination alleviated the Cr toxicity and promoted plant growth by decreasing Cr accumulation, H 2 O 2 and MDA level in maize. Furthermore, dual PGPB inoculation with SA application also improved plant performance under Cr-toxicity. Results obtained from this study indicate that PGPB inoculation and SA application enhanced Cr tolerance in maize seedlings by decreasing Cr uptake from root to shoot. Additionally, combination of both PGPB and SA also reduced oxidative stress by elevating the activities of enzymatic and non-enzymatic antioxidant, also indicated by improved carbohydrate metabolism in maize plant exposed to Cr contamination. Comparatively, alleviation effects were more pronounced in PGPB inoculated plants than SA applied plants alone. The results suggest that combined use of PGPB and SA application may be exploited for improving production potential of maize in metal (Cr) contaminated soil. [ABSTRACT FROM AUTHOR]

The effect of potassium sulfate (K2SO4) on adaptability of sugarcane to sodium chloride (NaCl) stress was investigated under hydroponic conditions. Two sugarcane cultivars, differing in salinity tolerance, were grown in half strength Johnson's solution at 80 mM NaCl with 0, 2.5 and 5.0 mM potassium (K) as K2SO4. Salinity disturbed above and below-ground dry matter production in both sugarcane cultivars. However, salt sensitive cultivar showed more reduction in shoot dry matter and higher root:shoot ratio compare to the salt tolerant cultivar under. Application of K significantly (p < 0.05) improved dry matter production in both sugarcane cultivars. The concentration of Na was markedly increased with increasing salinity; however, the application of K reduced its uptake, accumulation and distribution in plant tissues. Salinity induced reduction in K concentration, K-uptake, K utilization efficiency (KUE) and K:Na ratio in both sugarcane cultivars was significantly improved with the addition of K to the saline growth medium. [ABSTRACT FROM AUTHOR]

[Display omitted] • A global meta-analysis of nitrogen inhibitors to reduce N 2 O emissions across agro-system. • Overall, DCD and DMPP mitigated N 2 O emissions by 47% and 39%, respectively. • Relative efficacy of DCD was higher in chemically fertilized and acidic soils. • DCD is the exclusive option for vegetable fields, while DMPP is more suitable for maize fields. The production of biofuels from crop biomass is now seen as a practical renewable energy alternative, reducing overdependence on fossil fuels and limiting global warming from greenhouse gases. With respect to nitrogen emissions from biomass, it is claimed that nitrification inhibitors (NIs), particularly dicyandiamide (DCD) and 3,4-dimethylpyrazole phosphate (DMPP), can reduce these nitrogen losses. Nevertheless, the effectiveness of these NIs to reduce N 2 O emissions and NH 3 volatilization under different environmental conditions remains largely unclear. To this aim, a global meta-analysis was performed using 366 observations from 149 peer-reviewed research studies to quantify the responses of N 2 O emissions and NH 3 volatilization to the application of DCD and DMPP under different conditions. Based on the meta-analysis, DCD and DMPP can significantly reduce N 2 O emissions by 47% and 39%, respectively. The efficiency of DCD in reducing N 2 O emissions was much higher (12%) than that of DMPP when used together with chemical fertilizers. Interestingly, DCD tended to be more effective (9–10%) in incubation and field trials , while DMPP showed 39% higher efficacy. Concerning NH 3 , fertilizer-type, and soil pH, specific effects of NIs were not significant overall. Although DCD (pot experiments) and DMPP (incubation experiments) showed 30% and 46% higher NH 3 emissions, respectively, their effects were not significant under field conditions. According to meta-analysis, DCD and DMPP have demonstrated great potential to reduce N 2 O emissions. Importantly, the efficacy of such eco-friendly interventions could further be improved if the preferences described above are followed. Therefore, it will take further investigation to understand the mechanisms underlying the relatively higher efficacy of one NI over the other under specific conditions, including crop type, the nature of experiment, and other edaphic factors. [ABSTRACT FROM AUTHOR]

A long-term energy crisis has resulted in increased combustion of biomass fuel in industrial and household sectors in Pakistan. We report results of a study on the emission characteristics of rice husk, rice straw, corncobs and bagasse since they are frequently used as biomass fuel and differed remarkably in physico-chemical and combustion characteristics. Emission concentrations and emission factors were determined experimentally by burning the biomass fuel using a burning tower. Modified combustion efficiency (MCE) of rice husk, rice straw, corncobs and bagasse was >0.97 indicating that combustion was dominated by flaming mode. Emission factors of gaseous pollutants CO, CO2, NO2, NO, NO x and SO2 for rice straw were calculated to be 17.19 ± 0.28, 1090.07 ± 24.0, 0.89 ± 0.03, 1.48 ± 0.04, 3.16 ± 0.08 and 0.38 ± 0.03 g kg−1 respectively which were significantly (p < 0.05) higher compared to those from rice husk (14.05 ± 0.18, 880.48 ± 8.99, 0.19 ± 0.01, 1.38 ± 0.02, 2.31 ± 0.04 and 0.11 ± 0.03 g kg−1), corncobs (8.63 ± 0.12, 595.44 ± 10.38, 0.16 ± 0.01, 0.70 ± 0.01, 1.23 ± 0.02 and 0.02 ± 0.00 g kg−1) and bagasse (12.39 ± 0.08, 937.03 ± 9.07, 0.36 ± 0.03, 1.44 ± 0.02, 2.57 ± 0.04 and 0.18 ± 0.02 g kg−1). Total emissions of CO, CO2, NO2, NO, NO x and SO2 were estimated to be 3.68, 230.51, 0.05, 0.36, 0.60 and 0.03 Gg for rice husk, 33.75, 2140.35, 1.75, 2.91, 6.20 and 0.75 Gg for rice straw, 1.11, 76.28, 0.02, 0.02 and 0.03 Gg for corncobs and 42.12, 3185.53, 1.22, 4.90, 8.74 and 0.61 Gg for bagasse respectively. Rice straw, however, had significantly (p < 0.05) higher potential of gaseous pollutant emission factors. Bagasse had the highest values of total emissions followed by rice straw, rice husk and corncobs. Rice straw and bagasse, on cumulative basis, contributed more than 90% of total emissions of gaseous pollutants. Results reported in this study are important in formulating provincial and regional emission budgets of gaseous pollutants from burning of agricultural residues in Pakistan. [ABSTRACT FROM AUTHOR]

Among different abiotic stresses, drought stress is the leading cause of impaired plant growth and low productivity worldwide. It is therefore essential to understand the process of drought tolerance in plants and thus to enhance drought resistance. Accumulating evidence indicates that phytohormones are essential signaling molecules that regulate diverse processes of plant growth and development under drought stress. Plants can often respond to drought stress through a cascade of phytohormones signaling as a means of plant growth regulation. Understanding biosynthesis pathways and regulatory crosstalk involved in these vital compounds could pave the way for improving plant drought tolerance while maintaining overall plant health. In recent years, the identification of phytohormones related key regulatory genes and their manipulation through state-of-the-art genome engineering tools have helped to improve drought tolerance plants. To date, several genes linked to phytohormones signaling networks, biosynthesis, and metabolism have been described as a promising contender for engineering drought tolerance. Recent advances in functional genomics have shown that enhanced expression of positive regulators involved in hormone biosynthesis could better equip plants against drought stress. Similarly, knocking down negative regulators of phytohormone biosynthesis can also be very effective to negate the negative effects of drought on plants. This review explained how manipulating positive and negative regulators of phytohormone signaling could be improvised to develop future crop varieties exhibiting higher drought tolerance. In addition, we also discuss the role of a promising genome editing tool, CRISPR/Cas9, on phytohormone mediated plant growth regulation for tackling drought stress. [ABSTRACT FROM AUTHOR]

Potassium (K) deficiency is becoming a major productivity constraint in semi-arid agriculture. It is an essential mineral nutrient that has key role in various plant physiological and biochemical functions. Balanced nutrient application always tends to ensure better plant growth and development. Therefore, in the present study, efficacy of different K fertilizers for mediating maize plant growth and productivity in the presence and absence of KSB inoculant was assessed. A potassium solubilizing rhizobacterial strain, Klebsiella oxytoca KSB-17, was used in a 5 × 2 factorial pot experiment involving maize plant. The treatments comprised of control, waste mica (WM), K chemical fertilizer (KCF), WM-enriched compost (WMEC) and KCFenriched compost (KCFEC). Compared to control treatment, KCF fertilization increased all plant physiological parameters both in presence and absence of KSB inoculation. From the results obtained, KCFEC followed by CF alone with KSB, demonstrated the most pronounced effect with significant increase in plant height (50%), shoot biomass (59%), root biomass (73%), root length (92%), plant K uptake (154%), grain starch (16%), protein (31%), oil content (22%) as well as photosynthetic rate (104%), transpiration rate (30%) and water use efficiency (54%) compared to control. Potassium solubilizing bacteria (KSB) prompted down-regulation of plant antioxidant enzyme activities against all K fertilizer treatments. Compared to control treatment, catalase (CAT) activity decreased significantly on application of KCF as well as with KCFEC in the presence of KSB inoculation. Regardless of KSB inoculation, plant growth, physiological, antioxidant and K nutritional traits showed slight improvement with either of WM fertilizers compared to control. Our findings concluded that K enriched compost with efficient KSB inoculant can be used to enhance maize growth and productivity in semi-arid agroecosystems. [ABSTRACT FROM AUTHOR]

Phytoremediation, assisted with different amendments, is receiving much attention around the world due to its high efficiency, low cost and ease of handling. The current study was constructed to determine the combined performance of the citric acid (CA) and 5-aminolevulinic acid (5-AA) to enhance chromium (Cr) extraction through sunflower. Healthy seeds of sunflower were grownup in Cr contaminated soil (0, 5, 10 & 20 mgkg-1) and externally provided with CA (0, 2.5 &5 mM) and 5-AA (0, 10 & 20 mg L-1) at juvenile stage. The results showed a significant reduction in sunflower agronomic traits and biomass under Cr stress. In response to Cr stress, higher production of the reactive oxygen species (ROS) significantly reduced soluble proteins, photosynthetic pigments and activities of anti-oxidant enzymes. The combined addition of CA and 5-AA considerably mitigated the Cr-induced toxic effects on sunflower. Citric acid (CA) and 5-AA application enhanced plants' agronomic and physiological attributes by lowering electrolyte leakage and ROS production. Furthermore, the introduction of 5-AA and CA significantly up-regulated the actions of antioxidants enzymes in leaves and root of sunflower. With increasing soil Cr concentration, more Cr uptake and accumulation was observed which was further boosted with mutual applications of CA and 5-AA. Results of our work summarize that, CA and 5-AA combined application can effectively mitigate Cr stress and enhance Cr extraction capability of sunflower. [ABSTRACT FROM AUTHOR]

In continental Antarctica, autotrophs are exclusively represented by cyanobacteria, algae, lichens and mosses. Consequently, Antarctic soil communities are expected to be rather simple and primarily dominated by microorganisms. Recently, a change in abundance of mosses and lichens has been observed in continental Antarctica in response to an increase of the active permafrost layer, but the implication of this change to soil micro-organisms remains little known. Here we aim to clarify to what extent the abundance of mosses and lichens affects soil biogeochemistry in Victoria Land, with a particular focus on soil microbial abundance and associated soil enzymatic activity. To achieve this aim, we assessed the structure of soil microbiome and the activity of hydrolytic C, N, and P enzymes along a gradient in soil physico-chemical conditions and plant cover. Moss cover strongly relates to the amount of soil organic carbon (SOC), soil water and nutrient content. Soils with higher content of organic carbon were characterized by higher microbial biomass and showed a relatively higher abundance of fungi as compared to bacteria. More specifically, PLFAs biomarkers for Actinomycetes and Gram-positive bacteria were mainly associated to soils with lower SOC. In order to sustain a higher microbial biomass, total activity of hydrolytic enzymes increased with increasing SOC content. Eco-enzymatic stoichiometry, based on C to P and C to N ratios, indicates a higher investment in N- and P-hydrolytic enzymes (ratio < 1), particularly at low SOC content. Oppositely, an increase in C-hydrolytic enzyme activity (ratio ≈ 1) was observed with increasing accumulation of organic carbon. Such a result seems to indicate a stronger role of soil pH at low SOC on enzymatic stoichiometry (abiotic control) whereas with increasing accumulation of organic matter the enzymatic stoichiometry is more affected by microbial metabolism (biotic control). • The relative abundance of fungi increases in soils with higher organic C content. • Microbes with ruderal life-strategy are associated to soils with lower organic C content. • After normalization by organic matter, enzyme activity is promoted by higher soil pH. • N and P are more limiting for microbes in soils with lower organic C content. [ABSTRACT FROM AUTHOR]

Increasing atmospheric CO 2 concentration and nitrogen deposition are predicted to increase fresh carbon (C) inputs in soils because of higher net primary productivity. However, relationship between soil C cycling and increased inputs of fresh C in soils is not clear. Moreover, most of the studies on soil organic carbon (SOC) focus on upper 20 cm although >50% SOC is present below this depth. We designed this study to unravel the response of SOC to 0% (control), 0.3%, 0.6%, 1.2% and 2.4% addition of maize litter (C4) to a surface (0–15 cm) and deep layers (55–75 cm) of a C3 soil. The isotopic difference between the maize litter and soil allowed distinguishing soil-derived (native) CO 2 -C from litter-derived CO 2 -C and calculating the priming effect (PE). Total respiration was measured over 78 d incubation whereas the PE was determined 39 d and 78 d after incubation. Our results showed that all the litter addition levels induced PE -stimulation of mineralization of the extant SOC in response to availability of fresh organic matter (FOM)- in surface and deep soil layers. Moreover, the PE was significantly higher in the deep than surface soil layer in response to all litter additions, except 2.4% treatment during the 2nd harvest. This result suggests that the deep SOC would mineralize at higher rates under similar supply of FOM to surface and deep soils in this agroecosystem. We also showed a significantly positive linear relationship between PE and litter addition rates for both soils implying continuous loss of SOC under increasing organic matter inputs. In conclusion, our study reveals that the deep soil C would be more vulnerable to priming effect in response to litter addition than the surface soil. [ABSTRACT FROM AUTHOR]

Relations between nitrogen (N) nutrition and salinity tolerance in plants are multifaceted and varies significantly depending on many soil and plant factors. Saline environment might experience an N dilemma due to the opposing effects of salt ions on N uptake, translocation and metabolism within the plant body. Adequate regulation of N under saline conditions can be a promising approach to alleviate salinity’s effects on plants by ameliorating ion toxicity and nutrient imbalances through its impacts on the uptake and redistribution of salt ions within the plant. Certain N-containing compounds including proline, glycine betaine, proteins and polyamines help the plants to tolerate salinity through their involvement in improving water uptake and water use efficiency, membrane integrity, enzyme activation, hormonal balance, chlorophyll synthesis, stimulation of photosystems and CO2 assimilation under salinity stress. Nitrogen, particularly NO3− represents a stress signal that triggers the activation of antioxidant enzymes to protect the plants against salinity-induced oxidative damage. Furthermore, the source/form of N application can affect not only N-interactions but also the behavior of other nutrients in stress environment. The present review deals with N-salinity relations in plants, particularly glycophytes, emphasizing on N-induced mechanisms which can improve plant adaptation to saline environment. [ABSTRACT FROM AUTHOR]

Contamination of agricultural soils with trace metals present lethal consequences in terms of diverse ecological and environmental problems that entail entry of metal in food chain, soil deterioration, plant growth suppression, yield reduction and alteration in microbial community. Metal polluted soils have become a major concern for scientists around the globe. Phytoremediation involves the hyperaccumulation of metals in different plant parts. Phytoremediation of metals from polluted soils could be enhanced through inoculation with metal resistant plant growth promoting (PGP) bacteria. These PGP bacteria not only promote plant growth but also enhance metal uptake by plants. There are a number of reports in the literature where PGP bacterial inoculation improves metal accumulation in different plant parts without influencing plant growth. Therefore, there is a need to select PGP bacterial strains which possess the potential to improve plant growth as well as expedite the phytoremediation of metals. In this review, we have discussed the mechanisms possessed by PGP bacteria to promote plant growth and phytoremediation of metals. The central part of this review deals with the recent advances in microbial assisted-phytoremediation of metals. [ABSTRACT FROM AUTHOR]

In many tropical regions, slash-and-burn agriculture is considered as a driver of deforestation; the forest is converted into agricultural land by cutting and burning the trees. However, the fields are abandoned after few years because of yield decrease and weed invasion. Consequently, new surfaces are regularly cleared from the primary forest. We propose a reclamation strategy for abandoned fields allowing and sustaining re-cultivation. In the dry region of south-western Madagascar, we tested, according to a split-plot design, an alternative selective slash-and-burn cultivation technique coupled with compost amendment on 30-year-old abandoned fields. Corn plants ( Zea mays L.) were grown on four different types of soil amendments: no amendment (control), compost, ashes (as in traditional slash-and-burn cultivation), and compost + ashes additions. Furthermore, two tree cover treatments were applied: 0% tree cover (as in traditional slash-and-burn cultivation) and 50% tree cover (selective slash-and-burn). Both corn growth and soil fertility parameters were monitored during the growing season 2015 up to final harvest. The amendment compost + ashes strongly increased corn yield, which was multiplied by 4-5 in comparison with ashes or compost alone, reaching 1.5 t/ha compared to 0.25 and 0.35 t/ha for ashes and compost, respectively. On control plots, yield was negligible as expected on these degraded soils. Structural equation modeling evidenced that compost and ashes were complementary fertilizing pathways promoting soil fertility through positive effects on soil moisture, pH, organic matter, and microbial activity. Concerning the tree cover treatment, yield was reduced on shaded plots (50% tree cover) compared to sunny plots (0% tree cover) for all soil amendments, except ashes. To conclude, our results provide empirical evidence on the potential of recultivating tropical degraded soils with compost and ashes. This would help mitigating deforestation of the primary forest by increasing lifespan of agricultural lands. [ABSTRACT FROM AUTHOR]

Soil salinity is one of the most pernicious environmental hazards affecting crop growth and productivity in arid and semi-arid climates. In saline soils, the crop plants encounter nutrients deficient conditions mainly due to antagonistic affinity of sodium (Na+) and chloride (Cl−). The accumulation of salts in the rhizosphere restricts plant growth, the severity of which depends on the source and concentration of the salt. Therefore, we hypothesized that sodium containing salts could have toxic effects on maize plants either in a single or in combined form. To evaluate the interactive effect of sodium salts on plant growth, ionic homeostasis, and seed quality attributes, a pot study was performed using maize as a test plant at the research area of the College of Agriculture, University of Sargodha. Selected salts including, NaCl, Na 2 SO 4 and their combination (NaCl + Na 2 SO 4), were applied in equal ratio for different salinity levels (7, 10, 13 and 16 dS m−1) and the untreated control. The results show that all the measured growth, yield, biochemical and quality attributes of maize were negatively affected with increasing concentration of all the salt sources; however, severity of these effects were more intense when NaCl was applied at all salinity levels. It is concluded that all salts (NaCl, Na 2 SO 4 and NaCl + Na 2 SO 4) had negative effects on biochemical, qualitative, growth and yield characteristics of maize plant. Most importantly, NaCl was found to be more harmful compared to Na 2 SO 4 and mixtures of both salts due to the dominance of Na+ and Cl-ions. Among all salinity levels, the more detrimental effects of NaCl occurred at salinity level of 16 dS m−1. [Display omitted] • A pot study was established for evaluation of salinity sources and their formulations at different levels. • Higher salinity increased the Na: K ratio in maize tissues, and caused reduction in yield. • NaCl was more toxic than Na 2 SO 4 for maize and mixture of both at all salinity levels. [ABSTRACT FROM AUTHOR]

Being analogue to arsenic (As), phosphorus (P) may affect As dynamics in soil and toxicity to plants depending upon many soil and plant factors. Two sets of experiments were conducted to determine the effect of P on As fractionation in soils, its accumulation by plants and subsequent impact on growth, yield and physiological characteristics of sunflower (Helianthus annuus L.). Experimental plan comprised of two As levels (60 and 120 mg As kg−1 soil), four P (0-5-10-20 g phosphate rock kg−1 soil) and three textural types (sandy, loamy and clayey) with three replications. Among different As fractions determined, labile, calcium-bound, organic matter-bound and residual As increased while iron-bound and aluminum-bound As decreased with increasing P in all the three textural types. Labile-As percentage increased in the presence of P by 16.9–48.0% at As60 while 36.0–68.1% at As120 in sandy, 19.1–64.0% at As60 while 11.5–52.3% at As120 in loamy, and 21.8–58.2% at As60 while 22.3–70.0% at As120 in clayey soil compared to respective As treatment without P. Arsenic accumulation in plant tissues at both contamination levels declined with P addition as evidenced by lower bioconcentration factor. Phosphorus mitigated the As-induced oxidative stress expressed in term of reduced hydrogen peroxide, malondialdehyde while increased glutathione, and consequently improved the achene yield. Although, P increased As solubility in soil but restricted its translocation to plant, leading to reversal of oxidative damage, and improved sunflower growth and yield in all the three soil textural types, more profound effect at highest P level and in sandy texture. [Display omitted] • Arsenic can have serious repercussions both for human and animal health by compromising the soil, water and food quality. • Phosphorus could alter As fractions in soils, an increase in L-As, Ca–As, OM-As and R–As while decrease in Fe–As and Al–As. • Arsenic-induced oxidative stress in term of H 2 O 2 and MDA could efficiently be ameliorated with P in sunflower. • Phosphorus could increase As solubility and mobility in soil, but restricted its accumulation in plant tissues. Ameliorative effects of P against As toxicity in sunflower were more profound at highest P level and in sandy texture. P had a marked effect on As fractionation in all the three textured soils but the effect was highest at elevated P level, and in sandy soil. P-induced resistance to As toxicity was associated with an inhibition in As accumulation, and protection against oxidative stress by activating the antioxidant system. [ABSTRACT FROM AUTHOR]

The sunflower (Helianthus annuus L.) is an important oilseed crop all over the world. Seed of 18 hybrids including one check "N.K-S 278" was planted during spring and autumn seasons 2008 following randomized complete block design with three replications. Mean squares from analysis of variance showed highly significant differences among all the traits during autumn season. Similar results were also obtained during spring except seed yield per plant, head diameter and 100-achene weight. Mean, range and coefficient of variation indicated that all the traits showed higher values for spring sown over the autumn sown except 100-achene weight, which showed higher in autumn sown (5.8 g) than spring (5.3 g). An increase in head diameter, seed yield plant-1 and oil content were recorded during spring as compared to autumn while 100-achene weight increased during autumn season. Traits i.e., 100-achene weight and oil content showed positive and significant correlation with yield plant-1 during spring. Days to maturity, plant height and head diameter showed positive and highly significant correlation with yield plant-1 during autumn. Positive and highly significant correlation was observed for days to flower initiation with days to maturity and plant height during both spring and autumn seasons. Performance of hybrids varied with respect to season. Hybrid PAC-AGR-306 performed best during spring, while hybrid FSS-63 during autumn season. [ABSTRACT FROM AUTHOR]

Organic amendments (animal manure and biochar) to agricultural soils may enhance soil organic carbon (SOC) contents, improve soil fertility and crop productivity but also contribute to global warming through nitrous oxide (N 2 O) emission. However, the effects of organic amendments on N 2 O emissions from agricultural soils seem variable among numerous research studies and remains uncertain. Here, eighty-five publications (peer-reviewed) were selected to perform a meta-analysis study. The results of this meta-analysis study show that the application of animal manure enhanced N 2 O emissions by 17.7%, whereas, biochar amendment significantly mitigated N 2 O emissions by 19.7%. Moreover, coarse textured soils increased [ l n R R ‾ = 182.6%, 95% confidence interval (CI) = 151.4%, 217.7%] N 2 O emission after animal manure, in contrast, N 2 O emission mitigated by 7.0% from coarse textured soils after biochar amendment. In addition, this study found that 121–320 kg N ha−1 and ⩽ 30 T ha−1 application rates of animal manure and biochar mitigated N 2 O emissions by 72.3% and 22.5%, respectively. Soil pH also played a vital role in regulating the N 2 O emissions after organic amendments. Furthermore, > 10 soil C: N ratios increased N 2 O emissions by 121.4% and 27.6% after animal and biochar amendments, respectively. Overall, animal manure C: N ratios significantly enhanced N 2 O emissions, while, biochar C: N ratio had not shown any effect on N 2 O emissions. Overall, average N 2 O emission factors (EFs) for animal manure and biochar amendments were 0.46% and −0.08%, respectively. Thus, the results of this meta-analysis study provide scientific evidence about how organic amendments such as animal manure and biochar regulating the N 2 O emission from agricultural soils. [Display omitted] • Organic amendments (animal manure and biochar) may increase SOC stocks but also influence N 2 O emissions. • Animal manure significantly increased N 2 O emission by 17.7%. • Biochar amendment significantly mitigated N 2 O emissions by 19.7%. • Maximum reduction was observed with medium doses of animal manure (121–320 kg N ha-1) and biochar (⩽ 30 T ha−1). [ABSTRACT FROM AUTHOR]

Micro- and nano-plastics have widely been recognized as major global environmental problem due to its widespread use and inadequate waste management. The emergence of these plastic pollutants in agroecosystem is a legitimate ecotoxicological concerns for food web exchanges. In agriculture, micro/nano plastics are originated from a variety of different agricultural management practices, such as the use of compost, sewage sludge and mulching. A range of soil properties and plant traits are affected by their presence. With the increase of plastic debris, these pollutant materials have now begun to demonstrate serious implications for key soil ecosystem functions, such as soil microbial activity and nutrient cycling. Nitrogen (N) cycle is key predictor of ecological stability and management in terrestrial ecosystem. In this review, we evaluate ecological risks associated with micro-nano plastic for soil-plant system. We also discuss the consequence of plastic pollutants, either positive or negative, on soil microbial activities. In addition, we systematically summarize both direct and hypothesized implications for N cycling in agroecosystem. We conclude that soil N transformation had showed varied effects resulting from different types and sizes of plastic polymers present in soil. While mixed effects of microplastic pollution on plant growth and yield have been observed, biodegradable plastics have appeared to pose greater risk for plant growth compared to chemical plastic polymers. Image 1 • Micro and nano-plastic sourced from a variety of agricultural practices. • Micro and nano-plastic can alter soil N biogeochemistry. • Micro and nano-plastic effects on crop are inevitable. • Nano-plastic may ends up in human/animal body. [ABSTRACT FROM AUTHOR]