Rhizosphere dynamics in contaminated soils: Unravelling plant, metal and microbe relationships

Heavy metal contamination from both natural and anthropogenic sources poses a significant environmental challenge, impacting human and animal health, as well as microbial populations. Microbes exposed to elevated metal concentrations develop resistance mechanisms, involving both physiological and genetic adaptations, to detoxify and transform metals. Recent advancements have elucidated the roles of metal-metabolizing bacteria and transport proteins during metal detoxification. Microbial inoculation with phytoremediation is termed as rhizoremediation, which enhances degradation of toxic compounds in soil, offering a promising solution to contamination issues. The synergistic relations between plants and microbes in the rhizosphere highlight the importance of root exudates in mediating microbial communities for plant nutrition and metal biotransformation. It is for these reasons that it is imperative to better understand these interactions in order to design more effective convention for the detoxification of metals for enhanced soil quality. The potential application of plant-microbe synergism in the remediation of metal pollutants using environmentally friendly and economically viable methods in soil remain scarce

A study on the trends and seasonal fluctuations of black carbon aerosols in the elevated region of Ooty, Western Ghats, Tamil Nadu, India

The accelerating effects of climate change, driven by rising greenhouse gas emissions, necessitate identifying key contributors like aerosols, mainly black carbon (BC), due to their significant impact on global warming. This study investigates the temporal and seasonal dynamics of BC aerosols in Ooty, Tamil Nadu, India, using a decade (2013–2023) of data from an Aethalometer. Annual BC concentrations varied from 0.51 µg/m³ (2020) to 1.1 µg/m³ (2023), with a decadal mean of 0.75 ± 0.26 µg/m³. Distinct season al variations were observed, with summer BC concentrations ranging from 0.9 to 1.6 µg/m³ (mean: 1.3 µg/m³) and monsoon values significantly lower at 0.2–0.5 µg/m³ (mean: 0.4 µg/m³). Winter exhibited a seasonal mean of 1.1 µg/m³, while post-monsoon BC concentrations averaged 0.6 µg/m³. Temperature (20–28.6°C), relative humidity (49–93%), and rainfall (0.4 7.81 mm/day) influenced the observed trends. April consistently showed peak BC levels (up to 1.87 µg/m³), while 2020 recorded the lowest due to reduced emissions. Seasonal trends revealed increasing BC levels from December to April, declining during the monsoon months (June–November). These findings underscore the need for sustained monitoring and mitigation strategies in high-altitude regions to address BCs’ climatic impacts, aiding global efforts against climate change

Economics of Coconut Cultivation Using Treated Sago Industrial Wastewater and Fresh Water in Salem District of Tamil Nadu

The study attempts to examine the socio- economic profile and economics of coconut cultivation using treated sago industrial wastewater and fresh water in the Salem district of Tamil Nadu. A sample of 180 farmers receiving treated wastewater from nearby industrial units and another 180 farmers receiving fresh water (control farms) were selected through a multistage purposive sampling technique. The major finding of economic analysis of coconut cultivation revealed that the gross income of the sample farm using treated sago industrial wastewater was high at ₹ 1,31,408.00 as a result of the better yield of nuts (12540) as compared to that obtained by irrigation with fresh water (12245). The net income per hectare of coconut was ₹ 46,128.64 and ₹ 34,245.72 for the farm using treated wastewater and control farms, respectively. The study; therefore could establish that using treated industrial wastewater for irrigation will be advantageous in terms of net returns and to an extent substitute use of fresh water for irrigation, besides helping to save on use of and expenditure of organic and inorganic fertilizers

Soil fertility dynamics in the Northeastern agroclimatic zone of Tamil Nadu: a targeted analysis of Tiruvannamalai district

Soil fertility degradation due to poor nutrient management is a growing concern in many farming areas. This study focuses on assessing the soil health of Tiruvannamalai district, Tamil Nadu, by examining key factors like pH, organic carbon (OC), electrical conductivity (EC) and the availability of essential nutrients (nitrogen, phosphorus, potassium) and micronutrients (zinc, iron, copper, manganese, boron). A systematic soil sampling method was employed, collecting 129 samples from 18 blocks using a 5 × 5 km grid at 0-15 cm depth. The results showed that the soils were primarily neutral to slightly alkaline, with pH values ranging from 7.15 to 7.41. Electrical conductivity was low (<0.26 dS/m), indicating minimal salinity. Organic carbon levels were also low, with more than half of the samples (53.06%) falling below optimal levels, ranging from 0.29% to 0.64%. The analysis revealed widespread nutrient deficiencies, with 65% of the soils low in nitrogen, 63.06% lacking phosphorus and 79.44% deficient in potassium. Additionally, significant micronutrient shortages were detected, with zinc (83.89%), iron (83.06%), copper (76.67%), manganese (88.89%) and boron (75.28%) all showing depletion. These results highlight the urgent need for improved soil management practices, including targeted fertilization and nutrient restoration efforts, to enhance soil fertility and ensure sustainable agricultural productivity in the region

Bioconversion of coir ETP sludge: An eco-friendly path to circular economy

The accumulation of sludge from Effluent Treatment Plants (ETPs) in coir industries has become a serious concern, raising critical questions about the eco-friendly management of large volumes of coir industry ETP sludge in coir-producing countries like India. This study aimed to explore a viable solution for bioprocessing the sludge and assess its potential as a soil amendment. Based on the C: N ratio and the initial characteristics of the ETP sludge, cow dung, and poultry manure were identified as potential amendments for sustainable bioconversion. The mixture was inoculated with TNAU Biomineralizer, a specialized culture that aids in decomposition. The bioconversion experiment used six treatment combinations (T1 to T6) to monitor nutrient transformations. Compost from treatment T6 (50% Sludge + 25% Poultry Manure + 25% Cow Dung + TNAU Biomineralizer) exhibited a significant improvement in nutrient content. The efficacy of the composted sludge was further assessed through a pot culture experiment using the Amaranthus variety CO 6, where different proportions of the composted sludge were applied alongside recommended agricultural practices. The results revealed that treatment T8 (100% Composted Sludge + Silica Solubilizing Bacteria) and the recommended package of practices combined with 100% Composted sludge significantly enhanced growth parameters, including root length, shoot length, and the number of leaves, outperforming other treatments. This study highlights that the bioconversion of coir industry ETP sludge with organic amendments and TNAU Biomineralizer offers a sustainable and eco-friendly solution, presenting a promising approach to advancing the circular economy

Exploring potentials of the physical and biochemical characteristics of Gracilaria gracilis and Gracilaria edulis for enhancing plant growth under abiotic stress

Seaweed may assist agricultural crops to adapt with abiotic stress and are widely used in agriculture, especially as biostimulants that improve plant growth and resistance to abiotic stressors. The study focuses on the biochemical characteristics of these seaweeds and their effect as plant biostimulant to improve germination and crop growth. Seaweeds were collected from Mandapam area of Ramanathapuram district and identified as Gracilaria gracilis and Gracilaria edulis from AJC Bose Indian Botanic Garden, West Bengal and their physico-chemical properties were evaluated. Higher protein levels were obtained in G. edulis (16.72 %), swelling capacity (SWC) in G. gracilis (23.25 mL g-1) is more compared to G. edulis, however, water holding capacity (WHC) of G. edulis (11.31 g g-1) was higher. The findings demonstrate that G. edulis has superior WHC, whereas G. gracilis has higher SWC, which improves soil moisture retention and nutrient availability. Further study shows that the two species\u27 mineral compositions differ significantly, with G. gracilis being higher in potassium (6413.5 ppm) and sodium (1051.5 ppm), which may help with osmotic management in plants. Growth parameters were significantly improved by the treatment (T2–T5). In comparison to control T1, treatment T5 (10 % papermill effluent + G2 sps @ 7.5 %) exhibited the longest roots (51 ± 0.37 cm) and shoots (34 ± 0.35 cm), remarkable seed vigor index (26.88 ± 0.30) and a high germination percentage (96 ± 0.06 %). Overall, the results provide support to the usage of these seaweeds as organic fertilizers in difficult environmental situations to enhance crop growth

Assessing the pollutant removal potential of native reeds in sewage and paper mill effluents

Reed plants are cost effective method of remediating the wastewater. To test the removal efficiency of pollutants from sewage and paper mill effluents, four different reed plant species, Canna indica (Indian Shot), Colocassia esculenta (Taro), Typha domingensis (Southern Cattail) and Xanthosoma sagittifolium (Tannia), were compared for their removal efficiency of pollutants from sewage and paper mill effluents. Because of the high cost and limited effects of present physico-chemical treatments in wastewater treatment plant, this reed bed system can act as a cheaper process, that are essential to remove the organic pollutants, thus make them suitable for agricultural and irrigation purposes. In this study, initially, the raw effluent of sewage and paper mill was characterized. The four reed plants were separately screened with both the effluents by adopting the treatments for the four reeds and seven days retention time as two factors with 2 replications in pots. Each day, the treated effluent was collected from the pot and analysed. Up to day 7, the screening was done with both the effluents. The result shows that the Canna indica and Colocassia esculenta could be the better option for pollutant removal from the sewage and paper mill effluent respectively. The removal efficiency was higher in Canna indica (60%) for sewage wastewater and Colocassia esculenta (65%) for paper mill effluent. This removal percentage shows that the tolerating nature of the plants to the wastewater. The efficiency of the removal of pollutant by reeds can be further improved by bioaugmentation process which aids the action of microbes in the rhizosphere of the reed plants which may be used in the reed bed system

Impact of climate change on oilseed production - A review

Oilseeds are vital to global agriculture, providing essential edible oils, high-protein livestock feed and raw materials for bio-based industries. Climate change poses a threat to the productivity, quality and sustainability of oilseed crops. This review critically examines the impacts of major climate stressors, including rising temperatures, altered precipitation patterns, elevated atmospheric CO₂ levels, increased ozone and the heightened frequency of extreme weather events on the growth, yield and oil quality of key oilseed crops such as soybean, groundnut, rapeseed-mustard, sunflower, safflower and sesame. It explores the physiological and biochemical mechanisms underlying crop responses to climate-induced stress, focusing on reductions in oil content and shifts in fatty acid composition. Climate-related stressors can lead to yield declines ranging from 10 % to 40 %, with heat stress during flowering and seed filling causing up to a 70 % reduction in seed set in sensitive varieties. The review also evaluates adaptive strategies, including the development of climate-resilient cultivars through advanced breeding and biotechnology, the implementation of conservation agriculture and integrated nutrient management and the role of digital tools in monitoring and mitigating stress impacts. Emphasizing the urgent need for integrated research, policy support and sustainable farming practices, this review aims to guide future efforts in enhancing the resilience of oilseed crops