Tamil Nadu in particular is a key rice-producing region in peninsular India. Hydrochemistry, viz., redox potential (Rh), soil temperature and dissolved oxygen (DO), of rice soils can determine the production of greenhouse gas methane (CH₄). In recent decades, the cultivation of crops organically became a viable option for mitigating climate change. Hence, this study aimed to investigate the effects of different organic amendments on CH₄ emission, Rh, DO, and soil and water temperature (T) in relation to the yield of paddy. The treatments composed of viz., control, blue-green algae (BGA), Azolla, farm yard manure (FYM), green leaf manure (GLM), blue-green algae + Azolla, FYM + GLM, BGA + Azolla + FYM + GLM, vermicompost and decomposed livestock manure. With the addition of BGA + Azolla, the highest reduction in CH₄ emission was 37.9% over the control followed by BGA. However, the same treatment had a 50% and 43% increase in Rh and DO, respectively, over the control. Established Pearson correlation analyses showed that the CH₄ emission had a positive correlation with soil (r = 0.880 **) and water T (r = 0.888 **) and negative correlations with Rh (r = −0.987 **) and DO (r = −0.963 **). The higher grain yield of 26.5% was associated with BGA + Azolla + FYM + GLM application. Our findings showed that there are significant differences in CH₄ emissions between different organic amendments and that hydro-parameters may be a more important controlling factor for methane emissions than temperature. The conclusion has been drawn based on valid research findings that bio-fertilization using BGA and Azolla is an efficient and feasible approach to combat climate change, as it assists in reducing methane emissions while simultaneously boosting crop yield by fixing nitrogen into the soil in the studied agro-climatic zone.

Seed orientation and its impacts on germination and seedling establishment mainly depend on the type of germination (hypogeal (or) epigeal), seed size and shape. Higher germination per cent is noticed when seeds are sown in the horizontal position. Planting seeds in a downward position can lead to a variety of physiological, chemical and morphological changes in seedlings. Consequences are usually manifested as noticeable modifications in their development. Vigorous seeds have strong, resilient seedlings due to their well-balanced metabolism and coordinated subcellular activity, making them well-suited for tough environments. Proper plumule and radicle growth require additional hormones and energy to ensure seedling survival. Four necessary factors must be considered while deciding the sowing depth viz., soil moisture, optimum soil temperature, soil aeration and atmospheric humidity required for seed germination, emergence and seedling growth. Variations are observed in germination behaviour and seedling growth for different sowing depths. The necessary factors are very much important for efficient nursery seedlings production. This review looks at the effects of seed depth and orientation on the germination and growth of important agricultural, horticultural and silvicultural crops.

Standard unit operations/equipment have not evolved for the traditional rice varieties of the Cauvery Deltaic region of Tamil Nadu. The fame of traditional rice is increasing nowadays owing to its health benefits. Non-standard unit operations may cause rice grains to crack during milling, accumulating more broken rice and yields in products of inferior quality. As a result, research into the physical properties of rice is crucial for the development of rice processing equipment that minimizes post-harvest losses during milling. Hence, an assessment was made to evaluate 30 traditional rice cultivars on their Physical (grain length, width, thickness, shape, and size), gravimetric (bulk, true, tapped density, porosity, Carr’s index, and Hausner ratio), and engineering characteristics (equivalent, arithmetic, square mean, and geometric mean diameter) using standard protocols, with the goal of reviving and preserving older varieties. The results from the analysis showed significant variations (p < 0.05) between all properties that were evaluated. According to length, a substantial amount of traditional rice varieties were long grain (76.7%), whereas (16.7%) belonged to the medium type and (3.3%) were short-grain types, respectively. There were variations among the three different categories of local rice grains when it comes to size, ranging from 3.26 to 4.69 mm for arithmetic mean diameter, 2.84 to 4.00 mm for geometric mean diameter, and 3.02 to 4.28 mm for square mean diameter, respectively. Sphericity, aspect ratio, and surface area measurements of the samples varied from 37.7% to 81.2%, 0.26 to 1.00, and 25.4 to 50.1 mm², respectively. Of the 30 varieties, 28 were under the high amylose category, and 2 belonged to the intermediate type. The Pearson correlation was established to study the interrelationships between the dimensions and engineering properties. Principal component analysis (PCA) reduced the dimensionality of 540 data into five principal components (PC), which explained 95.7% of the total variance. These findings suggest that it is possible to revive old landraces through careful selection and analysis of these properties. The superior characteristics of these traditional varieties can be further evaluated for breeding programs in order to improve the cultivation of these cherished rice landraces to enhance nutritional security.

Background: The growing demand for sustainable water management in agriculture has led to the exploration of unconventional water sources, including treated industrial wastewater. Brewery wastewater (BWW), with its inherent nutrient content, seems promising for irrigation. Nevertheless, there is limited knowledge regarding the influence of BWW on soil properties, crop nutrients and overall productivity in the Tamil Nadu context. This study delves into the intricate relationship between BWW irrigation and its impact on soil properties, plant responses and, ultimately, suitability for sustainable agricultural practices. Comparing BWW with Narugampally River water (NRW) serves as a baseline to assess potential differences in its effects. Methods: Laboratory analyses were conducted on BWW and NRW to characterize their irrigation potential. A pot experiment was also carried out in a completely randomized design (CRD) with four treatments covering 100%, 75%, 50% and 25% BWW, along with an additional 100% control (NRW) treatment. The analysis of the BWW samples revealed elevated levels of TDS, BOD, COD, CO₃ ⁻, HCO₃⁻, K⁺, NO₃⁻-N, SO₄ ⁻, B⁺, SSP, KR and TH beyond the permissible limits of the FAO irrigation water quality standards. However, the mean values of pH, EC, TSS, Ca²⁺, Mg²⁺, Na⁺, Cl⁻ and MH remained below the permissible limits according to FAO standards. In the NRW, all the studied parameters fall within the allowable limits. Results: The results of the pot culture experiments revealed that the height and stem girth of the maize plants in the soils irrigated with different concentrations of BWW did not significantly differ (P < 0.05). Furthermore, 100% BWW irrigation significantly (P < 0.05) increased the leaf area, chlorophyll content, shoot and root biomass and uptake of NPK and other cations in maize leaves. The same treatment significantly increased the pH, EC, OC, available NPK, exchangeable Ca, Mg, Na and soil CEC compared with those of the soils irrigated with 100% NRW. Principal component analysis (PCA) was used to identify key properties contributing to variance, highlighting the positive impact of organic carbon on soil properties and plant growth. Conclusion: This study provides a comprehensive assessment of the impact of BWW on soil and crop productivity in Tamil Nadu, filling a critical knowledge gap in sustainable water management for agriculture in water-scarce regions.

The effect of drupe size on in vivo and in vitro germination and its dormancy mechanism in teak have been studied in this paper. Teak drupes were size graded to five categories namely very large with more than 15 mm, large with 13 to <15 mm, medium with 11 to <13 mm, small with 9 to <11 mm and very small with less than 9 mm of diameter. Under in vivo pot culture condition very low germination percent of drupes was observed. It was observed that very large size drupe had highest 100 drupe weight, 100 true seed weight and seed filling capacity, but it was negatively correlated with in vivo germination of teak drupes. When true seeds isolated from the drupes were grown under in vitro condition in half strength MS medium the germination percent was significantly increased up to 54.1. True seeds obtained from small size graded drupes recorded highest germination per cent in MS media. This showed that the drupe size did not play major role in the germination and early growth in teak. Very small size graded drupes have low seed filling capacity, and it leads to decrease the germination percent. Poor germination of drupes showed the presence of mechanical and physiological dormancy in drupes. Similarly, the presence of morphological and embryo dormancy in teak may limit the true seed germination potential to 54.1 per cent. In addition, in vitro germination of true seeds will be a promising approach to obtain large number of saplings in teak.