Gunasekaran Yazhini

Heavy-metal contamination and uncertainty regarding the long-term stability of soil carbon represent interconnected challenges for sustainable soil management. Although carbon sequestration and heavy-metal remediation have been widely investigated, their functions are generally considered separately, highlighting the need for integrated approaches. This review examines biogenic mineralization as a potential pathway for coupling mineral carbon stabilization with heavy-metal immobilization in contaminated soils, with particular emphasis on microbially induced carbonate precipitation (MICP). The review synthesizes the microbial and geochemical mechanisms governing carbonate formation through ureolysis, carbonic anhydrase activity, the oxalate–carbonate pathway, denitrification, and sulfate reduction and evaluates the interactions of resulting carbonate minerals with heavy metals through adsorption, co-precipitation, surface complexation, and lattice incorporation. Particular attention is given to carbonate mineral stability, metal-specific behaviour, life-cycle carbon requirements, non-target soil and plant effects, and evidence from laboratory, mesocosm, and field-scale studies. The synthesis indicates that biogenic carbonate formation offers a conceptual framework for linking mineral carbon stabilization with heavy-metal immobilization; the two functions are supported by largely separate bodies of evidence that have not yet been jointly demonstrated in the same system, and the magnitude and persistence of either benefit depend on microbial pathway, soil properties, contaminant chemistry, mineral phase, and environmental conditions. Ureolysis-driven MICP remains the most extensively investigated pathway; however, its remediation efficiency does not necessarily indicate a net climate benefit because reagent production, microbial cultivation, ammonium management, and carbonate dissolution can substantially affect the overall carbon balance. Furthermore, carbonate precipitation may immobilize cationic metals while potentially increasing the mobility of oxyanionic contaminants such as As and Cr under alkaline conditions. Overall, biogenic mineralization represents a promising but context-dependent strategy. Full life-cycle carbon accounting, mechanism-specific validation, assessment of non-target effects and remobilization, and long-term field trials are needed to establish its durability and practical environmental benefits.

Brinjal (Solanum melongena) is one of the most tropical vegetable crops cultivated worldwide. Rhizosphere microbial dynamics play a crucial role in plant nutrition, providing valuable insights into soil fertility and sustainable agricultural practices. This study aims to identify sustainable nutrient management practices for brinjal, focusing on the rhizosphere microbiome by examining various nutrient management approaches, including integrated nutrient management (INM), inorganic fertilization, and organic fertilization. Root architectural analysis, LC-MS-based metabolite profiling, and shotgun metagenomics were employed to assess the various nutrient management-induced changes in metabolites and the microbial community. The result suggested that superior root features, including volume (16.3 cm³), surface area (399.48 cm²), and total root length (794.89 cm), were achieved under INM. Additionally, it encompassed the highest number and diversity of root metabolites, including both primary and secondary compounds. This can be the reason for INM maintaining a balance between the representation of bacteria (87.4%) and fungi (12.4%), with Actinomycota and Ascomycota being the dominant groups. Further diversity analyses revealed that INM soils supported the highest microbial richness and OTU abundance, while inorganic fertilization favored greater evenness of taxa but lower richness. Organic soils harbored unique, less abundant taxa, reflected in higher Fisher’s alpha values. The beta diversity analysis indicated distinct microbial community structures across different treatments. Therefore, INM is a sustainable solution for brinjal cultivation, since it improves crop performance, soil health, and microbial ecosystem services.

Climate change leads to an increase in the frequency and severity of droughts, which have a negative impact on agriculture by altering plant growth and lowering water availability, placing food production systems at risk of sustainability. In order to improve drought resistance and ensure food security in the face of growing water shortages, this research was conducted to determine the physiological and enzymatic responses of tomato plants to drought stress. This study was conducted at Tamil Nadu Agricultural University, Coimbatore, involving 3 hybrids, viz., H1: EC169966 × LE118, H2: EC177824 × LE118 and H3: Arka Ashish × LE 27, along with their parents, P1: EC177824, P2: LE27, P3: EC169966, P4: LE118 and P5: Arka Ashish, under 50 % and 100 % field capacity conditions in factorial completely randomized design (FCRD) with 3 replications. Results indicated a significant change in physiological and enzymactic activities. Here, the parent P2 and hybrid H2 showed superior tolerance, with higher relative water content, proline, leaf water potential, membrane and chlorophyll stability index. Added to that, the response of enzyme activities including peroxidase, nitrate reductase, catalase, polyphenol oxidase and superoxide dismutase was found to be increase notably in drought-tolerant hybrids and parents, which correlated strongly with physiological markers of drought resistance. These modifications highlight the capacity of some genotypes to preserve photosynthetic efficiency and cellular integrity in water-limited environments. The results highlight the significance of choosing and developing drought-tolerant cultivars in order to maintain agricultural production in areas vulnerable to drought and address issues related to global food security.

As the world grapples with the escalating threat of global warming, exploring sustainable agricultural practices has become imperative. Carbon sequestration is one such efficient method to mitigate carbon emissions and reduce global warming. Among the numerous sequestration options, terrestrial methods, notably via horticultural crops, have enormous potential. Horticultural crops, which encompass a diverse array of fruits, vegetables, plantations, and ornamental plants, offer a unique chance to sequester a considerable amount of atmospheric carbon dioxide. In particular, perennial horticultural systems provide numerous benefits over annual crops, such as increased productivity, reduced water and input requirements, and higher economic returns via carbon credits. However, the transition from annual to perennial crops presents logistical and financial challenges. The carbon sequestration capacity of plantations and horticulture crops is larger, at 16.4 Gt C, compared to the agroforestry system, which is at 6.3 Gt C. In order to fully use this capacity, it is essential to employ effective carbon management systems. These methods include growing higher biomass, recycling agricultural waste, employing animal manure, switching to perennial crops, adopting crop rotation, and encouraging agroforestry systems. Although there are advantages, substantial initial investments and continuous management are required to ensure effectiveness, and these demands might hinder widespread acceptance. This review emphasizes the critical role of horticulture systems in improving soil carbon levels, soil organic matter dynamics, different forms of carbon, and their overall potential for carbon sequestration. By unlocking the potential of horticultural crops to sequester carbon, we can help minimize atmospheric carbon dioxide levels, lessen the impact of climate change, and ensure nutritional security and economic benefits.

Sodicity is one of the major salt stresses that impair crop production. Exopolysaccharide-producing sodic tolerant bacteria (EPS-STB) play a significant role in reducing the sodic stress in plants by hampering the uptake of sodium. In this context, this study aims to isolate the EPS-STB for alleviating sodic stress in rice under a sodic environment. Thus, artificial sodicity was created in culture media, and 253 bacteria were isolated from the rice rhizosphere of sodic soils in Trichy and Chinna Salem of Tamil Nadu in India. Fifty bacterial isolates were initially screened based on EPS production, sodic tolerant ability, and plant growth-promoting activities. Further, these bacterial isolates were identified using 16S rDNA sequencing. The results suggested that the isolated bacteria possessed biofilm-forming abilities along with plant growth-promoting activities and osmolyte accumulation under sodic stress conditions. Bacillus rugosus L1C7T, Bacillus paralicheniformis L1C5L, Pseudomonas sp. L5C14T and Franconibacter helveticus L2C1L2 were chosen as better EPS-STB plant growth-promoting bacteria, and their impact on rice under sodic conditions was evaluated. Among the sodic tolerant bacteria, Franconibacter helveticus L2C1L2-inoculated rice plants increased dry matter production compared to the control. Thus, this study showed that the utilization of EPS-STB will become a promising tool to alleviate sodic stress in rice.

Soil quality index (SQI) is the tool for evaluating the sustainability of soil as affected by different factors such as land-use change and agricultural management practices. For a growing population, decreasing the land, maintaining soil quality is crucial to reach food security. Thus, the study aimed to select better crop rotation for the Inceptisol Deltaic region of Tamil Nadu using the SQI. Therefore, to develop SQI, samples were taken from the one-year-old already established field which comprising seven different crop rotations viz., Rice – Black gram, Rice- Sesame, Rice + Daincha – Maize + Green gram, Rice + Daincha – Bhendi, Rice + Daincha – Ragi, Rice + Daincha – Varagu, Rice + Daincha – Fodder Cowpea with first crop of green manure in all rotations. Nineteen physical, chemical, and biological properties of soil was analyzed. Minimum data set (MDS) were created based on principal component analysis (PCA) and Pearson’s inter-correlation. The MDS consist of Soil organic carbon (SOC), Labile carbon (LC), Dehydrogenase activity (DHA), Oxidizable carbon fraction 2 (OX2), Oxidizable carbon fraction 3 (OX3), available potassium (K), and urease. Scoring was given to MDS and SQI was calculated. The percent contribution of MDS toward SQI was in the order of SOC = LC = FDA (24%) > Available K (11%) > OX2 (6%) > DHA = urease (4%) >OX3 (3%). The results revealed that crop rotations had a significant impact on soil quality by altering their properties. The maize-based legume intercropped crop rotations recorded a higher SQI value (1.18).