Liming induces carbon dioxide (CO2) emission in PSB inoculated alkaline soil supplemented with different phosphorus sources

Impacts of long-term chemical nitrogen fertilization on soil quality, crop yield, and greenhouse gas emissions: With insights into post-lime application responses

The improvement in the agricultural production through continuous and heavy nutrient input like nitrogen fertilizer under the upland red soil of south China deteriorates soil quality, and this practice in the future could threaten future food production and cause serious environmental problems in China. This research is initiated with the objectives of evaluating the impacts of long-term chemical nitrogen fertilization on soil quality, crop yield, and greenhouse gas emissions, with insights into post-lime application responses. Compared to sole application of chemical nitrogen fertilization, combined application with lime increased soil indicators (pH by 6.30 %-7.76 %, Ca2+ by 90.06 %-252.77 %, Mg2+ by 184.47 %-358.05 %, available P by 5.05 %-30.04 %, and soil alkali hydrolysable N by 23.49 %-41.55 %. Combined application of chemical nitrogen fertilization with lime (NPCa (0.59), NPKCa (0.61), and NKCa (0.27) significantly improved soil quality index compared to the sole application of chemical nitrogen fertilization (NP (0.31), NPK (0.36), and NK (0.16). Compared to sole application of chemical nitrogen fertilization, combined application with lime increased grain yield by 48.36 %-61.49 %. Structural equation modeling elucidated that combined application of chemical nitrogen fertilization and lime improved wheat grain yield by improving soil quality. Exchangeable Ca2+, exchangeable Mg2+, pH, and exchangeable Al3+ were the most influential factors of wheat grain yield. Overall, the combined application of chemical nitrogen fertilization and lime decreased global warming potential (calculated from N2O and CO2) by 16.92 % emissions compared to the sole application of chemical nitrogen fertilization. Therefore, liming acidic soil in upland red soil of South China is a promising management option for improved soil quality, wheat grain yield, and mitigation of greenhouse gas emissions.

Isolation and characterization of phosphate solubilizing bacteria naturally colonizing legumes rhizosphere in Morocco

Low-cost and environmentally friendly agricultural practices have received increasing attention in recent years. Developing microbial inoculants containing phosphate (P) solubilizing bacteria (PSB) represents an emerging biological solution to improve rhizosphere P availability. The present study aims to explore PSB strains isolated from soils located at different bioclimatic stages in Morocco and present in various legumes rhizosphere to improve agronomic microbial fertilizer’s effectiveness. It was also aimed to test the isolated strains for their ability to solubilize P in NBRIP medium with Tricalcium P (Ca₃ (PO₄)₂) (TCP), rock phosphate (RP), and their combination as a source of phosphorus, by (2²) experiment design. Bacterial strains with a high P solubility index (PSI) were selected, characterized, and compared to commercial control. The vanadate-molybdate method was used to estimate P solubilization activity. Stress tolerance to salinity, acidity, drought, and temperature was tested. From all isolated strains (64), 12 were screened as promising biotechnological interest because of their P solubilization and their good resistance to different drastic conditions. Besides, the strain WJEF15 showed the most P solubility efficiency in NBRIP solid medium with a PSI of 4.1; while the WJEF61 strain was located as the most efficient strain in NBRIP-TCP liquid medium by releasing 147.62 mg.l^–1 of soluble P. In contrast, in the NBRIP-RP medium, the strain WJEF15 presented maximum solubilization with 25.16 mg.l^–1. The experiment design showed that a combination of RP and TCP with max level progressively increases P solubilization by 20.58%, while the WJEF63 strain has the most efficient concentration of 102.69 mg.l^–1. Indeed, among the selected strains, four strains were able to limit tested fungi growth. Thus, results reveal a potential effect of selecting PSBs to support cropping cultures as plant growth-promoting rhizobacteria (PGPR).

Advances in Biochar and PGPR engineering system for hydrocarbon degradation: A promising strategy for environmental remediation

In soil, polycyclic aromatic hydrocarbons (PAHs) have resulted in severe environmental deterioration, compromised soil characteristics, and negatively affect all life forms, including humans. Developing appropriate and effective clean-up technology is crucial in solving the contamination issues. The traditional methods to treat PHAs contaminated soil are less effective and not ecofriendly. Bioremediation, based on bioaugmentation and biostimulation approaches, is a promising strategy for remediating contaminated soil. The use of plant growth-promoting rhizobacteria (PGPR) as a bioaugmentation tool is an effective technique for treating hydrocarbon contaminated soil. Plant growth-promoting rhizobacteria (PGPR) are group of rhizospheric bacteria that colonize the roots of plants. Biochar is a carbon-rich residue, which acts as a source of nutrients, and is also a bio-stimulating candidate to enhance the activities of oil-degrading bacteria. The application of biochar as a nutrient source to bioremediate oil-contaminated soil is a promising approach for reducing PHA contamination. Biochar induces polyaromatic hydrocarbons (PAHs) immobilization and removes the contaminants by various methods such as ion exchange electrostatic attractions and volatilization. In comparison, PGPR produce multiple types of biosurfactants to enhance the adsorption of hydrocarbons and mineralize the hydrocarbons with the conversion to less toxic substances. During the last few decades, the use of PGPR and biochar in the bioremediation of hydrocarbons-contaminated soil has gained greater importance. Therefore, developing and applying a PGPR-biochar-based remediating system can help manage hazardous PAH contaminated soil. The goal of this review paper is to (i) provide an overview of the PGPR mechanism for degradation of hydrocarbons and (ii) discuss the contaminants absorbent by biochar and its characteristics (iii) critically discuss the combined effect of PGPR and biochar for degradation of hydrocarbons by decreasing their mobility and bioavailability. The present review focuses on techniques of bioaugmentation and biostimulation based on use of PGPR and biochar in remediating the oil-contaminated soil.

Comparative efficacy of phosphorous supplements with phosphate solubilizing bacteria for optimizing wheat yield in calcareous soils

Phosphorus (P) deficiency is the main hurdle in achieving sustainable crop production ps especially in calcareous soils. Using bio-fertilizers like phosphate solubilizing bacteria (PSB) could be a useful approach for sustainable P management as they improve P availability in soil via dissolution, desorption and mineralization reactions. In addition, application of organic amendments with PSB could further ameliorate soil conditions for sustainable management of immobilized nutrients in calcarious soils. Therefore, we performed pot experiment to study the role of PSB in nullifying antagonistic effects of liming (4.78, 10, 15 and 20%) on P availability from poultry manure (PM), farm yard manure (FYM), single super phosphate (SSP) and rock phosphate (RP) in alkaline soils. PSB inoculation improved wheat growth, P availability and stimulated soil acidification over control regardless of P sources and lime levels. Soil calcification adversely affected plant growth, P nutrition, induced soil salinity and alkalinity, however, PSB and manures application potentially nullified such harmful effects over mentioned traits. Individually, organic sources were superior than mineral sources however, the performance of mineral fertilizers with PSB was at par to sole application of manures. Furthermore, application of RP with PSB proved as effective as sole SSP. Therefore, using PSB as bio-fertilizer has huge potential for improving P availability in calcareous soils.

On-farm hydro and nutri-priming increases yield of rainfed pearl millet through physio-biochemical adjustments and anti-oxidative defense mechanism

Seed priming technique has a marvelous potential in enhancing seed germination and crop establishment under limited soil moisture conditions, which ultimately increases yield. Therefore, we investigated the effects of seed priming on physiology, growth, yield and antioxidant defense system of pearl millet (Pennisetum glaucum L.) under rain-fed condition. The experiments were conducted under laboratory as well as field conditions comprising three treatments i.e., non-primed seeds (control, T₀), priming with tap water (hydropriming) (T₁) and priming with 2% KNO₃ 2% for 6 hours at 25°C followed by shade drying (T₂). The results showed that chlorophyll content (10.37–14.15%) and relative water content (RWC) (12.70–13.01%) increased whereas proline (-19.44 to -25%) and soluble sugar (-15.51 to -29.13%) contents decreased on account of seed priming in pearl millet under field conditions. The seed priming significantly improved the plant height, final plant stand and grain weight which resulted in increased yield. Enhanced activities of superoxide dismutase (SOD) (5.89 to 8.10 unit/g/seed/min), catalase (CAT) (22.54 to 39.67 µmol/min/g/seed) and ascorbate peroxidase (APX) (8.92 to 22.10 µmol/cm/min/g) and concomitant decrease in H₂O₂ and malondialdehyde (MDA) content suggests their role in imparting oxidative tolerance at initial stages of growth in primed seed. The lab studies suggest that the improved yield might be attributes to increased seed germination and seedling vigor. It is recommended that the hydropriming (tap water) or KNO₃ (2%) priming of seeds for 6 hours under ambient conditions is effective to enhance growth and yield of pearl millet under rainfed conditions.

Gibberellic acid and urease inhibitor optimize nitrogen uptake and yield of maize at varying nitrogen levels under changing climate

Worldwide, nitrogen (N) deficiency is the main yield limiting factor owing to its losses via leaching and volatilization. Urease inhibitors slow down urea hydrolysis in soil by inhibiting urease enzyme activities whereas gibberellic acid is growth regulator. That is why, we evaluated the role of urease inhibitor [N-(n-butyl)thiophosphorictriamide (NBPT)] and gibberellic acid (GA₃) in improving nitrogen uptake and yield of maize under different N levels (120 and 150 kg ha^-1) along with control. Both N levels alone and in combination with GA₃ and NBPT significantly increased yield and yield components of maize over control. In addition, 150 kg N ha^-1 + NBPT + GA₃ produced highest biological, grain, and stover yields, 1000 grain weight, plant height, and N uptake exhibiting 33.15%, 56.46%, 27.56%, 19.56%, 23.24%, and 78% increase over 150 kg N ha^-1, respectively. The sole use of gibberellic acid or NBPT with each level of N also improved the yield and yield components of maize compared to sole N application and control. Furthermore, application of 120 kg N ha^-1 along with NBPT and GA₃ performed at par to 150 kg N ha^-1 + NBPT + GA₃ but it was superior than sole applied 150 kg N ha^-1 for all the studied traits. These results imply that application of GA₃ and/or NBPT can reduce dependence on urea and improve the yield and N uptake in maize by slowing urea hydrolysis in calcareous soils and shall be practiced.

Soil organic carbon and labile and recalcitrant carbon fractions attributed by contrasting tillage and cropping systems in old and recent alluvial soils of subtropical eastern India

Conservation agriculture-based sustainable intensification (CASI) technologies comprising zero-tillage with crop residue retention (>30%) on the soil surface, diversified cropping systems, and balanced nutrient management are recognized as operative and efficacious strategies to ensure food security in the parts of South Asia. The present investigation was a component of CASI technologies undertaken in the farmers’ field of Malda (old alluvial Inceptisol) Coochbehar (recent alluvial Entisol) district, West Bengal (subtropical eastern India). This study was conducted to evaluate the short-term impact of contrasting tillage (zero and conventional) and cropping systems (rice–wheat and rice–maize) on total organic carbon (TOC) and its fractions, viz., labile pool-1 (LP1), labile pool-2 (LP2) and recalcitrant carbon (RC) fractions after 4-year trial of conservation agriculture (CA) in the old and recent alluvial soils. Soil samples were collected from three depths (0–5, 5–10, and 10–20 cm), and thus, our study was focused on two factors, viz., cropping system and tillage. Results pointed that TOC along with LP1, LP2, and RC fractions under rice–maize (RM) cropping system were significantly (p<0.05) greater (15–35%) over rice–wheat (RW) system as a result of higher residue biomass addition. Zero-tillage (ZT) improved the C fractions by 10–20% over conventional tillage (CT) in all aspects. TOC and its fractions were observed to be greater under the ZT system in the topmost soil depths (0–5 and 5–10 cm), but the same system failed to improve these at 10–20 cm. Interestingly, the CT increased all the fractions at 10–20 cm depth due to the incorporation of crop residues. The concentration of TOC along with its fractions decreased with increasing soil depth was evident. Comparatively, all the C fractions, including TOC were maximum in soils from Malda sites as compared to Coochbehar sites because of a higher amount of residue biomass application, higher clay content, and greater background content of C in these soils. All the studied C fractions showed a significant correlation (r = >0.635; p<0.01) with TOC among all the soil depths in both the districts but the relationship with soil texture showed some interesting results. TOC fractions were significantly correlated (p<0.01) with clay particles indicating that its higher stabilization with clay in old alluvial Inceptisol (Malda); while in recent alluvial Entisol (Coochbehar), sand particle showed its strong relation with TOC fractions. Higher stratification ratio (SR) in the ZT system suggested that the concentration of TOC and its fractions are confined to the upper soil layers whereas in the case of CT, by and large, the distribution of these was comparatively high in subsequent soil depths due to residue incorporation effect. The concentration of C fractions in soils followed the order: TOC > RC > LP2 > LP1. The present investigation concluded that ZT under the RM system increases the turnover rates of C in both soil types but the amount of clay influences the stabilization/storage of C.

Comparing the phosphorus use efficiency of pre-treated (organically) rock phosphate with soluble P fertilizers in maize under calcareous soils

In calcareous soils, phosphorus (P) availability to plant is impaired due to the formation of insoluble complexes with calcium and magnesium. Therefore, this study was executed to compare the P use efficiency (PUE) of four different P sources [rock phosphate (RP), acidulated rock phosphate (ARP), single super phosphate (SSP) and di ammonium phosphate (DAP)] alone or pre-treated with organic amendments (farm yard manure (FYM) enriched compost, simple compost and humic acid (HA)) along with control in maize crop under calcareous soils. All treatments irrespective of P sources received 90 kg P₂O₅ ha^-1. Phosphorus application regardless of its sources and combination with organic amendments significantly improved maize growth, yield as well as P uptake and PUE. Rock phosphate when applied alone was recorded inferior but its performance significantly improved with compost or its pre-addition with FYM and HA, that further enhanced upon acidulation. Maize grain yield increased by 21, 22.2, 67.9 and 94% with RP, ARP, ARP enriched compost and ARP+ compost respectively, over control. Similarly, PUE of DAP improved from 31.7 to 43.1 and 39 with sample and enriched compost correspondingly. Post-harvest soil and grain P were at par for SSP, ARP and DAP alone or in conjugation with organic amendments when averaged across the amendments. These results suggested that pretreatment of P sources with organic amendments is an economical and more feasible approach to improve maize yield and PUE. Moreover, on-farm acidulation of RP may give at par results with SSP and DAP with cheaper rate and hence recommended for P management in maize in alkaline calcareous soils.

Analysis of Sources and Trends in Agricultural GHG Emissions from Annex I Countries

The vast majority of the scientific community believe that anthropogenic greenhouse gas (GHG) emissions are the predominant cause of climate change. One of the GHG emission sources is agriculture. Following the International Panel on Climate Change (IPCC) guidelines regarding GHG emission calculation, agriculture is responsible for around 10% of the overall global emissions. Agricultural GHG emissions consist of several emission source categories and several GHGs. In this article were described the results of multivariate statistical analyses performed on data gathered during the period 1990–2017 from the inventories of 43 Annex I countries (parties to the United Nations Framework Convention on Climate Change, UNFCCC, listed in Annex I of the Convention). Trends in the agricultural GHG emissions were analyzed. Generally, the global agricultural GHG emissions are increasing, while the emissions from Annex I countries are decreasing. Apart from the application of urea, emissions from all other sources, such as enteric fermentation, manure management, rice cultivation, agricultural soils, field burning of agricultural residues, and liming are decreasing. Based on multivariate analysis, the most different countries, in terms of GHG emission sources composition in agriculture and emission trends, are Australia, Japan, New Zealand and USA. The rest of the Annex I countries are mostly from Europe and their shares and trends are similar, with slight differences between countries depending, among others, on the date of joining the European Union.

Can information and communication technology reduce CO2 emission? A quantile regression analysis

By employing China's provincial panel data covering period 2001-2016, the present study empirically investigates the impact of ICT on CO₂ emission intensity. Specifically, this paper utilizes Internet penetration and mobile phone penetration as proxies to measure ICT respectively and employs quantile regression method to estimate the benchmark model at five quantiles (0.1, 0.25, 0.5, 0.75, and 0.9). It is demonstrated that Internet penetration at the national level has a significant negative effect on the CO₂ emission intensity for all quantiles. In addition, Internet penetration has a significant negative effect on CO₂ emission intensity at all quantiles except for 0.1 quantile for China's eastern provinces and has a significant negative effect on CO₂ emission intensity at all quantiles for China's central provinces, whereas Internet penetration has no significant negative impact on CO₂ emission intensity at all quantiles for China's western provinces. By comparison, the reduction effect of Internet penetration on CO₂ emission intensity in China's eastern and central provinces is more obvious and in contrast with the reduction effect of Internet penetration on CO₂ emission intensity in China's eastern provinces, it is greater in China's central provinces. Finally, the impact of mobile phone penetration on CO₂ emission intensity is generally consistent with the impact of Internet penetration. This study provides further evidence that developing countries can simultaneously achieve economic development and reduce carbon emissions through ICT.