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The study aimed to investigate the correlation between meteorological parameters and the spread of the COVID-19 pandemic in Islamabad, Pakistan. The meteorological parameters include temperature minimum (°C), temperature maximum (°C), temperature average (°C), humidity minimum (%), humidity maximum (%), humidity average (%), and rainfall (mm). The data of COVID-19, such as the number of new confirmed cases and deaths was obtained from the Ministry of Health, Pakistan. The correlations of various types, i.e., Pearson, Spearman, and Kendall correlations between meteorological parameters and COVID-19, were employed for data analyses. The results exhibited a highly significant relationship between COVID-19 and temperature minimum and temperature average among all meteorological parameters. The study findings may help competitive authorities to combat this disease in Pakistan. Electronic supplementary material The online version of this article (10.1007/s42398-020-00125-x) contains supplementary material, which is available to authorized users.

The use of mineral fertilizers has long been associated with the improved growth of crop plants as well as increased yield potential per unit area. However, the incessant practice of imbalanced fertilizers application has increased the economic and environmental costs for the agricultural sector. The deficiency of potassium (K) has been identified as a primary crop production challenge in certain semi-arid regions where soil-K reserves are increasingly being depleted. This study aimed to isolate and characterize K-solubilizing bacterial strains from the rhizosphere and root nodules of chickpea. Initially, 50 rhizobacterial strains and 50 rhizobial strains were isolated using Aleksandrov’s medium. Each of these collections was narrowed down to 25 strains, following a rigorous qualitative screening based on different physiological, morphological and biochemical tests. From these, five strains each of rhizosphere and nodule origins were selected based on qualitative as well quantitative determination of various growth promoting traits. In addition to efficient potassium and phosphate solubilization, the selected strains displayed better growth conditions, as evident by glucose substrate use at 25◦C and pH 7. In this study, we found that strains SKB3 (rhizosphere) and JKR7 (rhizobia) were the most efficient K-solubilizers. Additionally, they possessed diverse plant growth promoting traits such as root colonization, the synthesis of siderophores, exopolysaccharides, chitinase activity, indole-acetic acid production and 1-aminocyclopropane-1-carboxylic acid deaminase activity. Overall, our results suggest that the application of bacterial K-solubilizers could be employed as a useful K-supplement in K-limited agroecosystems. Moreover, the use of these K-solubilizers may help lead in alleviating the negative environmental impacts associated with chemical fertilizer. I am very grateful to all of those with whom I have had the pleasure to work during this project, especially the Department of Soil and Environmental Sciences, College of Agriculture, University of Sargodha, Sargodha, Pakistan, the Soil & Water Sciences Department (SWD), Institute of Food and Agricultural Sciences (IFAS), University of Florida, USA, and the Higher Education Commission (HEC), Islamabad, Pakistan. Each of the members of the SWD, IFAS, University of Florida, USA, specifically L.Q. Ma, Letuzia Maria De Oliveira and Evandro Da Silva have provided me with extensive personal and professional guidance and have taught me a great deal about both scientific research and life in general during my six months stay there under International Research Support Initiative Program (IRSIP), HEC, Pakistan. The authors would also like to extend their sincere appreciation to the acknowledgment of the research supporting project (RSP-2021/95, King Saud University, Riyadh, Saudi Arabia).

Soil salinization limit crop yield and deteriorate product quality in arid and semi-arid agroecological regions. Under such conditions regulation of mineral nutrients may help to sustain crop productivity. Therefore, a pot experiment was carried out to identify optimal sulfur level and source for enhancing salt adaptability of sunflower (Helianthus annuus L.). A uniform salinity level of 100 mM NaCl was developed in each pot and then six S treatments viz. S0, control; S1, 20 mg sulfur kg-1 soil; S2, 40 mg sulfur kg-1 soil; S3, 60 mg sulfur kg-1 soil; S4, 80 mg sulfur kg-1 soil and S5, 100 mg sulfur kg-1 soil were applied by using elemental S and K2SO4 as sulfur source. Supplementation of sulfur caused reduction in tissue Na+ accumulation and electrolyte leakage while increase in tissue K+ and Ca2+ with a subsequent increase in relative water content and photosynthetic rate of sunflower. Increasing sulfur levels in the form of K2SO4 depicted linear increase in plant growth and yield attributes up to 80 mg sulfur kg-1 soil beyond which there was decline in these growth characteristics suggesting that sulfur as K2SO4 at 80 mg sulfur kg-1 soil might be optimum in mitigating NaCl toxicity in sunflower.

Tannery effluents are rich source of chromium (Cr) and organic carbon (C), however, hexavalent Cr (Cr6+) is many-fold more toxic than trivalent Cr (Cr3+). We examined the extent of total Cr, Cr3+ and Cr6+ pollution of agricultural soils under long-term tannery effluent irrigation in Kasur, Pakistan. Effects of Cr species on morphological and physiological responses of wheat including patterns of Cr3+ and Cr6+ uptake, their translocation factor (TF) and bioconcentration factor (BCF) were studied. Nine soil samples had significantly variable total organic C and total Cr, Cr3+ and Cr6+ contents. Pot study showed that morphological characteristics of wheat were largely unaffected by total Cr, Cr3+ and Cr6+ contents, however, physiological responses including contents of chlorophyll a, chlorophyll b, total chlorophyll, carotenoids and total proteins; and chlorophyll a:b ratio were significantly affected by contents of Cr species. Results further suggested that the relationships between total Cr and physiological attributes of wheat were controlled by Cr6+ rather than Cr3+ contents and, hence, Cr3+:Cr6+ ratios determined the effects of Cr on wheat growth and development. Uptake, TF and BCF values for Cr3+ and Cr6+ showed significant variations and BCF values showed negative correlation with total organic C contents. Results of our study highlight the significance of understanding the effects of Cr species and Cr3+:Cr6+ ratios rather than the total Cr contents when assessing the Cr behavior in soils and its effects on plant growth, especially phytotoxicity of tannery-based organic fertilizers before its application in the field.

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.

Globally, agriculture sector is the significant source of greenhouse gases (GHGs) emissions into the atmosphere. To achieve the goal of limiting or mitigating these emissions, a rigorous abatement strategy with an additional focus on improving crop productivity is now imperative. Replacing traditional agriculture with soil conservation-based farming can have numerous ecological benefits. However, most assessments only consider improvements in soil properties and crop productivity, and often preclude the quantitative impact analysis on GHGs emissions. Here, we conducted a meta-analysis to evaluate crop productivity (i.e., biomass, grain, total yield) and GHGs emissions (i.e., CO2, N2O, CH4) for three major soil conservation practices i.e., no-tillage, manures, and biochar. We also examined the yield potential of three major cereal crops (i.e., wheat, rice, maize) and their significance in mitigating GHGs emissions. None of the manures were able to reduce GHGs emissions, with poultry manure being the largest contributor to all GHGs emissions. However, pig-manure had the greatest impact on crop yield while emitting the least CO2 emissions. Use of biochar showed a strong coupling effect between reduction of GHGs (i.e., CH4 by -37%; N2O by -25%; CO2 by -5%) and the increase in crop productivity. In contrast, no-tillage resulted in higher GHGs emissions with only a marginal increase in grain yield. Depending on crop type, all cereal crops showed varied degrees of GHGs mitigation under biochar application, with wheat responding most strongly due to the additional yield increment. The addition of biochar significantly reduced CO2 and N2O emissions under both rainfed and irrigated conditions, although CH4 reductions were identical in both agroecosystems. Interestingly, the use of biochar resulted in a greater yield benefit in rainfed than in irrigated agriculture. Despite significant GHGs emissions, manure application contributed to higher crop yields, regardless of soil type or agroecosystem. Moreover, no-tillage showed a significant reduction in CH4 and N2O emissions under rainfed and irrigated conditions. Notably , biochar application in coarse while no-till in fine textured soils contributed to N2O mitigation. Most importantly, effectiveness of no-tillage as a countermeasure to GHGs emissions while providing yield benefits is inconsistent. Overall, the decision to use farm manures should be reconsidered due to higher GHGs emissions. We conclude that the use of biochar could be an ideal way to reduce GHGs emissions. However, further understanding of the underlying mechanisms and processes affecting GHGs emissions is needed to better understand the feedback effects in conservation agriculture.

Forest ecosystem carbon (C) storage primarily includes vegetation layers C storage, litter C storage, and soil C storage. The precise assessment of forest ecosystem C storage is a major concern that has drawn widespread attention in global climate change worldwide. This study explored the C storage of different layers of the forest ecosystem and the nutrient enrichment capacity of the vegetation layer to the soil in the Castanopsis eyeri natural forest ecosystem (CEF) present in the northeastern Hunan province, central China. The direct field measurements were used for the estimations. Results illustrate that trunk biomass distribution was 48.42% and 62.32% in younger and over-mature trees, respectively. The combined biomass of the understory shrub, herb, and litter layers was 10.46 t·hm−2, accounting for only 2.72% of the total forest biomass. On average, C content increased with the tree age increment. The C content of tree, shrub, and herb layers was 45.68%, 43.08%, and 35.76%, respectively. Litter C content was higher in the undecomposed litter (44.07 %). Soil C content continually decreased as the soil depth increased, and almost half of soil C was stored in the upper soil layer. Total C stored in CEF was 329.70 t·hm−2 and it follows the order: tree layer > soil layer > litter layer > shrub layer > herb layer, with C storage distribution of 51.07%, 47.80%, 0.78%, 0.25%, and 0.10%, respectively. Macronutrient enrichment capacity from vegetation layers to soil was highest in the herb layer and lowest in the tree layer, whereas no consistent patterns were observed for trace elements. This study will help understand the production mechanism and ecological process of the C. eyeri natural forest ecosystem and provide the basics for future research on climate mitigation, nutrient cycling, and energy exchange in developing and utilizing sub-tropical vegetation This research was financially supported by research funding from Central South University of Forestry and Technology and the Hunan province finance department (No.70702-45200003)

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 (N2O) emission. However, the effects of organic amendments on N2O 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 N2O emissions by 17.7%, whereas, biochar amendment significantly mitigated N2O emissions by 19.7%. Moreover, coarse textured soils increased [ = 182.6%, 95% confidence interval (CI) = 151.4%, 217.7%] N2O emission after animal manure, in contrast, N2O 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 N2O emissions by 72.3% and 22.5%, respectively. Soil pH also played a vital role in regulating the N2O emissions after organic amendments. Furthermore, > 10 soil C: N ratios increased N2O emissions by 121.4% and 27.6% after animal and biochar amendments, respectively. Overall, animal manure C: N ratios significantly enhanced N2O emissions, while, biochar C: N ratio had not shown any effect on N2O emissions. Overall, average N2O 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 N2O emission from agricultural soils. The part of work contributed by Muhammad Aammar Tufail, has received funding form the European Union’s Horizon 2020 Research and Innovation program under the Maria Skłodowska-Curie grant agreement no. 722642 (project INTER-FUTURE

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 accumulation in plant tissues, leading to reversal of oxidative damage and improved sunflower growth and yield in all the three soil textural types, more profound effect in sandy texture.

No-tillage (NT) practice is extensively adopted with aims to improve soil physical conditions, carbon (C) sequestration and to alleviate greenhouse gases (GHGs) emissions without compromising crop yield. However, the influences of NT on GHGs emissions and crop yields remains inconsistent. A global meta-analysis was performed by using fifty peer-reviewed publications to assess the effectiveness of soil physicochemical properties, nitrogen (N) fertilization, type and duration of crop, water management and climatic zones on GHGs emissions and crop yields under NT compared to conventional tillage (CT) practices. The outcome reveals that compared to CT, NT increased CO2, N2O, and CH4 emissions by 7.1, 12.0, and 20.8%, respectively. In contrast, NT caused up to 7.6% decline in global warming potential as compared to CT. However, absence of difference in crop yield was observed both under NT and CT practices. Increasing N fertilization rates under NT improved crop yield and GHGs emission up to 23 and 58%, respectively, compared to CT. Further, NT practices caused an increase of 16.1% CO2 and 14.7% N2O emission in the rainfed areas and up to 54.0% CH4 emission under irrigated areas as compared to CT practices. This meta-analysis study provides a scientific basis for evaluating the effects of NT on GHGs emissions and crop yields, and also provides basic information to mitigate the GHGs emissions that are associated with NT practice. Awais Shakoor would like to express his gratitude for the grant provided by the University of Lleida, Spain. The authors would like to appreciate the valuable comments from the editors and anonymous reviewers to improve the quality of this study.

Salinity is a major constraint in improving agricultural productivity due to its adverse impact on various physiological and biochemical attributes of plants, and its effect on reducing nitrogen (N) use efficiency due to ion toxicity. To understand the relationship between sodium chloride (NaCl) and increased N application rates, a pot study was performed in which the ammonical (NH4+) form of N was applied as urea to maize crops at different rates (control, 160, 186, 240, 267, 293, and 320 kg N ha−1) using two salinity levels (control and 10 dS m−1 NaCl). The results indicate that all biochemical and physiological attributes of the maize plant improved with increased concentration of N up to 293 kg ha−1, compared to those in the control treatment. Similarly, the optimal N concentration regulated the activities of antioxidant enzymes, i.e., catalase activity (CAT), peroxidase activity (POD), and superoxide dismutases (SOD), and also increased the N use efficiencies of the maize crop up to 293 kg N ha−1. Overall, our results show that the optimum level of N (293 kg ha−1) improved the salinity tolerance in the maize plant by activating stress coping physiological and biochemical mechanisms. This may have been due to the major role of N in the metabolic activity of plants and N assimilation enzymes activity such as nitrate reductase (NR) and nitrite reductase (NiR).

Abiotic stresses are supposed to negate crop productivity leading to food insecurity. Plant growth-promoting rhizobacteria (PGPR) can significantly facilitate plant growth directly or indirectly by suppressing various plant pathogens, producing different phytohormones, mineralization and decomposition of organic matter, triggering antioxidant system, producing siderophores, and improving the bioavailability of different mineral nutrients. Among the PGPRs, Pseudomonas are ubiquitous and their occurrence in stressed environment has also been reported. Pseudomonas can produce different enzymes and metabolites that help plants withstand varied biotic and abiotic stresses. Pseudomonas-induced salt or drought tolerance has extensively studied at the physiological and biochemical levels in plants. The potential of Pseudomonas has also been explored under some other abiotic stress factors like water, temperature, nutrients, and heavy metals. Furthermore, in this chapter, we will elaborate the interactions among plant, Pseudomonas spp., and various abiotic environmental stresses with an objective to explore the underlying mechanisms and stress tolerance in plants as promises of Pseudomonas.

The quality of life on Earth is inevitably related to the quality of environment. Industrialization has led to the production of pollutants and contaminants especially inorganic contaminants such as mineral acids, metals, and inorganic salts. Numerous innovative and novel techniques have been designed to minimize the hazardous effects of these contaminants, and bioremediation is one of these approaches. In contrast to conventional remediation techniques, the key advantage of bioremediation is its low cost and environmentally friendly operation as compared with other typical approached. Researchers were previously focused on typical bioremediation approaches, but now advanced molecular techniques of bioremediation using multi omics approaches have been introduced to explore and comprehend the functional and structural characteristics of participating biotic factors. Several molecular techniques including 16S rRNA sequences analysis, denaturing gradient gel electrophoresis, ecological diversity, and omics approaches have been established and considered to be potent and vital tool for the degradation, eradication, and detoxification of contaminants from the nature.

Ammonium nitrate (NH4NO3) is a chemical compound that is mostly found as a colorless and/or white to gray crystalline solid, odorless beads, and easily soluble in water. The molecular weight, specific gravity, melting, and boiling point of NH4NO3 are 80.06, 1.725, 169.51 °C, and 210 °C, respectively (Rao, 2014). Higher temperature (>210 °C) easily decomposes NH4NO3 and producing toxic gasses, especially nitrogen oxides, and may also cause an explosion (Han et al., 2015). At room temperature, pure NH4NO3 neither flammable or combustible, but when heated, normally, it is decomposed into non-explosive gases such as oxygen. Nevertheless, it can also be decomposed into explosive material by detonation (Xia et al., 2019). Ammonium nitrate is strongly oxidant that easily detonates under certain circumstances, which include higher temperature (>210 °C), confinement, and impurities (Health Safety Executive, 2004). The authors would like to appreciate the valuable comments from the editors and anonymous reviewers to improve the quality of this study. The authors confirm that no funding was received for his work.

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.

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, Na2SO4 and their combination (NaCl + Na2SO4), 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, Na2SO4 and NaCl + Na2SO4) had negative effects on biochemical, qualitative, growth and yield characteristics of maize plant. Most importantly, NaCl was also found to be more harmful compared to Na2SO4 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.

Nitrogen (N) metabolism is of great economic importance because it provides proteins and nucleic acids which in turn control many cellular activities in plants. Salinity affects different steps of ...

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 ...

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., CO2 (carbon dioxide), CH4 (methane), and N2O (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. CO2 (RR = −0.108) and CH4 (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 N2O (RR = −0.13) and CH4 (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 CO2 compared to N2O and CH4 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 CO2, N2O, and CH4 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.

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. Awais Shakoor would like to express his gratitude for the grant provided by the University of Lleida, Spain. The part of work contributed by Muhammad Aammar Tufail, has received funding from the European Union’s Horizon 2020 Research and Innovation program under the Maria Skłodowska-Curie grant agreement no. 722642 (project INTERFUTURE). The authors would like to appreciate the valuable comments from the editors and anonymous reviewers to improve the quality of this study.

Legume plants are an essential component of sustainable farming systems. Phosphorus (P) deficiency is a significant constraint for legume production, especially in nutrient-poor soils of arid and semi-arid regions. In the present study, we conducted a pot experiment to evaluate the effects of a phosphorus-mobilizing plant-growth promoting rhizobacterial strain Bacillus cereus GS6, either alone or combined with phosphate-enriched compost (PEC) on the symbiotic (nodulation-N2 fixation) performance of soybean (Glycine max (L.) Merr.) on an Aridisol. The PEC was produced by composting food waste with addition of single super phosphate. The bacterial strain B. cereus GS6 showed considerable potential for P solubilization and mobilization by releasing carboxylates in insoluble P (rock phosphate)-enriched medium. Inoculation of B. cereus GS6 in combination with PEC application significantly improved nodulation and nodule N2 fixation efficiency. Compared to the control (without B. cereus GS6 and PEC), the combined application of B. cereus GS6 with PEC resulted in significantly higher accumulation of nitrogen (N), P, and potassium (K) in grain, shoot, and nodule. The N:P and P:K ratios in nodules were significantly altered by the application of PEC and B. cereus GS6, which reflected the important roles of P and K in symbiotic performance of soybean. The combined application of PEC and B. cereus GS6 also significantly increased the soil dehydrogenase and phosphomonoesterase activities, as well as the soil available N, P, and K contents. Significant positive relationships were found between soil organic carbon (C) content, dehydrogenase and phosphomonoesterase activities, and available N, P, and K contents. This study suggests that inoculation of P-mobilizing rhizobacteria, such as B. cereus GS6, in combination with PEC application might enhance legume productivity by improving nodulation and nodule N2 fixation efficiency.

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.

Relations between phosphate and arsenate are important but inconsistent to influence arsenic (As) phytotoxicity depending on many plant and soil factors. Present research aimed to investigate the phosphate and arsenate interactions in sunflower (Helianthus annuus L.) grown in alkaline calcareous soil for 18 weeks under natural environmental conditions at three arsenate [0 (As0), 40 (As40), and 80 (As80) mg As kg−1 soil as sodium arsenate] and three phosphate [0 (P0), 100 (P100), and 200 (P200) mg P2O5 kg−1 soil as diammonium phosphate] levels. The plants were grown in pots according to completely randomized design with five replications. Ionic and physiological parameters were measured at 40 days after treatment completion. Arsenic contamination with As40 and As80 increased root and shoot As concentration with relatively higher concentration in roots, malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) while decreased plant P, chlorophyll, protein, and glutathione (GSH), and consequently plant growth, yield, and yield attributes. Addition of P100 and P200 under As stress reduced As transfer from soil to roots to shoots, MDA concentration, SOD, CAT, and POD activities while increased GSH, leaf protein, chlorophyll, and growth characteristics as well as achene yield compared to As-treated plants without additional P. In conclusion, P-induced inhibition of As transfer from soil to roots to shoots and reduction in MDA concentration accompanied with an increase in the synthesis of protein, chlorophyll, and GSH could be the main mechanisms responsible for lowered As toxicity in sunflower, leading to mitigation of potential risks of As contamination to food chain and human health.

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 x 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.

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 (qCO2), net C mineralization (NCM), net CO2 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, qCO2, NCM and net CO2 efflux. Moreover, residue significantly increased the net CO2 efflux, NCM and qCO2 and, at the same time, decreased net N mineralization. Extractable NH4+-N, NO3−-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 qCO2 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 N2O emission by N immobilization and sorption to biochar.

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 NaHCO3-Pi by 69% in maize, 62% in cowpea and 93% in intercropped plots compared to control plots. Similarly, a significant increase in the NaHCO3-Po 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-Po (12.87 ± 0.50 mg P kg-1 soil) and NaOH-Pi (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-Pi), while the use of NPKEC decreased the HCl-Pi 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 NaHCO3-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.

Use of wastewater is known to provide nutrients for crop plants, but its potential to improve phosphorus (P) availability in semi-arid regions is poorly understood. In this study, seasonal changes in soil P availability as well as associated phyiscochemical and biochemical indicators were investigated from the wastewater irrigated urban soils of Faisalabad, Pakistan. Soil sampling was carried out during summer and winter season from four wastewater irrigated sites of varied stream flow i.e. upstream wastewater (UWW), midstream wastewater (MWW), lowerstream wastewater (LWW) and downstream wastewater (DWW), and canal water irrigation (CWI) as a reference site. Across seasons, MWW site had significantly higher soil organic carbon (SOC), water extractable organic carbon (WEOC), microbial biomass carbon (MBC), microbial biomass phosphorus (MBP) as well as the availability of phosphorus i.e. NaHCO3–P and H2O–P compared to CWI site. In both sampling seasons, MWW site also recorded significantly higher soil enzyme activities compared to the rest of wastewater sites. Moreover, significantly higher total P and electrical conductivity (EC) of soil was noticed at DWW site across both summer and winter seasons. Biplot principle component analysis also indicated seasonally a stronger shift in soil total P and EC at DWW site. On the other hand, availability of P was closely related to soil active carbon pools at MWW site. However, buildup of soil salinity particularly at DWW site along with lower P availability and associated changes in other soil properties, call for careful assessment of wastewater use in these urban soils.

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.

Application of raw and treated wastewater for irrigation is an extensive practice for agricultural production in arid and semiarid regions. Raw textile wastewater has been used for cultivation in urban and peri-urban areas in Pakistan without any systematic consideration to soil quality. We conducted a laboratory incubation study to investigate the effects of low C/N ratio raw textile wastewater on soil nitrogen (N) contents, labile carbon (C) as water-soluble C (WSC) contents, and activities of urease and dehydrogenase enzymes. The 60-day incubation study used an alkaline clay loam aridisol that received 0 (distilled water), 25, 50, and 100% wastewater concentrations, and microcosms were incubated aerobically under room temperature at 70% water holding capacity. Results revealed that raw wastewater significantly (p 50% of the soil total Kjeldahl N (TKN) contents and served as the major N pool. However, nitrification index (NO3 −-N/NH4 +-N ratio) decreased at high wastewater concentrations. A significant negative correlation was observed between EON and WSC (p

Agricultural lands, because of their large area and exhaustive management practices, have a substantial impact on the earth's carbon and nitrogen cycles, and agricultural activities consequence in discharges of greenhouse gases (GHGs). Globally, greenhouse gases (GHGs) emissions especially carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from the agricultural sector are increasing due to anthropogenic activities. Although, the application of animal manure to the agricultural soil as an organic fertilizer not only improves soil health and agricultural production but also has a significant impact on GHGs emissions. But the extent of GHGs emissions in response to manure application under diverse environmental conditions is still uncertain. Here, a meta-analysis study was conducted using field data (48 peer-reviewed publications) published from 1989 to 2019. Meta-analysis results showed that poultry manure considerably increased CO2, CH4, and N2O emissions than pig and cattle manure. Furthermore, application of poultry manure also increased (¯(〖lnRR〗^ ) =0.141, 95% CI =0.526-0.356) GWP (global warming potential) of total soil GHGs emissions. While, the significant effects on CO2, CH4, and N2O emissions also occurred at manure rate > 320 kg N ha-1 and > 60% water filled pore space. The maximum concentrations of CO2, CH4, and N2O emissions were observed in neutral soils (¯(〖lnRR〗^ ) =3.375, 95% CI =3.323-3.428), alkaline soils (¯(〖lnRR〗^ ) =1.468, 95% CI =1.403-1.532), and acidic soils (¯(〖lnRR〗^ ) =2.355, 95% CI =2.390-2.400), respectively. Soil texture, climate zone and crop type were also found significant factors to increase GHGs emissions. Thus, this meta-analysis revealed a knowledge gap concerning the consequences of animal manure application and rate, climate zone, and physicochemical properties of soil on GHGs emissions from agricultural soils. Awais Shakoor would like to express his gratitude for the grant provided by the University of Lleida, Spain. The authors would like to appreciate the valuable comments from the editors and anonymous reviewers to improve the quality of this study.

Salt stress is one of the major abiotic constraints that inflicts impaired growth and reduces production potential in crop plants. Under salt stress conditions, numerous plant growth processes are affected, i.e., hormonal and nutritional imbalance, ion toxicity, physiological disorders, and susceptibility to insect and pest attack. The growing menace of salinity is predicted to intensify both in its extent and severity, posing a stern challenge for developing a resilient food production system in coming years. Various agro-biotechnological interventions are being employed to improve salt stress tolerance in plants. However, the complexity associated with plant salinity tolerance has only allowed marginal progress for breeders and genetic engineers. Use of soil microbial resources to promote plant growth by alleviating the exposed stress factor has gained much needed attention in recent times. The application of plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) based bioinoculant strategy is perceived to enhance plant growth under salt stress. Microbial inoculation evoked plant stress tolerance response and improved plant growth, which is mainly triggered by modulating nutritional and hormonal balance, producing plant growth regulators, solubilizing nutrients, and inducing disease resistance. In this chapter, we describe causes of soil salinization and discuss potential impacts of salinity stress on plants. In addition, we also discussed the action mechanisms of plant growth promotion and/or regulation exhibited by PGPR and AMF, and highlighted their intrinsic traits that can be up scaled to increase their usefulness as a value-added product for stress agriculture.

Cadmium (Cd), one of the most abundant toxic heavy metals, is of great concern as an important environmental pollutant and toxicant. At higher concentrations, this metal interferes with the physiological, biochemical, and molecular processes of living systems and poses serious threats to living systems by entering the food chain through bioaccumulation and biomagnification. In contrast to conventional physicochemical techniques, biological methods, which use bacteria, fungi, and plants, have been proved promising as approaches to heavy metal remediation. The microbial ability to bind heavy metals (including Cd) and plant potential for hyperaccumulating toxic heavy metals provide an economical and viable solution for remediating metal-polluted sites. Coupling the synergistic effects of plants and microbes (bacteria and mycorrhizal fungi) as rhizoremediation and mycorrhizoremediation provides a striking environmentally friendly solution for remediating Cd-polluted sites. Bacteria and mycorrhizal fungi are essential components of sustainable soil–plant systems that play a role in increasing plant growth and nutrient uptake, especially under stress conditions. Therefore, soil management using biofertilizers and potential hyperaccumulator plant species as biotechnological tools has enormous potential for the remediation of large-scale polluted sites. This chapter elucidates the potential of these biotechnological tools for remediating Cd contamination from the environment.

Soil salinization is a widespread problem and a major abiotic constraint affecting the global food production and threatening food security. Plant growth, development and yield are severally reduced under saline conditions. Rice (Oryza sativa L.) is the staple food in many countries which feeds millions of people across the world. However, rice plant, being glycophyte in nature, is sensitive to salinity which results in several adverse morphological, physiological, biochemical, and molecular changes leading to reduction in biomass production and grain yield. Effects of salinity on rice occur at two stages that is, at the initial phase of plant development the osmotic effects rapidly reduce plant growth and the second slow phase of plant response to salinity when symptoms of salinity-induced toxicity appear. At morphological levels, shoot and root growth, above- and below-ground biomass production, number of tillers and spikelets and grain yield of rice are adversely affected. Disruption in photosynthetic activity and pigment production, membrane permeability and integrity, Na+/K+ balance across the membrane and production of reactive oxygen species causing oxidative damage are the major responses of rice at physiological level. In addition to agronomic practices to reduce soil salinity, salt tolerance cultivar of rice have been developed containing traits such as ion exclusion and tolerance of both the osmotic and tissue effects of salinity. The modern biotechnological marker-based genetic engineering approaches have helped the researchers to use a combination of genes to develop salt-tolerant and high yielding rice varieties. The other approaches to reduce salinity stress in plants include the use of salt-tolerant microbial inoculants/biofertilizers, silicon and manganese fertilization and phytohormones.