T. Sherene Jenita Rajammal

The increasing demand for sustainable agricultural production, coupled with declining soil health, inefficient nutrient use and poor irrigation water quality, necessitates the development of innovative and eco-friendly technologies. Among the nanomaterials, two-dimensional graphene oxide (GO) has gained attention due to their extraordinary physical and chemical properties, including high specific surface area, a better number of oxygen-containing functional groups, high adsorption capacity and surface chemistry. Green synthesis approaches using biomass, agricultural residues and plant extracts are highlighted for their potential to reduce environmental impacts and promote sustainable nanomaterial production. This review further discusses advanced characterisation methods such as Fourier transform infrared spectroscopy, x-ray diffraction pattern, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller surface area analysis and x-ray photoelectron spectroscopy for understanding their structure and function. These analytical techniques provide critical insights into the structural attributes that determine the agricultural performance of GO nanomaterials. Soil–nanomaterial interactions, adsorption of nutrients, controlled release of nutrients and removal of sodium ions from saline irrigation water were thoroughly assessed. Based on existing evidence, application of GO may enhance soil aggregation, water holding capacity, nutrient utilisation efficiency and irrigation water quality and help sustain crop production. However, challenges related to large-scale production, long-term environmental fate, biosafety, economic viability and regulatory standardisation have hindered widespread adoption in agriculture. Future research should prioritise scalable and cost-effective production technologies, long-term field validation, standardised risk assessment protocols and integration with precision agriculture to facilitate commercial adoption.

Drought stress, a major constraint in maize (Zea mays L.) productivity around the world. This study assessed the effectiveness of a phosphoric acid (H₃PO₄)-hydrolysed Sargassum-based biostimulant in improving drought tolerance and sustaining maize productivity under water-deficit conditions. A field experiment was conducted during the 2025–26 rabi season at Sakkampatty, Theni District, Tamil Nadu, India, using a randomised block design (RBD) with nine treatments and three replications. Biochemical characterisation of the biostimulant identified phenolics, flavonoids, tannins, terpenoids, phytosterols, carbohydrates, proteins and biologically active functional groups. The biostimulant significantly improved physiological traits, growth, yield attributes and grain yield compared with the drought-stressed control. Among the drought-stressed treatments, application at 3.0 kg ha-1 (T₇) recorded the highest chlorophyll stability index (CSI),membrane stability index (MSI), relative water content (RWC), proline accumulation, antioxidant enzyme activities and grain yield (39.58 g plant-1), representing an approximately 115 % increase over the drought-stressed control (T₂). These findings suggest that the H₃PO₄-hydrolysed Sargassum biostimulant has potential as an eco-friendly approach for enhancing drought tolerance and sustaining maize productivity under water-limited conditions. Multi-location and multi-season studies are required to validate its effectiveness across diverse agro-climatic conditions.

Aims: To develop an acid-hydrolysed Sargassum-based biostimulant formulation and evaluate its biochemical characteristics and effectiveness in improving seed germination and early seedling growth of maize. Study Design: A laboratory seed germination experiment was conducted using a Completely Randomised Design (CRD), with four treatments and three replicates. Place and Duration of Study: The study was conducted at the Department of Soil Science and Agricultural Chemistry, Anbil Dharmalingam Agricultural College and Research Institute, Tamil Nadu Agricultural University, Tiruchirappalli, Tamil Nadu, India, from April to July 2026. Methodology: Sargassum biomass collected from Mandapam, Rameswaram, Tamil Nadu, was washed, shade-dried, powdered, and subjected to partial acid hydrolysis using 5% (v/v) nitric acid at a 1:10 solid-to-liquid ratio for 24 h at 30°C. The hydrolysed extract was characterised for phenolics, tannins, flavonoids, terpenoids, and phytosterols. Fourier-transform infrared spectroscopy (FTIR) and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) were used to characterise the hydrolysed extract. Maize CO(H)M8 hybrid seeds were treated with 1, 2, and 3% acid-hydrolysed Sargassum formulation and evaluated using the roll-towel method for germination and seedling growth. Results: The acid-hydrolysed extract contained phenolics (5.92 ± 0.14 mg GAE mL⁻¹), tannins (4.15 ± 0.11 mg TAE mL⁻¹), flavonoids (3.84 ± 0.09 mg QE mL⁻¹), terpenoids (2.71 ± 0.07 mg LE mL⁻¹), and phytosterols (2.24 ± 0.05 mg CE mL⁻¹). FTIR analysis showed characteristic absorption bands at 3344, 1631, 1324, and 1041 cm⁻¹, indicating changes in functional groups following acid treatment. MALDI-TOF MS showed major peaks at m/z 2053, 4664, 7569, 9322, 11934, 13736, and 18475. The Sargassum-based treatments improved maize seed germination and seedling growth compared with the untreated control. The 3% formulation recorded the highest germination (95.2%), root length (12.6 cm), shoot length (13.4 cm), stem girth (3.8 mm), fresh weight (1.42 g seedling⁻¹), and dry weight (0.33 g seedling⁻¹). Conclusion: The acid-hydrolysed Sargassum-based formulation enhanced maize seed germination and early seedling growth, with the 3% formulation showing the best overall performance. The developed formulation has potential as a sustainable seaweed-based biostimulant for improving maize seedling establishment.

Microbial biofilms are organised populations of microbes covered with a self-made extracellular polymeric matrix and are at the core of climate-smart farming and sustainable agriculture. Biofilms enhance soil health by stabilising soil structures, enhancing microbial diversity and promoting nutrient cycling and thereby naturally supporting plant growth and resilience. One way biofilm-forming plant growth promoting rhizobacteria (PGPR) might be helping plants is by making them better able to take up nutrients through the solubilization of elements such as nitrogen, phosphorus and potassium; at the same time, they release phytohormones and compounds that alleviate stress to make plants resistant to abiotic stresses like salinity and drought. Root colonisation becomes more durable and pathogen biocontrol can be done more efficiently by biofilm matrices, which protect microorganisms from environmental stresses. Rhizospheric interactions exemplified by cross-kingdom biofilms with fungi are the most effective ways to exchange nutrients and enhance ecosystem resilience. The growth of stable biofilm communities and their microbial diversity can be supported by agricultural techniques such as the use of organic additives and conservation tillage. Recent developments emphasise the use of biofilm-based inoculants as biofertilizers, bio-stimulants and biocontrol agents in an effort to lower chemical inputs and greenhouse gas emissions in agroecosystems. More research and innovative applications like multi-strain consortia and biofilm-enhanced seed coating provide promising ways of harnessing microbial biofilms for increased agricultural productivity and soil quality, as well as environmental sustainability in the face of climate change.

Developing and distributing crop production technologies that promote sustainable crop intensification is crucial for ensuring food and nutritional security for the growing global population. This challenge remains one of the most pressing issues for governments in the twenty-first century. According to the Ministry of New and Renewable Energy, India produces approximately 500 million tons of crop waste annually. Conservation agriculture offers a promising solution to manage crop residues by maintaining a permanent soil cover through mulching and incorporating crop residues into the soil. Soil is fundamental to agricultural productivity and plant growth. However, the fraction of arable soil is limited and requires careful management to prevent nutrient depletion. Soil fertility depends significantly on organic matter and soil carbon content, which are key indicators of soil health. Crop residues enrich the soil with essential nutrients, improving crop yields and altering soil characteristics. They influence water infiltration, flow and runoff and help regulate soil temperature by shielding the surface from direct sunlight. Increased residue cover reduces evaporation rates, conserving soil moisture. Agricultural residues typically contain vital nutrients up to 80 % nitrogen, 25 % phosphorus, 20 % potassium and 50 % sulphur. Incorporating these residues into the soil enhances fertility, maintains health and supports sustainable agriculture, ensuring long-term productivity.

A field experiment was conducted at Tamil Nadu Agricultural University, Trichy, under the All India Coordinated Research Project (AICRP), to assess the effect of organic amendments and micronutrient enrichment on maize (Zea mays L.) performance in sodic soil. The study utilized vermicompost (VC) and farmyard manure (FYM) combined with an inorganic micronutrient mixture, applying eleven treatments in a Randomized Complete Block Design (RCBD) with three replications. Plant growth (height, leaf area, stem girth) and yield attributes (cob length, cob girth, kernel count, grain weight) were recorded and analyzed using Principal Component Analysis (PCA) to identify key influencing traits. The results demonstrated a significant improvement in maize growth and yield by applying a micronutrient mixture at 25 kg ha-1 enriched with VC (1:10) and zinc-solubilizing bacteria (ZSB). This treatment recorded the highest cob length (21 cm), girth (5.41 cm), kernels per cob (573.8 kernels/Cob) and grain weight (3.96 kg), highlighting the synergistic effect of organic amendments, micronutrient enrichment and microbial inoculation. PCA revealed that the first principal component (PC1) captured 96.88 % of the variance, primarily influenced by cob girth, grain weight, stem girth, leaf area and plant height. Biplot analysis effectively distinguished treatment effects, highlighting the efficacy of fortified vermicompost with ZSB. This study emphasizes the potential of integrating organic and inorganic inputs with PCA as a powerful tool for identifying key yield determinants in sodic soils, contributing to sustainable agricultural practices.

A comprehensive study was conducted at block level in Salem District, Tamil Nadu, India, to evaluate the major ionic chemistry and to assess the suitability of ground water for irrigation purpose. A total of 200 groundwater samples were systematically collected through grid survey and analyzed for major ionic constituents and irrigation water quality parameters. The resulting water quality parameters were interpreted based on established hydrochemical guidelines. The classification of groundwater samples under various quality categories based on pH, electrical conductivity (EC), residual sodium carbonate (RSC) and sodium adsorption ratio (SAR) indicates that many blocks (70 %) in the study area exhibit good-quality groundwater suitable for irrigation. However, exceptions (30 %) were observed in the blocks of Omalur, Mecheri, Kolathur and Pethanaickenpalayam having been observed with saline and alkali water quality. This might be due to the underlying metamorphic and crystalline rocks carrying the element calcium and sodium rich minerals are responsible for the development of saline/alkali groundwater. It was observed that mushrooming of industrial complexes in these blocks might also be the reasons for the development of saline or alkali groundwater. The need for this work is to evaluate groundwater quality for irrigation in Salem District and identify areas affected by saline and alkali contamination due to natural and industrial influences.

The pulp and paperboard industries are the major industrial sector that consumes significant amounts of fresh water and generates large volumes of wastewater. The treatment of this wastewater resulted in the production of a substantial amount of sludge, which posed serious environmental challenges. This study explored a sustainable solution by converting PBS into biochar through slow pyrolysis of temperatures up to ≤ 500 °C, offering an alternative approach to waste management and resource conservation. The physicochemical parameters of paper board sludge biochar (PBSB) exhibited a neutral pH of 7.49, electrical conductivity of 0.09 dS m⁻¹, organic carbon of 38.12% and CaCO₃ of 24.5%. Proximate analysis of PBSB revealed an increased fixed carbon of 76.43%, total organic carbon (TOC) of 7.13%, and reduced volatile matter and moisture levels. The TGA analysis of the dried paperboard sludge sample showed a 20% mass reduction when heated to 350 °C. During this process, more than 90% of the volatile components were removed.. The micro nutrients viz., Fe 5.06 mg L⁻¹, Mn 419.3 mg L⁻¹, Cu 26.3 mg L⁻¹, and Zn 66.1 mg L⁻¹ contents were observed in PBSB. FT-IR analysis identified the presence of various carbon-containing functional groups, including C–Cl, C–N, C–C, H–C = O, C–H, and –C≡C–H, indicating substantial chemical transformations during pyrolysis. SEM–EDX analysis revealed that PBSB has fine particle size and a coarse fluffy spongy porous structure ideal for water adsorption. Elemental analysis (XRD) showed high carbon and oxygen content with significant amounts of aluminosilicates, carbonates, and nutrients like phosphorus and potassium, suggesting PBSB as a potential slow-release fertilizer. This research highlights the potential of biochar derived from paperboard waste as a sustainable solution for waste management and resource recovery. Graphical Abstract