Herbicide-Microbial Interaction in Rice (Oryza sativa L.)
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Date
2021
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Department of Soil Science & Agricultural Chemistry, BAU, Sabour
Abstract
The present investigation entitled “Herbicide-Microbial Interaction in Rice (Oryza sativa L.)” was carried out during kharif seasons of 2019 and 2020 on a sandy loam soil of Bihar Agricultural College farm, Sabour, Bhagalpur, Bihar with four objectives: (1) To study the effect of various doses of herbicides on microbial population, microbial biomass carbon and enzyme activities at different days of interval under laboratory incubation experiment, (2) To study the effect of pre and post emergence herbicide on microbial population, microbial biomass carbon and enzyme activities at different days interval in rice field, (3) To study the effect of herbicide on chemical properties of soil and (4) To study the effect of herbicide on weed and yield attributes and yield of rice crop. The soil of the experimental field moderately well drained fine loamy one occurring on level to nearly recent alluvial plain loamy, surface slightly eroded having pH-7.8, low in available nitrogen, medium in available phosphorus and available potassium. Incubation experiment was conducted under factorial completely randomized design with five treatments T1 (pyrazosulfuron ethyl 10 % WP 15 g a.i. ha-1), T2 (pyrazosulfuron ethyl 10 % WP 30 g a.i. ha-1), T3 (carfentrazone ethyl 40 % DF 25 g a.i ha-1), T4 (carfentrazone ethyl 40 % DF 50 g a.i ha-1), T5 (Control) and four replication.Whereas, in case of field experiment, conducted under factorial randomized design (FRBD) with six treatment T1 (pyrazosulfuron ethyl 10 % WP 15 g a.i. ha-1), T2 (pyrazosulfuron ethyl 10 % WP 30 g a.i. ha-1), T3 (carfentrazone ethyl 40 % DF 25 g a.i ha-1), T4 (carfentrazone ethyl 40 % DF 50 g a.i ha-1), T5 (weed free) and T6 (weedy) and four replications. The experimental results revealed that the application of herbicidal treatments made on effect of microbiological properties (microbial population, microbiol biomass carbon and enzyme activity) and chemical properties under incubation experiment as well as rice filed experiment differ significantly among different herbicidal treatments. Under incubation experiment, the application of herbicidal treatments declined microbial population, microbial biomass carbon and enzyme activity except for urease activity at 7 days after application. While, at 28 DAA significant increases in all herbicidal treatments as compared to control. Maximum increasement produced by the treatment T2 (pyrazosulfuron ethyl 10 % WP 15 g a.i. ha-1) followed by T3 (carfentrazone ethyl 40 % DF 25 g a.i ha-1), over control, respectively.
In case of field experiment, the application of pyrazosulfuron ethyl (pre-emergence T1 and T2) and carfentrazone ethyl (post emergence T3 and T4) produced effect on biological properties such as microbial population, microbial biomass carbon and enzyme activity such as dehydrogenase, acid and alkaline phosphatase made a decline at 30 days after application but did not show any inhibitory effect on urease enzyme activity. Thereafter at 90 DAA, significant increase has been observed in all microbiological parameters like bacteria (19.97 to 37.56 %), actinomycetes (15.52 to 33.78), Fungi (15.74 to 27.35) as well as microbial biomass carbon status, dehydrogenase, acid and alkaline phosphatase and urease enzyme activities. At 145 DAA, further decline microbiological parameters was observed in all experimental plot. Application of pyrazosulfuron ethyl and carfentrazone ethyl did not show any significant effect on chemical properties of soil. The maximum growth parameters, yield attributes and yield (57.88 q ha-1) were recorded under the treatment T5 (weed free) followed by T2 (pyrazosulfuron ethyl 10 % WP 30 g a.i. ha-1), T4 (carfentrazone ethyl 40 % DF 50 g a.i ha-1) respectively, over control. The application of T2 (pyrazosulfuron ethyl 10 % WP 30 g a.i. ha-1), significantly lower (37.75 No. m-2) weed density, weed dry weight (22.87 gm-2) and found statistically similar T4 (carfentrazone ethyl 40 % DF 50 g a.i ha-1) but significantly highest compared to T6 (weedy).
Thus, it can be concluded that the application of pyrazosulfuron ethyl (pre emergence T1 and T2) and carfentrazone ethyl (post emergence T3 and T4) effect on biological properties such as microbial population, microbial biomass carbon and enzyme activities declined at 30 DAA but in case of urease enzyme activity no adverse effect was observed. Moreover, at 90 DAA significant increase under herbicidal treatment was observed as compared to hand weeding and untreated plot. Thereafter, there was no significant effect on chemical properties of soil was found. Overall, there was no long term adverse effect created on microbiological properties in transplanted rice grown soil.