This article presents an R package ridgregextra which provides various outputs related to ridge regression analysis. The package automatically finds the ridge parameter value k which makes the variance inflation factors (VIF) values closest to 1 while keeping them above 1 as addressed in M.H. Kutner et al. [Applied Linear Statistical Models, 5th ed., McGraw Hill, New York, 2004] opposite to other R packages available for ridge regression. This automatic and principled approach for selecting the ridge parameter enhances model interpretability and stability, addressing a key gap in existing softwares. Besides, most of the other packages also do not suggest a ridge parameter value k which can be confusing for practitioners. Additionally, there is no method in the literature which produces the VIF-based ridge parameter estimator. Ridgregextra package provides ridge regression results depending on the automatically selected ridge parameter value while giving regression tables (VIF, mean squared error (MSE), coefficient of determination ( $ R<^>2 $ R2), regression coefficients (Betas), standard errors of the coefficients (Stdbetas) for the ridge parameter values generated between certain lower and upper bounds defined by the user. In addition, it provides three sets of graphs consisting k vs. VIF values, Betas and the Stdbetas. These visual diagnostics facilitate a comprehensive understanding of the trade-offs involved in ridge regularization, empowering users to make informed decisions.
The dieback disease caused by Fusarium solani poses a significant challenge to tea cultivation. Trichoderma has the potential to combat this disease effectively without any residual effects. Out of several Trichoderma isolates collected from Dooars region of the West Bengal, India, the most potent strain was assessed under field conditions for the management of dieback disease in the Darjeeling, Dooars, and Assam zones. T. asperellum sprays at 1000 and 1200 ml/ha concentrations were found to be effective in managing the disease at all locations during both seasons. In Darjeeling, the infected shoots were 7.9 and 7.6 at 1000 and 1200 concentrations, respectively, compared to 27.3 in the untreated control during season I. During season II, the number of infected shoots was 8.1 and 7.3, respectively, compared to 29.9 in the control group. In Dooars such shoots were 8.6 and 8.2 respectively, against 31.3 shoots in control during season‑I and during season II the infected shoots were observed as 7.8 and 7.2 respectively, as compared to 29.9 in control plot. A similar trend was observed in Assam during both seasons. There was an increase in tea yield in T. asperellum-sprayed plots at all locations. During season I in Darjeeling, the tea yields were 422 and 425 kg at both concentrations, respectively, compared to 377 Kg in the untreated control. They were 395 and 399 Kg, respectively, in season II, compared with 354 Kg in the untreated control. In Dooars 1694 and 1703, Kg tea yield was obtained with these concentrations, which was higher than the untreated control (1519 Kg) in the first season, and a similar pattern was noted during the second season in terms of yield. A similar yield enhancement was observed in Assam during both seasons. The formulation did not harm beneficial insects across all zones, and no phytotoxicity was observed on tea leaves. The findings of this study suggest that T. asperellum is a promising agent for reducing tea dieback disease. It has negligible phytotoxicity and increases production without harming beneficial insects.
Rice improvement in rain-fed agroecosystems requires a reliable assessment of drought tolerance in locally adapted germplasm. The present investigation was designed to evaluate the genetic diversity in drought-tolerant Ahu rice (Oryza sativa L.) cultivars of Assam, India, with SSR (simple sequence repeat) genotyping. Fifty drought-tolerant lines were screened out among 325 germplasm lines collected. A genetic variation study using 40 SSR markers revealed distinct genetic variation among the rice landraces, with two drought-tolerant lines, Nagina22 (N22) and APO, serving as references. The allelic count per locus throughout the twelve chromosomes varied from 2 to 6. The allelic mean per locus was 3.30, with an average PIC (Polymorphic Information Content) of 0.6938. The UPGMA algorithm-based dendrogram segregated the genotypes into six distinct clusters with a high degree of genetic variation. Five rice cultivars (Dumai, Tarabali, Payjihari4, Baismuthi, and Gerem dhan1) with robust drought tolerance tendency were further characterized by means of elevated production of ROS scavenging enzymes, cellular osmolytes. The present study will help the breeders in parental screening for the upcoming breeding programs of drought-tolerance.
This study examines the effects of climatic variability on bacterial and fungal populations, as well as enzymatic activities innutrient-rich, organic soils that support tea plants (Camellia sinensis L). Conducted from 2016 to 2019 across five district tea estates (TEs) in the Jorhat district of Assam, India, this research investigates the intricate relationships among these parameters. The findings indicate that bacterial and fungal communities exhibit optimal growth within a temperature range of 18 to 30 degrees C, establishing a critical threshold for their metabolic activity. A significant positive correlation was observed between the abundance of these microbial populations and the corresponding soil enzymatic activities, underscoring the essential role of these robust microbial communities in sustaining vital soil processes. Hierarchical cluster analysis identified two distinct groups of TEs that displayed consistent patterns of microbial behaviour across varying seasonal conditions. Furthermore, principal component analysis demonstrated that the first three principal components accounted for over 80% of the variability observed in the microbial and enzymatic data sets. This research contributes valuable insights into the dynamic interactions between seasonal fluctuations and soil health, highlighting the crucial contributions of bacterial and fungal populations, along with their enzymatic activities, to the complex ecosystem underlying tea cultivation.
Tea (Camellia sinensis L.) cultivation in North-East India (NEI) including northern part of West Bengal is currently facing growing threats from climate change. Over recent decades, the region has witnessed a decline of more than 200 mm in annual rainfall and a temperature rise of about 1.3 °C. These shifts have caused soil-moisture deficits, extended dry spells during plucking seasons, and greater dependence on groundwater for crop sustenance. Several tea estates have already suffered yield reductions and quality deterioration due to such climatic stresses. In this context, groundwater recharge emerges as a promising adaptation strategy to replenish aquifers, sustain root-zone moisture, and alleviate the prevailing water stress. This literature review compiles and analyses studies published between 2000 and 2024 on groundwater-recharge methods adaptable to tea-growing ecosystems. Techniques such as percolation tanks, check dams, recharge pits or shafts, injection wells, and induced recharge systems have demonstrated effectiveness in enhancing water availability. Case studies from India and abroad report groundwater-level rises of 1-3 m and irrigation reductions of up to 25% following adoption. Moreover, these interventions improve microclimate regulation, nutrient and water use efficiency, and soil conservation, while also benefiting local drinking-water access. The review further highlights challenges in implementation and emphasizes the importance of an integrated framework encompassing policy support, hydrogeological mapping, community engagement, and long-term monitoring. Ultimately, the findings underscore the urgent need for the NEI tea industry to embrace groundwater-recharge strategies as a pathway for ensuring water security, climate resilience, and sustainable tea cultivation in the decades ahead.
