Soil biotic and abiotic factors influencing plant diseases in rice based cropping system with different regimes of conservation agricultural practices
| dc.contributor.advisor | Dr. Subrata Dutta | |
| dc.contributor.author | DASGUPTA AMRITA | |
| dc.date.accessioned | 2023-12-20T17:18:27Z | |
| dc.date.available | 2023-12-20T17:18:27Z | |
| dc.date.issued | 2023-12-20 | |
| dc.description.abstract | Conservation agriculture (CA) aims to conserve, improve and make more efficient use of natural resources through integrated management of soil, water and biological resources combined with external fertilizer inputs. At early stage of CA there appear some serious issues related to supplying sufficient nutrients to the crops to achieve economically viable yields. These issues can be addressed by strengthening microbial interaction and optimizing soil biological activity through self-sustaining biological systems rather than reliance on external inputs or synthetic fertilizers. Modern agriculture is input and energy intensive and highly torturous in nature thus, becoming threats not only to microbial world but to whole ecology and environment. Thus, it is high time for the farmers and agriculturists to address the issues of environmental sustainability along with eco-friendly management practices for harnessing sustained crop productivity to ensure the future food security goal. Conservation agriculture (CA), offers low mechanical disturbance, crop rotation, retention of diverse crop residues and release of diversified chemical compounds as rhizo-depositions to soil and maintaining a protected, cozy habitat for microbes is well ahead biodynamic technology for sustainable crop production. Practices of CA are capable of regenerating and conserving top soil by restoring microbes, and ecosystem services and manage the disease dynamics in field crops under natural conditions. Scanty of literature has been available on the details of microbial population dynamics along with vis –a-vis plant disease dynamics under intensification of CA practices. In the current experiment, microbial dynamics, disease dynamics and yield was assessed and some of the important disease prediction models were developed under rice-wheat-green gram (R-W-G) and rice-mustard-black gram (R- M-B) cropping system under different degrees of CA practices. In the present study, it was observed that zero tillage was found to significantly increase the total bacterial, total fungal, total Actinomycetes and total Bacillus population, whereas, reduced tillage favoured the total phosphate solubilizing bacteria (PSB), total Pseudomonads population and nitrogen fixing bacterial (NFB) population. Real time (RT) PCR was performed to evaluate the population dynamics of Alphaproteobacteria, ii Betaproteobacteria and Gammaproteobacteria under three tillage different systems and it was found that intensification of CA practices favoured the Proteobacterial population dynamics, when compared to conventional tillage system. In the current study, dehydrogenase enzyme activity was also performed for better understanding of microbial enzyme activity under different tillage systems in combination with different nutrient- residues level. Zero tillage along with NR2 (100% residue + 50% RDF) performed the best, with highest enzyme activity in both the cropping system, proving effects of tillage systems and residue retention on microbial activity. Thus, a hypothesis that keystone microbial clads were well conserved in CA under microclimate created due to less soil disturbance, habitat restoration, cover cropping, crop rotation etc. ,is put forward. Population dynamics of Sclerotium rolfsii was evaluated along with the suppressiveness and conducivenesss of the soil under different regime of CA practices. In both the cropping systems (R-W-G & R-M-B), the maximum sclerotial population of Sclerotium rolfsii was observed in conventional tillage system as compared with CA practices. A meta-analysis was performed to assess the changes in microbial abundance under varying degrees of CA. Different tillage practices were the most important factors in defining the structure of bacterial communities and β-diversity matrix showed that reduced tillage (RT) and zero tillage (ZT) are closely related to each other whereas conventional tillage (CT) is distantly related to them, which is the reflection of management followed in these scenarios. Abundance at genus level showed that zero tillage and reduced tillage exhibited higher abundance of Bacillus when compared to conventional tillage. Streptomyces and Spingomonas showed similar kind of result, with maximum abundance in reduced tillage, followed by conventional tillage and zero tillage. Pseudomonas, on the other hand, showed maximum abundance in reduce tillage, followed by zero tillage and conventional tillage. The present study clearly demonstrated that the structure and diversity of soil bacteria in reduced tillage were significantly different compared with other tillage practices. Also the dynamics of naturally occurring plant diseases of rice (blast, brown spot, bacterial blight and sheath blight), wheat (leaf blight disease), green gram (Cercospora leaf spot disease), mustard (Alternaria blight and downy mildew) and black gram (Cercospora leaf spot disease) under rice-wheat-green gram and rice-mustard-blackgram cropping system were evaluated and it was observed that severity of some of the diseases are comparatively less with increasing intensity of CA practices and it was also observed iii that severity of the majority of rice diseases were less in reduced tillage system. Studies were also conducted for understanding the influence of different weather factors, micro- climatic variables and soil temperature on important diseases in R-W-G and R-M-B cropping system under varying degrees of CA practices. Disease prediction equations were developed based on 2 years data (2019-20 & 2020-2021) for few important diseases to understand the significant disease predicting weather and micro-climatic variables under different rgime off CA practices. In case of Cercospora leaf spot disease of green gram, different prediction models (multiple regression model, logistic regression model and canonical discriminant function model) had been compared and it was observed that canonical discriminant analysis model performed better in predicting the disease risk in comparison to other two models. Outcome of this study will be helpful to the farmers for adopting CA, particularly, in tropic and subtropical countries where agriculture is greatly relying on the benefits derived from plant–microbe interactions. | |
| dc.identifier.uri | https://krishikosh.egranth.ac.in/handle/1/5810204016 | |
| dc.language.iso | English | |
| dc.publisher | Plant Pathology, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia – 741252 | |
| dc.sub | Plant Pathology | |
| dc.theme | Pathology | |
| dc.these.type | Ph.D | |
| dc.title | Soil biotic and abiotic factors influencing plant diseases in rice based cropping system with different regimes of conservation agricultural practices | |
| dc.type | Thesis |