Biochar and fulvic acid amendments mitigate negative effects of coastal saline soil and improve crop yields in a three year field trial

Genome-wide identification of the AP2/ERF gene family from Limonium bicolor and functional characterization of LbAP2/ERF32 under salt stress

AP2/ERF transcription factors (TFs) play important roles in plant growth and development, plant morphogenesis and response to environmental stresses. However, their biological roles in recretohalophytes are still not fully revealed. Limonium bicolor L. is a typical recretohalophyte, which secretes excessive salt ions through the salt glands on the epidermis. Here, 64 LbAP2/ERF genes were identified in L. bicolor genome, which were unevenly distributed on the eight chromosomes. Cis-elements related to growth and development, stress response and phytohormone response are distributed in multiple LbAP2/ERF promoters. Expression analysis indicated that LbAP2/ERF genes responsed to NaCl, PEG and ABA. And the salt gland density, salt secretion of leaves and overall salt tolerance of LbAP2/ERF32 silenced lines were significantly reduced. In agreement, the genes related to salt gland development and ion transport were significantly changed in LbAP2/ERF32-silenced lines. Our findings provided fundamental information on the structure and evolutionary relationship of LbAP2/ERF gene family in salt gland development and salt secretion of L. bicolor and gave theoretical guideline for further functional study of LbAP2/ERF genes in response to abiotic stress.

Putting Biochar in Action: A Black Gold for Efficient Mitigation of Salinity Stress in Plants. Review and Future Directions

Soil salinization is a serious concern across the globe that is negatively affecting crop productivity. Recently, biochar received attention for mitigating the adverse impacts of salinity. Salinity stress induces osmotic, ionic, and oxidative damages that disturb physiological and biochemical functioning and nutrient and water uptake, leading to a reduction in plant growth and development. Biochar maintains the plant function by increasing nutrient and water uptake and reducing electrolyte leakage and lipid peroxidation. Biochar also protects the photosynthetic apparatus and improves antioxidant activity, gene expression, and synthesis of protein osmolytes and hormones that counter the toxic effect of salinity. Additionally, biochar also improves soil organic matter, microbial and enzymatic activities, and nutrient and water uptake and reduces the accumulation of toxic ions (Na+ and Cl), mitigating the toxic effects of salinity on plants. Thus, it is interesting to understand the role of biochar against salinity, and in the present Review we have discussed the various mechanisms through which biochar can mitigate the adverse impacts of salinity. We have also identified the various research gaps that must be addressed in future study programs. Thus, we believe that this work will provide new suggestions on the use of biochar to mitigate salinity stress.

Biochar derived from rice husk: Impact on soil enzyme and microbial dynamics, lettuce growth, and toxicity

This study was set to investigate the effects of rice husk biochar (RHB) on soil characteristics and growth of lettuce (Lactuca sativa). A comprehensive research approach was employed to examine the effect of different RHB concentrations (i.e., 0-1.5%) on soil pH, soil enzyme activities (i.e., alkaline phosphatase, beta-glucosidase, and dehydrogenase), soil microbial community, lettuce growth, and earthworm toxicity. The results showed that, within the studied RHB concentration range, the RHB application did not have significant effects on the soil pH. However, the enzyme activities were increased with increasing RHB concentration after the 28 d-lettuce growth period. The RHB application also increased the abundances of the bacterial genera Massilia and Bacillus and fungal genus Trichocladium having the plant growth promoting abilities. Furthermore, the study revealed that the root weight and number of lettuce leaves were significantly increased in the presence of the RHB, and the growth was dependent on the RHB concentration. The improved lettuce growth can be explained by the changes in the enzyme and microbial dynamics, which have resulted from the increased nutrient availability with the RHB application. Additionally, the earthworm toxicity test indicated that the tested RHB concentrations can be safely applied to soil without any significant ecotoxicity. In conclusion, this study underscores the potential of RHB as a soil amendment with positive effects on crop growth, highlighting the utilization of agricultural byproducts to enhance soil biological quality and plant growth through biochar application.

Organic Amendments promote saline-alkali soil desalinization and enhance maize growth

Secondary soil salinization in arid and semi-arid regions is a serious problem that severely hampers local agricultural productivity and poses a threat to the long-term sustainability of food production. the utilization of organic soil amendments presents a promising approach to mitigate yield losses and promote sustainable agricultural production in saline-alkali soil. In this study, we established four distinct treatments, chemical fertilizer (CK), humic acid with chemical fertilizer (HA), carboxymethyl cellulose with chemical fertilizer (CMC), and amino acid with chemical fertilizer (AA), to elucidate their respective impacts on the reclamation of saline soil and the growth of maize. The findings of our study reveal notable variations in desalination rates within the 0-40 cm soil layer due to the application of distinct soil amendments, ranging from 11.66% to 37.17%. Moreover, application of amendments significantly increased the percentage of soil macro-aggregates as compared to the CK treatment. Furthermore, HA and AA treatments significantly augmented soil nutrient content (HA: 48.07%; AA: 39.50%), net photosynthetic rate (HA: 12.68%; AA: 13.94%), intercellular CO2 concentration (HA: 57.20%; AA: 35.93%) and maize yield (HA:18.32%; AA:16.81%). Correlation analysis and structural equation modeling unveiled diverse mechanisms of yield enhancement for HA, CMC, and AA treatments. HA enhanced yield by increasing organic matter and promoting soil aggregate formation, CMC improved soil water content and facilitated salt leaching due to its excellent water-holding properties, while AA increased yield by elevating soil organic matter and effective nitrogen content. Among the array of soil amendment materials scrutinized, HA treatment emerged as the most promising agent for enhancing soil conditions and is thus recommended as the preferred choice for treating local saline soils.

Biomass composite with exogenous organic acid addition supports the growth of sweet sorghum (Sorghum bicolor 'Dochna') by reducing salinity and increasing nutrient levels in coastal saline-alkaline soil

INTRODUCTION

In coastal saline lands, organic matter is scarce and saline stress is high. Exploring the promotion effect of intervention with organic acid from biological materials on soil improvement and thus forage output and determining the related mechanism are beneficial to the potential cultivation and resourceful, high-value utilization of coastal mudflats as back-up arable land.

METHOD

Three exogenous organic acids [humic acid (H), fulvic acid (F), and citric acid (C)] were combined with four kinds of biomass materials [cottonseed hull (CH), cow manure (CM), grass charcoal (GC), and pine needle (PN)] and applied to about 0.3% of medium-salt mudflat soil. The salinity and nutrient dynamics of the soil and the growth and physiological differences of sweet sorghum at the seedling, elongation, and heading stages were observed under different treatments to screen for efficient combinations and analyze the intrinsic causes and influencing mechanisms.

RESULTS

The soil salinity, nutrient dynamics, and forage grass biological yield during sweet sorghum cultivation in saline soils differed significantly (p < 0.05) depending on the type of organic acid-biomass composite applied. Citric acid-pine needle composite substantially reduced the soil salinity and increased the soil nutrient content at the seedling stage and improved the root vigor and photosynthesis of sweet sorghum by increasing its stress tolerance, allowing plant morphological restructuring for a high biological yield. The improvement effect of fulvic acid-pine needle or fulvic acid-cow manure composite was manifested at the elongation and heading stages.

DISCUSSION

Citric acid-pine needle composite promoted the growth of saline sweet sorghum seedlings, and the effect of fulvic acid-pine needle composite lasted until the middle and late stages.

Biochar improves soil quality and wheat yield in saline-alkali soils beyond organic fertilizer in a 3-year field trial

The objective of this study was to examine the effects of biochar compared to organic fertilizer on soil quality and wheat yield in the saline-alkaline lands. A 3-year field trial was conducted on moderately saline-alkaline land in the Yellow River Delta region (YRD) with six treatments: biochar (B1: 5 t, B2: 10 t, B3: 20 t ha^-1 year^-1) and organic fertilizer (OF1: 5 t, OF2: 7.5 t ha^-1 year^-1) as well as control (CK). The results showed that both biochar and organic fertilizer increased total organic carbon (TOC), total nitrogen (TN), NH₄⁺-N, and NO₃^--N, and reduced pH, thereby increasing soil microbial biomass carbon (MBC) and nitrogen (MBN), MBC/TOC ratio, and MBN/TN ratio, but organic fertilizer increased soil nutrients and microbial biomass better than biochar. Correlation analysis revealed that soil water content (SWC), soil salt content (SSC), and Na⁺ were the most important factors influencing wheat yield. When compared to CK, the SSC and Na⁺ decreased by 5.55-7.52% and 3.86-9.39%, respectively, and SWC increased by 5.14-5.62% in the biochar treatment, while they increased by 1.07-10.19%, 1.08-7.58%, and 2.96-3.84% in the organic fertilizer treatment, respectively. Accordingly, wheat yield of biochar treatment was 0.90-14.71% higher than that of organic fertilizer treatment (4.49-4.80 t ha^-1) and CK (4.47 t ha^-1). Collectively, B2 had the lowest SSC and Na⁺ and the highest yield and was significantly better than the organic fertilizer treatment, as well as efficiently increasing soil nutrients and microbial biomass, suggesting that it may be a better agricultural practice for improving soil quality and increasing wheat yield in the YRD.

Understanding the salinity stress on plant and developing sustainable management strategies mediated salt-tolerant plant growth-promoting rhizobacteria and CRISPR/Cas9

Soil salinity is a worldwide concern that decreases plant growth performance in agricultural fields and contributes to food scarcity. Salt stressors have adverse impacts on the plant's ionic, osmotic, and oxidative balance, as well as numerous physiological functions. Plants have a variety of coping strategies to deal with salt stress, including osmosensing, osmoregulation, ion-homeostasis, increased antioxidant synthesis, and so on. Not only does salt stress cause oxidative stress but also many types of stress do as well, thus plants have an effective antioxidant system to battle the negative effects of excessive reactive oxygen species produced as a result of stress. Rising salinity in the agricultural field affects crop productivity and plant development considerably; nevertheless, plants have a well-known copying mechanism that shields them from salt stress by facilitated production of secondary metabolites, antioxidants, ionhomeostasis, ABAbiosynthesis, and so on. To address this problem, various environment-friendly solutions such as salt-tolerant plant growth-promoting rhizobacteria, eco-friendly additives, and foliar applications of osmoprotectants/antioxidants are urgently needed. CRISPR/Cas9, a new genetic scissor, has recently been discovered to be an efficient approach for reducing salt stress in plants growing in saline soil. Understanding the processes underlying these physiological and biochemical responses to salt stress might lead to more effective crop yield control measures in the future. In order to address this information, the current review discusses recent advances in plant stress mechanisms against salinity stress-mediated antioxidant systems, as well as the development of appropriate long-term strategies for plant growth mediated by CRISPR/Cas9 techniques under salinity stress.

Remediation of organic amendments on soil salinization: Focusing on the relationship between soil salts and microbial communities

Soil salinization has emerged as a major factor with an adverse influence on agricultural green development worldwide. It is necessary to develop high-efficiency and ecologically beneficial management measures for alleviating soil salinization. The experiment of application for cow manure (CM), biochar (BC), and bio-organic fertilizer (BIO) in soil with light salinity was conducted to investigate the remediation of organic materials on soil salinization with melon (Cucumis melo L.) by reducing the availability of saline ions and shifting the soil microbial community. Results showed that BC treatment significantly decreased the EC values of the soil and soil solution by 19.23% and 27.02% and the concentrations of Na⁺, K⁺, and Cl^- by 13.28%, 13.08%, and 15.21%, respectively, followed by CM and BIO treatments. High-throughput sequencing identified that organic amendments significantly improved the richness of the soil bacterial community and increased the relative abundances of Acidobacteria and Firmicutes by 33.11% and 111.2%, respectively, and the beneficial salt-tolerant bacterial genera Flavobacterium, Bacillus and Arthrobacter by 32.04%, 38.92% and 35.67%, respectively. Additionally, soil Na⁺, Ca²⁺, K⁺ and Cl^- were significantly negatively correlated with Acidobacteria and Flavobacterium and were also the most important factors driving the changes in the structure of the soil bacterial communities. The bacterial networks were more complex in the organic amendments treatments than in CK, reflecting through more nodes and links and a higher average clustering coefficient, density and modularity. This study provided a comprehensive understanding of the application of organic amendments in alleviating soil salinization and improving soil bacterial and fungal communities and provides scientific support for agriculture green development.

Long-Term Amelioration Practices Reshape the Soil Microbiome in a Coastal Saline Soil and Alter the Richness and Vertical Distribution Differently Among Bacterial, Archaeal, and Fungal Communities

Globally soil salinity is one of the most devastating environmental stresses affecting agricultural systems and causes huge economic losses each year. High soil salinity causes osmotic stress, nutritional imbalance and ion toxicity to plants and severely affects crop productivity in farming systems. Freezing saline water irrigation and plastic mulching techniques were successfully developed in our previous study to desalinize costal saline soil. Understanding how microbial communities respond during saline soil amelioration is crucial, given the key roles soil microbes play in ecosystem succession. In the present study, the community composition, diversity, assembly and potential ecological functions of archaea, bacteria and fungi in coastal saline soil under amelioration practices of freezing saline water irrigation, plastic mulching and the combination of freezing saline water irrigation and plastic mulching were assessed through high-throughput sequencing. These amelioration practices decreased archaeal and increased bacterial richness while leaving fungal richness little changed in the surface soil. Functional prediction revealed that the amelioration practices, especially winter irrigation with saline water and film mulched in spring, promoted a community harboring heterotrophic features. β-null deviation analysis illustrated that amelioration practices weakened the deterministic processes in structuring coastal saline soil microbial communities. These results advanced our understanding of the responses of the soil microbiome to amelioration practices and provided useful information for developing microbe-based remediation approaches in coastal saline soils.

Evaluation of coastal farming under salinization and optimized fertilization strategies in China

Nitrogen (N) application and salinity are key factors influencing crop yield and net economic benefit in coastal saline-alkali soils. Integrated analysis and optimization of the benefits of wheat-corn cropping under different nitrogen applications in saline soils could provide lay the scientific basis for sustainable development of agriculture in coastal farmlands. A total of 571 pair-reviewed literature data on two-factor cross-over trials, involving soil salinity and nitrogen application, were integratively analyzed. Based on multi-objective optimization of crop yield, agronomic and net economic benefits, and soil nitrate residue in coastal saline-alkali soils, area-specific nitrogen application strategies were developed. The results showed that increasing the N application rate under 1.8-2.9‰ salinity can increase crop yield and economic benefits. The net economic benefit of crops was negative under 3.5‰ salinity. Above that threshold of 3.5‰, it is not suitable for planting food crops. Consequently, it is necessary to strengthen the management of saline-alkali soils. While the application rate of 2.78 × 10⁸ kg N in winter wheat/summer corn cropping ensured environmental protection, farmers preferred 3.08 × 10⁸ kg of nitrogen dose. These were respectively 40.4% and 33.9% lower than the traditional dose and with relatively higher benefits too.

Treatment of the saline-alkali soil with acidic corn stalk biochar and its effect on the sorghum yield in western Songnen Plain

Due to biochar could improve the physical and chemical properties of soil and promote crop growth, it is widely used in soil remediation, especially in saline soil. However, it is rarely studied of the application of acidic biochar in saline-alkali land. A field experiment with acidic corn stalk biochar (ACSBC) as a soil amendment was carried out in the western Songnen Plain of China. ACSBC (0, 0.15, 0.3, 0.45, 0.6, 0.75, 1, 6 and 15 t ha^-1) was added to the topsoil to evaluate the combined effects on soil and sorghum yield. During the seeding and harvest period, the content of soil water, nutrient elements, cation exchange capacity (CEC), organic matter (OM), soluble cations (K⁺, Ca²⁺, Mg²⁺) increased, Na⁺ content showed opposite trend. However, soil pH decreased averagely with 0.3 and 1.0 during the seeding and harvest period respectively, salinity decreased with 19.37% and 18.14%, exchange sodium percentage (ESP) decreased with 37.08% and 37.04%. The sorghum yield increased 32.98% averagely, significantly by 51.37% and 47.33% with the 0.6 and 1 t ha^-1 of ACSBC treatments respectively. These experimental results show that proper application of ACSBC in saline-alkali soil can effectively improve soil properties and increase sorghum yield.

Soils and Beyond: Optimizing Sustainability Opportunities for Biochar

Biochar is most commonly considered for its use as a soil amendment, where it has gained attention for its potential to improve agricultural production and soil health. Twenty years of near exponential growth in investigation has demonstrated that biochar does not consistently deliver these benefits, due to variables in biochar, soil, climate, and cropping systems. While biochar can provide agronomic improvements in marginal soils, it is less likely to do so in temperate climates and fertile soils. Here, biochar and its coproducts may be better utilized for contaminant remediation or the substitution of nonrenewable or mining-intensive materials. The carbon sequestration function of biochar, via conversion of biomass to stable forms of carbon, does not depend on its incorporation into soil. To aid in the sustainable production and use of biochar, we offer two conceptual decision trees, and ask: What do we currently know about biochar? What are the critical gaps in knowledge? How should the scientific community move forward? Thoughtful answers to these questions can push biochar research towards more critical, mechanistic investigations, and guide the public in the smart, efficient use of biochar which extracts maximized benefits for variable uses, and optimizes its potential to enhance agricultural and environmental sustainability.