STUDIES ON THE EFFECT OF HERBICIDES ON PLANT PATHOGENIC AND BENEFICIAL MICROORGANISMS IN GROUNDNUT
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Date
1990
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AAU, Anand
Abstract
Groundnut (Arachls hypogaea L.) is the main oilseed crop of India. Gujarat is the leading state of India in growing the groundnut during kharif as well as summer season. During growing the successful crop, applied herbicides in original or in degraded form may cause inhibitory or stimulatory or showed no change in soil ecosystem. Benthiocarb, at double to the recommended'dose, effectively discouraged the growth and development'of Aspergillus niger in-vitro on potato dextrose agar. Alachlor, at half to the recommended dose and recommended dose, showed poor visual growth of Fusarium solani on PDA, whereas Benthiocarb and 2,4-D, at double to the recommended dose, gave poor growth of Rhizoctonia bataticola. In-vitro Pendimethalin at half to the recommended dose showed poor visual growth of Pythium aphanidermatum as compared with control. Among all the herbicides tested (in-vitro), against X. campestris pv. oryzae, lowest bacterial count (3.75) was recorded on PDA, when recommended and double to the recommended dose of Basalin (3.75) was used. Whereas, half to the recommended dose of 2,4-D developed lowest colonies (14.50) of Azotobacter sp. on Ashby's media. Significantly lowest colonies(2.00) of Rhizobia were observed on yeast extract raannitol agar when half dose of Atrazine and recommended dose of Benthiocarb were used in laboratory evaluation. Herbicides viz., Atrazine, Basalin, Pendimethalin, Isoprotxiron, and Alachlor gave the cent per cent mortality of both the plant pathogenic nematodes viz., M. incognita and R. reniformis, but 2,4-D and Benthiocarb, were not found effective against both the nematodes pathogenic to tomato and castor respectively. Plots amraended with FYM showed corrparatively higher Azotobacter and other microbial population on Ashby's and PDA respectively. All the treatments were found nonsignificant so far the Rhizobial population was concerned. On 30th day after spraying of Alachlor, and Isoproturon at recommended dose, showed tremendous decrease in the microbial population on PDA,, Whereas, Alachlor, Basalin and Isoproturon, increased the Azotobacter population significantly in comparison with control without FYM, Significant: reduction in Rhizobial population was observed when all the three herbicides were used with and without FYM, during summer groundnut (1987-88). At the time of harvesting, significant reduction in microbial population (on PDA) was noticed in ammended as well as unammended soil with FYM, In the same way. Azotobacter population was greatly reduced in comparison with control without FYM(8.27). Alachlor, Basalin and Isoproturon at recommended dose increased the Rhizobial population, when the plots were unaramended with FYM in summer groundnut (1987-88). Highest reduction in nematode population was observed within a month period in the treatment receiving recommended dose of Basalin with FYM (52.46%). At the time of harvesting, highest increase in the nematode population was recorded in the recommended dose of Basalin with FYM (34.42%), All the treatments showed non-statistical difference in the seed germination in summer groundnut. Whereas, Isoproturon alone at recommended gave the highest incidence of collar-rot. While, lowest weed population was noticed in R.D, of Isoproturon, Highest pod yield was noticed in control treatment with FYM(1.267 kg/plot). No any adverse effect of herbicides on modulation in summer groundnut (1987-88) was noticed. Initial microbial population (grown on PDA) was at par in all plots in kharif groundnut(1988-89). Whereas, in case of Azotobacter population, there was no significant difference. Highest Rhizobial population was observed in the unamraended plots with FYM, as compared with ammended plots with FYM, before spraying of herbicides. Basalin and Alachlor at R.D, showed tremendous reduction; within a month period in the microbial population(grown on PDA). Least Azotobacter population was noticed in the plots. when sprayed with R.D. of Isoproturon with FYM19,18;. Whereas, population build up of Rhizobia was observed in control without FYMa02.07)within 30 days, in kharif groundnut(1988-89) At the time of harvesting, all the herbicides viz., / Alachlor, Basalin and Isoproturon at recommended dose reduced the microbial population in all the treatments (on PDA). Whereas, Isoproturon gave highest Azotobacter covint. Highest Rhizobial count was recorded in the plots treated with R.D, of Isoproturon alone (230.79), in 3diarif groundnut (1988-89), Among all the three herbicide tested, pre-application of R.D. of Basalin showed highest nematode reduction (47.92%) within the month period. At the harvesting, minimum reduction in nematode was observed in the control treatment without PYM (0.66%). Highest germination was observed in the control without FYM amraended soil (65.83%). Whereas, lowest weed population was found in plots treated with R.D. of Alachlor alone(2,99 ). All the treatments showed the equal effect on pod yield of groundnut and total modulation in kharif groundnut (1988-89), Initial microbial population was at par in all the treatments which were to receive the herbicides without FYM, the same trend was observed in the Rhizobial population.in summer groundnut (1987-88). After spraying of Alachlor, highest microbial population was observed (on 30th day of spraying) in the plots sprayed with R,D, of Alachlor. Highest Azotobacter count was observed when Alachlor was used at doxiaie R.D. Highest Rhizobial population (318,16) was observed in the plots sprayed with double dose of Alachlor with PYM (on 30th day of herbicide application;, At the time of harvesting there was to statistical difference in microbial population on PDA. All the treatments significantly reduced the Azotobacter count except R.D. of Alachlor with FYM, While, R.D.'of Alachlor, had no any adverse effect on the Rhizobial count (on YEMA media) in summer groundnut (1987-88;. Highest reduction (on 30th day after the application of herbicides) in nematode population was noticed in the treatment receiving FYM alone (42.60%). At harvesting, highest increase in the nematode population was recorded in the plots sprayed with half dose of Alachlor alone in summer groundnut. In summer groundnut, highest seed germination(87.27%) was recorded in the plots sprayed with R,D, of Alachlor + FYM. Lowest collar-rot incidence was observed in plots sprayed with dovible dose of Alachlor alone. Lowest weed population was observed in the plots sprayed with double dose of Alachlor alone ;3.10). Highest pod yield of groundnut was found in plots ammended with PYM and sprayed with half dose of Alachlor (1,900 kg/plot). Whereas, none of the treatment of Alachlor in combination with FYM showed any adverse effect on modulation. During kharif, Alachlor was sprayed at different doses. R.D, and 2 R,D, of Alachlor in unammended soil with FYM, significantly reduced the general microbial population (observed on 30th day on PDA). Tremendous reduction in Azotobacter was observed in the plots sprayed with half R.D. of Alachlor alone, R.D. of Alachlor increased the Rhizobial activity (count on YEMA). At the time of harvesting of kharif groundnut, highest microbial population (122.29) was observed in control without FYM, Lowest Azotobacter count was observed in the treatment receiving half dose of Alachlor alone (16.55), Whereas, ' highest Rhizobial population was noticed in the treatment receiving double dose at Alachlor alone (451,49), Spraying of Alachlor in Icharif groundnut showed highest nematode reduction (on 30th day of application) in the treatment receiving FYM alone (33.56%). At harvesting, highest nematode population was recorded in the treatment receiving FYM alone (24.66%). In kharif, groundnut, highest germination was recorded in plots sprayed with half dose of Alachlor + PYM, In case of weeds, lowest weed population was observed in the plots sprayed with double dose of Alachlor alone (1,66). Highest pod yield of groundnut was recorded in the plots sprayed with half dose of Alachlor alone(0.553 kg/plot). None of the treatments showed any' adverse effect on total modulation.
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Keywords
Plant Pathology, Agriculture, A Study